Science 2 part 2

Another type of surrogate mother lends only her uterus. She receives the fertilizedegg from the woman who has healthy ovaries but lacks a functional uterus.In Vitro Fertilization Literally it means “fertilization Figure 13. Vitro Fertilizationin a glass”. The sperm meets theegg cell outside the woman’s body. http://images.google.com.ph/images?hl=tl&lr=&q=After few divisions, the fertilized egg images+of+in+vitro+fertilization&btnG=Hanapincell is then introduced into thedonor’s uterus or another woman’suterus. If everything is fine, theembryo will implant into the uterusdeveloping into a fetus. This isspecially recommended if thefallopian tubes are blocked. Thisprocess is done in laboratory with a68% fertilization rate. Challenge! A 25 year-old woman has her uterus removed due to cancer. However, her ovaries are intact and her egg cells are healthy. She takes a “super-ovulation” drug and has her egg cells removed, and they are fertilized in vitro with her husband’s sperm. One fertilized ovum was implanted into the uterus of the woman’s best friend. Who are the genetic parents? Gestational parents?Gamete Intra-fallopian Transfer (GIFT) Since IVF is expensive, scientists have now tried another technology to solvereproductive problems. Presently, a new technology called Gamete Intra-fallopianTransfer (GIFT) solves this problem, by moving fertilization to the woman’s body rather thanin a glassware. The woman takes a super ovulation drug for a week and then has severalof her largest egg cells removed, then a man donates a sperm sample and the physicianseparates the most active cells. The collected oocyte and sperms are deposited together inthe woman’s fallopian tube where there is no obstruction so that implantation can occur.Oocyte Banking and Donation Do you know that egg cells or oocytes can also be stored just like the sperms? Yes!It can be done. A woman wishing to have a baby later in her life when fertility declines canset aside oocytes while still young. However, this process is not as easy as freezing spermcells in the bank. Healthy women can also donate healthy oocytes to other women, but it’s - 20 -

not that easy. There are several processes that you have to undergo. Isn’t this exciting?Now, age does not matter in conceiving a baby. What matters is money since you have topay the egg bank. Because of this technology, even menopause women, like a 62- year oldcan conceive a child! Isn’t this amazing? They do this with the egg fertilized in laboratorydish and later on transferred to her uterus as long as appropriate hormones are given. All these are examples of the wonders of technology.What you will doSelf-Test 4.11. What is artificial insemination?2. How can a surrogate mother assist an infertile couple?3. What is GIFT?4. Why is it difficult to freeze egg cells than sperm cells?5. What are the causes of male infertility? Key to answers on page 28.What you will doActivity 4.1 Look for magazines and newspapers and cut out articles related to the effects ofsmoking on the health of the developing embryo and newborn babies.Birth Control Methods Why control birth? Well, the world’s population is now very close to 6.5 billion andthe carrying capacity of mother earth is only around 8 billion, which means that we arealready very close to the limit. Governments of the world should work together to solve therapidly growing population for the benefit of humanity. Birth control methods then arenecessary. Contraception is the use of devices or practices that work “against conception”.These methods either block the fusion of sperm and egg cell, or they make the femalessystem’s environment hostile to sperm or to the pre-embryo’s implantation. Below areexamples of birth control devices: - 21 -

Figure 14. Birth Control Devices http://www.uwm.edu/People/cortneyExamine the table below. These are the different birth control methods. BIRTH CONTROL METHODSBarrier and Spermicidal Method Mechanism Advantages Disadvantages SuccessCondom and Worn over penis Protection against Disrupt 95-98%spermicide (male) or inserted sexually spontaneity, into vagina, and transmitted reduces 83-97% kill sperm that diseases sensation 80-95% escape 78-95% 85-97%Diaphragm Kill sperm and Inexpensive Disruptand blocks cervix spontaneity, mustspermicide be fittedCervical cap Kill sperm and Inexpensive, can May slip out ofand blocks cervix be kept in for 24 place, must bespermicide hours fittedSpermicidal Kills and blocks Inexpensive Messyfoam or jelly cervixSpermicidal or Kills sperm, and Easy to use and Irritates 25 % ofsuppository blocks cervix carry users - 22 -

BIRTH CONTROL METHODSHormonal Prevents Does not interrupt Raises risk of 90-100%Combination ovulation and spontaneity, heart disease inbirth control pill implantation, lowers cancer some women, 91-100% thickens cervical risk, lightens weight gain andMinipill mucus menstrual flow breast tenderness 99% 99.8%Depo-Provera Blocks Fewer side Weight gain implantation, effects 79-87%Norplant deactivates 75-91% sperm, thickens Easy to use, last Menstrual 99.85%Behavioral cervical mucus 3 months changes, weight 99.6%Rhythm gain, injection 95-99%method Prevents Easy to use, lastWithdrawal ovulation, alters 5 years Menstrual uterine lining changes, doctorSurgical must implantVasectomy Prevents ovulation,Tubal ligation thickens cervical mucusOthersIntrauterine No intercourse No cost Difficult to do,device during fertile time hard to predict timing Removal of penis No cost from the vagina Difficult to do before ejaculation Sperm cells Permanent, does Requires minor never reach penis not interrupt surgery, difficult spontaneity to reverse Oocytes never reach the uterus Permanent, does Requires surgery, not interrupt infection, difficult spontaneity to reverse Prevents Does not interrupt Severe menstrual implantation spontaneity cramps, infection - 23 -

