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as replication fork. DNA polymerase adds new (b) Secondary structure of tRNA is complementary bases in one direction only, i.e. 3' 5’-3’. The strand with polarity 3’-5’ has continuous Amino acid replication. On the other strand with polarity arm 5’-3’, fragments of newly synthesized strand are formed which are joined later by DNA ligase. This 5' is called discontinuous synthesis. D arm T & C arm Continuous Template DNA Extra arm synthesis (parental strands) 5' 3' Discontinuous synthests 3' 5' 3' 5' Anticodon arm Newly synthesised strands It is called semiconservative because in daughter Anticodon strands one strand is parental and other strand The actual structure of tRNA looks like inverted is newly synthesised. L. 134. (a) Because DNA molecule is too large and it requires very high energy for separation of 141. Refer answer no. 136. two strands of DNA. 142. Refer answer no. 81 (a) for diagram. This tRNA adds methionine and marks the beginning of (b) DNA polymerase adds new comple-mentary bases in one direction only, i.e. 5’-3’. The translation. strand with polarity 3’-5’ has continuous replication. On the other strand with polarity 143. ‘‘i’ gene transcribes the mRNA for repressor 5’-3’, fragments of newly synthesized strand protein, the repressor protein when present binds are formed which are joined later by DNA to the operator region of lac operon and does not ligase. This is called discontinuous synthesis. allow RNA polymerase to transcribe structural genes. Thus the lac operon is switched off by repressor. (c) Replication does not initiate randomly at any place in DNA. There is a definite region where 144. (a) ‘i’: inhibitor gene which codes for repressor the replication originates. Such regions are protein, ‘p’: promoter region where RNA termed as origin of replication (ori). polymerase binds. 135. (a) The transcriptional products of RNA (b) Inducer is lactose. When lactose is present, polymerase III are tRNA, 5SrRNA, and the repressor protein is unable to bind to the snRNAs (small nuclear RNAs) operator, the polymerase enzyme transcribes (b) Addition of Methyl guanosine triphosphate at the structural genes. Thus the operon is 5’ end of mRNA is called capping and addition of poly-A tail at 3’ end of mRNA is called switch on. tailing. 145. (a) Molecule M is repressor (b) This will block access of RNA polymerase to structural genes and operon is switched off. (c) Heterogeneous nuclear RNA 136. (a) For diagram Refer answer no. 100. (c) Inducer, in this case is lactose, will prevent the (b) Promoter gene provides binding site for RNA binding of M with the operator. It inactivates polymerase. repressor and allows RNA polymerase to 137. For diagram Refer answer no. 100 access promoter. RNA polymerase enzyme (b) The template strand becomes coding strand transcribes the structural genes present in when the replication polarity is reversed. lac operon. (c) Refer answer no. 133(b). 146. The method/technique is DNA fingerprinting Procedure: DNA fingerprinting involves following 138. (a) Refer answer no. 100 (b), 133 (b). steps- 139. mRNA : 5' AUG ACC UUU CAU UCG UGU AA 3' Isolation of DNA --> digestion of DNA by restriction endonucleases --> separation of DNA Polypetide : Met Thr Phe His Ser Cys fragments by electrophoresis --> transferring The codon is triplet, AUG acts as start codon and also codes for metheonine. (blotting) of separated DNA fragments to 140. (a) It is called as adaptor molecule because it acts synthetic membranes such as nitrocellulose or as carrier of amino acid, type of AA it carries depend upon the anitcodon loop the tRNA nylon --> hybridisation using labelled VNTR has. probe --> detection of hybridised DNA fragments by autoradiography. 150 Biology–12

147. (a) Restriction endonuclease (b) DNA fingerprinting can be used for estab- (b) Agarose gel lishing paternity disputes (1) and determine (c) Synthetic membranes, such as nitrocellulose population and genetic diversities (1) or nylon 156. (a) Bacteriophage, because it infects bacteria. (d) VNTR (b) Two types of culture media were used in order (e) Hybridisation to make protein coat of viruses radioactive by (f) Autoradiography using radioactive sulphur and the other one 148. Satellite DNA do not code for any proteins, but to make DNA radioactive by using radioactive phosphorous. Radioactivity helped to identify they form a large portion of human genome. These if DNA or protein entered the bacterial cell sequences show high degree of polymorphism and during infection or not. form the basis of DNA fingerprinting. (c) Blender was used to separate the viral 149. Refer answer no. 143. protein coats from the surface of bacteria 150. Refer answer no. 143. and centrifuge was used to separate lighter 151. DNA polymorphism arises due to mutation at supernatant containing viral protein coats from denser residue containing bacteria. genetic level. (d) The conclusion drawn was that the DNA was (a) It is the basis of DNA finger printing and the only genetic material, which passed from genetic mapping of human genome. It is virus to bacteria. high frequency of inheritable mutation observed in a population. Such mutation are 157. Genetic material should be able to: not expressed as these are present in non- coding region but accumulate with time in an (i) Generate its replica individual. (ii) Chemically and structurally stable (b) VNTR (Variable Number Tandem Repeats) are also called minisatellites which are (iii) Provide scope for slow mutation short nucleotide repeats in the DNA which are very specific in each individual. These (iv) Express itself in mendelian way are inherited from the parents and act as personal inherited identity test in DNA DNA is more stable than RNA because of fingerprinting. presence of –H and not –OH at 2’ position, presence of thymine instead of uracil which 152. Each cell of body has similar DNA and DNA in is less reactive, DNA is double stranded, DNA an individual comes from both the parents. The mutates slowly than RNA and RNA cannot polymorphism of individual is inheritable. If we replicate on its own. isolate this DNA and do DNA fingerprinting, it will help to determine paternity. 158. Refer answer no. 122. 153. The method/technique is DNA fingerprinting. 159. (a) Refer answer no. 122. Procedure: DNA fingerprinting involves following (b) Avery, Macleod and McCarty purified steps- biochemicals (proteins, DNA, RNA, etc) from heat-killed S cells to see which one could Isolation of DNA --> digestion of DNA by transform live R cells into S cells. They also restriction endonucleases --> separation of DNA discovered that protein-digesting enzymes fragments by electrophoresis --> transferring (proteases) and RNA-digesting enzymes (blotting) of separated DNA fragments to (RNases) did not affect transformation, so synthetic membranes such as nitrocellulose or the transforming substance was not a protein nylon --> hybridisation using labelled VNTR or RNA. Digestion with DNase did inhibit probe --> detection of hybridised DNA fragments transformation, suggesting that the DNA by autoradiography. caused the transformation. They concluded that DNA is the hereditary material 154. (a) Expressed Sequence Tags, Identifying all the genes that are expressed as RNA Sequence 160. Refer answer no. 158. Annotation, sequencing the whole set of genome coding or non coding sequences and 161. Refer answer no. 122. later assigning different region with functions 162. (a) Refer answer no. 122. (b) Yeast Artificial Chromosome, used as cloning vectors (cloning/amplification) (b) Oswald Avery, Colin MacLeod, Maclyn McCarty followed up Griffith’s experiment. 155. (a) VNTR: Variable Number of Tandem Repeat(s) (½) (c) They concluded that DNA is the hereditary material. For explaination, refer answer 154 They are used as probe (½) (b). Molecular Basis of Inheritance  151

163. Alfred Hershey and Martha Chase in 1952 conducted some experiments with bacteria and bacteriophages. Bacteriophage Radioactive (32P) labelled DNA Radioactive (35S) labelled protein capsule Infection Blending Centrifugation No radioactivity (35S) Radioactive (35P) detected in cell detected in cell + + Radioactivity (35S) No radioactivity detected in supernatant detected in supernatant • They grew bacteriophages in a medium polarity 3’–5’ and coding strand has polarity that contained radioactive phosphorous and 5’–3’. radioactive sulphur separately. (b) During initiation of transcription in • Bacteriophages became radioactive after bacterium, sigma factor binds to RNA few generations. Those grown on radioactive polymerase to initiate transcription. Once the phosphorus had radioactive DNA as phosphorus RNA polymerization is over, Rho factor binds is the component of DNA. to RNA polymerase and it gets dissociated from template strand thus terminating • Those grown on radioactive sulphur had transcription. radioactive protein shell as sulphur is the component of protein. (c) RNA polymerase I transcribes rRNA and RNA polymerase III transcribes tRNA, 5 Sr RNA • The labelled bacteriophages from both media and snRNA. were allowed to infect E. coli. 166. Transcription in eukaryotes is catalysed by three • In both the cases viral coats were removed from different DNA dependent RNA polymerase, bacteria by agitating them in a blender. I, II and III . RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S), RNA polymerase II • The virus particles were separated from the transcribes heterogeneous nuclear RNA (hnRNA) bacteria by spinning them in a centrifuge. and RNA polymerase III transcribes tRNA, 5 No radioactivity was detected in E. coli but SrRNA, and snRNAs (small nuclear RNAs). was detected in supernatant in case where bacteriophages were labelled with radioactive RNA polymerase II binds to promoter and sulphur. Whereas, radioactivity was detected in initiates transcription. It uses nucleoside E.coli where bacteriophages were labelled with triphosphates as energy source and polymerizes radioactive phosphorus. to continue elongation. After termination, the precursor of mRNA, hnRNA is formed. Splicing • This indicated that DNA is the genetic material removes introns and exons are joined in defined that is passed from virus to bacteria. 164. The aim of the experiment carried by Messelson order, methyl guanosine triphosphate is added to and Stahl was to prove that DNA replication is 5’ end, the process is called capping, poly-A tail semi-conservative. is added to 3’ end, the process is called tailing. For explanation Refer answer no. 88. Capping and tailing are necessary to protect mRNA from RNA degrading enzymes present 165. (a) A is template strand, B is coding strand. Both in cytoplasm. Fully processed mRNA is now are identified on the basis of polarity with transported to cytoplasm for translation. respect to promoter. Template strand has 152 Biology–12

167. (i) Codons ‘a’ is AUG and ‘b’ is UAA/UGA/UAG Thymine and Guanine and Cytosine are (ii) AUG codes for methionine, UAA/UGA/UAG constant and equals one. are stop codons, they do not code for any (b) amino acid. H H H H (iii) When two charged tRNAs are brought close PC PC enough in ribosomes, peptide bond is formed PC PC between two amino-acids, the process is H H H H energetically favoured. Ribosome (23S rRNA in bacteria called ribozyme) acts as catalyst hydrogen to form peptide bond. bonds 168. Refer answer no. 93. 169. (a) • A nucleotide in DNA has three components – H H H H HO C P nitrogenous base, de-oxy-ribose pentose sugar CP CP C P 5' and phosphate group. H H H H • Nitrogenous bases are of two types- purines 171. (a) Refer answer no. 122. (Adenine and Guanine), and pyrimidines (b) Oswald, MacLeod and McCarty worked to (cytosine, uracil, thymine) (uracil is present determine the transforming principle of only in RNA and thymine is present only in DNA). Griffith’s experiment. They purified proteins, • Nitrogenous base + pentose sugar = nucleoside, DNA and RNA from heat killed S-cells to see e.g. deoxyadenosine, deoxyguanosine. The two are joined by N-glycosidic linkage. which out of three could transform R-cells • Nucleoside + Phosphate = nucleotide, the two into S-Cells. They established that DNA are joined by phosphoester bond. transformed the non-virulent strain into • The free –OH group is the 3’ end of DNA and the free phosphate group is 5’ end of DNA. virulent one. • The backbone of DNA is formed of sugar and 172. (a) Refer answer no. 122. phosphate, the nitrogenous bases are linked (b) Refer answer no. 166 (b). to sugar at an angle. 173. (a) Refer answer no. 122. (b) Double helix model of DNA (b) Refer answer no. 166 (b). (i) It is made of two polynucleotide chains, 174. (a) Refer answer no. 122. where sugar and phosphate form the (b) Refer answer no. 166 (b). backbone. The bases project inside. 175. (a) Refer answer no. 122. (ii) The two chains are anti-parallel to each (b) Refer answer no. 166 (b). other. 176. (a) Steps of transcription in bacteria are: (iii) The nitrogenous bases are joined to each (i) I n i t i a t i o n : D N A d e p e n d e n t R N A other by hydrogen bonds. A forms two polymerase binds with sigma factor(σ) hydrogen bonds with T and C forms three and attaches to the promoter site of the hydrogen bonds with G. purines always come in opposite to pyrimidines and DNA. vice-versa. This maintains the distance between the two strands. (ii) Elongation: RNA polymerase moves towards 3’ end, polymerisation of RNA (iv) Two chains are coiled in right-handed fashion. The pitch of helix is 3.4 nm. In occurs in 5’-3’ direction. each turn, 10 base pairs are present. Distance between two consecutive bp is (iii) Termination: When RNA Polymerase 0.34 nm. reaches at the terminator site, it binds (v) The plane of one base pair stacks over to ρ factor and gets dissociated from DNA another, and presence of hydrogen bonds and transcribed RNA falls off along. provides stability to helical structure. (b) Processing of hnRNA before becoming 170. (a) (i) Maurice Wilkins and Rosalind Franklin functional mRNA of eukaryotes gave X-ray diffraction data of DNA (i) The hnRNA has to travel to cytoplasm (ii) He proposed that for a double stranded form nucleoplasm. In cytoplasm many DNA, the ratios between Adenine and RNA degrading enzymes are present. So, for protection, a cap of methylated guanosine triphosphate is added at 5’end of hnRNA. (ii) Introns are removed by enzyme called spliceosomes. The exons are then joined in defined order. This is called splicing. (iii) Then a poly-A tail having 200-300 adenylate residues are added at 3’-end in template independent manner. Molecular Basis of Inheritance  153

(iv) This is now fully processed mRNA and is 181. When lactose in added to the medium, it ready to be transported to cytoplasm for enters cell due to the activity of permease translation. enzyme. Lactose acts an inducer. It inactivates repressor and allows RNA polymerase to 177. Refer answer no. 171. access promoter. RNA polymerase enzyme 178. (a) The code that determines the sequences of transcribes the structural genes present in lac operon. When lactose is digested, there is no amino acids in proteins inducer, the repressor binds to the operator. The RNA polymerase access is blocked and (b) • Some amino acids are coded by more than the transcription is stopped. Thus operon is in one codon, hence the code is degenerate switch off condition. • One codon codes for only one amino acid, 182. Refer answer 92 and 93. hence, it is unambiguous and specific. When lactose is digested, there is no inducer, • AUG has dual functions. It codes for the repressor binds to the operator. The RNA Methionine (met) , and it also act as initiator polymerase access is blocked and the transcription codon. is stopped. Thus operon is switched off. Also refer answer no. 112. 183. (a) Repetitive DNA : a small stretch of DNA is repeated many times. Satellite DNA: smaller 179. Major types of RNA and their roles in protein peaks of DNA obtained during density synthesis of prokaryote: mRNA: It carries gradient centrifugation. the codons coded in DNA to protein synthesis machinery; tRNA: It carries the corresponding (b) When repetitive DNA is separated from amino acid for polypeptide synthesis; rRNA : bulk genomic DNA during density gradient It acts as catalyst ribozyme for the formation centrifugation, bulk DNA forms major peak of peptide bond and is the site of protein and other small peaks are called satellite synthesis where the bond formation is favoured DNA. energetically due to very close location. (c) To resolve paternity issues and rape cases. 180. Translation • mRNA dependent polymerisation of amino acids 184. Refer answer no. 158. to form a polypeptide is called translation. But 185. Refer answer no. 158. before an amino acid is added to the protein chain, it is linked to their cognate tRNA in the 186. Refer answer no. 158. presence of ATP. This is called charging of tRNA or aminoacylation of tRNA. 187. (a) Replication occurs at S-phase of cell cycle. • First the smaller subunit of ribosome joins with (b) Replication starts at a specific region called mRNA at start codon. Then the larger subunit origin of replication (ori). The two strands attaches. Larger subunit has two sites for of DNA unwind and form a small opening subsequent amino acids to bind. The start codon in helix called as replication fork. Helicase is recognised by initiator tRNA. enzyme separates two strands of DNA to form a replication fork. • The charged tRNA now binds with appropriate codon in mRNA forming complementary base The major enzyme used for DNA replication pairs with tRNA anticodon. Two tRNA carrying is DNA dependent DNA polymerase. amino acids are placed so close to each other that it is favoured energetically to form peptide bond Deoxyribonucleoside triphosphates act as between two amino acids. Ribosome moves from substrates as well as provide energy for codon to codon along mRNA and amino acids are polymerization reaction. DNA polymerase added one by one thus forming a polypeptide adds new complementary bases in one chain. Ribosome also acts as catalyst for the direction only, i.e. 5’-3’. The strand with formation of peptide bond. 23S rRNA in bacteria polarity 3’-5’ has continuous replication. On is called ribozyme which acts as catalyst. the other strand with polarity 5’-3’, fragments of newly synthesized strand are formed which • At the end, release factors binds to the stop are joined later by DNA ligase. This is called codon, thus terminating translation and release discontinuous synthesis. complete polypeptide from the ribosome. (c) After replication, the daughter DNA has • In addition to start codon, codes for polypeptide one parental strand and other is newly and stop codon, a mRNA has additional sequences synthesised strand, so it is called as semi which are not translated but are required for conservative replication. efficient translation process. These are called untranslated regions. They are present at both 188. Refer answer no. 88. -5’ and -3’ ends, before start codon and after stop codon. 154 Biology–12

189. (a) 5' 3' 191. (a) Refer answer no. 130. (b) In S phase of cell cycle the replication in Template DNA eukaryotes occur. If cell division is not (Parental strands) followed after DNA replication it would result in chromosomal anomaly, i.e. polyploidy. 192. Refer answer no. 88. Continuous 5' Discontinuous 193. (a) It is DNA replication fork synthesis 3' synthesis (b) 5' 3' Newly Template DNA (Parental strands) synthesised 3' strands 5' 5' 3' DNA replication occurs due to high energy Continuous synthesis requirement of DNA for opening in one 5' Discontinuous 3' synthesis stretch. There point of separation occurs with the help of replication fork giving it a Y appearance. Newly (b) Two enzymes involved in the process of DNA 3' synthesised 5' replication are: 5' strands 3' (i) Helicase required to unwind of DNA (c) Source of energy is Deoxyribonucleo-side strand triphosphates Helicase, DNA dependent DNA polymerase, DNA ligase. (ii) Topisomerase released the tension of DNA (d) DNA polymerase adds new comple-mentary strand. bases in one direction only, i.e. 5’-3’. The strand with polarity 3’-5’ has continuous 190. The replication of DNA take place at S-phase of the cell cycle. It begins at origin of replication replication. On the other strand with polarity of ori. It requires high energy, dozen of enzymes and protein factors. The main enzyme 5’-3’, fragments of newly synthesized strand is DNA dependent DNA polymerase. DNA monophosphates present inside the nucleoplasm are formed which are joined later by DNA are first phosphorylated and activated. These are dATP, dGTP, dCTP and dTTP. The helicase ligase. This is called discontinuous synthesis. unwinds the two strands at ori site by destroying 194. Refer answer no. 88. Hydrogen bonds. The tension caused due to 195. Refer answer no. 88. unwinding in the uncoiled part is released by 196. (a) (i) Heavy isotope of nitrogen was fully topoisomerase enzyme. With the help of above incorporated into DNA strands and enzymes both strands of DNA become open for replication. The point of separation proceeds in after the density gradient centrifugation both direction giving it a Y appearance called replication fork. in CsCl, the DNA strands were found near the lower end of test tube in heavy density. (ii) The light isotope of DNA was found to be the part of DNA, the DNA after centrifugation was found of hybrid and light density. (b) They concluded that DNA replicates semi conservatively. Generation I Generation II 15N-DNA 14N-DNA 14N-DNA 15N-DNA 15N-DNA 20 min 40 min 14N-DNA 14N-DNA Gravitational force 14N14N 14N15N 14N14N 14N15N Light Hybrid Light Hybrid SeparaSetipoanratoiofnDoNf DANbAybCy Cenenttrriiffuuggaatitoinon Molecular Basis of Inheritance  155

