BIOLOGY 2016.pdf 1

23. K.C.S.E2010 PP1 No.30 What is meant by the apical dominance (3 marks)  The inhibition of growth of lateral buds; by auxins; produced by the growing apical bud. 24. K.C.S.E2011 PP1 No.29 State four reasons why water is significant in seed germination  Activate enzyme; provide a medium for enzymatic activities (to break down stored foods to soluble form);  Hydrolyses; dissolves food materials; a medium of transportation of dissolved food substances / Oxygen/ nutrients of growing region (of redicle and plumule);  soften seed coat to facilitate emergence of radical 25. K.C.S.E 2011 PP2 No.6 (a) An experiment was carried out to investigate the population of a certain micro-organism. Two -Petri-dishes were used. Into the petri- dish labeled m, 60cm3of a culture medium was placed while 30cm3 of the same culture medium was placed in petri-dish labeled N. Equal numbers of the micro- organisms were introduced in both petri- dishes. The set-ups were then incubated at 350c. The number of micro-organisms in each petri-dish was determined at irregular intervals for a period of 60 hours. The results were as shown in the table below. Relative M 40 40 180 280 1200 1720 1600 1840 1560 600 number of 40 40 120 200 680 560 560 600 600 400 N micro- 0 5 10 15 23 30 35 42 45 60 organisms Time in hours 201

(i)On the same axes, draw the graphs of relative number of micro- organisms against time on the grid provided. ( 7 marks) (ii)After how many hours was the difference between the two populations greatest? (1 mark)  42 Hrs (iii) Work out the difference the two populations at 50 hours (2 marks) Graph mat 50 hrs = 1240 Graph N = 547 1240 = 547, = 693+4 M:1220- 20 = 1200 – 1240 N: 540 - 20 = 520 – 56 Ans = 680-40 = 640 – 720 (iv) With a reason state the effect on the population of micro- organisms in petri-dish M if the temperature was raised to 600c after 20 hours (2marks)  Pop growth decreases/reduces, high temp kill the main organism/ denatures enzymes (v)Account for the shape of the curve for population in petri-dish N between 46hours and 59 hours. (3marks)  Pop (growth rate) decreases, death rate is higher than rate of multiplication, due to exhaustion of nutrients (in the culture medium), accumulation of toxic wastes, and shortage of O2, overcrowding /shortage of space. 202

26. K.C.S.E2012 PP1 No.20 State three aspects that can be used to estimate growth in seedlings. (3 marks)  Dry mass/ mass/ weight/ height/ length;  Surface area;  Reject Biomass; 27. K.C.S.E2012 PP1 No.25 State the role of the following hormones in the life cycle of insects: (2 marks)  Ecdysone causes metamorphosis/ causes moulting/ ecdysis;  Juvenile hormone; Maintains larval characteristics/ formation of larval cuticle/ inhibits metamorphosis/ inhibits moulting/ ecrlysis; 28. KCSE 2013 PP1 NO 19 State three factors in seeds that cause dormancy. (3mks)  Immature embryo hard seed coat testa  Presence of growth inhibitors eg. Abscisic acid  Lack of factors that enhance germination, i.e. water optimum temperature and oxygen/ air. 29. KCSE 2013 PP1 NO 27.(a) State two differences between complete and incomplete metamorphosis (2mks) Complete metamorphosis Incomplete metamorphosis (a)Organisms goes through four (a)Organism goes through three distinct stages. distinct stages. (b)Laval and pupal does not (b)Nymph show resemblance resemble the adult with the adult. 30. K.C.S.E PP2 2013 NO 6 A scientist carried out an investigation to find out population growth of mice under laboratory conditions .Twenty young mice were placed in a cage. The results obtained from the investigation were as shown in the table below. Time in 0 2 4 6 7 10 12 16 18 months Number 20 20 65 155 310 455 450 145 160 of mice  (a)On the grid provided, draw a graph of the number of mice against time (6mks) 203

 (b) Account for the changes in mice population between. (i)0 to 2months (2mks)  The mice have not reached reproductive maturity thus the rate of population growth is still constant. (ii)2 to 6 months (2mks)  The mice have adapted to the environment; the rate of population growth increases gradually (iii) 6to 10months (2mks)  The population increased rapidly; all mice have reached reproductive maturity and resources all also available in plenty. (iv) 10 to 12 months (2mks)  Growth of population is stunted or constant; organisms are too old and cannot reproduce; rate of death is equal to rate of birth. (c) (i)Between which two months was the population change greatest (1mk)  Between months 6 and 7 204

(ii)Calculate the rate of change over the period in (c) (i) above. (2mks)  Population growth rate = ∆S x 100 Initial = 310-115 x 100 115 = 195 x 100 115 = 169.56% (d)What change in population would be expected if the investigation was continued to the 19th Month?(1mk)  Population would continue fluctuating.  (e)To obtain the observed results state two variables that were kept constant during the investigation (2mks)  Amount of food supplied Size of the cage/ space. 31. K.C.S.E.2014 PP1 No.2 a) What is meant by the term seed dormancy? (1 mark)  A period ( of rest) in which a seed performs to physiological processes slowly and utilizes little food) (b. State three causes of seed dormancy. (3 mark)  Chemical / growth / germination inhibitors;  Hard / impermeable seed coat;  Long / freezing temperatures; rej unfavorable temperature  Under developed / immature embryo, rej premature / undeveloped embryo  Low concentration of hormones / enzymes. 32. K.C.S.E.2014 PP1 No.6 State three roles of auxins in a plant stem. (3 mark)  Cell division  Cell elongation  Development of adventitious roots  Causes apical dominance  Causes tropic responses 205

33. K.C.S.E.2015 PP1 No.18 The diagram below shows an experimental set-up to investigate the conditions necessary for germination. Test tube P was placed in a refrigerator while Q was left at room temperature. The set-ups were observed regularly for two weeks but no germination occurred.  Explain the observations in P and Q. P (2 marks) Q (3 marks) 34. K.C.S.E.2014 PP1 No.19 (a)Using the axes provided below, sketch a curve to illustrate the growth pattern observed in the phylum arthropoda. (2 marks)  (b) Explain the growth pattern observed observed in arthropods. (3marks) 206

FORM IV 13. GENETICS Specific Objectives - Concepts of genetics - Variation within plant and animal species - Review of chromosomes - Brief mention of genes and DNA (without details of the molecular structure of genes and DNA) - First law of heredity - Mendel’s experiments - monohybrid inheritance (3:1 ratio) - Complete and incomplete dominance, backcross/testcross - Inheritance of ABO blood groups and Rh factor - Sex determination in humans - Linkage - Sex linked genes, sex linked characteristics e.g. Colour blindness, Haemophilia, Hairy ears and Nose - Mutations - Types of mutations - Causes and consequences of chromosomal mutations - Gene mutations(only cover the following examples of genetic disorders: Albinism, Sickle cell Anaemia, Haemophilia, Colour blindness) - Practical applications of genetics - Blood transfusion - Plant and animal breeding using artificial selection - Genetic counselling - Genetic engineering - Practical Activities - Measure and record heights of class members and plot the data on graphs - Demonstrate chromosome behaviour in mitosis and meiosis by using clay / plasticine / insulated coloured wires/coloured thread - Carry out investigations on finger prints and tongue rolling By the end of the topic, the learner should be able to: a) distinguish between continuous and discontinuous variations b) describe the structure and properties of chromosomes c) state the first law of inheritance and describe Mendel’s work d) construct and use punnet square/checker board e) distinguish between F1 and F2 generations, genotype and phenotype, haploidy and diploidy, homozygosity and heterozygosity, dominance and recessiveness, linkage and sex linkage, mutations and mutagens f) predict and explain the inheritance of the ABO blood groups and Rhesus (Rh) factor 207

g) state examples of genetically inherited disorders h) explain causes of chromosomal mutations i) explain the practical application of genetics. 208