What you will do Self-Test 4.2 Based on the summary of birth control methods, which do you think is the bestmethod and why? What you will do Activity 4.2 Go to the nearest health center in your place and interview the health officer. Askthem about their program on population control. List down their program and take note ofthe family planning methods that are available and how they administer them to thecommunity. If possible, try to familiarize yourself with the devices available in the healthcenter. Let’s Summarize 1. Reproduction is the ability of organisms to produce offspring similar to the parents. 2. The female reproductive system includes ovaries, oviducts, uterus and vagina. 3. External genitalia include the vestibule containing separate openings of the vagina and urethra, the labia minor, labia major and the clitoris. 4. Fertilization of an egg occurs in the oviduct. The fertilized egg then attaches itself to the uterus. 5. The menstrual cycle is a series of events within the human female reproductive system. It prepares the uterus for a fertilized egg. 6. The human male reproductive system includes the testes, scrotum, penis, tubes to carry sperm, glands and the urethra. 7. Embryonic and fetal development occurs during pregnancy in humans. 8. Human pregnancy can be divided into three trimesters. Organogenesis is completed by the eight week. 9. Birth or parturition, results from strong, rhythmic uterine contractions that bring about the three stages of labor: dilation of the cervix, expulsion of the baby, and delivery of the placenta. 10. Infertility is the inability of the sperm to fuse with the egg cell. 11. There are several assisted reproductive technologies such as: artificial insemination, surrogate motherhood, in vitro fertilization, gamete intra-fallopian transfer, and oocyte banking and donation. 12. Contraception prevents pregnancy. 13. Contraceptive methods include preventing the release of mature gametes - 24 -

PosttestTest I. Identify the word/phrase being described or defined in each item.__________ 1. Considered as the ovulation period for regular menstrual cycle__________ 2. The stage where organs are formed during fetal development__________ 3. The part of the male reproductive organ that is cut during vasectomy__________ 4. The type of birth control device that is used for safe sex__________ 5. It involves the fertilization of the egg in a “glass”__________ 6. The part of the female reproductive system where the egg is fertilized__________ 7. The technology where the doctor places donated sperm in the woman’s reproductive tract__________ 8. The female sex hormone__________ 9. The periodic shedding of tissues and blood from the inner lining of the uterus__________10. The thick, whitish fluid consisting of sperms and secretions from several glands of the male reproductive tractTest II. Provide the function of the different parts of the male and female reproductive system. Organ Function Testes Uterus Clitoris Vagina Scrotum Vas deferensSeminal vesicleProstate gland Urethra Penis Key to answers on page 28. - 25 -

Key to AnswersPretest 6. fallopian tube 7. Artificial insemination Test I. 8. estrogen 1. 14th day 9. menstruation 2. 1st trimester 10. semen 3. vas deferens 4. condom Function 5. vitro-fertilization Produce the sperm cells Site for the implantation of the zygote Test II. Part of the external female genitalia that is Organ composed of erectile tissue Testes The place where the penis is inserted in the female Uterus The folded skin that covers the testes Clitoris The tube connected to the epididymis where sperms pass Vagina Paired structures that add fructose and proteins to Scrotum the sperms. Vas deferens A small gland that produces alkali fluid Canal that serves as passageway for sperms and Seminal vesicle urine in males The male sex organ inserted in the vagina Prostate gland Urethra PenisLesson 1Activity 1.11. 28 days2. It moves out of the uterus.3. The egg is fertilized and attaches to the uterus for implantation.4. ImplantationSelf-Test 1.1Ovary Ovulation Fallopian Tube UterusMenstruation Zygote - 26 -

Lesson 2Self-Test 2.11. To compensate for the millions of sperms that will die along the way or even before they reach the egg.2. Testes epididymis vas deferensejaculatory ducts urethra outsideLesson 3Self-Test 3.11. It starts to divide and moves down to the uterus for implantation.2. Ovulation refers to the release of egg from the ovary, while fertilization is the union of the egg nucleus and sperm nucleus.3. First trimester is from the first to the third month, organogenesis starts. Second trimester extends from the start of the 4th month to end of the 6th month, baby is about 30 cm. Third trimester extends from the 7th month until birth, baby is about 50cm long.4. Pregnancy that occurs outside of the fallopian tube5. The uterus contracts (due to hormone) to force the baby out of the birth canal.Activity 3.1 Measuring the Growth Rate of the Embryo 50 40 30 Size of Fetus in 20 mm 10 0 1234567891 Weeks After Fertilization - 27 -

Lesson 4Self-Test 4.11. A process where the doctor places donated sperm in a woman’s reproductive tract.2. She can be artificially inseminated with the man’s donated sperm and carries on with the pregnancy.3. Moving fertilization to the woman’s body rather than in a glassware.4. Because they are very sensitive to temperature changes.5. Causes of male infertility are: a. hormonal imbalance b. varicose vein in the scrotum c. low sperm count d. motility problemPosttestTest I. 6. fallopian tube1. 14th day 7. Artificial insemination2. 1st trimester 8. estrogen3. vas deferens 9. menstruation4. condom 10. semen5. vitro-fertilizationTest II. Function Organ Produce the sperm cells Testes Site for the implantation of the zygote Uterus Part of the external female genitalia that is Clitoris composed of erectile tissue The place where the penis is inserted in the female Vagina The folded skin that covers the testes Scrotum The tube connected to the epididymis where Vas deferens sperms pass Paired structures that add fructose and proteins to Seminal vesicle the sperms. A small gland that produces alkali fluid Prostate gland Canal that serves as passageway for sperms and Urethra urine in males The male sex organ inserted in the vagina Penis - 28 -