(c) The first genetic material is RNA. Evidences by agitating them in a blender. The virus to support this are- particles were separated from the bacteria by spining them in a centrifuge. Essential life processes such as metabolism, translation, splicing, etc. evolved around (ii) Bacteria which were infected with viruses RNA. that had radioactive DNA were radioactive, indicating that DNA was the material that RNA acts as genetic material in some passed from the virus to the bacteria. organisms. (iii) Bacteria that were infected with viruses that had radioactive proteins were not radioactive. It also acts as catalyst in some important This indicates that proteins did not enter biochemical reactions in living systems. the bacteria from the viruses. Hence, DNA is genetic material that is passed from virus to 197. Watson and Crick proposed that DNA replication bacteria. is semi-conservative. Also refer answer no. 88. 199. Refer answer no. 93. 198. Hershey and Chase's experiment. Their experiment is to prove unequivocally 200. Refer answer no. 77 and 78. that DNA is the genetic material and not the 201. (a) Francois Jacob and Jacque Monod. pwrhoitcehina.ttTachkesybwacotrekreiudmwEit.hcoTil2. bacteriophage, They grew some (b) Refer diagram of answer no. 93. viruses on a medium that contained radioactive (c) Refer answer no. 78. phosphorus (32P) and some others on medium that contained radioactive sulphur (32S). (i) Radioactive phages were allowed to attack E. coil bacteria. The infection proceeded the viral coats were removed from the bacteria 202. DNA fingerprinting DNA fingerprinting technique was developed by Alec Jeffery. This enabled us to quickly compare the DNA sequences of two different individuals. Paternal chromosome Maternal chromosome Chromosome 7 Chromosome 7 Chromosome 2 Chromosome 2 Chromosome 16 Chromosome 16 DNA from individual A DNA from individual B Number of short tandem repeats C AB Number of short tandem repeats 0 11 Chromosome 7 12 Chromosome 2 11 10 Chromosome 16 9 8 7 6 5 4 3 2 1 DNA from crime scene (C) Amplified repeats, separated by size on a gel, give a DNA fingerprint Schematic representation of DNA fingerprinting. 156 Biology–12

In this technique, some specific regions of 204. Lac operon consists of regulatory gene 'i', DNA called repetitive DNA are identified. a promoter gene, operator gene and three These sequences do not code for any protein. structural genes, z, y, a They are separated from bulk genomic ' DNA in the form of different peaks during density When lactose is present in the medium, it gradient centrifugation. These small peaks are bind with repressor protein, this inactivates called satellite DNA. Depending on the base the repressor which does not bind with the composition (A-T rich or C-G rich), length of operator. RNA polymerase binds to the promoter segment, and number of repetitive units, satellite and transcription occurs. 'Z' gene makes beta DNA is classified into further categories called galactosidase, 'y' gene makes permease and 'a' micro-satellite, mini-satellite etc. gene makes transacetylase. The repetitive sequences show high degree of p i po z y a In presence polymorphism, the variation arises at genetic of inducer level due to mutations. If an inheritable mutation Transcription is observed in a population at high frequency, it is referred to as DNA polymorphism. As it is Repressor mRNA lac mRNA present in non-coding region, such mutations are not expressed but accumulate in an individual Translation with time. Inducer b-galactosidase Permease Transacetylase This high degree of polymorphism is called Variable Number Tandem Repeats VNTR. These (Inactive repressor) are mini-satellites with large number of repeats. This variability in the number of tendem repeats 205. (a) An operon is a polycistronic structural gene is exploited in the DNA fingerprinting. which is regulated by a common promoter and regulator gene. DNA fingerprinting involved following steps: (b) Lac operon consist of one regulatory gene Isolation of DNA; digestion of DNA by restriction i, which codes for the repressor protein, endonucleases; separation of DNA fragments promoter (P) and operator (O) by electrophoresis; transferring (blotting) Structural genes z, y, a code for enzymes b-galactosidase, permease and transacetylase, of separated DNA fragments to synthetic respectively. membranes such as nitrocellulose or nylon; The regulator gene i keeps on synthesizing the repressor protein in absence of inducer, this hybridisation using labelled VNTR probe; repressor binds to the operator region of the operon and prevents transcription by RNA detection of hybridised DNA fragments by polymerase. autoradiography. The repressor is inactivated in the presence of an inducer (lactose) that binds with it, this The bands obtained give a characteristic pattern allows RNA polymerase's access to structural for an individual which differs from others. genes and transcription proceeds. DNA isolated from single cell is amplified using p i po z y a In absence PCR and is subjected to DNA analysis. of inducer DNA fingerprinting is used in forensic science Repressor mRNA Repressor binds to the operator to identify criminals, rapists, solving paternity region (O) and prevents RNA issues. It also helps us to determine genetic polymerase from transcribing diversity in a given population and establish the operon evolutionary relationship among organisms. Repressor po z y a In presence 203. (a) t-RNA is clover leaf shaped molecule pi of inducer which has an anti-codon loop with bases Transcription complementary to specific codon and also has an amino acid acceptor end where acts Repressor mRNA lac mRNA as amino acid attachment point. The type of amino acid attached depends upon the Translation sequence of anticodon loop. It reads the codon on one end and bind with specific amino acid Inducer b-galactosidase Permease Transacetylase on other end. (Inactive repressor) (b) During splicing, introns are enzymatically removed from hnRNA, exons join in a definite order. Molecular Basis of Inheritance  157

206. (a) Lactose acts as inducer thus absence of lactose replication switches off the operon. Gene i produces repressor and in the absence of lactose it binds DNA Transcription mRNA Transcription Protein to the operator which prevents transcription of the structural genes z, y and a. Central dogma pi p z y a In absence Yes, these is exception present in retroviruses of inducer such as AIDS virus, in which DNA is formed from RNA by reverse transcription with the Repressor mRNA Repressor binds to the operator help of enzyme reverse transcriptase. region (O) and prevents RNA polymerase from transcribing (b) Oswald, MacLeod and McCarty worked to the operon determine the transforming principle of Griffith’s experiment. They purified proteins, Repressor DNA and RNA from heat killed S-cells to see which out of three could transform R-cells (b) Gene expression is regulated in eukaryotes into S-Cells. They established that only DNA at transcription leve, processing level or transformed the non-virulent strain into translation level. virulent one. 207. (a) Central dogma can be depicted in the following diagram Assertion & Reason Type Questions For question numbers 1-14: Two statements are Reason (R): Each enzyme may consist of two or given one labelled Assertion (A) and the other labelled more different polypeptides. Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. 6. Assertion (A): Core enzyme catalyses chain elongation of RNA. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Reason (R): The presence of sigma factor is required for initiation of transcription. (b) Both Assertion and Reason are true but Reason is NOT the correct explanation of Assertion. 7. Assertion (A): tRNA acts as an adapter molecule. (c) Assertion is true but Reason is false. (d) Assertion is false and Reason is also false. Reason (R): tRNA recognizes codon sequence of 1. Assertion (A): The uptake of DNA during mRNA during translation. transformation is an active, energy requiring 8. Assertion (A): The genetic code is degenerate. process. Reason (R): For a particular amino acid more Reason (R): Transformation occurs in only those bacteria, which possess the enzymatic machinery than one codons can be used. involved in the active uptake and recombination. 2. Assertion (A): R-type of Pneumococcus is non- 9. Assertion (A): Same tRNA can recognise more virulent. than one codons differing only at the third Reason (R): R-type of Pneumococcus can be position. virulent by having transformation with S-type of Pneumococcus. Reason (R): The specificity of a codon is 3. Assertion (A): Adenine and guanine are double- particularly determined by the first two bases. ring bases. R e a s o n ( R ) : A d e n i n e a n d g u a n i n e a r e 10. Assertion (A): Initiation step of protein pyrimidines. synthesis in prokaryotes and eukaryotes has 4. Assertion (A): Sequences of bases in one several differences. polynucleotide chain of DNA can determine the sequence of bases in the other chain. Reason (R): They both form mRNA-tRNA Reason (R): In a DNA, amount of adenine equals complex with smaller subunit of ribosome. that of thymine and amount of guanine equals that of cytosine, i.e., A = T and C = G. 11. Assertion (A): UAA, UAG and UGA terminate protein synthesis. 5. Assertion (A): The concept of one gene- one enzyme was changed to one gene-one Reason (R): They are not recognised by tRNA polypeptides. 12. A s s e r t i o n ( A ) : C o n s t i t u t i v e g e n e s a r e continuously being expressed. Reason (R): Constitutive genes are frequently needed for various metabolic functions. 158 Biology–12

13. Assertion (A): No lac mRNA is made in the Reason (R): Lactose inactivates the repressor presence of glucose. gene. Reason (R): In the presence of glucose and 1. (b) Answers 5. (a) lactose activity of lac operon is not needed. 6. (b) 10. (b) 11. (a) 2. (b) 3. (c) 4. (b) 14. Assertion (A): Lactose in lac operon is promoter 7. (b) 8. (a) 9. (a) gene. 12. (a) 13. (a) 14. (d) Case Based Questions 1. DNA replication is a complex multistep process (c) Polymerase e helps in elongation of that requires enzymes, protein factors and metal lagging strand ions. DNA replication in eukaryotes occurs in the (d) Polymerase d is largest and main enzyme for DNA replication in eukaryotes. nucleus during the S-phase of the cell cycle. It is semidiscontinuous in eukaryotes. In prokaryotes, 2. The process of copying genetic information from template strand of DNA into RNA is called replication takes place in the cytoplasm. DNA replication in bacteria occurs prior to fission. transcription. It is mediated by RNA polymerase. Nucleoid or viral chromosome is a single molecule Transcription takes place in the nucleus of of nucleic acid, it may be linear or circular. eukaryotic cells. In transcription, only a segment Nucleic acid in a virus is either DNA or RNA but of DNA and only one of the strands is copied into never both. RNA. (i) In viral DNA, how many origin of replication (i) What are regions of transcription unit in a are present? DNA molecule? (a) Single (b) Twice (a) Promoter (c) Multiple (d) None (b) Structural gene (ii) Select the main enzyme involved in DNA (c) Terminator replication. (d) All of these (a) DNA ligase (ii) Monocistronic structural genes are found in (b) DNA dependent DNA polymerase which organisms? (c) Topoisomerase (a) Prokaryotes (b) Bacteria (d) Helicase (c) Viruses (d) Eukaryotes (iii) Read the given statement and select the (iii) W h i c h e n z y m e h e l p s i n t a i l i n g o r option that correctly fill in the blanks. polyadenylation? Enzyme (i) _______ acts over the Ori site (a) Poly-A polymerase and unwinds the two strands of DNA by (b) Exonucleases destroying (ii) _______ bonds. (c) RNA polymerase I (a) (i)-Helicase, (ii)-Glycosidic (d) RNA polymerase II (b) (i)-Helicase, (ii)-Hydrogen (iv) Assertion: A single RNA polymerase in (c) (i)-Unwindase, (ii)-Phosphodiester prokaryotes synthesis all types of RNAs. (d) (i)-Unwindase, (ii)-Glycosidic Reason: Prokaryotic RNA polymerase has (iv) DNA strand, built up of Okazaki fragments sigma (s) factor. is called (a) Both assertion and reason are true and (a) lagging strand (b) leading strand reason is the correct explanation of (c) complementary strand assertions. (d) parental strand (b) Both assertion and reason are true but (v) Select the incorrect statement about DNA reason is not the correct explanation of polymerase in eukaryotes. assertion. (a) Polymerase α is required for initiation of replication. (c) Assertion is true but reason is false. (b) When the RNA primer gets removed the (d) Both assertion and reason are false. gap is filled by DNA polymerase b in (v) Read the given list of materials. eukaryotes. (1) RNA polymerase enzyme (2) DNA template Molecular Basis of Inheritance  159

(3) RNA primers Which DNA sequence would be needed to produce the following polypeptide sequence? (4) Okazaki segments Alanine-Arginine-Lysine-Phenylalanine. (5) Four types of ribonucleotides triphosphates (6) Divalent metal ions Mg2+ as a cofactor. Which of the above given materials are required (a) CGT GCT TTC AAA for transcription? (b) CGT GCT TTC TTT (a) (1), (2), (3) and (4) (b) (1), (2), (5) and (6) (c) CGU GCU UUC AAA (c) (1), (2), (5) and (6) (d) All of these (d) CGU GCU UUC TTT 3. The process of translation requires transfer of genetic information from a polymer of amino (iv) Identify the non-sense codons among the following. acids. The relationship between the sequence (a) AUG (b) GUG of amino acids in a polypeptide and nucleotide (c) UAA (d) UGG sequence of DNA or mRNA is called genetic code. George Gamow suggested that in order to code (v) A polypeptide is made using synthetic mRNA for all the 20 amino acids, code should be made molecules as shown. up of three nucleotides. Synthetic mRNA Polypeptide produced used (i) What is a codon? (a) A length of DNA which codes for a UUUAAAUUUAAA Phenylalanine-lysine- particular protein. phenylalanine-lysine (b) A part of the tRNA molecule to which a specific amino acid is attached. What are the DNA codes for the amino acids (c) A part of the tRNA molecule which phenylalanine and lysine? recognises the triplet code on the Phenylalanine Lysine messenger RNA. (d) A part of the messenger RNA molecule (a) AAA TTT that has a sequence of bases coding for (b) AAA UUU an amino acid. (c) GGG CCC (ii) Three consecutive bases in the DNA molecule provide the code for each amino acid in a (d) TTT GGG protein molecule. Ans. 1. (i) (a) (ii) (b) (a) 16 (b) 20 (iii) (b) (iv) (a) (c) 24 (d) 64 (v) (d) (iii) Listed below are some amino acids and their corresponding m-RNA triplets. 2. (i) (d) (ii) (d) Amino acid mRNA triplet (iii) (a) (iv) (b) Phenylalanine UUU AAG (v) (c) Lysine CGA Arginine GCA 3. (i) (d) (ii) (d) Alanine (iii) (b) (iv) (c) (v) (a) qqq 160 Biology–12

Topics Covered 6 Evolution 6.1 Origin of Life 6.2 Evolution of Life Forms – A Theory 6.3 What are the Evidences for Evolution? 6.4 What is Adaptive Radiation? 6.5 Biological Evolution 6.6 Mechanism of Evolution 6.7 Hardy-Weinberg Principle 6.8 A Brief Account of Evolution 6.9 Origin and Evolution of Man C hapter map Stabilising Spontaneous Disruptive generation Special creation Directional Darwin’s Contribution Abiogenesis Natural selection Origin of life Mutation Speciation Modern synthetic theory Adaptive Radiation EVOLUTION Human evolution Evidences Population Dryopithecus Hardy-Weinberg Ramapithecus Embryological Morphological Biochemical Divergent and Anatomical Paleontological equilibrium Australopithecus evolution Homo habilis (Homology) Factors affecting Homo erectus Convergent Hardy Weinberg Homo sapiens evolution (Analogy) equilibrium Gene flow Recombination Mutation Genetic drift Natural selection 161

Evolutionary Biology is the study of history of life forms on earth. Topic 1. Origin of Life in a closed flask by S. L. Miller in 1953. The flask • Universe is about 20 billion years old. c8o0n0otCai.nEeldectCroHd4e,s H2, NH3 and water vapours at provided electric discharge. Miller • Big bang theory says that origin of universe occurred with a huge explosion followed by continuous observed formation of amino-acids in the closed expansion and cooling; hydrogen and helium formed; gases condensed under gravitational force flask. and formed galaxies. Electrodes • Earth is a part of a galaxy called Milky Way. It formed about 4.5 billion years back. To vacuum CH4 Spark discharge pump NH3 • No atmosphere was present on early earth. Water H2O Water out vapours, methane, carbon-dioxide and ammonia H2 Gases Condenser were released from molten mass of earth. UV rays Water in from sun broke water vapours to form hydrogen and Water droplets oxygen. Hydrogen escaped and oxygen combined with ammonia and methane to form water and Boiling water Water containing carbon-dioxide. Ozone was also formed. organic compounds • Earth cooled further, water vapours condensed and Liquid water in trap fell as rain. As the Earth’s surface was uneven, the depressions filled up with water and formed oceans. Diagrammatic representation of Miller's Experiment • Life appeared 500 million years after the formation • Other scientists too performed similar experiments of earth, i.e. 4-billion years back. and they observed formation of sugars, nitrogen bases, pigments and fats. • Some scientists believed that life came from outside space; spores were transferred to different planets • It is believed that the first non-cellular forms of life including earth. originated in water about 3 billion years back. • Oparin and Haldane proposed that first form of • First cellular form originated 2000 million i.e., 2 life originated through chemical evolution from billion years ago. pre-existing non-living organic molecules. Organic molecules were formed from inorganic constituents. • Reducing atmospheric conditions similar to an early earth were artificially created in a laboratory Topic 2. Evolution of Life Forms – A Theory • Religious literature has three suggestions: There had been extinctions of different life forms in the past and new life forms arose. All living organisms that we see today were created as such Variations among population enable them to survive in existing natural conditions. This is The diversity was always the same since creation called survival of the fittest. Fitness here refers and will remain the same in future. to reproductive fitness, better fit organisms leave more progeny, therefore, will survive more and Earth is about 4000 years old hence are selected by nature. This is called natural selection and is responsible for evolution. • Charles Darwin after his voyage in HMS Beagle, concluded that • Alfred Wallace gave similar conclusion as Darwin when he studied Malay Archipelago. All existing Existing life forms shared similarities to varying life forms share similarities and share common degrees not only among themselves but also with ancestors and geological history is related to life forms existed million of years ago. Many of biological history of earth. such life forms do not exist anymore. 162 Biology–12