1. K.C.S.E1996 PP1 No.1 State the function of Deoxyribonucleic acid (DNA) molecule (1mk)  Controls/regulates/enzymes/ synthesis is the material for inheritance 2. K.C.S.E1996 PP1 No.18 In an experiment black mice were crossed and the offspring were back and brown. The gene for black color is dominant over that of brown color. Using letter B to represent the gene for black color and b to represent the gene for brown color (a) Work out the genotypes of the F1 generation (4 marks)  Parents genotype Bb x Bb  Gametes Bb Bb  F1 generation BB Bb Bb bb (b) What is the phenotype ration of the spring (1 mark) 3 black : 1 brown 3. K.C.S.E1997 PP1 No.16 In a breeding experiment, plants with red flowers were crossed. The produced 123 plants with red flowers and 41 with white flowers (a) Identify the recessive character  White Give a reason  Fewer numbers/ lower ratio; lower in numbers/ absence of white in parents and absence in offspring. (b)What was the genotype of the parent plants that gave rise to the plants with red and white flowers?  Heterozygous Rr. Accept appropriate letters  Rejects R.w appropriate/ letters (o-dominance)  (c) If the white flowers were selfed, what would be the genotypes of their offspring?  Double recessive/rr/homozygous (recessive) 209

4. K.C.S.E1998 PP1 No.12 In a family with four children, three were found to have normal skin pigmentation while one was an albino. Using letter A to represent gene for normal skin pigmentation and a to represent the gene for albinism a) What are the genotypes of the parents?  Aa, Aa, Acc, both are Aa b) Work out the genotype of (i) Normal pigmentation  Normal children AA, Aa, (ii) The albino child  Albino child aa (c)What is the probability that the fifth child will be an albino?  25% ¼ 5. K.C.S.E1999 PP1 No.7 An investigation plants with red flowers were crossed with plants with white flowers. All the plants in the F1 generation had pink flowers. a) Give a reason for the appearance of pink flowers in the F1 generation.  Co dominance. Acc; partial/incomplete/equal b) If the plants the F1 generation were selfed, state the phenotypic ratio of the F2 generation.  1 red flower  2 pink flowers  1 white flower Acc 1:2:1 6. K.C.S.E.2000 PP1 No.11 The chart below represents the result of successive crosses, staring with red- flowered plants and white flowed plants and in which both plants are pure breeding.  Parental genotypes: Red flowers x white flowers  First fillial generation  Selfed  Second final generation 210  3 red flowers: 1 white flower o 3: 1

a) What were parental genotypes? Use letter R to represent the gene for red color and r for white color  RR and rr (i) What was the color of the flowers in the first filial generation?  Red (ii) Give a reason for your answer in b (i) above  Complete dominant; i.e Rd dominant/ white recessive b) If 480 red flowered plants were obtained in the second filial generation, how many F2 plants and white flowers? Show your working.  Ratio of filial generation: 3: 1  (i.e. in every 4 flowers 3 are red 1 is white  Therefore 480 red flowers means ¾ of the total number  Total number of flowers 480 x 4 = 640 o3  So ¼ of 640 flowers are white in F2 plants  ¼ x 640 = 160 flowers 7. K.C.S.E2001 PP1 No.9 Name three types of chromosomal mutations  Inversion duplication, deletion, translocation, non- disjunction 8. K.C.S.E2001 PP1 No.14 Tallness in pea plants is due to a dominant gene. Two tall pea plants were crossed and their F1 generation was in the ratio of 3 tall: 1 short. Using letter T to represents the gene for tallness and t for shortness give the a) (i) Genotype of the parents  Tt, Tt (ii) Gamete of the parents  Tt and Tt (iii) Genotype ratio of the F1 generation  1TT; 2Tt; 1tt/ 1 tall homozygous; 2 tall heterozygous o short homozygous 1:2:1 b) What is meant by the term testcross in genetic studies?  Crossing a homozygous recessive organism with an organism which shows dominant characteristics. 211

9. K.C.S.E2002 PP1 No.5 State two characters that researchers select in breeding programme  High yielding / hybrid vigor / heterosis; resistance to disease early maturity.  Resistance to drought / salinity. 10. K.C.S.E2002 PP1 No.11 Give an example of a sex – linked trait in humans on: Y CHROMOSOME  Tuft and hair sprouting from pinna / baldness; hairy pinna; X CHROMOSOME  Colour blindness / haemophilia. 11. K.C.S.E2003 PP1 No.12 a) What is meant by the term sex – linkage?  Genes are located on the sex chromosomes; they are transmitted along with those determining sex. b) Name two sex – linked traits in humans.  Colour blindness  Hair ears / pinna  Haemophila  Baldness c) In Drosophila Melanogaster, the inheritance of eye colour is sex – linked. The gene of red eye is dominant. A cross was made between a homozygous red – eyed female and a white – eyed male. Work out the phenotypic ration of F1 generation. (Use R to represent the gene for red eyes). 212

12. K.C.S.E2004 PP1 No.12 Across between a red flowered plant and white flowered produced plants with pink flowers. Using letter R to represent the gene for red colour, and W for white colour a)What were the parental genotypes? (1mks)  RR WW b) Workout a cross between F1 plants (4mks) o (1mk) c) Give the i) Phenotypic ratio of F2 plants 1 2 1 ii) Genotypic ratio of F2 plants (1mk)  2RW; 1WW (d)Name a characteristic in humans, which is controlled through a multiple genes?  (ABO) blood grouping; blood groups; reject Rh factor 13. K.C.S.E2005 PP1 No.12 In a garden with plants of same species, 705 plants had red flowers while 224 had white flowers. a)Work out the ratio of red to white flowered plants (1mk)  3:1 213

b) (i)Using letter R to represent the dominant gene, work out a cross between F1 offspring and a white flowered plant.(4mks) (ii)What is the genotypic ratio from the cross in b (i) above (1mk)  Genotypic → 2 Rr : 2 r r c) What is meant by the term allele? (1mk)  A pair of Genes that control given characteristics 14. K.C.S.E2006 PP2 No.2 a) Name two disorders in human caused by gene mutation. (2mks)  Albinism; sickle cell anemia; Haemophilia; colour blindness b) Describe the following chromosomal mutations. (2mks) (i). Inversion  Occurs when chromatids/ chromosomes break at 2 places and when rejoining the Middle piece rotates and joins in an inverted position. (ii) Translocation.  Occurs when a section of chromatid break off and becomes attached to another chromatid of another chromosome. 214

c) In mice the allele for black fur is dominant to the allele for brown fur. What percentage offspring would have brown fur form across between heterozygous black mice? Show your working. Use letter B to represent the allele for black colour. (4mks) 15. K.C.S.E2007 PP1 No.20 a) What is meant by the term allele? ( 1 mark)  It is an alternative form of a chromosome, similar in structure but may have different composition (b) Explain how the following occur during gene mutation: (i) Deletion (1 mark)  Occurs when some nucleotides of a part of a gene break off and disappear (ii) Inversion (1 mark)  Occurs when the nucleotides of a part of gene become inverted by taking a 1800 turn. (c)What is a test- cross? (1 mark)  Testing the genotype of an individual by crossing with the recessive trait 16. K.C.S.E2007 PP2 No.5 In maize the gene for purple colour is dominant to the gene for white colour. A pure breeding maize plant with purple grains was crossed with a heterozygous plant. (a) (i)Using letter G to represent the gene for purple colour, work out the genotype ratio of the offspring ( 5 marks) 215