ReferencesBooks:Campbell. N.A. (1996). Biology (4th ed.). California: Benjamin Cummings Publishing, Menlo Park, CaliforniaDaniel, L., Ortleb, E. & Biggs, A. (1994). Life Science. Glencoe. Macmillan/McGraw-Hill, California.Kaskel, A., Hummer P.J. & Daniel, L. (1988). Biology: An everyday experience. Ohio, USA: Merill Publishing Company. Columbus,Lewis, R. (1998). Life. (3rd ed.) USA: WCB McGraw-Hill Companies, Inc.Mader, S. (2001). Biology. (7th ed.) USA: The McGraw-Hill Companies , Inc.Seeley, R.R., Trent, S.D. & Tate, P. (1992). Essentials of anatomy and physiology. (3rd ed.) USA: McGraw-Hill. Boston Burr Ridge.Wong, H.K. Biology key ideas. (1983). Engle Wood Cliffs, New Jersey: Prentice-hall Inc.Electronic Sources:Retrieved Feb. 5, 2005 from http://images.google.com.ph/imageRetrieved Feb. 5, 2005 from http://images.google.com.ph/imagesRetrieved Feb. 5, 2005 http://images.google.com.ph/imagesRetrieved Feb. 5, 2005 http://images.search.yahoo.com/search/images - 29 -

Module 14 Genetics: The Study of Inherited Traits What this module is about This module will discuss the topic on how traits are passed on from parents tooffspring. It also includes the laws that govern the patterns of inheritance including thegenetic material involved, the DNA. This pattern of inheritance can be observed over aseries of generations as discussed in the different laws founded by Gregor Mendel. Thediscussion starts with the patterns of transmission of genetic traits to a more discrete topic –the DNA. There are three lessons included in this module. These are:  Lesson 1 – MENDEL’S Law of Inheritance  Lesson 2 – Non-Mendelian Patterns of Inheritance  Lesson 3 – DNA: The Genetic Material What you are expected to learn After going through this module, you are expected to: • Describe the Mendelian Laws of Inheritance. • Differentiate monohybrid cross from dihybrid cross. • Describe the composition of the genetic material. • Describe DNA replication and protein synthesis. • Define genetic engineering. How to learn from this module There are some pointers that you have to follow as you go over this module. Thesepointers will help you achieve the objectives of this module successfully.  Do not forget to take the pre-test.

 Go through the pages one by one since the topics are related to one another. If you miss one page, you may not understand the succeeding pages. Perform the activities as instructed and be sure to finish them. If ideas are not clear you can always go back to the pages where they are discussed. At the end of the module, do not forget to take the posttest. What to do before (Pretest)I. Multiple Choice. Choose the letter of the correct answer. Write the chosen letter on aseparate sheet of paper.1. Who is considered as the father of Genetics?a. Darwin c. Gregor Mendelb. Linnaeus d. Hugh de Vries2. Punnett squares are used to ________ the outcome of crosses of traits.a. assure c. numberb. dominate d. predict3. Which of the following are located in the chromosomes?a. Carbohydrates c. Pedigreesb. DNA codes d. Zygotes4. A codon is composed of: c. 3 bases a. 1 base d. 4 bases b. 2 bases5. A nucleotide is composed of: c. sugar only a. base only d. sugar, phosphate and base b. protein only6. The science that deals with the study of how traits are inherited from parents tooffsprings is calleda. Economics c. Politicsb. Genetics d. Polygenic7. The component in the nucleus of a cell that codes and stores genetic information iscalleda. DNA c. Nucleoplasmb. Nucleolus d. RNA8. An organism with two identical alleles for a trait is calleda. heterozygous c. homozygousb. homologous d. polyploid -2-

9. Which refers to the different forms of genes representing a certain trait?a. allele c. hybridb. chromosome d. locus10. Which of these is a combination of the dominant and recessive genes present in thecells of an organism?a. genotype c. neotypeb. lectotype d. isotype11. Which of the following is NOT a Mendelian law of inheritance? a. In every organism, there is a pair of factors that control the appearance of a particular trait. b. The first filial generation does resemble either parent. Therefore no allele is dominant over the other. c. During gamete formation, the pair of factors segregates or separates from each other. d. During fertilization, the genes come together again to form new combinations.12. What is a monohybrid cross? a. A cross using a single factor or character. b. A cross using two factors or characters. c. A diagram that determines the possible combinations of traits. d. None of the above.13. All are Non-Mendelian laws of inheritance EXCEPT,a. codominance c. incomplete dominanceb. multiple alleles d. law of segregation14. Which of the following describes DNA replication?a. parallel c. conservativeb. anti-parallel d. semi-conservative15. What is genetic engineering? a. It involves transcription and translation. b. A process of altering the genes, which you find in all living things. c. A method that scientists use to produce a genetic copy of another individual. d. None of the above.II. Problem Solving (5 points each)1. Provide the genotype of the given cross:Yellow color in peas (Y) is dominant over green peas (y). A homozygous yellow peaplant is crossed with a homozygous green pea plant. What will be the genotypes of allthe possible offspring? -3-