Topic 3. What are the Evidences for Evolution? • Fossils are the hard remains of life forms and are • Potato is a stem modification whereas sweet potato found in rocks. Fossils present in different layers of is a root modification, is another example of analogy. sediments indicate the geological period in which they existed. Industrial Melanism • Fossils show that some life forms existed on earth for • In 1850’s a collection of moths were made and it a limited period of time and new life forms originated was found that white winged moths were more in at different times of the earth’s history. number than dark-winged melanised moths. Similar collection was made after industrialisation, in 1920s, • Age of the fossils can be determined by carbon the proportion was reversed, dark-winged moths dating. were more in number than white winged moths. • Comparative anatomy and morphology of the • During pre-industrialisation era, there was forelimbs of whales, bats, cheetah and humans no pollution, trees were covered with lichens and show similarity but all perform different functions. the background was light. White coloured moths Such organs are called homologous organs and were not visible to predators and dark-coloured the evolution is called divergent evolution as moths were easily picked up by predators. After different organs diversified to different use of the industrialisation, pollution increased, lichens similar structure. died, tree surfaces became dark, so dark-coloured moths were not visible to predators and survived. Man Cheetah Whale Bat • None of the moth variant was completely wiped out. Thus nature selected the organism which better survived in the prevailing conditions. Humerus Evidences from Embryology RUalndaius Carpals • Embryos of vertebrates possess such features which Metacarpals are not present in adults. Features like gill slits, Phalanges brain, aortic arches, axial skeleton, spinal cord etc are present in embryos of fishes, salamander, Homologous organs in Animals tortoise, chick, rabbit and even man. This was first • Vertebrate hearts or brains also represent observed by Von Baer. Ernst Haeckel reinterpreted Baer’s law and said that 'ontogeny recapitulates homologous organs. phylogeny'. This means-an organism, in the course • Thorns of Bougainvillea and tendrils of Cucurbita of its development (ontogeny), goes through more or less the same successive stages as did the species in are other examples of homologous organs. Both of its evolutionary development (phylogeny).But this them are stem modifications. theory was disapproved by careful studies of Von Baer, he noted that embryos do not pass through the adult stages of other animals. Tendril Embryological evidence of evolution seen in plants Thorn • Examples: Bougainvillea Cucurbita The protonema stage of moss or fern gametophyte Homologous organs in plants resembles the filamentous green algae in structure, • Wings of butterfly and that of bird are analogous physiology, and growth pattern. This suggests an algal ancestry of bryophytes and pteridophytes. organs. Both have same function but are anatomically different. Such evolution is called The gymnosperms have normally become convergent evolution. independent of water in fertilization. However, • Eye of octopus and of mammal, flippers of penguins the primitive gymnosperms such as Cycas and and dolphins both are the examples of analogous Ginkgo have flagellated sperms and need water organs. for fertilization just like the pteridophytes. This Evolution  163

suggests that pteridophytes are ancestors of • All animals have more or less similar structure gymnosperms. of actin and tubulin protein which tells us about common ancestry. The seedlings of Acacia tree initially develop simple leaves, but the leaves that develop later • The genetic code is common to all life forms on earth are compound. is another example that we all arose from a common ancestor. Molecular Evidences of Evolution • The sequence of bases pairs in DNA, amino acids, Modern Synthetic Theory of Evolution • As Darwin was not able to explain how variations and proteins of organisms show striking similarity. arise, the research went on and the Darwin’s • Human DNA is only 1.8% different from that of theory was modified in the light of genetics. Now, chimpanzee. modern synthetic theory of evolution is the most accepted. It states that origin of species depends • There is hardly any difference between the amino upon the interaction of genetic variation and natural acid chains for cytochrome–protein. selection. Topic 4. What is Adaptive Radiation? an isolated geographical area, the evolution is called convergent evolution. • Darwin when he visited Galapagos islands, observed Placental mammals Australian marsupials varieties of finches in same island. He concluded that all varieties originated from seed eating Mole Marsupial mole finch. Other forms with altered beaks became insectivorous and vegetarian finch. This process of evolution in different species in a given geographical area starting from a point and radiating to other geographical areas is called adaptive radiation. 1 2 3 4 Anteater Numbat (anteater) Variety of beaks of finches that Darwin found in Mouse Marsupial mouse Galapagos Island • Australian marsupials evolved from common ancestor but adaptive radiation occurred within Australian island continent. Sugar glider Tasmanian wolf Lemur Spotted cuscus Marsupial mole Tiger cat Marsupial Banded anteater radiation Marsupial rat AUSTRALIA Flying squirrel Flying phalanger Koala Bandicoot Bobcat Tasmanian tiger cat Wombat Kangaroo Adaptive radiation of Marsupials of Australia Wolf Tasmanian wolf • Placental mammals in Australia also exhibited Convergent evolution of Australian Marsupials adaptive radiation and evolved into varieties and placental mammals of placental mammals. They appear similar to corresponding marsupials as given in the following figure. If more than one adaptive radiation occurs in 164 Biology–12

Topic 5. Biological Evolution • Darwin said that if resources are limited, population remains stable in size except for seasonal • Essence of Darwin's theory about evolution is fluctuations. All members vary in genetic makeup natural selection. The rate of appearance of new which is inheritable. If each member of a population forms is linked to life span of an organism. Shorter reproduces to its maximum, the population will grow the life span more will be chances to evolve due to exponentially. In nature, it is not possible as there accumulation of large number of variations. is competition for resources and population size remains limited. • In changed conditions, the variant which better fits survives and reproduces. This adaptability is inherited and has genetic basis. • Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution. Topic 6. Mechanism of Evolution can cause speciation whereas Darwinian variations were small, directional and arose gradually. • Hugo-de-Vries observed evening primrose and gave idea of mutation. He said that mutation is sudden (single step) large change and is directionless and Topic 7. Hardy-Weinberg Principle • In migration of an individual from one population to another, the allele frequency changes in new as • Frequency of occurrence of an allele of a gene in a well as old population. New alleles are added in new population can be found by using Hardy Weinberg population and they are lost from old population. principle. It says that the frequencies of alleles Such change occurs by chance and suddenly. This is in a population are stable and constant from called genetic drift. generation to generation. Total genes and their alleles in a population i.e. gene pool remains • Sometimes a new colony is started by a few members constant. This is called genetic equilibrium. of the original population. The new sample of population will have reduced genetic variation • It is represented by p2 + 2pq + q2 = 1. from the original population. The change in allele • Where p is frequency of allele A and q is frequency frequency is so different in the sample population that they become a different species. Thus, the of allele a' frequency of AA is p2 and that of aa is q2. establishment of a new population by a few original Frequency of Aa is 2pq. Sum total of all the allelic founders is called founder effect. frequencies is 1. • Five factors that affect Hardy Weinberg equilibrium are: gene migration, natural selection, genetic recombination, genetic drift and mutation. Types of Natural Selection • Allele frequency of a population changes due to Natural selection. Depending upon which traits are preferred in a population, three possibilities exist: Number of individuals Phenotypes Medium-sized with phenotype favoured by individuals natural are favoured selection Peak gets Only average Two peaks form, both extreme higher and trait is favoured Peak shifts traits are equally favoured narrower in one direction (only one trait is favoured) (a) (b) (c) Diagrammatic representation of the operation of natural selection on different traits (a) Stabilising (b) Directional and (c) Disruptive Evolution  165

Stabilizing selection: If the allele with average next generation than other ones, this will shift features contribute more to the next generations, the peak to one direction. Example: the size of the peak will get narrower. Both the smallest horse originally was that of dog. Due to selection and largest individuals are not preferred to be pressure, the height of horse increased and evolved passed to next generation. Such selection is called into modern horse. stabilizing selection. It reduces variation but does not change mean value. Example: Too small plants Disruptive selection: When the alleles for and too large plants do not get survival benefit. both extreme features are selected by nature, the Too small plants have to compete for sunlight and graph shows two peaks, such type of selection is too large plants are damaged due to wind. So the called disruptive selection. Example: In a squirrel, plants with medium height get survival benefit short tails are preferred as they are not caught and will outnumber other plants. by predators. Large tails help to keep the balance while running. Medium tails are not of any help Directional selection: If the allele with any and thus they are not preferred. one extreme feature will contribute more to the Topic 8. A Brief Account of Evolution • First cellular form of life appeared on earth about like Ichthyosaurs became fish like and went back 2000 million / 2 billion years ago. Later non-cellular into water around 200 mya. Land reptiles became aggregates evolved eventually changing to cellular huge. Tyrannosaurus rex was the largest with 20 ft forms. Some of these had ability to release oxygen. height and dagger like teeth. • Single celled organisms became multicellular forms. • About 65 mya, dinosaurs suddenly disappeared from 500 million years ago (mya), invertebrates were earth. Some of them evolved into birds and some formed, 350 mya jawless fishes evolved, 320 mya were killed due to sudden climatic changes. some sea weeds and few plants existed. • When reptiles came down mammals took over • First terrestrial organisms were plants, later this earth. First mammals were like shrews and animals evolved into land animals. About 350 mya a were viviparous. Mammals became dominant on fish with stout and strong fins envolved which could earth. For instance, animals resembling horse, live both on land and in water. hippopotamus, bear, rabbit were present in South America. With the continental drift, North America • Coelacanth, a lobefin fish was thought to be extinct joined with S. America. The animals from North but was caught from the Sea of South Africa. This moved to South America and became dominant. fish is thought to have evolved into amphibians. These amphibians evolved into reptiles who lay • Pouched animals of Australia survived due to lack thick shelled eggs which remain protected from of competition. drying in sun. • Some mammals evolved to live in water such as • 150-250 mya various reptiles dominated the earth, whales, dolphins, seals and sea cows. giant ferns got deposited to form coal. Some reptiles Topic 9. Origin and Evolution of Man • 1.5 mya, Homo erectus with large brains around • About 15 mya, primates called Dryopithecus and 900 cc were present. They probably ate meat. These Ramapithecus existed. They were hairy and walked fossils were discovered in Java in 1981. like gorillas and chimpanzees. • The Neanderthal man with brain size of 1400 cc • Dryopithecus was more ape like. lived near east and central Asia between 1,00,000- • Ramapithecus was more man-like. 40,000 years back. They probably used hides to • Few fossils of man-like bones belonging to 3–4 mya protect their body and buried their dead. have been discovered in Ethiopia and Tanzania • Homo sapiens arose in Africa and moved across which suggested that man like primates with 4 ft continents and developed into distinct races. During height, walked upright and moved to East Africa. ice age between 75,000-10,000 years ago, modern Homo sapiens arose. • 2 mya Australopithecines were present in East African grasslands. Evidence shows that they • Pre-historic cave art developed about 18,000 years hunted with stone weapons and ate fruit. ago. • A hominid, being more human like called Homo • Agriculture began around 10,000 years back and habilis was discovered. Its cranial capacity was human settlements started. between 650-800 cc. It too probably did not eat meat. 166 Biology–12

EXERCISE I. Multiple Choice Questions 10. Viviparity is considered to be more evolved 1. Which of the following is used as an atmospheric because: pollution indicator? (a) the young ones are left on their own (a) Lepidoptera (b) Lichens (b) the young ones are protected by a thick shell (c) Lycopersicon (d) Lycopodium (c) the young ones are protected inside the mother’s body and are looked after they are 2. The theory of spontaneous generation stated that: born leading to more chances of survival (a) life arose from living forms only. (b) life can arise from both living and non-living. (d) the embryo takes a long time to develop (c) life can arise from non-living things only. 11. Fossils are generally found in: (d) life arises spontaneously, neither from living (a) Sedimentary rocks nor from the non-living. (b) Igneous rocks 3. A n i m a l h u s b a n d r y a n d p l a n t b r e e d i n g programmes are the examples of: (c) Metamorphic rocks (a) reverse evolution (b) artificial selection (d) Any type of rock (c) mutation (d) natural selection 12. For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively. 4. Palaentological evidences for evolution refer to The expected frequency of MN-blood group the: bearing organisms is likely to be (a) development of embryo (a) 42% (b) 49% (c) 9% (d) 58% (b) homologous organs (c) fossils 13. Which type of selection is industrial melanism observed in moth, Biston bitularia: (d) analogous organs. 5. The bones of forelimbs of whale, bat, cheetah and (a) Stabilising (b) Directional man are similar in structure, because: (c) Disruptive (d) Artificial (a) one organism has given rise to another 14. The most accepted line of descent in human evolution is: (b) they share a common ancestor (c) they perform the same function (a) Australopithecus → Ramapithecus → Homo sapiens → Homo habilis (d) they have biochemical similarities (b) Homo erectus → Homo habilis → Homo 6. Analogous organs arise due to: sapiens (a) divergent evolution (b) artificial selection (c) Ramapithecus → Homo habilis → Homo erectus → Homo sapiens (c) genetic drift (d) Australopithecus → Ramapithecus → Homo (d) convergent evolution erectus → Homo habilis → Homo sapiens. 7. (p + q)2 = p2 + 2pq + q2 = 1 represents an equation 15. Which of the following is an example for link used in: species? (a) population genetics (b) mendelian genetics (a) Lobe fish (b) Dodo bird (c) biometrics (c) Sea weed (d) Chimpanzee (d) molecular genetics II. Fill in the blanks 8. Appearance of antibiotic-resistant bacteria is an 1. The first mammals were like _____ . example of: 2. ____ religious tells us about the theory of special (a) adaptive radiation creation. (b) transduction 3. Charles Darwin made a voyage around the world in a ship called ___ . (c) pre-existing variation in the population (d) divergent evolution 4. ____ is an extinct organism. 5. ____ indicates common ancestry. 9. Evolution of life shows that life forms had a trend of moving from: 1 Mark Questions (a) land to water 1. Write the similarity between the wing of a butterfly and the wing of a bat. What do you (b) dryland to wet land infer from the above with reference to evolution?  [Delhi 2012] (c) fresh water to sea water (d) water to land Evolution  167

OR 18. Mention how mutation theory of Hugo de Vries is different from Darwin's theory of natural Comment on the similarity between the wing of selection. [Foreign 2011] a cockroach and the wing of a bird. What do you 19. List the two characteristics of mutation that help infer from the above, with reference to evolution? in explaining evolution. [Delhi 2011 C]  [AlI India 2012] 20. Mention the key concepts about the mechanism of biological evolution/speciation according to 2. Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet (a) De Vries and (b) Darwin. [Delhi 2010 C] potato.  [Delhi 2009] 21. Write the probable differences in eating habits of Homo habilis and Homo erectus. [AlI India 2016] 3. Name any two vertebrate body parts that are homologous to human forelimbs.[AlI India 2008] 22. Write the hypothetical proposals put forth by 4. According to Hugo de-Vries what is saltation? Oparin and Haldane. [Foreign 2015]  [Delhi 2016] 23. Name the type of evolution that has resulted 5. Name the common ancestor of the great apes and in the development of structures like wings of man. [AlI India 2009] butterfly and bird. What are such structur called? 6. Name the scientist who disproved spontaneous  [Delhi 2014 C] generation theory.  [Delhi 2010] 24. Explain convergent and divergent evolution with 7. How does 'fitness' of a population help in the help of one example of each.  [Delhi 2010] evolution? [Delhi 2008 C] 25. Why are the wings of a butterfly and of a bat 8. State a reason for the increased population of called analogous?  [Delhi 2009] dark coloured moths coinciding with the loss of 26. Are the wing of a bird and the forelimb of a horse lichens (on tree barks) during industrialisation homologous or analogous? Name the type of period in England. [Delhi 2015] evolution that explains the development of such 9. Why are analogous structures a result of structures.  [Foreign 2009] convergent evolution? [AlI India 2014] 27. How does a population become 'founders' of a new species?  [All India 2012 C] 10. Identify the examples of convergent evolution from the following: 28. Coelacanth was caught in 1938 in South Africa. Why it is very significant in the evolutionary (a) Flippers of penguins and dolphins history of vertebrates?  [All India 2010 C] (b) Eyes of octopus and mammals (c) Vertebrate brains [Delhi 2013] 29. 1.5 mya Java man Homo habilis 11. \"Sweet potato tubers and potato tubers are the result of convergent evolution\". Justify the – more man-like statement. [Delhi 2013] 12. Identify the examples of homologous structures 2 mya Australopithecines from the following. – Hunted with stones (a) Vertebrate hearts Study the ladder of human evolution given above (b) Thorns in Bougainvillea and tendrils of and answer the following questions. Cucurbita. (a) Where did Australopithecines evolve? (c) Food storage organs in sweet potato and potato.  [Delhi 2013] (b) Write the scientific name of Java man. 13. State the significance of the study of fossils in  [Delhi 2010 C] evolution. [Delhi 2012] 30. State two postulates of Oparin and Haldane with reference to origin of life. [All India 2017] 14. State the significance of biochemical similarities amongst diverse organisms in evolution. 31. Write the names of the following: (a) A 15 mya primate that was ape-like  [Delhi 2012] 15. Are the thorn of Bougainvillea and tendril of (b) A 2 mya primate that lived in East African Cucurbita homologous or analogous? What type grasslands [CBSE 2018] of evolution has brought such a similarity in them. [Delhi 2009] 2 Marks Questions 16. Write the term used for resemblance of varieties of 32. Explain with the help of an example the type of placental mammals to corresponding marsupials evolution homology is based on.  [Delhi 2015 C] in Australia. [Delhi 2013 C] 33. How do Darwin’s finches illustrate adaptive radiation? [AlI India 2008] 17. Name the placental mammals corres-ponding to the Australian spotted Cuscus and Tasmanian 34. According to Hardy–Weinberg’s principle the allele frequency of a population remains constant. 'tiger cat' which have evolved as a result of convergent evolution. [AlI India 2008 C] How do you interpret the change of frequency of alleles in a population? [AlI India 2009] 168 Biology–12

35. Name the scientist who has used the setup 41. Explain Darwinian theory of evolution with the shown. Write the purpose of 'a' in the set-up and help of one suitable example. State the two key the conclusion the scientist arrived at. concepts of the theory. [Delhi 2014]  [Delhi 2013 C] 42. Rearrange the following in increasing order of a evolution: b Gnetales; Ferns: Zosterophyllum; Ginkgo  [AlI India 2014 C] 43. Name the first human like hominid. Mention his food habit and brain capacity. [AlI India 2015 C] 44. Name the ancestors of a man based on the features given below: (a) Human-like, meat-eater with 900 cc brain, lived in Java. (b) More human-like with brain size 1400 cc, lived in Central Asia, used hides and buried their dead. (c) Human-like, vegetarian, with brain capacity between 650 cc and 800 cc. c (d) Man-like primate, that existed about 15 mya. Fossils found in Tanzania.[AlI India 2013 C] 36. The figure given represents Miller's apparatus 45. What was proposed by Oparin and Haldane on used for his experiment. Name the chemicals origin of life? How did S. L. Miller's experiment found in the samples drawn from 'c'. How did this support their proposal? experiment support evolution?[All India 2013 C] [Foreign 2014, Delhi 2011 C] a 46. Mention the contribution of S. L. Miller's experiment on origin of life  [AIl India 2013] b 47. Write the Oparin and Haldane’s hypothesis about the origin of life on Earth. How does meteorite analysis favour this hypothesis? [AIl India 2013] 48. List the two main propositions of Oparin and Haldane.  [AIl India 2013] 49. (a) Explain the theory of biogenesis. (b) How did Miller demonstrate experi-mentally the chemical evolution that happened three billion years ago?  [Delhi 2010 C] 50. Select two pairs from the following which exhibit divergent evolution. Give reasons for your c answer. 37. (a) Select the homologous structures from the (a) Forelimbs of cheetah and mammals combinations given below: (b) Flippers of dolphins and penguins (i) Forelimbs of whales and bats (c) Wings of butterflies and birds (ii) Tuber of potato and sweet potato (d) Forelimbs of whales and mammals  (iii) Eyes of octopus and mammals  [AlI India 2015] (iv) Thorns of Bougainvillea and tendrils of 51. E xplain divergent evolution with two examples.  [Foreign 2015) Cucurbita. 52. Is sweet potato analogous or homologous to potato (b) State the kind of evolution they represent. tuber? Give reasons to support your answer.  [AlI India 2015]  [Delhi 2015 C] 38. Explain how natural selection operates in nature 53. State the evolutionary relationship giving by taking an example of white winged and dark reasons between the thorn of Bougainvillea and winged moths of England. [AlI India 2014 C] tendril of Cucurbita.  [AlI India 2015 C] 39. What is adaptive radiation? How did Darwin 54. Identify the following pairs as homologous and explain this process of evolution?[Delhi 2008 C] analogous organs: 40. Name the scientist who influenced Darwin and (a) Sweet potato and potato how? [Delhi 2016] (b) Eye of octopus and eye of mammals Evolution  169