(i)Phenotype purple grains Purple grains  (ii) State the phenotype of the offspring (1 mark)  All purple coloured grained maize plants (b)What is genetic engineering? (1 mark)  It is the scientific modification of the genetic composition of an organism to obtain specific characteristics (c)What is meant by hybrid vigour? (1 mark)  It is when best characteristics are developed from both parents and offspring better than either parent. 17. K.C.S.E2008 PP1 No.6 (a)What is meant by non- disjunction? (1 mark)  Failure of homologous same to separate during meiosis/ prophase I  Failure of sister chromosomes to separate during meiosis Prophase II (b)Give two examples of continuous variation in humans (2 marks)  Height/ skin colour/ weight 18. K.C.S.E 2008 PP2 No.2 A pea plant with round seeds was crossed with a pea plant that had wrinkled seeds the gene for round seeds is dominant over that for wrinkled seeds. Using letter R to represent the dominant gene state: (a)The genotype of parents if plant with round seed was heterozygous (2 marks)  Round seed plants  Wrinkled seed plants (b) The gametes produced by the round and wrinkled seed parents  Round seed parents  R and r  r and r / both r / r accept of the gamete are circled 216

(c The genotype and phenotype of F1 generation. Show your working (3 marks)  (d)What is a test – cross? (1 mark)  Cross between individuals of unknown genotype with a homozygous receive individual/ organisms  Cross both an individual showing a character for dominant gene with a homozygone recessive individual/organism 19. K.C.S.E2009 PP1 No.5 a) What is meant by the following terms (i) Hybrid vigour (1 mark)  Production of plants and animals that have superior/ greater productivity/ have beneficial/ characteristics than either of their parents. (ii) Polyploidy? (1 mark)  Condition in which an individual has more than two sets of chromosomes (b) State two causes of chromosomal mutations (2 marks)  Radiations such as alpha, gamma, beta UV and X- rays least one (Rej: symbols α, β and increases in temperature)  Chemicals such as calchicine, phenols, bromate, pesticides. At least one  Heavy metals e.g. lead mercury. Rej symbols  Viruses such as Papilloma. Rej: mustard gas- affects gene mutation  Rej: cosmic rays as mutageous on chromosomes 20. K.C.S.E 2009 PP2 No.1 When the offspring of purple and white flowered pea plants were crossed, they produced purple and white flowered plants in the ratio of 3: 1. Using letter H to represent the gene for purple colour (a) State the genotype of: (i) Parents (2 marks)  HH; and hh; 217

(ii) F1 Generation (1 mark)  Hh (b)Work out the cross between plants in the F1 generation (4 marks) o (c) Account for the colour the flowers in plants of the F1 generation (1 mark)  The RJ if namation on the left is wrong if give the gene for purple colour is dominant/ gene for white colour is recessive; 21. K.C.S.E2010 PP1 No.10 State two advantages of hybrid vigour. (2marks)  Resistance to pests/disease/adverse weather condition  Increase yield  Earlier maturity/early maturity Sclereids  Stomata on upper epidermis/absence of stomata in lower epidermis  Absence of cuticles  Poorly developed vascular bundles 22. K.C.S.E2010 PP1 No.27 What is meant by the term non-disjunction? (1 mark)  Failure of homologous chromosomes to segregate during meiosis/ anaphase I/ meiosis I  Failure of sister chromatid to segregate during meiosis/ anaphase II / meiosis II. (a) Give an example of a genetic disorder caused by: (i)Non-disjuction; (1 mark)  Down’s syndrome; Turner’s syndrome; Klinefelter’s syndrome  Surnerz syndrome  Acc. Mongolism for Doran’s syndrome 218

(ii) Gene mutation (1 mark)  Albinism; single cell anaemia; heamophilia; colour blindness  Chondrodytrophic dwarfism/ Achondroplasia 23. K.C.S.E2010 PP2 No.5 When pure breeding black guinea pigs were crossed with pure breeding white guinea pigs, the offsring had a coat with black and white patches. (a)Using letter G to represent the gene for black coat colour and letter H for white coat colour, work out the genotypic ratio of F2. b) State the phenotypic ratio of F2. (1 mark)  Black: Black & white: White = 1: 2: 1 c) i) Name the term used when two alleles in heterozygous state are fully expressed phenotyically in an organism. (1 mark)  Codominance; (Rej: incomplete dominance, partial dominance, equal dominance, blending inheritance. ii) Give an example of a trait in human beings where the condition whose term is named in (c) (i) above expresses itself. (1 mark)  ABO blood group inheritance. Acc. Blood group(Rej; Rhesus factor sickle cells trait. 219

24. K.C.S.E2011 PP1 No.24 a) Difference between the following terms: (i) Dominant gene and recessive gene;  Dominant gene expresses itself in both its homozygous and heterozygous state whole recessive gene can only express itself in the homozygous state. (ii) Continuous variation and discontinuous variation  Continuous variation is a characteristic for which there is continuum or range while discontinuous variation is a characteristic for which there are discrete/ distinct/ separate/ definite categories or units; (b) What would be the expected results from a test cross?  Either) all offsprings show dominant characteristics; or half offsprings show the recessive while the other halve show dominant characteristics. 25. K.C.S.E2011 PP2 No.2 In humans, hairy ears are controlled by a gene on the Y Chromosomes. (a)Using letter YH to represents the chromosome carrying the gene for hairy ears, work out a cross between a hairy eared man and his wife. (4 marks) o (b) (i) What is the probability of the girls having hairly ears? (1 mark)  Zero/o/nil acc 0/2; rej 0/4=0 (ii)Give reason for your answer in (b (i) above. (1mark)  The gene for heavy ears is on Y chromosome which girls do not inherit from fathers OWTTE Muscular destrophy c) Name two disorders in humans that are determined by sex linked genes (2marks)  Haemophilia;  Colour blindness;  Premature baldness;  Muscular dystrophy; 220

26. K.C.S.E2012 PP1 No.8 What is the probability of a couple with blood group AB getting a child with blood group AB? Show your working. (4 marks)  Probability is 1/2 or 0.5/ 50% Reject probability if not simplified using a punet square; 27. K.C.S.E2012 PP2 No.1 In a certain plant species which is normally green, a recessive gene for colour (n) causes the plants to be white in colour. Such plants die at an early age. In the heterozygous state, the plants are pale green in colour but grow to maturity. (a) Give a reason for the early death of the plants with the homozygous recessive gene. (2 marks)  Lack of chlorophyll the plants do not manufacture food/ photosynthesise; plants die as soon as stored food reserves get depleted. (b) If a normal green plant was crossed with the pale green plant, what would be the genotype of the first filial generation (F generation)? Show your working. (4 marks) 221