2. In fruit flies, long wing (L) is dominant to short wing (l). Two heterozygous long-winged fruit flies both (Ll) are crossed. What are the possible phenotypes of their offspring? Key to answers on page 28.Lesson 1. MENDEL’S Law of Inheritance Look around you and notice the amazing variations among living organisms. Haveyou ever wondered how this happened? What could be responsible for this? These aresome of the questions that will be answered as you go over the module. Now focus on the diagram below. It is composed of different organisms. Could youidentify some differences and similarities among them? Variation is a fascinating feature ofliving things. It can exist among organisms of the same species (roses) or among differentspecies (dogs and cats). Start your study of variation by comparing the different organismsin the said diagram. Figure 1. Variation among living organisms www.yahoo.com images -4-

Did you ever notice how much brothers and sisters look alike? Within your family,you share many of the same traits, don’t you? You can start studying variation amonghumans by observing yourself and the members of your family.What you will doActivity 1.1 Observing Yourself, Relatives and Friends1. Examine the table below and identify the features that you and your friends have from the list. There are two traits that are diagrammed. Do you find these traits among you and your friends? Part of the body/Trait AppearanceType of hairEarlobes Straight Wavy or kinky hairColor of the skinHairline Attached UnattachedDimplesHandedness Light or fair DarkNose Straight With widow’s peak With dimples Without dimples Right handedness Left handedness High-bridged Low-bridged Figure 2. Variation in hairline and earlobes (pictures from clip art collection)2. Now focus your attention to the traits of you family members. Your family members include your mother, father, brothers and sisters. Answer the following questions: a. Who among your family members look similar to you? b. Who has the most number of differences with you? -5-

Mendel and His Garden Peas Heredity is the study of how traitsare passed on from the parents to theoffspring. Genetics is the study of heredityand variation. An understanding of the fieldwill help you understand why you havesimilarity with your parents.Do you know the first person whoworked on the topic inheritance? His nameis Gregor Mendel, an Austrian by nationalityand a monk by vocation. Figure 3 Figure 4 He worked and lived in a monastery Gregor Mendel Pea Plantswith large gardens planted with different www.yahoo.com imageskinds of peas. Are you familiar with peas (chicharo)? These are how peas look like. He got interested in peas and noted several of their distinguishing character traits. Aclearer picture of the traits is shown below: Constricted (v) Figure 5. Mendel’s Pea Traits www.yahoo.com images -6-

Why do you think Mendel chose green peas for his experiments? Well, peas havetraits that are easily noticeable. They are easy to breed and grow, which make it easy toreproduce new generations of peas in a short period of time and in large numbers. It has been observed that pea plant normally pollinates itself because it has perfectflowers, or flowers with both the male and female reproductive organs. The pollen grainsfrom the same flower can pollinate the eggs cells or ovules from the same flower. However,to cross-pollinate, Mendel tried to remove the stamens while still young. Then, when thepistil matured, he dusted it with the pollen grains from another pea plant.Mendel’s First Experiment In his first set of experiments, he needed to cross-pollinate pure breeding pea plants.To get plants that are pure breeding, he allowed the pea plants to self-pollinate for manygenerations. For instance, yellow seed peas were self-pollinated until all the pea plants in agiven generation produced all yellow seed peas. His purpose here was to cross these purebreeding peas with other pure breeding peas and observe the kind of offspring that will beproduced.Monohybrid Cross Monohybrid cross involves a cross using a single factor or character trait. How didMendel execute this? Well, after producing a pure breeding stock, he started crossing ormating the pea plants. In our discussion we will use X to represent crossing or mating.The peas that he crossed had different expressions of a given trait like for example, roundor wrinkled seeds, green and yellow pods, etc. He accomplished this by carefully cross-pollinating the peas by covering the flowers to avoid accidental pollination from other peas. At first, he used P1 Xonly one trait like theseed shape. So he Round seed Wrinkled seedcrossed a pure breed ofround seeds with the F1 (offspring)pure wrinkled seeds. Hedid this several times All round seedsand from each cross hegot the same result as Figure 6shown in Figure 6. Mendel’s cross using pure-breed round and wrinkled seed The P1 in thecross stands for the firstparents (the purebreeds). The F1 stands -7-

for the first filial generation or first offspring. Notice that all the offspring are peas withround seeds. These are also called as the hybrids because they are the result of a crossbetween two pure-breeding plants. They resemble one another and one of the parents.Mendel got similar results for all the seven pairs of traits he investigated, as shown in Table1.Table 1. Mendel’s results of the cross between pure breed pea plantsTRAITS STUDIED PARENTS FIRST FILIAL GENERATION (F1)SEED SHAPE Round X Wrinkled All roundSEED COAT COLOR Colored X White All coloredSEED COLOR Yellow X Green All yellowPOD SHAPE Inflated X Constricted All inflatedPOD COLOR Yellow X Green All greenFLOWER POSITION Axial X Terminal All axialSTEM LENGTH Long X Short All long Did you ever wonder what happened to the wrinkled trait and to the other traits? Whywas it that only the round trait came out? You will learn more as we go over the otherinteresting topics on heredity. Continue and more power!Try this: A pure bred red gumamela flower is crossed with a purebred yellow gumamela flower. If the F1 were all gumamela withred flowers, how would you represent this cross? You canrefer to Figure 6 on page 7. The solution is similar to thisexcept for the diagrams and labels. Key to answers on page 29.Crossing the Hybrid Plants Where then is the trait for the wrinkled seed? Will it appear in the next generation?Determined to know what happened to the other lost trait, Mendel continued hisexperiments. This time he used these hybrids to produce another type of offspring. Whatdo you think came out after he tried to cross a hybrid with another hybrid? Do you have anyguess? Just like you, these were also some of the questions that drove Mendel to go onwith his experiments. Continue reading the module and find out what happened! -8-