(c) Thorns of Bougainvilleas and tendrils of 68. Australian marsupials and placental mammals Cucurbita are suitable examples of adaptive radiation and (d) Forelimbs of bat and whale. [Delhi 2014] convergent evolution. Explain giving reasons.  55. Write about the ancestry and evolution of bat,  [AlI India 2010 C] 69. \"Nature selects for fitness\". Explain with suitable horse and human on the basis of a comparative example.  [Delhi 2009 C] study of their forelimbs. What are these limbs 70. How does Darwin's theory of natural selection explain the appearance of new forms of life on categorized as?  [Delhi 2013 C] 56. How do paleontological evidences support earth?  [AlI India 2008] evolution of organisms on earth?  71. Describe the mechanism of evolution as explained  [AlI India 2013 C] by Hugo de Vries.  [AlI India 2012 C] 57. What does the comparison between the eyes of 72. What does the following equation represent? octopus and those of mammals say about their Explain. ancestry and evolution?  [AIl India 2013 C]     p2 + 2pq + q2 = 1 [AlI India 2011 C, 2015] 58. In England, before industrialization set in, there 73. Describe the three different ways by which were more white-winged moths than dark-winged natural selection can affect the frequency of a moths. However the number reversed in the heritable trait in a population. same area when industrialization set in. How does this observation support natural selection?  [AlI India 2011 C, Foreign 2014]  [AIl India 2013 C, 2008 C] 74. (a) Describe Hardy-Weinberg Principle. (b) List any four factors which affect genetic 59. Choose two pairs of homologous struc-tures from equilibrium. the following and mention why they are so called: (c) Describe founder effect.  [Foreign 2014] (a) Hearts of humans and monkeys 75. Giving three reasons, write how Hardy Weinberg (b) Eyes of octopus and mammals equilibrium can be affected.  [AlI India 2014 C] (c) Thorns of Bougainvillea and tendrils of 76. How is genetic drift different from gene migration? Explain  [AlI India 2008 C] Cucurbita 77. S t u d y t h e s c h e m a t i c r e p r e s e n t a t i o n o f (d) Flippers of penguins and dolphins  evolutionary history of plant forms given below  [Delhi 2012 C] and mention: 60. Divergent evolution leads to homologous Mosses Ferns Conifers Flowering plants structures. Explain with the help of an example.  [AIl India 2011 C] 61. Convergent evolution leads to analogous Psilophyton structures. Explain with the help of an example.  [AIl India 2011 C] Psilophyton 62. Why are thorn of Bougainvillea and tendrils of Tracheophyte ancestor Cucurbita called homologous? What does this homology indicate?  [AIl India 2011 C] Chlorophyte ancestor 63. What is divergent evolution? Explain taking an example of plants.  [Delhi 2008] (a) The plant form Ferns and Conifers are most related to. 64. With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given (b) The nearest ancestors of flowering plants. population the frequency of occurrence of alleles (c) The most primitive group of plants. of a gene is supposed to remain the same through (d) Common ancestry of Psilophyton provides to. generations? [CBSE 2018] (e) The common ancestor of Psilophyton and seed ferns. 3 Marks Questions (f) The common ancestors of mosses and 65. (a) How did Darwin explain adaptive radiation? tracheophytes.  [Delhi 2012 C] (b) Give another example exhibiting adaptive 78. (a) Rearrange the following in an ascending order radiation.  [Delhi 2016] of evolutionary tree: reptiles, salamander, lobefins, frogs. 66. What is adaptive radiation? When can adaptive radiation be referred to as convergent evolution? (b) Name two reproductive characters that probably make reptiles more successful than Give an example. [Delhi 2015] amphibians.  [AlI India 2009 C] 67. Explain the interpretation of Charles Darwin 79. Mention any three characteristics of Neanderthal when he observed a variety of small black birds man that lived in near East and Central Asia. on Galapagos Islands.  [Delhi 2015]  [Delhi 2014] 170 Biology–12

80. Describe the experiment that helped Louis Pasteur to dismiss the theory of spontaneous generation of life. [Delhi 2016] 81. State the theory of Biogenesis. How does Miller’s experiment support this theory?  [Delhi 2012] 1 2 3 4 (b) How did Darwin explain the existence of 82. (a) State Oparin-Haldane’s hypothesis? different varieties of finches on Galapagos Islands? [AlI India 2009, 2009 C] (b) How does S.L. Miller’s experiment support it?  [Foreign 2016] 91. Branching descent and natural selection are the two key concepts of Darwinian Theory of 83. Write the hypothetical proposal put forth by Oparin and Haldane.  [Foreign 2015 C] Evolution. Explain each concept with the help of a suitable example. 84. “Post-industrialization, the population of [AlI India 2011] melanised moth increased in England at the 92. Differentiate between homology and analogy. Give one example of each  [All India 2016] expense of white-winged moths.” Provide explanations.  [Foreign 2016] 93. Differentiate between divergent and convergent evolution. Give one example of each OR How did industrialization play a role in natural  [All India 2016] selection of light and dark coloured moth in 94. What are analogous structures? How they are England?  [Delhi 2015 C] different form homologous structures? Provide OR one example for each  [Foreign 2015] How does industrial melanism support Darwin’s 95. How does the study of fossils support evolution? theory of Natural Selection? Explain. Explain.  [All India 2015 C]  [AlI India 2012] 96. Explain convergent evolution taking one example 85. Explain convergent evolution with the help of two examples.  [Foreign 2015 C] for plants.  [Delhi 2012 C] 86. What are analogous structures? How are they 97. Convergent evolution and divergent evolution are different from homologous structures? Provide the two concepts explaining organic evolution. one example for each.  [Foreign 2015 C] Explain each one with the help of an example.  [Foreign 2011] 87. Explain divergent evolution with two examples.  [Foreign 2015 C] 98. 88. What do you infer from the resemblance between flying squirrel and flying phalanger with reference to their evolution.  [Delhi 2015 C] (a) (b) 89. Sugar glider What do these pictures 'a' and 'b' illustrate with reference to evolution? Explain.  [Foreign 2009] Tasmanian wolf 99. Explain taking one example of vertebrate anatomy that evolution of life forms has occurred Marsupial mole Marsupial Tiger cat on earth.  [All India 2009 C] radiation Banded 100. The study of anteater Koala AUSTRALIA (a) Fossils of dinosaurs (b) Forelimbs of cheetah, bat, whale and human Bandicoot Marsupial (c) Thorns of Bougainvillea and tendril of Cucurbita rat Wombat Kangaroo Show that evolution of life forms has indeed take place on earth. Explain. [AIl India 2008 C] (a) Mention the specific geographical region where these organisms are found. 101. Explain adaptive radiation with the help of a (b) Name and explain the phenomenon that suitable example.  [Delhi 2015] has resulted in the evolution of such diverse species in the region. 102. (a) Explain adaptive radiation with the help of a suitable example. (c) Explain giving reasons the existence of placental wolf and tasmanian wolf sharing (b) Cite an example where more than one adaptive radiation has occurred in an isolated the same habitat. [Delhi 2009] geographical area. Name the type of an 90. (a) Write your observations on the variations seen in the Darwin’s finches shown below. evolution your example depict and state why it is so named. [All India 2014] Evolution  171

103. Name and explain the evolutionary concept 111. (a) Differentiate between analogous and represented in the illustration given below: homologous structures. Sugar glider (b) Select and write analogous structures from the list given below: Tasmanian wolf Marsupial mole Ancestral Tiger cat (i) Wings of butterfly and birds Stock Banded (ii) Vertebrate hearts anteater (iii) Tendrils of bougainvillea and cucurbita (iv) Tubers of sweet potato and potato  [CBSE 2018] Koala 5 Marks Questions 112. Explain the salient features of Hugo de Vries Bandicoot Marsupial theory of mutation. How is Darwin’s theory of rat natural selection different from it? Explain. Wombat Kangaroo  [Delhi 2011]  [All India 2012] 113. Difference between Hugo-de Vries and Darwin's theory. 104. Darwin observed a variety of beaks in small black birds inhabiting Galapagos Islands. Explain what 114. (a) Name the primates that lived about 15 million conclusions did he draw and how. years ago. List their characteristic features.  [All India 2009 C] (b) (i) W here was the first man-like animal 105. Fitness is the end result of the ability to adapt found? and get selected by nature. Explain with suitable example.  [Delhi 2010] (ii) Write the order in which Neanderthals, Homo habilis and Homo erectus appeared 106. (a) Natural selection operates when nature on earth. State the brain capacity of each selects for fitness. Explain. one of them. (b) The rate of appearance of new forms is linked to the life span of an organism. Explain with (iii) When did modern Homo sapiens appear the help of a suitable example.  [Delhi 2010] on this planet? [Delhi 2011] 107. (a) How does the Hardy Weinberg’s expression 115. (a) Anthropogenic actions have caused evolution (p2 + 2pq + q2 = 1) explain that genetic of species. Explain with the help of two equilibrium is maintained in a population? examples. (b) List any two factors that can disturb the (b) Differentiate between divergent and genetic equilibrium.  [AlI India 2010] convergent evolution.  [Delhi 2008 C] 108. (a) How did Hardy Weinberg explain that allelic frequencies in a population are stable and are 116. How does the shift in Hardy-Weinberg equation constant from generation to generation? lead to founder affect? Explain. [Delhi 2011 C] (b) Why does genetic equilibrium get disturbed 117. (a) Differentiate between analogy and homology in a population? Give reason. giving one example each of plant and animal respectively.  [AIl India 2008 C] 109. Write the characteristics of Ramapithecus, (b) How are they considered as evidence in Dryopithecus and Neanderthal man. support of evolution?  [Delhi 2016]  [All India 2017] 110. What is disturbance in Hardy-Weinberg genetic 118. How does the process of natural selection affect equilibrium indicative of? Explain how it is Hardy Weinberg equilibrium? Explain. List the caused. [All India 2017] other four factors that disturb the equilibrium.  [Al India 2013] Answers I. Multiple Choice Questions 1 Mark Questions 1. Wings in both the animals are meant to fly but 1. (b) 2. (c) 3. (b) 4. (c) 5. (b) 10. (c) the structure is different. This is an example of 6. (d) 7. (a) 8. (c) 9. (d) 15. (a) convergent evolution and analogous organs. 2. Convergent evolution 11. (a) 12. (a) 13. (b) 14. (c) 5. Homology 3. Flippers of whale, wings of bat. 4. Single step large mutation is saltation. II. Fill in the Blanks 1. shrews 2. conventional 3. H.M.S. Beagle 4. Dinosaur 172 Biology–12

5. Dryopithecus and Ramapithecus (b) M u t a t i o n s a r e d i r e c t i o n a l , s l o w a n d 6. Louis Pasteur continuous. Such mutations are inheritable 7. According to Darwin, fitness refers to reproductive and accumulate to give rise to a new species later. fitness. Those who best fit in an environment, reproduce well and survive. Hence are selected 21. Homo habilis did not eat meat whereas Homo by nature. He called it natural selection and is erectus were meat eaters. considered as one of the reasons for evolution. 22. Oparin and Haldane state that life emerged 8. During industrialisation period in England, due from pre-existing non-living organic molecules to industrial soot, the lichens were lost, tree such as RNA, protein etc and formation of life barks became dark, so the dark coloured moths was preceded by chemical evolution, i.e. organic camouflaged well with background. They were not molecules were formed from inorganic molecules. visible to predator birds and survived, reproduced and outnumbered the light coloured moths. 23. Convergent evolution. Such structures are called analogous structures. 9. Analogous structures have similar characters or function but have different origin. So they are 24. The morphology of forelimbs of whales, bats, called to be result of convergent evolution. cheetah and humans is similar but their functions are different. These are homologous organs 10. Flippers of penguins and dolphins and eyes of and such type of evolution is called divergent octopus and mammals. evolution. 11. Sweet potato and potato tubers, both act as Wings of butterfly and that of birds have same storage organs but sweet potato is modified root function but they are anatomically different. and potato is a modified stem thus represents Such organs are analogous organs and such type convergent evolution. of evolution is called convergent evolution. 12. Vertebrate hearts and thorns of Bouga-invillea 25. Refer answer no. 1. and tendrils of Cucurbita. 26. They are homologous. The type of evolution is divergent. 13. Fossils reveal morphological details of the 27. After a genetic drift, there is change in allele organisms which were present in the past and we can relate them to the organisms present today. frequency which is different from the original This can help us to understand the process of one. This difference may be the reason for evolution. We can also calculate the time at which the development of new species. The drifted the organisms existed in the past. population becomes the founders. 14. Biochemical similarities such as simil-arities in 28. Coelacanth is considered as living fossil and is proteins and genes performing similar functions thought to have evolved as first amphibian. among various organi-sms suggest that there is common ancestry. 29. (a) East African grasslands (b) Homo erectus 15. They are homologous organs and divergent evolution has brought such a similarity of origin 30. (i) First form of life could have come from pre- in them. existing non-living organic molecules / RNA & Protein 16. Convergent evolution 17. Spotted cuscus: Lemur; Tasmanian tiger cat: (ii) Formation of life was preceded by chemical evolution / formation of diverse organic Bobcat molecules from inorganic constituents 18. Hugo de Vries Darwin 31. (a) Dryopithecus, • Mutations are (b) Australopithecus • directionless • Mutations are direc- • They are sudden • tional 32. Homology is based on divergent evolution. They are random • They are gradual Homologous organs have similar anatomical structures but perform different functions. The variation is contin- Example: Thorn of Bougainvillea and tendril of uous and accumulates Cucurbita, both are modifications of stem. which give rise to new species later. 33. Original seed-eating finches migrated to different areas of Galapagos islands and adapted to 19. (i) Mutations give rise to variations which are different feeding methods with altered beak small and directional. structures. Some evolved into insectivorous and others into vegetarian finches. (ii) Accumulation of inheritable mutations are responsible for evolution. 34. If there is change in allele frequency, this may be due to gene migration or genetic drift or 20. (a) Mutations are directionless, sudden and mutation or genetic recombination due to sexual random. Evolution  173

reproduction or natural selection which leads to 41. Darwin theory of evolution says that in a evolution. population the rate of appearance of new forms 35. Miller. 'a' in the setup are electrodes which is linked to the life span of an organism. Shorter produced electric sparks simulated the life span more will be chances to evolve due lightening of clouds during pre historic to accumulation of large number of variations. time when there was reducing atmosphere. He According to him variations among individuals arrived at the conclusion by result that organic exist in nature. In changed conditions, the molecules like amino acids were formed from variant which better fits survives and reproduces. inorganic molecules thus suggesting chemical This adaptability is inherited and has genetic evolution. basis. 36. Amino acids, fats, sugars, nitrogen bases and Branching descent and natural selection are pigments were found in samples drawn from ‘c’. the two key concepts of Darwinian Theory of These organic molecules were formed from the Evolution. inorganic molecules like methane, water vapours, 42. Zoosterophyllum, Ferns, Gnetales, Ginkgo hydrogen gas and ammonia. This supports 43. Homo habilis. They did not eat meat. The brain chemical evolution. capacities were between 650-800cc. 44. (a) Homo erectus 37. (a) Forelimbs of whales and bats, thorns of (c) Homo habilis (b) Neanderthal man Bougainvillea and tendrils of Cucurbita. (d) Ramapithecus (b) They represent divergent evolution. 45. Refer answer no. 22. S. L. Miller simulated the 38. In 1850’s a collection of moths was taken and conditions present on primitive earth in the lHma2ba,oinrNatHatoi3nryeadinndactHlo8s20Oe0d°vCflaapasoknudwrseh,liectchetmrcoopdneetrasaitnpuerrdoevCiwdHea4ds, it was found that white-winged moths were electric discharge. He observed the formation of more in number than dark-winged melanised amino acids in closed flask. moths. Similar collection was made after industrialisation, in 1920s, the proportion was Electrodes reversed, dark winged moths were more in number than white-winged moths. To vacuum CH4 Gases Spark During pre-industrialisation era, there was pump NH3 discharge no pollution, trees were covered with lichens H2O and the background was light. White-coloured H2 Water out moths were not visible to predators and dark- coloured moths were picked by predators. After Condenser industrialisation, pollution increased, lichens died, tree surface became dark, so dark-coloured Water in moths were not visible to predators and survived. None of the moth variant was completely wiped Water out. Thus nature selected the organism which better survived in the prevailing conditions. droplets 39. The process of evolution in different species in a given geographical area starting from a point Water and radiating to other geographical areas is called adaptive radiation. In Galapagos Island, Boiling water containing Darwin observed that there were many varieties of small black birds which are now known as Liquid water organic Darwin finches on the island. According to him, compounds all varieties evolved from seed-eating common in trap ancestor, some of them modified their beaks and become insectivores, some became vegetarian Diagrammatic representation such as fruit eating and cactus eating. of Miller's Experiment 40. Thomas Malthus. 46. Refer answer no. 43. Thomas Malthus wrote essays about populations 47. Oparin Haldane–Refer answer no. 22. The and carrying capacities for the environment. meteorite analysis revealed similar compounds Malthus gave the idea about the consequences of overpopulation and the struggle to survive when which shows that similar processes are occurring resources are limited. Darwin related the concept on living organisms, if the resources are limited, elsewhere in space. the one who is reproductively fit will survive. This 48. Refer answer no. 22. gave rise to the concept of natural selection. 49. (a) The theory of biogenesis means life arose from non living materials or life arose from pre-existing life. (b) Refer answer no. 43. 50. Forelimbs of cheetah and mammals, forelimbs of whales and mammals. 51. Example 1: Refer answer no. 24 Example 2: Thorns of Bougainvillea and Tendrils of Cucurbita are the result of divergent evolution. 174 Biology–12