(c) If heterozygous plants were self-pollinated and the resulting seeds planted, work out the proportion of their offspring that would grow to maturity. (2 marks) 28. KCSE 2013 PP1 26.(a) (1mk) What is meant by the term sex linked genes?  Genes associated to sex – chromosome  (b)Name two sex linked traits in human beings. (2mks)  Hemophilia  Colorblindness 29. KCSE PP2 2013 NO 4 In an investigation, a variety of pea plants grown from seeds with smooth coats were crossed with plants grown from seeds with wrinkled coats. All the seeds obtained in the first filial (F1) generations had smooth seed coats. (a)Using letter R to represent the gene for smooth seed coat, work out the genotype of the F1 generation. Show your working. (3mks) (b)If the F1 generation was selfed, determine the phenotypic ratio of the second filial (F2) generation. Show your working. (3mks) 222

(c ) If the total number of seeds in the F2 generation was 14640, calculate the number of seeds with wrinkled coats. Show your working. (2mks)  1/4× 14,640 ; = 3660 seeds 30. KCSE PP1 2014 NO 8 Differentiate between phenotype and genotype as used in genetics.  Phenotype is the outward appearance of an organism while genotype is the genetic make-up of an organism. 31. KCSE PP1 2014 NO 14 State three structural differences between DNA and RNA. DNA RNA Double stranded Single stranded Hasthymine Has uracil Has the four nitrogen base pairing Lack the four nitrogen base pattern pairing pattern 32. KCSE PP2 2014 NO 4 a) How is sex determined in man? (4 marks)  Males have two dissimilar chromosomes X and y/heterogametic;  Females have two similar chromosomes X and X/homogametic;  Male gamete/sperms have either X or y chromosome, while all ova have X  chromosome;  if a sperm with X fuses with an ovum a female is formed and if a sperm with y fuses with an ovum a make is formed; (b) (i) Differentiate between sickle cell anaemia and sickle cell trait. (2 marks)  Sickle-cell trait is heterozygous while sickle cell anaemia is a homozygous condition; 223

(ii)Explain why people with sickle cell trait have an adaptive survival advantage over nominal individuals in malaria endemic regions. (2 marks)  People with sickle cell trait are resistant to malaria; because the plasmodium cannot survive in sickle shaped red blood cells; rej thrive for survive 33. KCSE PP1 2015 NO.4 Colour blindness is a sex linked trait controlled by a recessive gene b. If a mother is a carrier and the father is normal, what is the chance that their son will be colour blind? Show your working (4 marks) 34. KCSE PP2 2015 NO.3 (a)What is meant by the term genetics? * (1 mark) (b) State two examples of discontinuous variation. (2 marks) (c) A female with sickle cell trait marries a normal man. The allele for sickle cell is Hbs and the normal allele is HbA. Determine the probability that their first born will have the sickle cell trait. Show your working. (5 marks) 224

14. EVOLUTION Specific Objectives - Meaning of evolution - The origin of life - Special creation - Chemical evolution (Brief explanation required) - Evidences for organic evolution - Fossil records - brief mention of human evolution - Geographical distribution - continental drift - Comparative embryology - Comparative anatomy (Convergent and divergent evolution based on homology and analogy) - Cell biology - occurrence of cell organelles and blood pigments - Mechanisms of evolution - Lamarcks theory (Brief mention) - Evolution by natural selection - Natural selection in action e.g. peppered moth (industrial melanism) - Resistance to drugs, pesticides and antibiotics Practical activities - Compare vertebrate limbs - Compare wings of birds and insects - Education tour to an archaeological site/local museum By the end of the topic, the learner should be able to: a) explain the meaning of evolution and the current concepts of evolution b) describe the struggle for existence and survival for the fittest c) describe the evidences for organic evolution d) explain resistance to antibiotics, fungicides and pesticides. 225

1. K.C.S.E1995 PP1 No.8 Explain why Larmacks theory of evolution is not accepted by biologists today (2 marks)  Evidence does not support Larmacks theory  Acquired characteristics are not inherited characteristics are found in reproductive cells only 2. K.C.S.E1996 PP1 No.11 Give a reason why it is only mutation in genes of gametes that can influence evolution (1 mark)  Gametes form new offspring 3. K.C.S.E1997 PP1 No.9 State three pieces of evidence that support the theory of evolution  Fossil (records) paleontology; geographical distribution  Comparative anatomy/taxonomy; cell biology  Comparative serology; comparative embryology  Comparative immunology 4. K.C.S.E1998 PP1 No.19 Discuss the various evidences, which show that evolution has taken place. Comparative anatomy/taxonomy.  Members of a phylum group show similarities; organisms have similar structures/similar organs performing similar functions e.g. digestive system/urinary system, nervous system. Any correct example i.e. vertebrate heart.  The pentaductyle limbs/ any correct example; these are homologous organs/structures. Homologous – same origin structure different functions. Analogous structures – different structures performing the same function e.g. wings of insects, bats and birds. Analogous different origin structure, same function convergent.  Fossil records/palaeotology  These are remains of organisms preserved in naturally occurring materials for many years show morphological changes of organisms over a long period of time.  Comparative embryology.  Acc. Any 2 names embryos> vertebrate embryos the morphologically similar; suggesting the organisms have a common origin/ancestry. Geographical distribution.  Present conditions are thought to have been a large land mass joined together, as a result of continental drift; isolation occurred bringing about different patterns of evolution i.e. The Ilamas in the Amazon resemble the Camel. Any other example e.g. Kangaroos in Australia, Jaguar in South America, Camel in Africa. 226

 Comparative serology/physiology.  Antigen/antibody reactions/Rh factor/blood group/haemoglobin structure; reveal some phytogenetic structure. Relationship among organism/common ancestry. 5. K.C.S.E1999 PP1 No.4 State two advantages of natural selection to organisms  Assists to eliminate disadvantageous characteristics.  Allows best characteristics to be passed on to the next generation 6. K.C.S.E2000 PP1 No.7 Give reason why the following are important in the study of evolution: (a)Fossils records  Gives evidence of types of plants/ animals/ organism that exist at a certain geological age. Long ago  Gives evidence of morphological/ anatomical. Structure/ changes that have occurred over a long period of time. (b) Comparative anatomy.  Gives evidence of relationship among organisms  Gives evidence of common ancestry of a group of organisms; e.g. structural/ functional relationship among organization 7. K.C.S.E2002 PP1 N0.14 a) What is organic evolution  Emergence of present fauna and flora/ new life  Term/ species/ organisms from pre-existing forms gradually over a long period of time. (b)State two ways in which Home sapiens differs from Homo habilis  Standing upright/ erect posture. Higher intellectual capacity/ higher brain/ bigger capacity; communication through language speech. c) Distinguish between divergent and convergent evolution giving example in each case.  Divergent basic structural form is modified to serve different functions; e.g. vertebrate forelimbs, break structure in birds/ feet in birds’ convergent different structures are modified to pass or similar functions e.g. wings and birds and insects/ eye of human and octopus, vertebrates for humans e.g. squeal, legs of vertebrae and insects. 227