Now, with this in mind, he tried to cross the plants from the F1 generation (hybrid)with each other, meaning he used the round seed peas that were produced in his firstexperiment. The resulting plants from this cross, or the second filial generation (F2) wereof two types: about three fourths (3/4) had round seeds and about ¼ had wrinkled seeds. Atlast the wrinkled seed peas came out! Isn’tthis amazing? P1 Round seeds X Wrinkled Mendel was then satisfied with his seedsexperiment. Note that the F1 plants are nowthe parents of F2 plants. Again, Mendel’sfindings were similar for each of the seven F1 All round seedspairs of traits he studied. In the F2 generation, he was able to F2 ¾ round seeds and ¼ wrinkledcount 5,474 peas with round seeds, and seeds1,850 wrinkled seeds. What can you inferfrom the results? Do you have any answer? Fig. Result obtained by Self-pollinatingDo you notice that the round seeds are about F1 peasthree times as many as the wrinkled seeds?The ratio is nearly 3:1. Figure 7. Sample cross of hybrids Study carefully the simple diagrammade for you in Figure 7. This willsummarize the last discussions presented.Another representation of crossing hybrid plants is shown below:Figure 8. Crossing hybridwww.yahoo.com images -9-

Again, try this: A pure breed tall plant is crossed with pure breed short plant. All the F1 were tall. When the F1 were crossed, the offspring were ¾ tall and ¼ short. How would you represent this in a diagram? Refer to Figure 6 for guidance. Key to answers on page 29. Is your answer correct? Well, congratulations! You finally made it!Mendel’s hypothesis based on his experiments Based on his first experiment Mendel was able to hypothesize that there must be afactor in plants that controls the appearance of a trait. Recall that in the cross betweenpure breed round and wrinkled seeds, only the round trait came out. The wrinkled trait washidden. This factor is now called a gene. Have you ever encountered this word before?Since there are two alternative expressions of a trait, he reasoned further that traits arecontrolled not only by one but a pair of factors now called alleles. This resulted to theformulation of his hypothesis which states that: In every organism, there is a pair offactors that control the appearance of a particular trait. Going back to the F1 generation, although they were round seeds, the seeds were nolonger like the pure round seed parent plants. The peas in the F1 had in them a factor forround seed and a hidden factor for wrinkled seed that would appear in the F2 generation. One parent has a pair of factors for round seeds, while the other parent has a pair offactors for wrinkled seeds. From these, Mendel was able to hypothesize that: “Onemember of the pair of factors may hide or prevent the appearance of the otherfactor.” The trait of round seed that appeared on the F1 is called a dominant trait. The traitwhich did not appear (wrinkled because its appearance was masked by the dominant trait iscalled a recessive trait. (Refer to Mendel’s pea traits on page 6.) What are the dominantand recessive traits of pea plants? In Genetics, the two factors mentioned by Mendel are called alleles. These allelescould be dominant or recessive. These alleles maybe represented this way: a capital letterfor the dominant trait, and a small letter for the recessive trait. We can use the first letter ofeither the dominant or recessive trait to represent a particular trait. For example, R forround seed and r for wrinkled seed. Or it could be regarding the color of pod where youcan represent G for green pod and g for yellow pod. Do not confuse yourself with the useof the first letter. Remember the same letter will be used for both the dominant andrecessive traits. They will only differ as to whether it will be capital letter or small letter. - 10 -

Now, since genes are in pairs, the pure breeding round plant will be symbolized RRand the pure breeding wrinkled seed rr. Are you still with me? I hope everything is stillclear. Now, do this simple activity:Do this: Represent the following traits using letters to fill-up theblanks in the table: Dominant Recessive Dominant Recessive (letters only) (lettersTall Short only)Curly hair Straight hairBrown eyes Blue eyesUnattached Attachedearlobe earlobe Key to answers on page 29. The alleles making up a pair maybe identical or not. For example, for round it is RRand this type of allele is homozygous or homozygote. If the allele is Rr like the F1generation, it is heterozygous or heterozygote. An individual maybe heterozygous forsome traits and homozygous for others. Today, the alleles which are represented by paired letters are referred to as theindividual genotype. The genotype therefore, refers to the genetic composition of theperson, while phenotype is the physical appearance or feature of the person. For example,RR allele is homozygous round in genotype and the phenotype is round. Is the explanationclear? I hope so. You might ask, “Do factors or genes change as they are transferred from onegeneration to the next?” Using Mendel’s experiment, the answer is no. “In successive generations, each factoris transmitted unchanged.” Remember that the factor for wrinkled in P1 generation is thesame as that found in F1 generation. This means that individual factors do not mix as theyare transmitted from generation to generation. Another hypothesis formulated by Mendel is known as “The Law of Segregation”,which states that: “During gamete formation, the pair of factors segregate or separate fromeach other.” These factors are located in the chromosomes and are transmitted to the - 11 -

offspring through the egg cell and the sperm cell. Figure 9 below shows how genes aretransmitted to the offspring.Figure 9 Science and Technology II The other Mendelian Law of inheritance is the Law of Recombination. It states thatduring fertilization, the genes come together again to form new combinations. We will no longer discuss these two laws in detail. Another topic on dihybrid crosswill be discussed in the next lesson. What you will do Self-Test 1.11. What is a dominant trait? Recessive trait?2. Differentiate monohybrid cross from dihybrid cross.3. What is a homozygote? Heterozygote?4. What is the pattern of inheritance for the first generation?5. What is the pattern of inheritance for the second generation? Key to answers on page 29.- 12 -