Both these structures are modified auxillary buds (b) Australian marsupials on stem but their functions are different. 66. For definition of adaptive radiation refer answer no. 63. When more than one adaptive 52. Analogous organs. Potato is a modified shoot. radiation appeared to have occurred in an But sweet potato is a modified stem. Both acts isolated geographical area representing different habitats, it is referred as convergent evolution. as storage organs. Australian marsupials placental mammals. 53. Refer answer no. 49. 67. Refer answer no. 37. 54. a–analogous organs. 68. Australian marsupials evolved from a common b–analogous organs. c–homologous organs. ancestor within the Australian continent. This d–homologous organs. is adaptive radiation. Placental mammals also 55. Ancestory is common. All have similar structure evolved into animals with similar features of but different functions. Such type of evolution corresponding marsupials, such as placental wolf and marsupial wolf, in a separate adaptive is called divergent evolution. These limbs are radiation. When two such evolutions take place which evolve into similar animals is called homologous organs. convergent evolution. 56. Fossils represent extinct organisms. Many of 69. According to Darwin, fitness means reproductive them appear similar to modern organisms. They fitness. Those who can better adapt to the changed environmental conditions, survive, reproduce and also tell us about the geological period in which outnumber others. They are selected by the nature. Example: in a population of bacteria (say A) growing the organisms existed. Life forms varied over on a given medium has built in variation in terms of ability to utilize a feed component. A change in time, some were restricted to certain geological the medium composition would bring out only that part of the population (say B) which can survive time. Others arose at different times in history under the new conditions. In due course of time this variant population outgrows the others and of the earth. appears as a new species. The rate of appearance of new forms is linked to the life span of an organism. 57. Both are analogous organs. They evolved Shorter the life span more will be chances to evolve differently but have similar functions. This due to accumulation of large number of variations. suggests that their ancestors were different. This 70. Darwin’s theory says that variations exist in nature and these help individuals to adapt better is an example of convergent evolution. in the changed environmental conditions. Such individuals will outbreed others which is called 58. Refer answer no. 36. survival of the fittest. The population which is 59. Hearts of humans & monkey. Thorns of better adapted will survive and is selected by the Bougainvillea and tendrils of Cucurbits. In both nature. These adaptations are inheritable. the cases origin is same. 71. Hugo-de-Vries observed evening primrose and 60. Refer answer no. 24, 49. gave idea of mutation. He stated that mutations 61. Refer answer no. 56. are single step and large, are directionless and 62. Refer answer no. 49. can cause speciation. 63. In divergent evolution the organisms have similar structures but these structures develop 72. The equation represents Hardy-Weinberg equilibrium. This states that if there is no along different directions due to adaptations to mutation, gene flow, reproduction, genetic drift and natural selection, the allele frequency of a different needs. population remains constant, i.e. equal to 1, from generation to generation. E.g.: Thorns of Bougainvillea and tendrils of Cucurbita. For explanation refer answer no. 49. p2 represents the frequency of homozygous dominant alleles, q2 represents the frequency of 64. Algebraic equation given by Hardy Weinberg for homozygous recessive alleles and 2pq represents a population frequency is as follows: the frequency of heterozygous alleles. p2 + 2pq + q2 = 1 73. The three different ways by which natural selection can affect the frequency of a heritable It can also be written as trait in a population are: (p + q)2 = 1 This states that the gene pool (total genes and their alleles in a population) remains a constant. For a diploid organism, p and q represent frequency of alleles ‘A’ and ‘a’ respectively, frequency of AA genotype in a population is p2 and for aa genotype is q2, 2pq represents frequency of genotype Aa. 65. (a) Adaptive radiation is a process of evolution in which different species in a given geographical area starting from a point and literally radiating to other areas of habitats. Evolution  175

(i) Stabilizing selection – If the allele with next generation than other ones, this will average features contributes more to the next shift the peak to one direction. Example: generations, the peak will get narrower. Both The size of horse originally was that of dog. the smallest and largest individuals are not Due to selection pressure, the height of horse preferred to be passed to the next generation. Such selection is called stabilizing selection. increased and evolved into modern horse. It reduces variation but does not change mean value. Example: Too small plants and (iii) Disruptive selection–When the alleles at too large plants will not get survival benefit. both extremes are selected by the nature, the graph shows two peaks, such type of selection Too small plants have to compete for sunlight is called disruptive selection. Example: In a and too large plants get damaged due to wind. squirrel, short tails are preferred as they are So the plants with medium height will get survival benefit and outnumber other plants. not caught by predators. Large tails help to (ii) Directional selection–If the allele with keep the balance while running. Medium tails any one extreme will contribute more to the are not of any help and thus are not preferred. Number of individuals Phenotypes Medium-sized with phenotype favoured by individuals are favoured natural selection Peak gets Only average Peak shifts Two peaks form, both Extreme higher and trait is favoured in one direction traits are equally favoured narrower (only one Extreme trait is favoured) (a) (b) (c) 74. (a) Hardy-Weinberg Principle states that if (ii) Genetic drift: If there is addition or loss there is no mutation, gene flow, reproduction, of genes in a population which happens genetic drift and natural selection, the allele suddenly and by chance, the gene frequency frequency of a population remains constant, of the resultant population becomes entirely i.e. equal to 1, from generation to generation. different from the original population. It is called genetic drift. (b) The four factors which affect genetic equilibrium are mutation, gene flow, ( iii) Mutation: The advantageous mutations will reproduction, genetic drift and natural exist in a population and accumulate with selection. (Any four) time and over few generations, eventually contributing to form a new species. (c) When from a large population a new population is formed whose allelic frequency 76. Refer answer no. 73. is entirely different from the old population. 77. (a) Psilophyton This new population with new combination (b) Seed ferns of allelic frequency is called founders and sometimes the variation is very different from (c) Chlorophyte ancestor the original population and thus becomes a new species. (d) Ferns, conifers and seed ferns 75. Three reasons by which Hardy-Weinberg (e) Tracheophyte equilibrium can be affected are: (f) Chlorophyte ancestor (i) Gene migration or gene flow: When individuals migrate into a population and get well 78. (a) Lobefins, frogs, salamanders, reptiles. adapted and reproduce, the genetic makeup (b) Reptiles are more successful as they lay thick- of the receiving population gets altered. shelled eggs which do not dry up in sun unlike those of amphibians. 176 Biology–12

79. Neanderthal man had brain size of 1400cc, they 82. (a) Refer answer no. 22. used hides to protect their body and buried their (b) Refer answer no. 43. dead. 83. Refer answer no. 43. 80. Pasteur took two pre-sterilized flasks with killed 84. Refer answer no. 36. yeast. He sealed one and left other open so that 85. Convergent Evolution states that different air could freely move in and out of the flask. He observed that no life occurred in closed flask in organisms possess organs that are anatomically contrast to open flask where life exist. By this different but perform similar functions or two or experiment he concluded that life came from more group of unrelated animals resemble each pre-existing life and the theory of biogenesis was other with similar mode of life or habitat. For proved. example: Cotton plug (i) Wings of butterfly and wings of birds Sealed flask (ii) Eye of octopus and eye of mammals Killed yeast 86. Analogous structures are anatomically different but perform similar functions. Example: wings of Flame birds and wings of insect. Potato & sweet potato (potato is stem & sweet potato is a root). Diagrammatic representation of Louis Pasteur Experiment Homologous structures have similar anato­m­ ical features but different functions. Example: thorn of 81. Theory of biogenesis states that the living Bougainvillea, tendril of Cucurbita and forelimbs organisms arise from preexisting living organisms of vertebrates. and not from nonliving material. Miller performed an experiment in a closed flask with electric 87. Divergent evolution different organisms possess discharge. This flask contained CH4, H2, NH3 and organs that are anatomically similar but perform water vapours heated at 800°C. This resulted in different functions. Examples: forelimb of whales, the formation of amino acids supporting the idea bats, cheetah and human have similar pattern of of chemical evolution. Miller’s experiment did not bones in forelimbs; thorns of Bougainvillea and support this theory of biogenesis as it supported tendrils of Cucurbita, are stem modifications. chemical evolution. 88. Evolution of marsupial mammals has resulted Electrodes in flying phalanger, through adaptive radiation. Evolution of placental mammals has led to the To vacuum CH4 Gases Spark evolution of a flying squirrel independently and pump NH3 discharge the resemblance between the two is the example H2O of convergent evolution in which more than H2 Water out one adaptive radiation occurred in an isolated geographical region. Condenser 89. (a) Geographical region is Australia Water in (b) The phenomenon is adaptive radiation. It is Water a process of evolution of different species in a droplets given geographical area which starts from a point and radiate to other geographical areas. Water (c) Two different organisms when occupy same Boiling water containing habitat evolve as having similar features. This is called convergent evolution. Placental Liquid water organic wolf and Tasmanian wolf both possessed compounds similar features but one is placental mammal in trap and other is marsupial. Diagrammatic Representation 90. (a) From the original seed eating finch, many of Miller's Experiment other forms with altered beaks arose enabling them to become insectivorous and vegetarian finches. (b) The process of evolution of different species in a given geographical area starting from one point and radiating to other geographical areas is called adaptive radiation. Darwin finches are the example of adaptive radiation. 91. Branching descent means that all species have common ancestor and got adapted (descended) in Evolution  177

different habitats. For example: Darwin finches - picture 'b' is of post industrial era when dark- all varieties arose from common seed eating finch coloured moths were more. and adapted to eat fruits, cactus and insects. For explanation: Refer answer no. 36. Natural selection means any variation which is 99. The forelimbs of man, cheetah, whale and bat are inheritable enables an individual to survive and reproduce in a given environmental conditions. similar in structure. All have humerus, radius, For example: During pre industrial era, white ulna, carpals, metacarpals and phalanges. But moths camouflaged against light background of in each organism they developed differently trees and were not picked up by predators. But according to need. Such structures are called after industries were set up, lichens died, trees homologous organs and evolution is called background became darker and white moths divergent evolution. were picked up by predators whereas dark moths camouflaged and managed to survive. However, 100. (a) Refer answer no. 55. both the variants existed at both the times. (b) Refer answer no. 97. 92. Homology Analogy (c) Refer answer no. 49. 101. Refer answer no. 88 (b) and (a) 1. It is based on diver- 1. It is based on con- 102. (a) Refer answer no. 88 (b) and (a) (b) Refer answer no. 86 gent evolution. vergent evolution. 103. The phenomenon is adaptive radiation for 2. Homologous organs 2. Analogous organs explanation refer answer no. 87 (b) 104. Refer answer no. 37. have similar ana- are anatomically 105. Refer answer no. 67. 106. Refer answer no. 67. (for both (a) and (b) tomical structures different but per- 107. Refer answer no. 72. (for both (a) and (b) 108. Refer answer no. 72. (for both (a) and (b) but perform differ- form same func- 109. Ramapithecus: hairy/ walked like gorillas and ent functions. tions. chimpanzees, more man like 3. Have common an- 3. Have different de- Dryopithecus: hairy/ walked like gorillas and chimpanzees, more ape-like cestry origin. velopmental origin. Neanderthal man: brain size is 1400cc, used hides 4. Examples: Thorns 4. E x a m p l e : F o r e - to protect their body / buried their dead of Bougainvillea limbs of whales, 110. Disturbance in Hardy-Weinberg equilibrium is and tendrils of Cu- bats, cheetah and an indicator of change of frequency of alleles in human. a population which results in evolution. curbita It is caused due to genetic drift, gene flow, gene 93. Divergent Convergent migration, genetic recombination, or natural Evolution Evolution selection. 1. Homologous organs 1. Analogous organs shows divergent shows convergent evolution. evolution. 2. C o m m o n a n c e s - 2. Different unrelated 111. (a) Analogous Homologous tral origin develop organisms develop structures structures similar anatomical adaptative anatom- organs to perform ically organs to per- Analogous structures Homologous struc- different functions. form same function. are anatomically dif- tures have similar 3. Examples: Thorns 3. E x a m p l e : F o r e - ferent but they per- anatomical struc- of Bougainvillea limbs of whales, and tendrils of Cu- bats, cheetah and form similar func- ture but different curbita. human. tions. Example: wings functions. Example: 94. Refer answer no. 84. of birds and wings of thorn of Bougainvil- 95. Refer answer no. 55 96. Refer answer no. 83. butterfly. lea and tendril of Examples potato & sweet potato. Refer answer Cucurbita. no. 50. Such evolution is also Such evolution is Steam tendrils of Passiflora and leaf tendrils of Pisum sativum. Both perform function of called as convergent also called as diver- climbing, but their origin is different. evolution. gent evolution. 97. Refer answer no. 91. 98. Picture (a) is of pre-industrial era in England. (b) Analogous structures are: When light-coloured moths were more and (i) Wings of butterfly and birds (ii) Tubers of sweet potato and potato 112. Hugo de Vries while working on evening primrose, stated that the mutations are single step large changes i.e. the mutations arise suddenly in a 178 Biology–12

population. This all of a sudden change is called This also shows that evolution occurs saltation which is responsible for speciation. faster due to anthropogenic actions. (b) When during evolution, different organisms Hugo de Vries Darwin evolve to use similar anatomical structure for • Mutations are different functions then it is called divergent • Mutations are direc- evolution whereas when organisms with directionless tional different anatomical structures evolve for similar use of organs is called convergent • They are sudden • They are gradual evolution. 116. Refer answer no. 72 and 27. • They are random • The variations are con- 117. (a) Refer answer no. 84. tinuous and accumulate (b) Homologous organs are developed as a gradually giving rise to result of divergent evolution and analogous new species. organs are produced as a result of convergent evolution. Both type of evolution operate 113. Refer answer no. 106 gradually and present excellent evidence in 114. (a) Dryopithecus was more ape like, hairy and support of evolution. 118. In natural selection, the inheritable variations walked like gorillas and chimpanzees. helped for the survival of an organism enabling it to reproduce. There may be change in allele Ramapithecus was more man-like. frequency in future generations if genetic (b) (i) F irst man-like animal was found in combination or mutation takes place. This may lead to the formation of new species. Other factors Ethiopia which influence Hardy Weinberg equilibrium are: (i) Gene Migration: Migration of individuals from (ii) Homo habilis, Homo erectus, one population to another. This may add or is the cause of loss of genes or alleles. Neanderthals (ii) Genetic drift: If change in allelic frequency occurs suddenly and new allelic frequency is Cranial capacity of Homo habilis was quite different from the original population 650-800 cc. Homo erectus: 900 cc and of then it is called genetic drift. Neanderthals: 1400cc. (iii) Mutation: Mutations occur randomly leading to new phenotypes and genotypes. this may (iii) Homo sapiens are thought to have lead to the formation of new species. appeared during ice age about 75000- (iv) Genetic recombination: It occurs due to 10000 years ago. crossing over during meiosis during the formation of gametes in sexually reproducing 115. (a) (i) Industrial melanism: Before industriali- sation, lichens covered the bark of trees organisms. This leads to new combination of which was favourable for white-winged moths to camouflage. genes. Post industrialisation, the smoke and soot caused lichens to die. This helped dark- winged moths to outnumber the white winged moths as they were not visible on dark background of tree trunks. (ii) Use of herbicides and pesticides has resulted in selection of resistant varieties and development of microbes resistant to antibiotics in very short period of time. Assertion & Reason Type Questions For question numbers 1-7: Two statements are given one 2. Assertion (A): The two main concepts of Darwin labelled Assertion (A) and the other labelled Reason (R). Select theory of evolution are ‘branching descent’ and ‘natural selection’. the correct answer to these questions from the codes (a), (b), Reason (R): Theory of natural selection based (c) and (d) as given below. on role of environment in evolution. (a) Both Assertion and Reason are true and Reason 3. Assertion (A): Replication of genetic material is the correct explanation of Assertion. affect Hardy-Weinberg’s equilibrium. (b) Both Assertion and Reason are true but Reason Reason (R): In the Hardy-Weinberg equilibrium, is NOT the correct explanation of Assertion. the term 2pq represents the frequency of the (c) Assertion is true but Reason is false. homozygous genotype. (d) Assertion is false and Reason is also false. 1. Assertion (A): Genetic drift is change of gene 4. Assertion (A): In evolutionary terms, an organism’s fitness is measured by its health. frequency from one generation to next. Reason (R): Genetic drift operates only in Reason (R): The idea of ‘survival of fittest’ was originally presented by Wallace. smaller populations Evolution  179

5. Assertion (A): Neanderthal man often had a 7. Assertion (A): Hardy-Weinberg principle states somewhat larger brain than the modern man. that allelic frequency of a population remain constant. Reason (R): Neanderthal man lived near east or central Asia and used hides to protect their body. Reason (R): Constancy is maintained through natural selection and mutation. 6. Assertion (A): Darwin’s finches show a variety of beaks suited for eating large seeds, flying insects 1. (b) Answers 5. (b) and cactus seeds. 6. (a) 2. (c) 3. (d) 4. (d) Reason (R): Ancestral seed-eating stock of 7. (c) Darwin’s finches radiated out from South American mainland to other areas of Galapagos Islands, where they found no competitors. Case Based Questions environment in a way reminiscent of metabolism. 1. The Alexander Ivanovich Oparin and J.B.S. Haldane stated that, process of chemical evolution  J.B.S Haldane described the sea containing can be divided into three steps. molecules of organic substances in abundance as ‘‘the hot dilute soup or primitive broth’’. • Origin of earth and primitive atmosphere:  When earth was broken from sun, it was a (i) Coacervates are: glowing fire and a rotating cloud of hot gasses, (a) colloidal aggregates (b) suspension vapours of various elements, pieces of rocks and metals called nebulous. (c) true solutions (d) particles  As the earth was moving away from sun, the temperature slowly decreased. (ii) Primitive earth’s atmosphere was:  This led to condensation of gases. (a) oxydising (b) reducing  The heavy elements (iron, nickel) sank to the (c) redox type (d) none of these centre and form solid core of earth. (iii) Coacervates were able to absorb and assimilate  Lightest elements (He, H, O, N, C) occupied atmosphere of the earth. (a) proteins (b) gases • Formation of ammonia, water and methane: (c) inorganic compounds (d) organic compounds  C o m p l e x m o l e c u l e s f o r m e d c o l l o i d a l (iv) Haldane coined the term aggregates in aqueous environment. It can absorb compounds made up of carbons. (a) rebiotic (b) prebiotic • Synthesis of simple organic compound: (c) postbiotic (d) probiotic  Formation of micromolecules. (v) Groups of monomers and ________ acquired lipid  When temperature of earth gradually cooled membranes and further developed into the first living down then the highly reactive free radicals cell condensed to form variety of saturated and unsaturated hydrocarbon. (a) trimers (b) colloide  H y d r o c a r b o n , a m m o n i a , w a t e r s h o w (c) polymers (d) none of these condensation, polymerization, reduction and oxidation. 2. The Miller-Urey experiment was an experiment that simulated the conditions though at the  This results into formation of various biologically active molecules like time to be present on the early Earth, and tested monosaccharides, amino acids, purines, for the occurrence of chemical origins of life. pyrimidines, fatty acids and glycerol etc. Specifically, the experiment tested Oparin and Haldane’s hypothesis that conditions on the  Oparin proposed that the proteinoids, nucleo primitive Earth favoured chemical reactions that proteins and other organic and inorganic molecules aggregated and precipitated in sea synthesized more complex organic compounds forming organized colloid aggregates called from simpler organic precursors. coacervates. • Tc(ChheHem4)ei,cxaaplmesrmwimeorneeinaatl(lNusesHae3ld)e,dwainandtseihdrye(daHrso2tgOeer)ni,le(mHae2rt)rh.aTayhnoeef  The coacervates were able to absorb and assimilate organic compounds from the glass flasks and flasks connected in a loop, with 180 Biology–12 one flask half-full of liquid water and another flask containing a pair of electrodes. The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water

vapour, and then the atmosphere was cooled • Two percent of the carbon had formed amino again so that the water could condense and acids that are used to make proteins in living trickle back into the first flask in a continuous cells. cycle. • Within a day, the mixture had turned pink in (i) Initially atoms could not combine with each other colour, and at the end of two weeks of continuous on the earth because it is operation, Miller and Urey observed that as much as 10–15% of the carbon within the system was (a) very cold (b) very hot now in the form of organic compounds. (c) full of dust and gas (d) none of these Tungsten electrode (ii) What combination of gases or elements was present Spark discharge on that time? Flask (a) H, O, N and C (b) H, O, He Gaseous mixture (c) H, C, Mg and He (d) H, Mg, N2 and He (CH4 + NH3 + H2 + H2O) Water out (iii) Which gas was very reactive and get combine with other element to form compounds Condenser Cold water in (a) Oxygen (b) Helium (c) Hydrogen (d) Nitrogen (iv) As temperature decreases steam condensed to (a) dry ice (b) vapour (c) ice (d) water (v) Which metal electrode was used by Miller and Urey (a) cadmium (b) Nichrome Aqueous medium (c) Tungsten (d) alloy containing organic Boiling water compounds Ans. 1. (i) (a) (ii) (b) Tap for (iii) (d) (iv) (b) withdrawing sample (v) (c) 2. (i) (b) (ii) (a) (iii) (c) (iv) (d) (v) (c) Diagrammatic representation qqq of Urey-Miller’s experiment Evolution  181