8. K.C.S.E2003 PP1 No.6 Distinguish between analogous and homologous structures.  Analogous structures – structures which (appear similar and) perform similar functions but have different origins.  Homologous structures – structures which have a common origin but (have evolved to) perform different functions. 9. (K.C.S.E2004 PP1 No.14 a) What is the difference between Darwinian and Lamarckian theories of evolution? (a) Lamarckian  Inheritance of acquired characteristics/ Environment induces production of inheritable character which is then inherited (b) Darwinian  Inheritance of genetically acquired characteristics/ character happens to appear spontaneously which then gives advantage to organisms therefore better- adaptable characters are then inherited by natural selection. Have a common (embryonic) origin modified to perform different functions; vertebrae for limb/ pentadactyl lim c) What is meant by the following terms? Give an example in each case. (6mks) i) Homologous structures  Structures with a common origin. Example – pentadactyl limbs in mammals ii) Analogous structures  Structures with different structural plan and different embryonic origin but evolve to perform similar functions. e.g wings of incents, wings of birds iii) Vestigial structures  Structures that have ceased to be functional. Example - coccyx 10. K.C.S.E2005 PP1 No.4 What is meant by (a)Organic evolution (1mark)  It is the process through which ancient simpler forms of life under went gradual series of small changes for many million years, to give rise to the modern species of life // accepts as a theory formed one large single land mass, which later broke up into parts which drifted from one another forming the present day continents. 228

(b) Continental drift  Theory states that he earth was one large single land mass, which later broke up into parts which drifted from one another forming the present day continents. 11. K.C.S.E2006 PP1 No.15 Explain continental drift as an evidence of evolution. (3mks)  Current continents existed as one large land mass/ Pingea/ Laureshia Guondaland; the present continent drifted leading to isolation of organisms; organism in each continent evolved along different lines hence emergence of new species, 12.(K.C.S.E2007 PP1 No.21 a)What is adaptive radiation ( 2 marks)  When organisms of the same origin become adapted (modified) in different ways in order to fit in the environment. The organisms are separated due to natural factors. (b) Give a reason why organisms become resistant to drugs (1 mark)  When an organism is exposed to drug fro sometime it becomes modified (adapted) to living in presence of the drug. The offspring produced therefore survive in presence of the drug. Hence drug resistant 13. (K.C.S.E2008 PP1 No.7 a)What is fossil (1 mark)  Premedial remains of dead organisms that lived in accent sample (b)How does convergent evolution occur (3 marks)  When two dissimilar species/ structures/ organisms of different embryonic origin; change in same and develop similar characteristics/ or modify to perform similar function 14. (K.C.S.E2009 PP1 No.10 a) (i) What is meant by vestigial structures? (1 mark)  Are those structures that have ceased to be functional over a long period of time and hence reduced in size. (ii) Give an example of a vestigial structure in human (1 mark)  Appendix/ coccyx/tail ( tail bone)/ semi - lunar folds of cornea of eye/ nictitating membrane caecum/ ear muscles/ body hair/ Acc. Post and nail (b) Explain why certain drugs become ineffective in curing a disease after many years of use. (2 marks)  Because the causative agents undergo mutations hence developing resistance mechanisms 229

15. K.C.S.E2010 PP1 No.24 a) State two ideas proposed by Lamark in his theory of evolution. (2 marks)  Use and disuse  Acquired traits can be passed on to offspring b) Why is Larmark’s theory not acceptable? (1 mark)  Acquired characteristics cannot be inherited  No evidence to support the theory 16. K.C.S.E2011 PP1 No.21 a) What is meant by convergent evolution?  Where different structure evolve to perform different functions (e.g. wings of insect / birds, eye of human and octopus) rej; if wrong example given Acc; if no example given (b) State two limitations of fossils as an evidence of evolution.  Missing links;  distoration of parts during sedimentation  Destruction of fossilsa by geolopical activities Acc; correct e.gs 17. K.C.S.E 2012 PP2 NO 2(d) Explain how comparative embryology is an evidence for organic evolution. (2marks)  Vertebrate embryos have similar morphological features; which suggest a common ancestry; invertebrates; Annelids & molluses have similar blastula/ trochophore larva; suggesting common ancestry; 18. K.C.S.E2012 PP1 No22 State the importance of divergent evolution to organisms. (2 marks)  Results in adaptations that enable organisms to exploit different ecological riches; leading to the formation of new species/ speciation;  Aspect of features undergoing modification must come out; ie Accept structures become modified to enable organisms exploit different ecological riches; 19. (K.C.S.E2012 PP1 No.26 (a) State the theories of evolution proposed by the following scientists. (2 marks)  Darwin: Natural selection; Accept complete correct explanations;  Jean-Baptiste Lamarck: - Theory of environmental influence in inherited characteristics/ inheritance of acquired characteristics; Rej use and disuse/ accept complete correct explanation 230

(b) State the evidence of evolution based on  Cell organelles - Similar organelles performing similar functions in different organisms suggest a common ancestry/ cell Biology;  Fossils - Fossil records/ paleontology/ by comparing the fossils of different organisms/ originate from a common ancestry. 20. KCSE 2013 PP1 NO 20 Explain the theory of evolution by natural selection. (2mks)  Organisms adjust to prevailing environmental condition and survive to reproductive maturity; it then passes the advantageous traits to its offspring. Organisms with disadvantages traits are eliminated 21. KCSE 2013 PP1 NO 21. (a) Explain the role of continental drift in evolution. (3mks)  Brought about variation of diversity in flora and fauna.  It has leas to adaptive radiation  (b)What is meant by the term organic evolution? (1mk)  Gradual change of organism from simple life forms to complex life forms over along period of time. 22. (KCSE 2014 PP1 NO 22) (2 marks) a) Name two vestigial structures in human beings.  Appendix  Tail /coccyx  Ace. nictitating membrane (b)Why are some bacteria able to resist the effect of antibiotics? (2 marks  They have a gene resistance / acquire it through mutation -The gene for resistance is passed for off springs establishing a population of resistant forms. 23. (KCSE 2015 PP1 NO.2 During a lesson, students observed the structure of bat, cat and human forelimbs to determine their evolutionary relationship. (a)State the name given to the structure of the limbs observed by the students.(1 mark) (b) Name the type of evolution illustrated by the structure of the limbs observed.(1 mark) (c) What evidence of evolution is illustrated by the limbs? (1 mark) 231

(d) State the significance of the type of evolution illustrated by the limbs. (1 mark) 23. (KCSE 2015 PP1 NO.10 The diagram below illustrates the skulls of adult human and chimpanzee. (a)State one difference between the two skulls in the following structures:(3 marks) Structure Chimpanzee Skull Human Skull (i) Parietal bones (ii) Mandible (iii) Browridge (b)State the significance of the evolution observed on the parietal bone in the chimpanzee and human skulls. (1 mark) 232