Cross with Two Factors (Dihybrid Cross) Mendel did not only study the inheritance of one pair of factors or alleles. He alsostudied the inheritance of two pairs of alleles. The cross that involves two pairs of alleles iscalled dihybrid. An easy way to do this cross is through the use of Punnett square. What is a Punnettsquare? It is a diagram named after Reginald C. Punnett, the man who devised it. ThePunnett square can help you predict the outcome of a given cross with ease. It allows us todetermine the possible combinations of genes in a given cross. For example, what is theexpected result if you try to cross two hybrids for the type of flowers in pea plants? Now,examine the diagram below. This is how it works:A Simplified Punnett Square A. The basic step for a cross between two heterozygous axial flowers will be: Aa X Aa 1. Next, figure out the possible gamete genotype, and try to separate the alleles, just like in the diagram below. 2. Place the possible gamete genotypes on the outside of a square. 3. Simulate fertilization by moving the gametes into each of the internal boxes (which simulate possible offspring); interpret the results. Based on the results you will find out that there are three genotypes produced bycrossing two hybrids. 1 homozygous axial; 2 heterozygous axial and 1 homozygousterminal flowers. - 13 -

Now, can you do this for a dihybrid cross? To familiarize yourself with the use ofPunnet square, try to examine the diagram below. It will show you how a Punnet square willlook like using two types of factors or alleles for a dihybrid cross: Figure 10. Phenotype and Genotype - 14 -

Next is another example of a dihybrid cross using the pea plants in Mendel’s work. Itdeals with the types of seeds and the color of seed pods among pea plants.P1 XPhenotype Round, yellow X Wrinkled, green RR YY rr yy RY ryGametes Rr YyF1 Phenotype Round, Yellow Genotype RrYy(F1 self-fertilized) RrYy X RrYyF2 RRYY RRYy RrYY RrYy RRYy - round, yellow RRyy Rryy rRyy - round, green rrYY rrYy rryY – wrinkled yellow rryy - wrinkled green Based on Mendel’s experiment, he got 315 round yellow, 105 round green, 101wrinkled yellow and 32 wrinkled green pea plants. This is equivalent to a phenotypic ratio of9:3:3:1. Meaning , there are 9 round yellow, 3 round green, 3 wrinkled yellow, and 1wrinkled green.Now let us see how good you are in doing a cross using a Punnett square. Do this activitybelow: - 15 -

What you will do Activity 1.2 Filling Up the Punnett SquareGiven this cross, TtGg X TtGg, fill-up the squares with the correct answer.Ovum T T t t♂♀Sperm G g G gTGTgtGtg Were you able to fill - up the table correctly? You can compare your answer with theanswer key at the back of this module. If you are through try to continue answering thesequestions: 1. How many are tall green? Short yellow? Tall yellow? Short yellow? 2. Give the phenotypic ratio. Key to answers on page 30. What you will do Self-Test 1.21. Given the cross AaBb X AaBb, construct a Punnett square and determine the write the genotypic ratio ( the probability that a particular genotype will occur) of the resulting cross. Key to answers on page 30. - 16 -

Lesson 2. Non-Mendelian Patterns of Inheritance History records that the works of Mendel were incomplete, because he failed todiscuss in detail the “ factors” or genes that he mentioned in his Laws of inheritance. After his time the Chromosomal Theory of Inheritance formulated by Sutton andBoveri became very popular as it explained that genes are found in the chromosomes.What are chromosomes? Chromosomes are structures found inside the nucleus of a cellthat carries the genes.Incomplete Dominance Why is it that in nature we do not always observe the dominant - recessiverelationship? Are you familiar with a red gumamela and a white gumamela? A crossbetween the two (red and white gumamela) will produce all pink flowers. With incompletedominance, we get a blending of the dominant and recessive traits so that the thirdphenotype is something in the middle, e.g red X white = pink flowers. There are cases inwhich the dominant allele isunable to completely hide theeffect of the recessive allele.The flowers in the F1 are pink,not red. The situation inwhich the F1 does notresemble either parent iscalled incompletedominance. In this case, noallele is completely dominantover the other. A clear pictureof incomplete dominance isshown in Figure 11. Hereplants with red flowers arecrossed with plants with whiteflowers. The F1 and F2generations are shown. Whatcan you say about theoffspring in the F1? It Figure 11 An example of Incomplete dominanceproduced all pink flowers www.yahoo.com imageswhile in the F2 1 red, 2 pinkand 1 white flower areproduced. - 17 -

Now do a simple activity by filling up the blanks with the correct answers.If BB – blackbb - white P1 BB x bb F1 ____(gray)(self-fertilized) Bb x Bb F2 BB Bb Bb bb ___ ____ ____ ____ (give the phenotypes) Key to answers on page 31. Now that you are familiar with incomplete dominance, let us move on to co-dominance.Codominance Another example that is non-Mendelian iscodominance. What is co-dominance? Codominancedescribes a situation in which both alleles are expressed atthe same time. The hybrid organism shows a third phenotype- not the usual “dominant” and not the “recessive” one… but athird, different phenotype. The observed red and white striped petals of some Figure 12. Codominancecarnation plants are example of codominance. Another www. yahoo.com imagescodominance is shown in the roan coat of cows, where bothbrown and white hair colors appear (see Figure 12).Multiple Alleles Do you know your blood type? What about your parent’s blood type? Do you knowthat your blood type could be inherited? Some issues on parentage can be resolvedthrough blood typing. It is true that individuals within a population have two alleles per gene. However,multiple alleles (3 or more) may exist for that gene within a population. A good example ofmultiple alleles is the ABO blood group of humans. A single gene controls ABO blood type. - 18 -