7 Human Health and Diseases Topics Covered 7.1 Health and Common Diseases 7.2 Immunity 7 .3 Acquired Immuno Deficiency Syndrome (AIDS) 7.4 Cancer 7.5 Drugs and Alcohol Abuse 7.6 Adolescene and Problems Related to Alcohol and Drug Abuse C hapter map HUMAN HEALTH AND DISEASES Health is affected by Infectious Non-Infectious (i) Genetic disorders (ii) infections (iii) life style Common Diseases in Human AIDS/HIV Cancer Causes by Pathogens • T-lymphocytes • Carcinogens Alcohol/Drug Abuse • Test: (i) ELISA • Benign Tumours • Opioids 1. Viral Diseases: Common Cold, • M alignant • Cannabinoids Dengue, Chikungunya (ii) Western blotting • Cocaine • Prevention and Tumours • Hallucinogens 2. B a c t e r i a l D i s e a s e s : T y p h o i d , • Test: CT, MRI, • Tobacco Pneumonia control • Addiction and Effects Biopsy • Prevention and control 3. P r o t o z o a n D i s e a s e s : M a l a r i a , Treatment: Amoebiasis • Surgery • Radiography 4. Fungal Diseases : Ringworm • Chemotherapy 5. Helminthic Diseases: Ascariasis, • Immunotherapy Filariasis/Elephantiasis Prevention and Control of Infectious Diseases Immunity Innate Acquired (i) Physical Barriers (i) Humoral/Antibody-Mediated (ii) Physiological Immunity Barriers (ii) Cell-Mediated Immunity (CMI) (iii) Cellular Barriers ( iv) Cytokine Barriers Vaccination and Immunisation Allergies Auto Immunity Lymphoid organs • L ymphoid organs (Primary, Secondary) • Bone Marrow • Thymus • Spleen • Lymph Nodes • MALT 182

Topic 1. Health and Common Diseases • Health is defined as the totality of physical, mental • Symptoms of pneumonia include fever, chills, cough, and social well being and not merely absence of headache and in severe cases, the lips and finger disease. nails may turn gray to bluish in colour. • Health can be affected due to: • Infection occurs through inhaling air-borne droplets from a cough or sneeze and also by sharing utensils, `` Defects in genes which are inheritable handkerchiefs, etc. `` Infectious agents or pathogens Other Bacterial Diseases `` Unhealthy life style. • Dysentery caused by Shigella • Proper diet, maintaining hygienic practices, regular • Plague caused by Yersinia pestis exercise, vaccination, proper disposal of wastes, control of vectors can help in maintaining health. • Diphtheria caused by Coryne bacterium diphtheriae • Diseases which are transmitted easily from one Viral Diseases person to another are called infectious diseases, e.g. common cold, influenza, AIDS, etc. Common cold • Diseases which are not transmitted from one person Caused by Rhino virus. to another are called non-infectious diseases, e.g. cancer, drug and alcohol abuse, etc. • It affects upper respiratory tract including nose and trachea • Disease-causing organisms are called pathogens and the diseases caused by them are called pathogenic • Symptoms of common cold are nasal congestion, diseases. nasal discharge, sore throat, cough, hoarseness, headache, tiredness and lasts for 3-7 days. • Common pathogens can be categorised into bacteria, virus, fungi, protozoans and helminths. • Infection occurs through droplets resulting from cough or sneezes of an infected person, either inhaled • The pathogens enter our body by various means, directly or transmitted through contaminated objects multiply and interfere with normal vital activities, such as pens, books, cups, door knobs, computer resulting in morphological and functional damage. keyboard or mouse, etc., and cause infection in a healthy person. • Pathogens have to adapt to life within the environment of the host. For example, the pathogens Dengue also called breakbone fever, caused by dengue that enter the gut must know a way of surviving in virus DEN-1, DEN-2, DEN-3, DEN-4 the stomach at low pH and resisting the various digestive enzymes. • This virus is transmitted by vector mosquito Aedes aegypti. Incubation period of this fever is 3-10 days. Bacterial Diseases • Dengue fever is classified into two types: Typhoid `` Classical Dengue fever mainly affects Caused by Salmonella typhi adolescents and adults. • Infection occurs through contaminated food and • Symptoms include sudden high fever with water. It affects parts of alimentary canal. characteristic skin rash, headache, pain behind the eyes, muscular and joint pain and • Symptoms of the disease are: weakness, gum bleeding, nausea and vomiting, `` High fever, weakness, headache, loss of appetite, gastrointestinal haemorrhage may occur. constipation, stomach pain, intestinal perforation and death in severe cases. `` Haemorrhagic fever mainly affects children under the age of 15. Adults can also suffer from • Typhoid is confirmed via Widal test haemorrhagic fever. • Mary Mallon nicknamed Typhoid Mary was a cook • Symptoms: Sudden high fever, plasma leakage, by profession and was a typhoid carrier. She was internal bleeding due to haemorrhage in blood responsible for spreading typhoid to families she vessels, decrease in blood platelet count, used to cook for. skin haemorrhage, very low blood pressure called dengue shock syndrome is a dangerous Pneumonia condition. Caused by Streptococcus pneumoniae and Haemophilus • Dengue can be diagnosed by detecting dengue influenzae. specific antibodies in patient serum via ELISA or PCR • Respiratory tract, especially alveoli of lungs, get filled with fluid which may be fatal if left untreated. Human Health and Diseases  183

• Treatment includes increase in fluid intake, • There is no specific treatment but use of non- controlling fever by using paracetamol. steroidal and anti-inflammatory drugs along with taking rest may reduce symptoms. Chikungunya caused by alpha virus ‘CHIKV’. Protozoan Diseases • Vector for this disease is mosquito Aedes aegypti and A. albopictus. Incubation period is 1-12 days. Malaria is caused by Plasmodium, vector of which is mosquito female Anopheles. • Symptoms are similar to dengue fever, characterized by severe joint pain (arthritis), high fever and rashes • There are three species of Plasmodium, P. vivax, on body. P. malariae, P. falciparum. P. falciparum causes malignant malaria hence is most dangerous. • Chikungunya is detected by PCR and other serological tests. • For completing its life cycle, the Plasmodium requires two hosts `` Mosquito (Primary Host) `` Human (Secondary host) When the mosquito bites another human, sporozoites are injected with bite Mature infective stages (sporozoites) Sporozoites Parasites escape from intestine and (sporozoites) migrate to the mosquito reach the liver salivary glands through blood Liver Salivary glands The parasite reproduces Fertilisation and Mosquito host asexually in liver cells, development take bursting the cell and place in the mosquito's releasing into the blood. intestine Human host Female mosquito Gametocytes Parasites reproduce asexually takes up gametocytes Female in red blood cells, bursting the with blood meal red blood cells and causing Male cycles of fever and other symptoms. Released parasites Sexual stages (gametocytes) infect new red blood cells. develop within red blood cells Stages in the life cycle of Plasmodium • Infection is caused by sporozoites of Plasmodium Amoebiasis/amoebic dysentery caused by which enters the human body through bite of female Entamoeba histolytica. This pathogen is transmitted Anopheles mosquito. via common housefly. • Sporozoites enter liver and multiply within the • The cysts are ingested by humans along with liver cells. Then they attack RBC which causes infected food, water or through direct contact with rupture of blood cells. Toxin haemozoin is released faecal matter. after rupturing of RBC. This toxin is responsible for • Symptoms include constipation, abdominal pain recurring chill and high fever. with cramps, stools with excessive mucous and • When a female Anopheles mosquito bites an infected blood clots. person, these parasites enter the mosquito’s body and undergo further development. Helminths Diseases • The parasites multiply within them to form Ascariasis caused by Ascaris sporozoites that are stored in their salivary • Infection is caused due to ingestion of eggs by a glands. When these mosquitoes bite a human, the sporozoites are introduced into human body and the person along with contaminated food, vegetables cycle continues. and water. These eggs are excreted along with faecal matter of infected person. 184 Biology–12

• Symptoms include internal bleeding, muscular pain, fever, anaemia and in severe cases intestinal passage is blocked. Eggs and worms released in environment along with faecal matter Eggs are ingested along with contaminated food Soil becomes contaminated with eggs Eggs get transferred to food with soil Spread of Ascariasis Elephantiasis/filariasis is caused by filarial worms • Diseases which are transmitted by contaminated Wuchereria bancrofti and W. malayi. This pathogen is food and water can be avoided by maintaining transmitted via female mosquitoes. personal and public hygiene such as keeping body clean, consuming clean food, water, fruits and • Symptoms: Due to accumulation of fluids in organs vegetables, proper disposal of waste and excreta, there is deformities in lower limbs and genital periodic disinfection of reservoirs. organs. • Diseases which are transmitted via direct contact Fungal Diseases can be prevented by avoiding contact with the infected persons or their belongings. Ringworm is a skin disease caused by Microsporum, Trichophyton, Epidermatophyton • Vector borne diseases can be controlled by eliminating vectors and their breeding places such as cleaning • Symptoms include appearance of dry, scaly lesions stagnant water in and around homes, regular on skin, nails and scalp with intense itching. Areas cleaning of household coolers, use of mosquito nets, such as groin, toes and other skin folds provide introducing fishes like Gambusia in ponds that congenial environment for fungus to grow in heat feed on mosquito larvae, spraying of insecticides in and moisture. ditches, drainage areas and swamps, etc. • Person gets infected by using infected articles like • Many infectious diseases like smallpox, polio, towels, clothes, comb and through soil. diphtheria, pneumonia and tetanus have been controlled by the use of vaccines. Measures to be adopted to avoid these diseases Topic 2. Immunity `` Physiological barrier: Acid in stomach, saliva in mouth, tears stops microbial growth. • The ability of a body to fight against disease causing organisms is called immunity. It is of two types: `` Cellular barriers: Leukocytes like PMNL – Poly Innate and acquired immunity. Morpho Nuclear Leukocytes, monocytes, natural killer cells and macrophages destroy microbes in Innate Immunity body by phagocytosis. • It is non-specific type of defence and is present at `` Cytokine barriers: Interferons are the proteins the time of birth. secreted by virus infected cells which protect non- infected cells to get infected by viruses. • It consists of four types of barriers `` Physical barriers: Skin, mucous lining of respiratory, gut and urogenital tract prevents entry of microbes in the body. Human Health and Diseases  185

Acquired Immunity • Different types of antibodies are produced in our body such as IgA, IgM, IgE, IgG • It is pathogen-specific type of defence system and is based on memory. • T-lymphocytes help B-cells to produce antibodies. • When body encounters a pathogen for first time, • They provide cell mediated immunity. the response produced is called primary response. It is of low intensity. Some immunity providing cells • They generate cell-mediated immune response. remain in the body as memory cells. It means, wherever they are required they go themselves and act against antigen. • Subsequent encounter with same pathogen gives intense response. This is called secondary response. • If there is an organ failure such as kidney, liver etc., This is due to the presence of memory cells. transplant is the only option. Before transplant, tissue matching and blood group matching is Difference between innate and acquired essential. This is because body can differentiate immunity: between self and non-self tissue and body rejects the transplanted organ as non-self tissue. Cell-mediated Innate immunity Acquired immunity immunity is responsible for this rejection. To avoid rejection, patient has to take immuno–suppressants • It is the first line of • It is the second line of for whole life. defence defence Active and Passive Immunity • This type of immunity is • This type of immunity is • If a person is exposed to antigens in the form of living or dead microbes or some other proteins, his present by birth acquired during the life body produces antibodies against antigens. Such type of immunity is called active immunity. It is • This is not pathogen • This is pathogen specific slow and takes time to respond. Example: chicken specific pox occurs only once in lifetime, vaccines in which inactive or attenuated microbes are injected in body • Response is immediate • Response takes few days (BCG, DPT) and body produces antibodies against the antigen. • Memory is absent • It is based on memory • When readymade antibodies are given directly to • Secondary response is of • Secondary response is protect against foreign agents, this is called passive immunity. The response against the pathogen is same intensity as intensified fast. Example is colostrum in which IgA is passed from mother to infant and antibodies like IgE is of first encounter with directly passed from mother to foetus through pathogen placenta. Tetanus injection or antitoxin against snake venom is also type of passive immunity. • Special type of lymphocytes which provide primary and secondary response are B-lymphocytes and T-lymphocytes. Antigen binding site Antigen binding site N Light chain Vaccination and Immunisation Heavy chain • Vaccination is a type of passive immunity and is based on the memory cells produced in body. CC • Vaccines are inactivated or weak pathogens or Structure of an Antibody Molecule antigenic protein preparation which are injected • B-lymphocytes produce special proteins called in body. antibodies in blood to fight with pathogens. Such • Body produces antibodies in response to injected type of response is called humoral response. material and produces memory cells. • Antibodies are special Y-shaped proteins with four peptide chains, of which two are smaller and are • If actual pathogen attacks the body, the memory called light chains and other two are longer called cells give aggravated response against pathogen and heavy chains. (H2L2). protects the person. • Hepatitis-B vaccine is produced from yeast by using recombinant DNA technology. Allergy • The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens. 186 Biology–12

• Antibody IgE is responsible for allergy. In primary lymphoid organs, like bone marrow • Common allergens are mites in dust, pollens, animal and thymus, immature lymphocytes differentiate into antigen-sensitive lymphocytes. dander. • Both bone-marrow and thymus provide micro- • Symptoms of allergy are unexplained running environments for the development and maturation nose, breathing difficulty or wheezing, sneezing, of T-lymphocytes watery eyes etc. In secondary lymphoid organs, spleen, lymph • Allergy is diagnosed by exposing patient to nodes, tonsils, Peyer’s patches of small intestine allergens. The cure for allergy is drugs like and appendix, the interaction of lymphocytes with antihistamines, adrenalin and steroids. antigen occurs and they proliferate to become effector cells. Auto Immunity • Sometimes due to unknown reasons, the immune • Spleen filters micro-organisms from blood and is reservoir of RBCs. system of a body attacks self-cells which cause damage to own body. This is called auto-immunity. • Small solid structures located at various points Example: Rheumatoid arthritis in lymphatic system are lymph nodes which traps micro-organisms or other antigens present in lymph. Immune System in the Body These antigens activate the lymphocytes and our • The human immune system consists of lymphoid immune system responds. organs, tissues, immunity providing cells and • 50% of the lymphoid tissues is present within lining soluble molecules like antibodies. of respiratory, digestive and urogenital tracts. This is called Mucosal Associated Lymphoid Tissue Lymphoid System: Organs where origin and/or (MALT) maturation and proliferation of lymphocytes occur. Topic 3. Acquired Immuno Deficiency Syndrome (AIDS) • This was first reported in 1981. needles and syringes, screening blood before transfusion and stringent monitoring in pregnant • Our immune system becomes non-functional during women. lifetime. • In our country the National AIDS Control • It is called syndrome because body shows group of Organisation (NACO) and other non-governmental symptoms of different diseases. organisation (NGOs) are doing a lot to educate people about AIDS replication of retrovirus in macrophage • Causal organism is Human Immuno Deficiency Virus (HIV). It is a retrovirus and its genetic Mode of Infection: material is RNA. `` Virus enters macrophage • The time period between infection and first appearance of symptoms may be from 5-10 years. `` Virus uses reverse transcriptase enzyme to produce viral DNA in the cell • AIDS is transmitted via unprotected sexual contact, using infected hypodermic needles, blood transfusion `` The viral DNA gets incorporated into host genome and from mother to unborn child via placenta. and DNA replicates and produces viral DNA • Risk of infection increases in the following cases: `` New viruses are produced within cells, thus Individual has multiple partners, drug addicts as macrophage acts as virus factory. they share hypodermic needles and repeated blood transfusion. `` pVriorduusceesntitesrsprhoeglepneyraTft-elrymdepshtroocyyintegsth(TeHh)elapnedr T-lymphocyte. • AIDS is diagnosed by Enzyme Linked Immuno- Sorbant Assay (ELISA). `` New virus again attacks helper T-lymphocytes and number of which ultimately decreases. • Anti-retroviral drugs are partially effective, only can prolong life but cannot prevent death. • The body starts showing symptoms of frequent fevers, diarrhea, and weight loss. Body gets infected Prevention of AIDS with various infectious diseases caused due to bacteria especially Mycobacterium, viruses, fungi • AIDS can be prevented by educating people about and even parasites like Toxoplasma. AIDS, regular medical checkups, using disposable Human Health and Diseases  187