15. (a) RESPONSE, RECEPTION AND CO-ORDINATION IN PLANTS Specific Objectives - Meaning of stimulus, response and irritability - Reception, response and coordination in plants - Response to a variety of external stimuli - Tropisms and tactic movements and their survival values - Production of auxins and their effects on plant growth - Reception, responses and coordination in animals - Components of the nervous system in a mammal - Structure and functions of the neurones - Functions of major parts of human brain - Simple and conditioned reflex actions - The role of hormones in coordination in a mammal - Effects of over secretion and under secretion of adrenaline and thyroxine in humans - Functional differences and similarities between endocrine and nervous systems - Effects of drug abuse on the human health - Structure and functions of parts of the mammalian eye (human) - Accommodation, image formation and interpretations - Common eye defects and their corrections - Structure and functions of parts of the mammalian ear (human) - Hearing (omit details of cochlea) - Balance and posture (mention only parts involved) - Practical activities - Carry out experiments to investigate tactic responses e.g. chemotaxis - use any of the following organisms: worker termites/fly maggots/earth worms/honey bee/grasshoppers/ woodlice - Carry out experiments on tropisms and etiolation - Determine the distance of blind spot - Carry out knee jerk experiment By the end of the two topics, (RECEPTION, RESPONSE AND COORDINATION IN PLANTS AND ANIMALS ),the learner should be able to: a) define irritability, stimulus and response b) explain differences between tactic and tropic responses and their survival values c) explain the production of plant hormones and their effects on tropisms (growth responses) d) relate the structure of the mammalian nervous system to its functions e) distinguish between simple and conditioned reflex actions l) explain the role of endocrine system in humans g) state the effects of drug abuse on the human health 233

h) relate structure to function of the human ear and eye i) explain defects of the eye and ear and their corrections. 234

1. K.C.S.E1995 PP1 No.14 The diagram below represents growing seedlings which were subjected to unilateral light at the beginning of an experiment (a) (i) State the results of P,Q and R after 5 days? (5 marks)  P – Will tend/ grow towards light  Q – Will remain straight/ little/ no growth  R – Will remain/ grow straight / Acc. Grow upwards (ii)Account for your answer in (a) (i) above (3 marks)  P – Growth substances or hormones/ auxins/IAA are produced by the stem tip. They move downwards and get disturbed to the side away from the side of light where they cause more rapid growth/ cell division/ elongation (that results in bonding)  The source of auxin has been removed and the auxins are not affected by light because the era has been covered. (b) If the tin foil were removed from the tip of the seedling R, what results would be observed after 2 days (1 mark)  Tip will bend towards the light (c)State the expected results after 3 days if the box were removed (1 mark)  All the seedlings will grow upwards. 2. K.C.S.E1996 PP1 No.16 A shoot of seedling exposed to light on one side bends towards the source of light as it grows (a) Name the response exhibited by the shoot of the seedling (1 mark)  Phototropism 235

(b) Explain how the bending towards the source of light occurs (3 marks)  Auxins / hormones; move diffuse to the demised/ away from the light side; causing elongation/ growth on the dark sides hence bending 3. K.C.S.E2003 PP1 No.15 A response exhibited by a certain plant tendril is illustrated below a) i) Name the type of response  Thigmotropism / haptotropism ii) Explain how the response named in (a)(i) above occurs  Contact with support; causes migration of auxine to enter the side; causing faster growth on the side away from centre of surface (causing tendrils curl around support.) b) What is the importance of tactic responses to microscopic plants?  Escape injurious stimuli / seek favorable habitats; move towards light / stimuli. c) State four applications of plant hormones in agriculture.  Selective weed killers  Encourage apical dominance  Encourage sprouting of side branches  Breaking seeds dormancy  Induce pathencarpy  Promotes flowering  Induce fruit fall  Accelerates ripening of fruits. 4. K.C.S.E2006 PP1 No.20 a) What name is given to response to contact with surface exhibited by tendrils and climbing stems in plants?  Thigmotropism/ Haptotropism; rej. Haptotrophism/ thigmotrophism 236

b) State three biological importances of tropisms plants.  Exposes leaves/ shoots for maximum/ a lot of absorption for sunlight for photosynthesis;  Enable roots of plants to seek/search water; rej mineral salts/ ions alone.  Enables plants stems to obtain mechanical support especially those that lack woody  stems  Enables roots to grow deep in soil fro anchorage  Enable pollen tube to grow towards embryo sac to facilitate fertilization 5. (K.C.S.E2007 PP1 No.23 a) Name the hormone that is responsible for apical dominance (1 mark)  Auxin (b) What is thigmotropism? (1 mark)  Growth response due to touch of a part e.g. tendrils 6. K.C.S.E2007 PP1 No.23 State one survival value for each of the following in plants: (a) Thigmotropism in stems; (1 mark)  Offers support to weak stems b) Geotropism in roots. (1 mark)  Allows roots to obtain support/anchorage 7. K.C.S.E2011 PP1 No.28 a) What is a tropic response?  It a growth movement in plastic/ part of a plant in response to a unidirectional stimulus; rej; unilateral (b) State two ways by which auxins regulate growth in seedlings  It a growth movement in plastic/ part of a plant in response to a unidirectional stimulus; rej; unilateral 8. KCSE 2013 PP1 NO 22 The diagram below illustrates a response by certain plant. 237

(a)Name the type of response (1mk) Thigmotropism (b)Explain how the response illustrated above occurs. (3mks)  Auxins migrates away from the point of contact, stimulating faster elongation on the outside thus curvature around the hard surface. 9. KCSE 2015 PP1 NO.9 In an experiment to investigate a plant response, the set up shown in the diagram below was used. (a)Name the type of response that was being investigated.(1 mark) (b)If the Klinostat was not rotating: (i) state the observations that would be made on the seedlings after three days;(2 marks) (ii)explain the observations in (b) (i) above.(3 marks) (c) If the experiment was repeated with the Klinostat rotating: (i) state the observation that was made on the seedlings after three days; (1 mark) (ii) give a reason for the observation made on the seedlings. (1 mark) 238

15 (b) RECEPTION, RESPONSE AND CO-ORDINATION IN ANIMALS 1. K.C.S.E1997 PP1 No.5 In an accident a victim suffered brain injury. Consequently he had loss of memory. Which part of the brain was damaged?  Cerebrum cerebral hemisphere/ cerebral cortex; 2. K.C.S.E1997 PP1 No.12 A person was able to read a book clearly at arm’s length but at normal reading distance. (a)State the defect the person suffered from?  Long sightedness/ hypermetropia (b)Why was he unable to read book clearly at normal distance  Eye ball too short/ eye lens are unable to focus because they are flat/weak, unable to focus the image on the retina; eyes are unable to accommodate/ change their focal length (c)How can the defect be corrected?  By wearing convex / biconvex lenses; accept converging lenses 3. K.C.S.E1998 PP1 No.6 In an experiment it was found that when maggots are exposed to light they move to dark areas. (a)Name the type of response exhibited by the maggots  Phototaxis (b)Name the advantages of the response to the maggots  To avoid desiccation/ drying/ dehydration 4. K.C.S.E1998 PP1 No.17 a) The diagram below represents a nerve cell. (i) Identify the nerve cell.  Sensory neurone/sensory nerve cell; reject sensory nerve (ii) Give a reason your answer in (a) (i) above  Cell body on a branch/ at the side of axon/off the axon/cell body unipolar both axon and dendron are long. (b)Name the structure labeled T 239  Myelin sheath; Acc Neurilema

c) Using an arrow indicates on the diagram the direction of movement of an impulse in the cell.  Direction of impulse from receptor towards cell body 5. K.C.S.E1999 PP1 No.9 The diagram below shows surface view of a human brain. (a)Name the parts labeled B and C.  B- Cerebellum  C- Medulla Oblongata; Acc Oblongata alone. Rej. Medulla alone (b)State three functions of the part labeled A  Control locomotion  motor area/sends impulse to affectors/controls  Voluntary  Vision/hearing/smell/taste.  Personality speech;  Mediates cranial (c)State what would happen if the part labeled B was damaged.  Loss of muscle co-ordination/balance 6. K.C.S.E2000 PP1 No.1 What is the function of the following cells in the retina of human eye? Cones  Discrimination of colours/ details/ accurate/ vision colour perception/ sensitivity to high intensity/ bright (b) Rodes  Dim light vision/ low light intensity 240