But there are three common alleles of this gene in human populations - IA, IB, and Io. The IAand IB are dominant over IO. Individuals with genotype IAIA or genotype IAIO have blood typeA. Those with genotype IBIB or genotype IBIO have blood type B. The IA and IB alleles arecodominant, thus individuals with genotype IAIB have blood type AB.Examine the table 2 below on the different blood groups. Table 2 Phenotype Genotypes antigens on red plasma antibodies(blood group) blood cells anti-B A IAIA, IAIO A anti-A B none AB IBIB, IBIO B anti-A and anti-B O IAIB A and B IOIO none The cross below shows how all four blood groups can arise from a cross between agroup A and a group B parent. Notice that a heterozygous blood type A and B can produce offspring with blood TypeO. But all blood Type O parents can only produce Type O children.Lesson 3. DNA: the Genetic Material In the last previous two lessons we discussed the patterns of inheritance in livingorganisms based on Mendel’s Laws. Now, it is necessary for you to know in detail the“factors” or genes that control inheritance that we repeatedly discussed. - 19 -

What is a gene? A gene is a segment of DNA that encodes a unique protein thatperforms a specialized function in the cell. A gene is capable of storing information andcapable of self-replication and can undergo mutations. But how does something so smallcontain all the genetic information of an organism? The answer to this question lies in thechemical make up of DNA.The chemical composition of DNA DNA, which stands for deoxyribonucleic Figure 13acid, is found within the nucleus of every cell. www.yahoo.com magesYour DNA is like your thumbprint. It is yours andyours alone. Unless you have an identical twin, noone else in this world has exactly the same DNAas you. DNA holds the genetic informationneeded to make and control all cellular activitieswithin a living organism. Examine figure 13. It shows thecomposition of a DNA molecule. DNA contains four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Aand G are double-ring structures called purines; T and C are single-ring structures calledpyrimidines. The nucleotide is the building block of DNA. It is made up of four bases, afive-carbon sugar deoxyribose, and a phosphate group.Watson and Crick Model In 1953, James Watson and Frances Crick worked out that DNA is like a “doublehelix”. A helix is a screw-shaped spiral. The DNA is double helix because of the twostrands which wind around each other. The double helix DNA is like a winding staircase.The two sugar-phosphate backbones make up the sides and the base pairs make up therungs or steps of the winding staircase. The model shows thatpaired nucleotide, which alwaysoccur as A-T or G-C, are linkedby hydrogen bonds. This iscalled the complementary basepairing. Figure 14 illustratesWatson and Crick model. Figure 14Watson and Crick Model ofDNA (www.yahoo.comimages) - 20 -

Why is DNA Important? All the characteristics that you have are affected by the DNA in your cells. It controlsthe color of your eyes, color of your hair, complexion, height and many more. Thesecharacteristics, just like what we have mentioned in the last two lessons, are traits that canbe inherited just like those in pea plants. How traits appear in you depends on the kind ofproteins your cells make. DNA stores the blueprints for making proteins.How DNA Copies Itself What is the process by which DNA copies itself? The following are the events whileDNA copies itself:  Step 1. An enzyme breaks the bond between the nitrogen bases. The two strands of DNA split.  Step 2. The bases attached to each strand then pair up with the free nucleotides found in the cytoplasm.  Step 3. The complementary nucleotides join to form new strands. Two new DNA molecules, each with a parent strand and each with a new daughter strand, are formed. The DNA replication is known as semi-conservativereplication, because one of the old strands is conserved in eachdaughter molecule. Figure 15 illustrates the semi conservativereplication of DNA. So now you are familiar with the DNA Figure 15molecule? The next topic that we will discuss is Semi-conservative DNA Replicationanother nucleic acid patterned from the DNA, theRNA. (www.yahoo.com images)What is RNA? Figure16. The RNA Structure www.yahoo.com images RNA stands for ribonucleic acid. Like DNA,RNA is a long strand made up of building blocks callednucleotides. But unlike DNA, RNA has a single chainand does not entwine in a double helix. Table 3 showshow DNA is compared to RNA. Figure 16 illustrates thestructure of RNA. RNA is a single stranded molecule with no helix.The four bases are guanine, cytosine, adenine, anduracil instead of thymine. - 21 -

Table 3. DNA Compared to RNA DNA RNAsugar Deoxyribose Ribosebasesstrands A,T,G,C A,U,G,Chelix Double strands Single strand yes No What you will do Activity 3.1 DNA ReplicationDirection: Provide the correct base pair on the columns provided. Split DNA New DNA Split DNA New DNA(old strand) strand (old strand) strand A T T A T A A T G C G C C G A T T A G C C G A T T A T A G C C G C G Key to answers on page 31.What you will doSelf-Test 3.1 1. Describe the composition of genetic material. 2. Describe DNA replication. Key to answers on page 31. - 22 -