Retrovirus Viral RNA core Viral protein coat Virus infects normal cell Plasma membrane Animal cell Viral RNA is introduced into cell Viral DNA Cytopla sm is produced by reverse Viral DNA incorporates transcriptase into host genome New viral RNA is produced by the infected cell New viruses DNA are produced Nucleus New viruses can infect other cells Replication of Retrovirus Topic 4. Cancer Cause of Cancer • Cancer is a disease in which cells divide continuously • Cancer causing agents are called carcinogens. and form masses of cells called tumour. Such cells lose the property of contact inhibition. Diagnosis • Contact inhibitions is the property of cells in • Cancer is detected by biopsy and histopathology, which cell division gets inhibited when they come radiography, X-rays, CT-scanning, MRI, in contact with other cells. immunological techniques and molecular diagnosis. • Tumours are of two types: • Treatment of cancer can be done by adopting one or combination of surgery, radiation, immunotherapy, `` Benign tumour remains confined to one place chemotherapy etc. and does not spread. • Cancerous cells are not detected by our own immune `` Cells of Malignant tumour grows rapidly, spread system so they are not destroyed. Patients are given through blood to other parts of body and become biological response modifiers such as a-interferons. neo-plastic, the new tumour develops at new place These drugs activate our immune system in such too. This property of cancerous cells to proliferate a way that cancer cells are detected and then to new areas is called metastasis. destroyed. • Tumour cells compete with normal cells by competing with them for nutrition. Normal cells starve and die. CARCINOGENS Ionising radiations Non-ionising Chemical Biological Genetic factors: like X-rays and radiations agents like agents like Cellular oncogenes gamma rays such as oncogenic or proto-oncogenes UV rays tobacco viruses under certain conditions 188 Biology–12

Topic 5. Drugs and Alcohol Abuse • Opoids, cannabinoids and coca alkaloids. Opoids: commonly called smack, heroine • The chemical di-acetyl morphine is obtained from latex of unripe fruits of Papaver sominiferum (Poppy Plant). It is white, odourless, bitter, crystalline compound. • Usually taken by snorting or injected hypodermally. • Opoids act as depressant and slow down body functions as they bind to opoid receptor in central nervous system (CNS) and gastrointestinal tract (GIT). CH3 O Leaves of Cannabis sativa N CH3 Coca alkaloid also known as cocaine is white to yellow-white powder which is obtained from the leaves O of coca plant Erythroxylum coca. H • It is a powerful nervous system stimulant and O acts on CNS, which produces sense of euphoria, increased energy and when used in excess causes HO hallucinations. Datura and Atropa belladonna also Chemical structure of morphine produce hallucinations. • Some medicines like barbiturates, amphetamines, Opium poppy benzodiazepines, LSD (Lysergic acid diethyl amides) are also abused and otherwise treat mental illness, Cannabinoids depression and insomnia. Similarly, morphine is a Cannabinoids commonly used as hashish, marijuana, sedative (which induces sleep) and pain killer which charas, ganja are obtained from inflorescence, flower is used for patients who have undergone surgery. It tops, leaves and resin of Cannabis sativa. is also abused by drug users. • Chemically it is tetrahydrocannabinol (THC) and • Nicotine is too a major type of drug addiction is amber or gold-coloured glassy solid when cold, mainly obtained from tobacco plant, Nicotiana viscous and sticky when warmed. tabacum. Tobacco is used by smoking, snorting • It is taken via inhalation and orally. and even chewing. • It shows its effect on cardiovascular system. • Nicotine stimulates adrenal gland, it secretes OH adrenaline and nor-adrenaline and increases blood pressure and heart rate. OH • Smoking and use of tobacco also increases the Skeletal structure of cannabinoid molecule chance of cancers of lung, throat, urinary bladder and mouth. Due to increase in the concentration of carbon-monoxide, the oxygen carrying capacity is reduced in blood. • Nicotine habit may also cause bronchitis, emphysema, coronary heart disease and gastric ulcers. • Statutory warning written on tobacco products is mandatory which says ‘smoking is injurious to health’. Now pictorial warnings are also present on tobacco products. Human Health and Diseases  189

Topic 6. Adolescence and Problems Related to Alcohol and Drug Abuse • The period between 12-18 years of age is adolescence interests in hobbies, change in sleeping and eating during which child undergoes changes in his attitude habits, fluctuations in weight, appetite, etc. and behaviour and also in biological, hormonal, structural and emotional attributes for active • With taking drugs intravenously, the risk of AIDS participation in society. These changes may lead and hepatitis-B increases. a child on wrong path like drug addiction, alcohol abuse etc. due to mental and psychological pressure. • When sports persons misuse the drugs and narcotics they show various side-effects. These effects are • Some of the reasons for drug and alcohol abuse different in male and females as given under. include curiosity, need for adventure, excitement and experimentation. Later, due stress of academics, `` In females there is increase of masculine to perform, impact of media, peer pressure, family features, mood swings, depression, aggressiveness, problems like unstable and unsupportive family may facial hair growth, abnormal menstrual cycle, also lead to alcohol and drug abuse. enlargement of clitoris, deepening of voice. • Child becomes addictive to alcohol and drugs `` In males, acne, aggressiveness, mood swings, because of the associated affects of euphoria and depression, reduction in size of testicles, temporary feeling of well-being. Tolerance level of premature baldness, decreased sperm production, body receptors increases with repeated use. Due to enlargement of prostate gland. this, receptors respond only to higher dose of drugs and alcohol. This leads to increased intake and • During pregnancy, use of alcohol and drugs shows addiction. adverse effects on developing foetus. Withdrawal Syndrome Prevention and Control • Body becomes dependent on drugs and if the intake • Avoid undue peer pressure: Child should not be of alcohol and drugs is stopped suddenly, the person forced to perform beyond his capacity in studies, shows unpleasant symptoms like anxiety, shakiness, sports or other activities. nausea, sweating etc. Such symptoms are called withdrawal symptoms. Body becomes normal again • Education and counselling: Child should after consuming alcohol or drugs. be taught to face problems and stress, accept disappointments and failure as a part of life. His Effects of Alcohol and Drug Abuse energy should be channelized by giving opportunities in sports, reading, music, yoga and co-curricular • Reckless behaviours, vandalism, violence are the activities. immediate adverse effects. • Seeking help from parents and peers: Parents • Excessive dose may lead to coma and respiratory and friends should be called immediately to guide failure, heart failure, cerebral hemorrhage, cirrhosis the child and for sorting out his/her problems in life. and in turn death. • Looking for danger signals: Parents, teachers • One can recognize the persons with drug addiction as and friends should remain alert if they see any their academic performance decreases, unexplained change in normal behaviour of child. Appropriate absence from school/college, lack of interest in measures should be taken. personal hygiene, withdrawal, isolation, depression, fatigue, aggressive and rebellious behavior, losing • Seeking professional and medical help: If problem is seen, the help of psychologists, psychiatrists and de-addiction and rehabilitation centres should be taken. EXERCISE I. Multiple Choice Questions 2. The organisms which cause diseases in plants 1. The term ‘Health’ is defined in many ways. The and animals are called: most accurate definition of the health would be: (a) Pathogens (b) Vectors (a) Health is the state of body and mind in a (c) Insects (d) Worms balanced condition (b) Health is the reflection of a smiling face 3. The chemical test that is used for diagnosis of (c) health is a state of complete physical, mental typhoid is: and social well-being (a) ELISA-Test (b) ESR-Test (d) Health is the symbol of economic prosperity. (c) PCR-Test (d) Widal-Test 190 Biology–12

4. The sporozoites that cause infection, when a (a) Auto-immune response female Anopheles mosquito bites a person, are (b) Humoral immune response formed in: (c) Physiological immune response (d) Cell-mediated immune response (a) Liver of the person (b) RBCs of mosquito II. Fill in the blanks (c) Salivary glands of mosquito 1. ____ is derived from the unripe capsules of white poppy. (d) Intestine of mosquito 5. The disease chikungunya is transmitted by: 2. All _____ are proteins but antigens are not. (a) House flies (b) Aedes mosquitoes 3. Plasma cells are descendants of ___. 4. The first antibiotic discovered was ____ . (c) Cockroach (d) Female Anopheles 6. Many diseases can be diagnosed by observing III. True or False the symptoms in the patient. Which group of symptoms are indicative of pneumonia? 1. CMIS releases antibodies. 2. The cells that actually release antibodies are (a) Difficulty in respiration, fever, chills, cough, headache plasma cells. (b) Constipation, abdominal pain, cramps, blood 3. Saliva contains ptyalin to kill the bacteria. clots 4. LSD is hallucinogen. (c) Nasal congestion and discharge, cough, 1 Mark Questions sorethroat, headache 1. What role do macrophages play in providing (d) High fever, weakness, stomach pain, loss of immunity to humans? [Delhi 2008] appetite and constipation 2. How do neutrophils act as a cellular barrier to 7. The genes causing cancer are: pathogen in humans?  [All India 2008] (a) Structural genes (b) Expressor genes 3. How do cytokine barriers help in evading viral infections? [Delhi 2015 C] (c) Oncogenes (d) Regulatory genes 8. In malignant tumors, the cells proliferate, grow 4. How does smoking tobacco in human lead to rapidly and move to other parts of the body to form oxygen deficiency in their body? [Delhi 2012] new tumors. This stage of disease is called: 5. Name the two intermediate hosts which the (a) Metagenesis (b) Metastasis human liver fluke depends on to complete its (c) Teratogenesis (d) Mitosis life cycle so as to facilitate parasitisation of its 9. When an apparently healthy person is diagnosed primary host.  [Delhi 2014] as unhealthy by a psychiatrist, the reason could be that: 6. Why is Gambusia introduced into drains and ponds?  [All India 2014] (a) The patient was not efficient at his work 7. How does haemozoin affect the human body when released in blood during malarial infection? (b) The patient was not economically prosperous  [Foreign 2014] (c) The patient shows behavioural and social 8. Malaria, typhoid, pneumonia and amoebiasis are maladjustment some of the human infectious diseases. Which (d) He does not take interest in sports one of these are transmitted through mechanical 10. AIDS is caused by HIV. Among the following, carriers?  [Foreign 2011] which one is not a mode of transmission of HIV? 9. Name any two techniques that serve the purpose (a) Transfusion of contaminated blood of early diagnosis of some bacterial/viral human (b) Sharing the infected needles diseases. [Foreign 2011] (c) Shaking hands with infected persons 10. How does malaria differ from Chikungunya with (d) Sexual contact with infected persons reference to their vectors? [Delhi 2010 C] 11. The substance produced by a cell in viral infection 11. Recently, Chikungunya cases were reported from that can protect other cells from further infection various parts of the country. Name the vector is: responsible.  [Delhi 2008] (a) Serotonin (b) Colostrum 12. What causes swelling of the lower limbs in (c) Interferon (d) Histamine patients suffering from filariasis?  [Delhi 2008] 12. Transplantation of tissues/organs to save 13. In what way is monocyte a cellular barrier with certain patients often fails due to rejection of reference to immunity?  [Delhi 2015 C] such tissues/organs by the patient. Which type of immune response is responsible for such 14. Why is colostrum a boon to the newborn baby? rejections?  [All India 2015 C] Human Health and Diseases  191

15. Name any two types of cells that act as ‘cellular 2 Marks Questions barriers to provide innate immunity in human.  [Delhi 2008] 35. Write the scientific names of causal organism of elephantiasis and ring worm in humans. Mention 16. Why is secondary immune response more intense the body parts affected by them.  [Delhi 2011] than the primary immune response in humans?  [All India 2014] 36. (a) Name the protozoan parasite that causes amoebic dysentery in humans. 17. What is an autoimmune disease? Give an (b) Mention two diagnostic symptoms of the example.  [Foreign 2014] disease. 18. When does a human body elicit an anamnestic (c) How is this disease transmitted to others? response?  [Delhi 2011 C, All India 2013]  [Delhi 2012] 19. State two different roles of spleen in the human 37. Name the two type of immune systems in a body.  [All India 2012] human body. Why are cell mediated and humoral 20. How do interferons protect us? [All India 2012] immunities so called?  [Delhi 2011] 21. What is it that prevents a child to suffer from a 38. Name the cells HIV (Human Immunodeficiency disease he/she is vaccinated against? Give one Virus) gains entry into after infecting the human body. Explain the events that occur in these cells reason.  [Delhi 2010]  [All India 2016] 22. How does colostrum provide initial protection 39. Differentiate between benign and malignant against diseases to new born infants? Give one tumours. [All India 2011] reason.  [Delhi 2009] 40. Name the plant source of the drug popularly 23. Some allergens trigger sneezing and wheezing in called “smack”. How does it affect the body of the human beings. What causes this type of response by abuser?  [Delhi 2012] the body? [Delhi 2009] 41. Why do sportspersons often fall a victim to 24. A boy ten years old had chicken-pox. He is not cocaine addiction?  [All India 2008] expected to have the same disease for the rest of 42. List the symptoms of ascariasis. How does a his life. Mention how it is possible. healthy person acquire this infection? [All India 2009] [All India 2012 C, 2014 ] 25. It was diagnosed by a specialist that the 43. A patient showed symptoms of sustained high immune system of the body of a patient has been fever, stomach pain and constipation, but no blood clot in stools. Name the disease and its suppressed. Name the disease the patient has pathogen. Write the diagnostic test for the disease. How does the disease get transmitted? been suffering from and its causative agent.  [Delhi 2013 C]  [Delhi 2007] 26. Retroviruses have no DNA. However, the DNA 44. Name the parasite that causes filariasis in of the infected host cell does possess viral DNA. humans. Mention its two diagnostic symptoms. How is this disease transmitted to others? How is it possible?  [All India 2015] 27. Why sharing of injection needles between two [Delhi 2012] individuals is not recommended?  [Delhi 2013] 28. How does HIV differ from a bacteriophage? 45. Explain what causes chill in humans during  [Delhi 2010 C] 29. What type of virus causes AIDS? Name its genetic malarial attack. Name the causative organism material.  [All India 2009] of malignant malaria.  [All India 2012 C] 30. Name the type of cells, the AIDS virus enters into 46. Name the causative organism, two symptoms and after getting in the human body.[All India 2009] mode of transmission of amoebiasis. 31. Name the two types of cells in which the HIV  [Delhi 2009, All India 2010, 2012 C] multiplies after getting entry into human body.  [All India 2008] 47. Name the causative organism, two symptoms and mode of transmission in ascariasis. 32. Indiscriminate diagnostic practices using X-rays [All India 2012 C] etc, should be avoided. Give one reason. 48. Name the causative organism, two symptoms and  [Delhi 2015] mode of transmission of ringworms. 33. Name two diseases whose spread can be [All India 2012 C] controlled by the eradication of Aedes mosquitoes.  [CBSE 2018] 49. Name the host and the site where the following occur in the life-cycle of a malarial parasite: 34. How do cytokine barriers provide innate (a) formation of gametocytes immunity in humans? [CBSE 2018] (b) fusion of gametocytes.  [Delhi 2010] 192 Biology–12

50. Define the term 'health'. Mention any two ways 63. Identify A, D, E and F in the diagram of an of maintaining it. [All India 2010] antibody molecule given below: 51. List the specific symptoms of typhoid. Name its A causative agent.  [All India 2009] B 52. List the specific symptoms of pneumonia. Name D-chain the causative organism.  [Foreign 2009] C 53. Name an allergen and write the response of the human body when exposed to it. [Delhi 2014 C] 54. Differentiate between active and passive F  [Delhi 2011] immunity.  [All India 2014 C] Bond/Bridge E-chain 55. A student on a school trip started sneezing and 64. State the functions of primary and secondary wheezing soon after reaching the hill station lymphoid organs in humans.  [Delhi 2011] for no explained reasons. But, on return to the plains, the symptoms disappeared. What is such 65. List the two types of immunity a human baby is a response called? How does the body produce it? born with. Explain the differences between the  [Delhi 2013] two types.  [All India 2011] 56. A young boy when brought a pet dog home started 66. What is colostrum? Why are breast-fed babies to complain of watery eyes and running nose. The likely to be healthy?  [Delhi 2011] symptoms disappeared when the boy was kept away from the pet. 67. Why does a doctor administer tetanus antitoxin and not a tetanus vaccine to a child injured in (a) Name the type of antibody and the chemicals a roadside accident with a bleeding wound? responsible for such a response in the boy. Explain.  [All India 2010] (b) Mention the name of any one drug that could 68. The barriers in the innate immunity are given in be given to the boy for immediate relief from the following table. Identify a, b, c, and d. such a response. [Delhi 2013] Type of barrier Barrier (i) Physical Skin, a 57. A student on a school picnic to a park on a windy (ii) Physiological b, in the eye day started sneezing and having difficulty in (iii) c Interferon breathing on reaching the park. The teacher (iv) Cellular WBC, d enquired whether the student was allergic to something. (a) What is an allergy?  [Delhi 2010 C] (b) Write the two unique characteristics of the 69. Name and explain the type of immunity that system involved in the response observed in is provided by injecting microbes deliberately the student.  [Delhi 2013] during immunisation into the human body. 58. How does a vaccine for a particular disease  [Delhi 2010 C] immunise the human body against that disease? 70. (a) How does a vaccine affect immunity?  [Delhi 2013 C] (b) How can we get immunised against tetanus?  [All India 2010 C] OR Write the events that take place when a vaccine 71. A for any disease is introduced into the human body. B 59. Why is a person with cuts and bruises following an accident administered tetanus antitoxin? Give reasons.  [All India 2013] 60. (a) Highlight the role of thymus as a lymphoid organ. (b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity.  [Delhi 2012] (a) What does the above diagram illustrate? 61. Name and explain the two types of immune (b) Name the labelled parts 'A' and 'B'. responses in humans.  [All India 2012] (c) Name the type of cells that produces this 62. Name the two types of immune systems in a molecule.  [Delhi 2009] human body. Why are cell mediated and humoral 72. (a) Name the lymphoid organ in humans where immunities so called?  [Delhi 2011] all the blood cells are produced. Human Health and Diseases  193