7. K.C.S.E2001 PP1 No.17 a) State the functions of the following parts of the mammalian ear; (i) Tympanic membrane  Receives sound waves (from the air); and vibrates / transforms sound wave into vibrations to transmit them to the ear osssicles / malleus; acc. Hammer for malleus. (ii) Eustachian tube  Equalizes the air pressure in the middle ear to that in the outer ear. (iii) Ear ossicles  Amplify / transmits vibrations from the tymphanic membrane in the inner ear / venestra ovalis / oval window. (b)Describe how semicircular canals perform their functions  There are three semi – circular canals; arranged in planes at right angle to each other; at the end of each canal is swelling called ampulla’s which contains receptors.  The movement of the cause movement of the fluid in at least one canal, the fluid movement deflects / displaces the coperta and thus stimulating the receptors / sensory hairs, the impulse / nerve sensory impulse is transmitted / conducted to the brain; by auditory nerve, about the movement of the body / head. 8. K.C.S.E2003 PP1 No.18 Describe the functions of the various parts of the human eye.  Sclerotic layer - (made up of collagen fibres thus) protects the eye maintains shape of eyeball.  Cornea - Allows light to enter the eye. Refracts light towards retina  Conjunctive - Protects cornea  Eyelids- Protects cornea from mechanical & chemical damage / protects eye form entry of foreign particles.  Choroids - (Contains black pigment which) prevents reflection of light within the eye / absorbed light. Nourishes the eye / retina / supply oxygen / remove CO2  Ciliary muscles - Alter shape of lens during accommodation  Suspensory ligaments - adjusts shape of lens during accommodation  Lens - Refracts light rays / focuses light on retina. Vitrerous aqueous humour once. Ciliary body produces aqueous humour.  Aqueous Humour - Nourishes cornea / lens  Irus - (pigmented thus) – gives the eye its colour / absorbs light controls amount of light entering the eye / adjusts size of pupil impulses. Refracts light  Pupil - light enters the eyes through pupil. 241

 Retina - has photoreceptor cells / rods / cones / image formation ;  Fever / yellow spot - visual acuity / most sensitive part of retina with only cones.  Blind spot - point where nerve fibre emerges from the optic nerve / where the optic nerve leaves the eye / point where blood vessels & nerve fibres enter the eye.  Optic nerve - transmit impulses to brain. 9. K.C.S.E2004 PP1 No.6 The diagram below shows the position of an image formed in a defective eye. (a)Name the defect:  Myopia/ shortsightedness / short sight (b)Explain how the defect named in (a) above can be corrected 2mks)  Concave lens / divergent lends; to diverge the rays so that the image is focused on the retina Acc. Concave. 10. K.C.S.E2005 PP1 No.1 Apart from hearing, state another function of the human ear. (1mk)  Maintain balance and posture of the body 11. K.C.S.E2005 PP1 No.19 How is the human eye adapted to its function? (20mks) 242

The presence of:-  The sclerotic layer which contains tough connective tissue fibres which helps it to support and protect the other parts of the eye ball.  The choroids which contain many blood capillaries which supply oxygen and nutrients of the retina and removes metabolic wastes from eye.  It’s highly pigmented, to prevent reflection of light within the posterior chamber of the eye ball.  The retina which contains photoreceptor cells called cones and rods. It is said to be the light sensitive part of the eye. Cones are adapted for light and colour vision while rods are adapted for dim light vision.  The vitreous humour-Which is under pressure. It helps to maintain the shape of the posterior chamber of the eye ball. It also plays an important part in the refraction of light rays enabling them to be focused on the retina.  The cornea, transparent and curved which helps to play an important role in focusing of the image on the retina. It accounts for the largest refraction of light rays.  The aqueous humour –Contains oxygen and nutrients, which nourish the cornea and the lens. It is under pressure thus helping to maintain the shape of the anterior chambers of the eye. It also plays a part in the refraction of light rays enabling them to be focused on the retina.  The Iris is heavily pigment, to prevent entry of light into the eye except through its central aperture called the pupil. It contains circular and radial muscles which constrict or dilate the pupil depending on the intensity of light.  The Iens is elastic, therefore allows changes in its shape depending on the tension exerted through the suspensory ligaments. This enables it to bring light rays causing from either near or far objects into sharp focus on the forea.  The ciliary’s body contains ciliary muscles whose contraction and relaxation alters the tension exerted on the suspensory ligaments. This in turn alters the shape of the lens enabling it to focus for both near and distant objects.  The eyelids which are movable and opaque structures can be closed through a reflex action to protect the eye from too much light or from foreign objects.  The eye muscles help to move the eye ball within the orbit. The lateral rectus muscles move the eye up and down whole the oblique muscles the eyeball in it’s up and down movement.  The lachrymal gland which continuously secretes a watery, saline and antiseptic fluid called tears. The tears moisten the cornea and wash foreign particles out of the eye.  The eyelashes, which are many hairs, protect the eye from the entry of small foreign particles. 243

 The eyebrows raised portion of the skin above the eye, thickly covered with hair, whose functions are to prevent sweat and dust from entering the eye. 12. K.C.S.E2006 PP1 No.10 State the importance of tactic response among some members of kingdom protoctista. (1mks)  Move towards favorable environment; accept converse 13. K.C.S.E2006 PP1 No.21 The diagram below represents a reflex area in humans.  a) Name the parts labeled X and Y  X- Motor neurone - accept of motor neurone rej. Axon alone  Y- Sense organ/ receptor b) Name the substance that is responsible for the transmission of an impulse across the synapse. (1mks)  Acetylcholine/ noradrenaline (Nerepinephrine) 14. K.C.S.E2006 PP1 No.22 a) State the function of ciliary muscles in the human eye. (1mark)  They contract and relax, to alter the shape of lens. b) State two functional differences between the rods and cones in the human eye. (2 marks)  Rodes Cones  Perceives light of low intensity perceives light of high intensity  Not Sensitive to colour Sensitive to colour  Have low visual acuity Have high visual acuity 244

15. K.C.S.E2006 PP1 No.23 State the function of each of the following parts of human ear. (4 marks)  Ear ossicles - transmits/ magnify/ amplify sound vibration. Rej. Sound waves  Cochlea - converts sound vibrations into nerve impulse  Semi circular canals - for body posture/ balance  Eustachian tube - balances pressure in middle ear to that of outside. 16. (K.C.S.E2007 PP1 No.22 (1 mark) a) Where in the human body are relay neurons found  In the central nervous system (spinal cord) (b) The diagram below represents a neurone (1 mark)  (i) Name the neurone (1 mark)  Motor neutron (ii) Name the parts labeled P and Q (2 marks)  P- Dendrites  Axoplasm (Axon) (c)State a function of myelin sheath (1 mark)  Insulates the axon 17. K.C.S.E2007 PP2 No.7 Describe the structure and functions of the various parts of the human ear (20 marks) The ear is an organ involved in perceiving sound and maintaining body balance and posture. It is made of the following sections;  Pinna – That is funnel shaped structure made of skin and cartilage. It receives sound waves and directs them to the ear tube.  External/auditory meatus – That is a canal lined with air and wax. It allows passage of sound waves to the middle ear. The hairs and wax trap dust particles that enter the ear.  Tympanic membrane – That is a thin flexible sheet-like structure receives sound waves and passes the vibration to the ossicles.  Middle ear that is composed of: 245

 Tiny bones known as ossicles – They are anvil and incus. They amplify vibration from the tympanic membrane.  Eustachian tube – That connects the ear to the nasal cavity. It balances pressure on both sides of the tympanic membrane.  Oral window – That is a thin flexible membrane that opens into the inner ear. It receives vibrations from the ossicles and passes them to the inner ear.  Inner ear that is composed of:  Vestibular apparatus - That are the semicircular canals, utricles and saccules. They help in maintenance of body balance and posture.  Cochlea – That is a coiled structure that has sensory cells for hearing. It connected to the auditory nerve that is involved in transmission of sounds to the brain 18. (K.C.S.E2008 PP1 No.13 (1 mark) a)Name the part of retina where image is formed  Yellow spot/ cornea (centralis) (b)State two characteristics of the image formed on the retina (2 marks)  Inverted; real; reversed; diminished 19. K.C.S.E2009 PP1 No.4 a) (i) Explain the changes that take place in the pupil and iris of a human eye when a person moves from a dark room to a room with bright light (3 marks)  Circular muscles of the Iris contract (C/C) while radial muscles relax (R/R) reducing the size of the pupil; hence less light enters the eye. (ii)What is the significance of the changes explained in (a) above (1 mark)  The retina is protected from damage (b) How does the human eye obtain nutrients? (3 marks)  Choroid has a dense network of blood capillary from which nutrients diffuse out to supply the eye. (c) Explain why images that form on the blind spot are not perceived (2 marks)  The blind spot has no photoreceptors/ rods & cones. Hence no impulses are generated to be transmitted to the brain (for interpretation) 20. K.C.S.E2010- PP1 No.6 State one function for each of the following: (a)Cerebellum (1mark)  Maintain balance/posture/control/muscular movement 246

(b) Medula oblongata (1 mark)  Control heart beat/ blood pressure/ breathing (rate) control involuntary activities/ response 21. K.C.S.E 2010 PP2 No.4 The diagram below shows how the iris and pupil of a human eye appear under different conditions. (a)Name the structures labeled X and Y (2 marks)  X – Pupil  Y – Circular muscles (b)i) State the condition that leads to the change in appearance shown in the diagram labeled B (2 marks)  Dimlight / low light intensity/ darkness/ dull light. ii) Describe the change that lead to the appearance of the iris and pupil as shown in the diagram labeled B. (4 marks)  Circular muscles in (iris) relax; while radial muscle contract; the pupil becomes bigger allowing more light to enter the eye. (iii)What is the significance of the change described in (b) (ii) above? (1 mark)  Allow one to visualize/ see objects under dim light; 22. K.C.S.E2011 PP2 No.4 (a) (a) The diagram below represents a section of the human brain. 247

(i) Name the structure labeled P and R.  P - cerebral hemisphere/cerebrum  R - Medulla oblongata (ii)State two functions of the part labeled Q  Muscular co-ordination, maintain body posture/balance/manual motor dexterity 23. K.C.S.E2011 PP2 NO 8(b) Describe how accommodation in the human eye is brought about when focusing on a near object. (7marks)  Light rays from a near object are more divergent & need to bend more,Ciliary muscles contract, suspensory ligments slaken, the lens becomes thicker/more convers/increases in curvature/reduces focal length, light from the object is refracted more in order to be focused sharply/form an image on the retina 24. K.C.S.E2012 PP1 No.9 State the importance of negative phototaxis to termites  Enables termites to seek favourable habitat away from light i.e.dark places hence avoid predation 25. K.C.S.E2012 PP1 No.10 What is meant by the term irritability? (1 mark)  Ability of an organism to detect/ perceive/ (interprete) and respond to changes in the environment/ stimulus; 26. K.C.S.E2012 PP1 No.7 Using a relevant example in each case describe simple and conditional reflex actions (20 marks)  Simple reflex action eg. withdrawal of finger from a sharp object/ hot object; its an automatic response to a specific stimulus; when the finger touches sharp object/ hot object, the pain receptors/ thermoreceptors in the skin are stimulant; and trigger off a nerve impulse; the nerve impulse is transmitted via the senses neurone; to the grey matter of the spinal cord/ CNS/ brain; the impulse is then transmitted via synapse; to the relay neurone; and then through another synapse; to the motor neurone; and then through another synapse; to the motor neurone; the impulse is then transmitted to the effector muscles in the hand; ace - efferent neurone for motor neurone  Afferent neurone for sense neurone  intermediate/ associative/ connector/interauncial neurone - for relay. The effector muscles/ biceps contract; and the finger is withdrawn from the hot object/ sharp object; conditioned reflex action - salivation in a dog/ human being (ace. any other relevant example) student in response to sound; it is an automatic response evoked from an animal 248

by unrelated stimulus; substituted for the one which normally elicits the response; it develops from a past experience; and involves modification of behaviour/involves learning; it weakens with time; and must be reinforced by repeating the related stimulus; the dog/ student salivates when the bell (for meals) rings; because they have learn to associate the ringing of the bell at meal time with food; everytime it rings (accept use of other relevant examples) they are offered food. 27. KCSE 2013 PP1 NO 23 The diagram below illustrates a defect in the eye  Explain how the defect illustrated above can be corrective corrected (2 marks)  Use of biconcave/concave lens/divergent lens; to diverge the rays and ma ke image be focussed on the retina; 28. KCSE 2013 PP2 NO 2 The diagram below represents the human ear.  (3mks) (a)Name the parts labeled E, F and G. 249  E- Semi circular canals  F- Oval window  G- Cochlea

(b)How is each of the following adapted to its function? (i)External auditory meatus; (2mks)  Presence of hairs and cells with tops small insects and secrete wax respectively  Hallow for channel wave to the tympanic membrane (ii)Ear ossicles (2mks)  Presence of muscles attached to prevent excessive vibrations which can damage the labyrinth.  Arranged as levers to amplify and transmit vibrations to the oval window.  Name one defect of the human ear. (1mk)  Tinnitus  Nerve or absolute deafness vertigo 29. KCSE 2014 PP1 NO 11 State three differences between tactic and tropic responses. (3 mark) Tactic responses Tropic responses Are temporary Are permanent Are locomotors Are growth responses Are fast Are slow Not influenced by growth hormones Are caused by growth hormones 30. KCSE 2014 PP1 NO 13 State one function of each of the following parts of a mammalian eye: (a) eye lashes(1 mark)  Trap foreign particles entering the eye  Produce fluid/tears; (b). lachrymal glands. (1 mark)  It produces fluid / tears which moistens the cornea / wash foreign materials out of the eye; produce fluid / tears with antiseptic properties / kill pathogens / harmful microorganism. 31 .KCSE 2014 PP1 NO 16 The diagram below illustrates a nerve cell. 250