(b) Where do the lymphocytes produced by the 87. A boy developed some allergic reactions when he lymphoid organ mentioned above migrate and straight entered into his air conditioned room after a game of football outside his house. Write any two how do they affect immunity?  [All India 2009] symptoms that could be noticed in such condition. 73. What is colostrum? Why is it important to be How does our body combat such conditions? given to the newborn infants?  [Foreign 2009]  [CBSE 2022] 88. (a) (i) W rite the Scientific name of the plant from 74. How does spleen act as a lymphoid organ? where natural cannabinoids are obtained. Explain.  [Foreign 2009] (ii) Mention the parts of the plant that are used 75. Explain the response initiated when a dose of for extracting the drug. vaccine is introduced into the human body. (iii) How does the drug affect human body?  [Delhi 2009 C] OR 76. Name the type of immunity that is present at the time of birth in humans. Explain any two ways (b) Epithelial lining of our intestine is considered as secondary lymphoid organ. Justify the by which it is accomplished.  [All India 2008] statement.  [CBSE 2022] 77. Name and explain the type of barrier of innate 89. List four reasons to justify the ban on intake of immunity where some cells release interferons cannabinoids by sportspersons. when infected. [Delhi 2007]  [All India 2008 C] 78. (a) Name the group of viruses responsible for 90. Mention one application for each of the following: causing AIDS in humans. Why are these (a) Passive immunization viruses so named? (b) Antihistamine (b) List any two ways of transmission of HIV (c) Colostrum infection in humans, other than sexual (d) Cytokinin-barrier [All India 2017] contact.  [All India 2012] 91. Name the group of cells the HIV enters after 79. Name the cells that act as HIV factory in humans getting into the human body. What happens in when infected by HIV. Explain the events that these cells and what are these cells subsequently occur in the infected cell.  [All India 2009, 2010 C, 2012] referred to as? Name the next group of cells the 80. Why are the tumor cells dangerous?  [All India 2010] HIV attacks from here. [All India 2017] 81. Why do normal cells not show cancerous growth? 92. (a) Name the source plant of heroin drug. How is it obtained from the plant?  [All India 2010 C] 82. (a) Explain the property that prevents normal (b) Write the effects of heroin on the human body. cells from becoming cancerous.  [CBSE 2018] 3 Marks Questions (b) All normal cells have inherent charac-teristic 93. Name the bacterium that causes typhoid. of becoming cancerous. Explain. Mention two diagnostic symptoms. How is this disease transmitted to others?  [All India 2012]  [Foreign 2009] 83. What is 'withdrawal syndrome'? List any two 94. Mention any two human diseases caused by symptoms it is characterised by. [Foreign 2014] round worms. Name their causative agents and 84. Write the scientific name of the source plant of their mode of transmission into the human body. the drugs, marijuana and hashish and mention  [All India 2015 C] their effect on the human body.  [Delhi 2014 C] 95. Name the causative organism of the disease 85. Name the plant source of the drug popularly amoebiasis. List three symptoms of the disease. called smack. How does it affect the body of the  [Delhi 2016] abuser?  [Delhi 2012] 96. (a) Name the infective stage of Plas-modium 86. Identify A, B, C and D in the following table: which Anopheles mosquito takes in along with [Delhi 2012 C] the blood meal from an infected human. Scientific name of Drug Harmful effects/ (b) Why does the infection cause fever in humans? the source plant Human body (c) Give a flow chart of the part of the life-cycle of part affected this parasite passed in the insect. 1. Papaver som- A Depressant/slows  [All India 2008] niferum body function 97. Trace the life cycle of malarial parasite in human 2. Cannabis sativa Cannabi- B body when bitten by infected female Anopheles. noids  [All India 2012] 98. (a) State what happens in the human body when 3. Erythroxylum C D coca malarial parasites infected RBCs burst to release the parasites in the blood. 194 Biology–12

(b) Mention the specific sites in the host body (c) Name the disease against which this injection where production of was given and the kind of immunity it (i) Sporozoites and provides.  [All India 2015] (ii) Gametocytes take place in the life cycle of 106. How does the HIV break down the immune the malarial parasites. [Delhi 2015 C] system of the AIDS patient?  [Delhi 2015 C] 99. (a) Write the scientific names of the two species 107. Prior to a sports event, blood and urine samples of filarial worms causing filariasis. of sportspersons are collected for drug tests. (b) How do they affect the body of infected person(s)? (c) How does the disease spread?[All India 2011] (a) Why is there a need to conduct such tests? 100. Study a part of the life cycle of malarial parasite (b) Name the drugs the authorities usually look given below. Answer the questions that follow: for. B (c) Write the generic names of two plants from which these drugs are obtained.[Delhi 2016] A C 108. Name the plant source of ganja. How does it affect the body of the abuser? [All India 2012] 109. You have attended a birthday party hosted by one of your classmates. You found some guests at the party sitting in a corner making a lot of noise and consuming ‘something’. After a while one of the boys from the group started screaming, behaving abnormally and sweating profusely. On enquiry you found that the group members were taking drugs. (a) Mention the roles of ‘A’ in the life cycle of the (a) Would you inform your parents/school malarial parasite. authorities? Yes / No. Give reasons in support of your answer. (b) Name the event ‘C' and the organ where this (b) Prepare a note to be circulated amongst the event occurs. schoolmates about the sources and dangers of any two drugs. (c) Identify the organ ‘B’ and name the cells being released from it. [Delhi 2012] (c) Write any two ways that you will suggest to your school principal so as to promote 101. Trace the life-cycle of malarial parasite in the human body when bitten by an infected female awareness amongst the youth against the use Anopheles. [All India 2012] of these drugs. [Foreign 2015] 102. Give the scientific name of the parasite that 110. You have a friend whose parents are too causes malignant malaria in humans. At what indulgent in his/her daily affairs. They think him/her to be still young which makes him/her stage does this parasite enter the human body? sad and is upset all the time. As he/she feels that the parents should give him/her opportunity to Trace its life cycle in the human body. take independent decision on some issues.  [Delhi 2009] 103. Name the two special types of lymphocytes in (a) Would you support your friend and why? humans. How do they differ in their roles in (b) Write the characteristics of this age group. immune response?  [All India 2012] (c) List two curative measures. [Foreign 2016] 104. On a visit to a Hill station, one of your friend suddenly became unwell and felt uneasy. 111. Peer pressure plays a negative role in triggering (a) List two symptoms you would look for to term smoking habits in adolescents. As a school it to be due to allergy. captain list any two activities you would like to (b) Explain the response of the body to an allergen. (c) Name two drugs that can be recommended organize with the help of senior students of your for immediate relief.  [Foreign 2016] school and any other two activities you would 105. A heavily bleeding and bruised road accident like your school authorities to organize for the victim was brought to a nursing home. The doctor students to tackle this problem. Explain how immediately gave him an injection to protect him these activities will help in doing so. against a deadly disease.  [All India 2015 C] (a) Write what did the doctor inject into the 112. A team of students are preparing to participate in the interschool sports meet. During a practice patient's body . session you find some vials with labels of certain (b) How do you think this injection would protect the patient against the disease? cannabinoids. Human Health and Diseases  195

(a) Will you report to the authorities? Why? 122. (a) Name and explain giving reasons, the type of immunity provided to the newborn by the (b) Name of a plant from which such chemicals colostrum and vaccinations. are obtained. (b) Name the type of antibody (c) Write the effect of these chemicals on human (i) Present in colostrum body. [Delhi 2015] (ii) Produced in response to allergens in 113. At what stage is Plasmodium picked up by the human body.  [Foreign 2014] female Anopheles? Describe the life cycle of the 123. Why are lymph nodes and bone marrows called parasite in this insect.  [All India 2015 C] lymphoid organs? Explain the functions of each 114. At what stage does Plasmodium gain entry into one.  [Delhi 2012 C] the human body? Write the different stages of its 124. A life cycle in the human body.   [Delhi 2010, 2011, All India 2012, 2013 C, 2015 C] 115. (a) Name the causative organisms for the following diseases. (i) Elephantiasis (ii) Ringworm (iii) Amoebiasis (b) How can public hygiene help control such diseases?  [Delhi 2014 C] 116. (a) Name the respective forms in which the malarial parasite gains entry into (i) human body and (ii) body of female Anopheles. (b) Name the hosts where the sexual and the asexual reproductions of malarial parasite occur respectively. (c) Name the toxin responsible for the appearances (a) Identify the molecule shown and the site of symptoms of malaria in humans. Why do labelled 'A'. these symptoms occur periodically? (b) Why is this molecule referred to as H2L2?  [Delhi 2009] Explain.  [Delhi 2011 C] 117. (a) Why do the symptoms of malaria not appear 125. a immediately after the entry of sporozoites into the human body when bitten by female Anopheles? Explain. (b) Give the scientific name of the malarial parasite that causes malignant malaria in humans.  [All India 2009] 118. A person is suffering from ascariasis. Mention the pathogen causing the disease and an organ of the b body affected, three symptoms and one mode of c transmission of the disease.  [Delhi 2009 C] CC 119. (a) How and at what stage does Plas-modium Identify a, b and c in the schematic diagram of an enter into a human body? antibody given above and answer the questions. (b) With the help of a flow chart only show the (a) Write the chemical nature of an antibody. stages of asexual reproduction in the life-cycle (b) Name the cells that produce antibodies in of the parasite in the infected human. humans. (c) Mention the type of immune response (c) Why does the victim show symptoms of high fever?  [Delhi 2008] provided by an antibody.  [All India 2010] 126. (a) List any two situations when a medical doctor 120. Write the scientific name of the pathogen that causes Amoebiatic dysentery. Enumerate four would recommend injection of preformed antibodies into the body of a patient. Name symptoms of the disease. How is the disease this kind of immunisation and mention its advantages. transmitted? [All India 2008 C] 121. What is the functional difference between B-cells and T-cells?  [Delhi 2015 C] 196 Biology–12

(b) Name the kind of immunity attained when (b) Why are biological modifiers like α-interferon instead of antibodies, weakened antigens are required for cancer treatment? How do they introduced into the body. [Delhi 2008 C] act to treat the disease? [CBSE 2022] 127. Name the cells HIV attacks first when it gains 133. (a) Name a drug used (i) as an effective sedative entry into a human body. How does this virus and pain killer (ii) for helping patients to cope with mental illnesses like depression, but replicate further to cause immuno deficiency in often misused. the body?  [Delhi 2010, 2013 C] 128. 'A' HIV (b) How does the moderate and high dosage of cocaine affect the human body? [Foreign 2011] Plasma 134. Name a human disease, its causal organism, 'D' membrane symptoms (any three) and vector, spread by (Host cell) intake of water and food contaminated by human faecal matter. [All India 2017] OR 'B' (a) Why is there a fear amongst the guardians that their adolescent wards may get trapped New viral RNA is in drug/alcohol abuse? 'C' produced by the (b) Explain ‘addiction’ and ‘dependence’ in respect infected cell of drug/alcohol abuse in youth. New viruses DNA 135. A person in your colony has recently been are produced diagnosed with AIDS. People/residents in the colony want him to leave the colony for the fear Nucleus of spread of AIDS. 'E' New viruses can infect other cells (a) List the possible preventive measures that you would suggest to the residents of your locality Study the diagram showing replication of HIV in a meeting organised by you so that they in humans and answer the following questions understand the situation. accordingly. (b) Write the symptoms and the causative agent of AIDS. [All India 2013] (a) Write the chemical nature of the coat 'A'. (b) Name the enzyme 'B' acting on 'X' to produce 5 Marks Questions molecule 'C'. Name 'C'. 136. Under polio prevention programme, infants in (c) Mention the name of the host cell 'D' the HIV India were given polio vaccines on a large scale attacks first when it enters into the human at regular intervals to eradicate polio from the body. country. (d) Name the two different cells the new viruses 'E' (a) What is a vaccine? Explain how it imparts subsequently attack.  [All India 2011] immunity to the child against the disease? 129. (a) What makes some viruses cause cancer in (b) With the help of an example each, differentiate humans? between active and passive immunity. (b) How do benign tumors turn malignant? How  [Foreign 2015] does the latter harm the human body? 137. (a) It is generally observed that the children [All India 2013 C] who had suffered from chicken-pox in their childhood may not contact the same disease 130. Do you support dope test being conducted on in their adulthood. Explain giving reasons the sports persons participating in a prestigious basis of such an immunity in an individual. Name this kind of immunity. athletic meet? Give three reasons in support of your answer.  [All India 2014 C] (b) What are interferons? Mention their role.  [All India 2016] 131. 'Prevention is better than cure' is an apt slogan to safeguard adolescents from drug abuse. List 138. A youth in his twenties met with an accident and any six steps that could be taken in this regard. succumbed to the injuries. His parents agreed  [All India 2013 C] to donate his organs. List any two essential clinical steps to be undertaken before any organ 132. (a) Explain the property of contact inhibition transplant. Why is the transplant rejected and its effect on normal human cells and cancerous cells. Human Health and Diseases  197

sometimes? What views would you share with (b) Name the group of genes that have been identified in normal cells that could lead to your health club members to promote organ cancer. How do these genes cause cancer?  donation?  [Delhi 2015 C] (c) Name any two techniques that are useful in detecting cancer patients often given 139. Describe the asexual and sexual phases of life α-interferon as part of the treatment? cycle of Plasmodium that cause malaria in (d) Why are cancer patients often given α– humans.  [Delhi 2013] interferon as part of the treatment? 140. (a) Cancer is one of the most dreaded disease. [Delhi 2014] Explain 'contact inhibition' and 'metastasis' with respect to the disease. Answers I. Multiple Choice Questions 13. Monocytes are the cells which can phagocytise and destroy microbes. 1. (c) 2. (a) 3. (d) 4. (d) 5. (b) 6. (a) 7. (c) 8. (b) 9. (c) 10. (c) 14. Colostrum has antibodies IgA which protect newborn baby from deadly diseases by providing 11. (c) 12. (d) passive immunity. II. Fill in the Blanks 15. Polymorpho-nuclear leukocytes (PMNL- neutrophils), Monocytes. 1. opium 2. antibodies 16. It is because of memory cells in the body left after 3. B-lymphocytes 4. penicillin primary response against an antigen. III. True or False 17. Autoimmune is a disease in which body’s immune system attacks self cells e.g. Rheumatoid 1. False 2. True 3. False 4. True arthritis. 1 Mark Questions 18. Anamnestic response of body occurs when there is attack of a pathogen on the body for second 1. Macrophage initiate immune response. They time and immune system responds strongly. destroy antigens and microbes by phagocytosis and become antigen presenting cells. They 19. (i) Spleen acts as a filter of the blood by trapping activate T-cells and B-cells. blood-borne microorganisms 2. Neutrophils destroy pathogenic microbes by (ii) It also has a large reservoir of erythrocytes. phagocytosis. 20. Interferons protect non-infected cells from viral 3. Virus infected cells secrete proteins called infection. interferons, which protect noninfected cells from 21. The vaccines generate memory–B and T-cells further infection. that recognize the pathogen quickly when 4. Smoking increases carbon monoxide in the the pathogen attacks and provides secondary blood which has greater affinity to bind with response by producing large amount of antibodies haemoglobin so it does not allow oxygen to bind against that particular pathogen. with haemoglobin. Smoking also damages walls 22. Colostrum has antibodies IgA which protect of alveoli and decreases respiratory surface newborn baby from deadly diseases by providing causing emphysema. passive immunity. 23. Body produces IgE antibodies on exposure to 5. Snail and sheep. allergens and release of chemicals like histamine 6. Gambusia fish feeds on mosquito larvae so it is and serotonin from the mast cells. 24. First exposure of the body due to chickenpox used to control breeding of mosquitoes in ponds produces memory cells. This will help body to and drains. protect against this disease by giving secondary response which is stronger. So the boy will not 7. Haemozoin is a toxin released in blood which suffer from chicken pox again in his lifetime. causes high fever. 25. Patient is suffering from AIDS and the causative agent is a retrovirus HIV. 8. Typhoid, pneumonia and amoebiasis are 26. It is possible due to reverse transcriptase transmitted through mechanical carriers. enzyme which makes DNA from RNA by reverse transcription. 9. ELISA and PCR 27. Sharing of needles can transmit diseases like 10. Malaria is transmitted via female Anopheles HIV, AIDS, Hepatitis–B from infected to non- infected individuals. and Chikungunya virus is transmitted through female Aedes mosquito. 11. Female Aedes mosquito 12. Due to blockage of lymph vessels, lymph accumulates in the lower limbs in patients suffering from filariasis. 198 Biology–12

28. HIV infects eukaryotic cells and has RNA as 40. Smack is obtained from Papaver somniferum or genetic material whereas Bacteriophage infects poppy plant. It acts as depressant and slows down bacteria and has DNA as genetic material. body functions. 29. HIV causes AIDS. Its genetic material is RNA. 41. Because cocaine acts as stimulant and enhances 30. Macrophages and Helper T-lymphocytes the performance of sports person by increasing 31. Refer answer no. 30. muscle strength, stamina and aggressiveness. 32. Indiscriminate diagnostic practices may cause 42. Symptoms include constipation, abdominal pain cancer. with cramps, stools with excessive mucous and 33. Diseases whose spread can be controlled by blood clots. Person acquires this infection via infected food, water or through direct contact eradication of Aedes mosquito are: with faecal matter. Dengue Chikungunya 43. Patient is suffering from typhoid. Pathogen is 34. Cytokine barriers provide innate immunity by Salmonella typhi. Diagnostic test is Widal test. Disease is transmitted through contaminated protecting non-infected cells from viral infection food and water. by secreting interferon. 44. Wuchereria bancrofti and W. malayi. Gross 2 Marks Questions deformities in lower limbs, genital regions etc. The transmission occurs though female 35. Casual organism for elephantiasis is Wuchereria mosquitoes. bacrofti and for ringworm is Microsporum, Trichophyton, 45. Chills are caused due to toxin haemozoin released in blood when RBCs are ruptured. Plasmodium Epidermatophyton. falciparum causes malignant malaria. Organs affected in elephantiasis are lower limbs, 46. Causative organism: Entamoeba histolytica scrotum and that with ring worms is skin. Symptoms: constipation, abdominal pain with 36. (a) Entamoeba histolytica cramps, stools with excessive mucous and blood (b) Constipation, abdominal pain , stools with clots. mucus and blood clot. Mode of transmission: infected food, water or through direct contact with faecal matter. (c) Contaminated food and water 47. Causative organism: Ascaris 37. Two types of immune system in our body are: Symptoms: internal bleeding, muscular pain, Active and passive immunity or innate or fever, anaemia and in severe cases intestinal acquired immunity or cell mediated and humoral passage is blocked immunity and Cell mediated immunity is so called because the T-lymphocytes kill the Mode of transmission: infected food, water. antigens. 48. Causative organism: Microsporum, Trichophyton Humoral immunity is so called because antibodies and Epidermophyton Symptoms: dry, scaly produced by B-lymphocytes attack and destroy lesions on various parts of the body such as skin, antigens present in blood. nails and scalp. 38. Cells are macrophages and Helper T-lymphocytes. Mode of transmission: acquired from soil or Viral RNA forms DNA by reverse transcription by using towels, clothes or comb of infected (reverse transcriptase) → directs the infected cells individuals to produce viral particles → new virus particles destroy macrophages and helper T-lymphocytes 49. (a) Host: human being, → New virus again attacks macrophages and site: RBC; helper T-lymphocytes and number of which ultimately decreases. (b) Host: mosquito, site: gut of mosquito. 39. Benign tumour Malignant 50. Health is defined as a state of complete physical, tumour mental and social well-being. Health can be maintained by balanced diet, personal hygiene (i) This type of tumour I t i s c a n c e r o u s and regular exercise. is non cancerous. tumour. 51. Symptoms include high fever, weakness, (ii) It does not show Metastasis occurs headache, loss of appetite, constipation, stomach m e t a s t a s i s a n d and cancer spreads pain, intestinal perforation. Causal organism is Salmonella typhi. remains confined to other parts of the 52. Symptoms include fever, chills, cough, headache. to one place. body. Causal organisms are Streptococcus pneumoniae (iii) C a u s e s l i m i t e d C a u s e s s e v e r e and Haemophilus influenzae damage. damage to internal organs. Human Health and Diseases  199