Translating the code of life: From DNA to RNA to protein. Proteins control the activities of the cell, and so the life of the entire organism. But,how does DNA make a unique protein that will perform special function?The following are the steps inmaking proteins:I. The DNA is inside thenucleus. It contains theinformation for makingproteins. This informationhas to be copied ortranscribed by the RNAcalled messenger RNA(mRNA).II. The copied informationcalled codon, which ismade up of threeconsecutive nitrogenousbases, is sent to thecytoplasm where it willenter the ribosomal RNA.III. Once inside the ribosome,translation begins, Figure 17. Protein synthesismeaning, the transfer of www.yahoo.com imagesRNA (tRNA) from thecytoplasm starts to bring the anticodon, the three consecutive nitrogenous pairs, thatfits the mRNA codon. A codon is a base triplet of nucleotides in mRNA which calls foran amino acid. Each anticodon represents one type of amino acid. Amino acids arethe basic units of protein molecules.IV. When all codons are converted into amino acids, translation stops and a proteinmolecule is produced.Always remember this: genes make proteins, proteins make cells, cells maketissues, tissues make organs, organs make organ systems, and organ systems makeyou!Biotechnology Another very interesting topic in science today is biotechnology. What isbiotechnology? The term refers to any technique that uses living organisms, or parts oforganisms, to make or modify products, improve plants or animals, or to developmicroorganisms for specific uses. Are you familiar with the latest biotechnologies? Well,under this topic we are going to discuss some very familiar biotechnologies. - 23 -

What is Genetic Engineering? Genetic engineering is a process of altering the genes which you find in all livingthings. It involves the transfer of genes or parts of DNA from one organism to another.Organisms whose genes are altered or modified for specific purposes are called transgenicorganisms.What are the uses of genetic engineering? The purposes of doing genetic engineering are many and various. A range of them arelisted below. These include:  repairing a genetic \"defect\" (as with the current early trials of gene therapy in humans);  enhancing an effect already natural to that organism (e.g. to increase its growth rate);  increasing resistance to disease or external damage (e.g. crops - blight, cold or drought);  getting a micro-organism to produce human insulin for diabetics, or a sheep to produce a human blood-clotting protein in her milk, in both cases a transgenic method; and  getting a tomato to ripen without going squashy - this can be done simply by taking one of its own genes, turning its \"pattern\" upside down and putting it back again!Isn’t this amazing? Continue reading the modules and enjoyWhat is Cloning? In 1997, a 7-month-old sheep named Dolly became acelebrity (Figure 18). Do you know why? Dolly is the first clonedanimal. What is cloning? Cloning is a method that scientists useto produce a genetic copy of another individual. In other words,Dolly is a clone of her mother. Well, actually, Dolly had three mothers. One mother gaveDolly her DNA, one mother supplied an egg, and the third mother,her surrogate mother, gave birth to her. Isn’t this interesting?Normally, an animal gets half of its DNA from its mother Figure 18and half from its father. Dolly is an identical twin of the motherwho gave her DNA. But Dolly is six years younger. However, www.yahoo.com imagesDolly and her mother are not identical in every way. Since Dollyand her “DNA mother” have different experiences, they aredifferent in many ways. Like human twins, clones have unique personalities. Unluckily, justlast year, Dolly, the first cloned sheep died after more or less 7 years of survival. - 24 -

Congratulations! At last you are through with the module. Did you enjoy it? Before you endthis module answer the self-test below and proceed with the summary and posttest. What you will do Self-Test 3.21. What is genetic engineering? Are you in favor of genetic engineering? Why?2. What do you think are some of the issues related to biotechnology? Why do you consider them as issues? Key to answers on page 32. Let’s Summarize 1. Heredity is the study of how traits are passed on from the parents to the offspring. Genetics is the study of heredity and variation. 2. Monohybrid cross involves a cross using a single factor or character trait. 3. Dihybrid cross involves a cross using two factors or character traits. 4. In Genetics, the two factors mentioned by Mendel are called alleles. These alleles could be dominant or recessive. 5. Alleles can be represented by paired letters and referred to as the individual genotype. The genotype refers to the genetic composition of the person. 6. The phenotype is the physical appearance or feature of the person. 7. Identical alleles are called homozygous while dissimilar alleles are called heterozygous. 8. The Law of Segregation states that during gamete formation, the pair of factors segregate or separate from each other. 9. The Law of Recombination states that during fertilization, the genes come together again to form new combinations. 10. The Punnett square is a diagram that allows us to determine the possible combinations of genes in a given cross. 11. A gene is a segment of DNA that encodes a unique protein that performs a specialized function in the cell. 12. DNA stands for deoxyribonucleic acids. It is a double-stranded molecule. 13. RNA stands fro ribonucleic acids. It is a single-stranded molecule. 14. DNA contains four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A and G are double-ring structures called purines; T and C are single-ring structures called pyrimidines. The nucleotide is the building block of DNA. It is made up of four bases, a five-carbon sugar deoxyribose, and a phosphate group. 15. The DNA replication is known as semi - conservative replication, because one of the old strands is conserved in each daughter molecule. 16. Protein synthesis involves transcription and translation. - 25 -

17. The situation in which the F1 does not resemble either parent is called incomplete dominance. In this case, no allele is completely dominant over the other.18. Codominance describes a situation in which both alleles are expressed at the same time.19. Biotechnology refers to any technique that uses living organisms, or parts of organisms, to make or modify products, improve plants or animals, or to develop microorganisms for specific uses.20. Genetic engineering is a process of altering the genes which you find in all living things. It involves the transfer of genes or parts of DNA from one organism to another. Organisms whose genes are altered or modified for specific purpose are called transgenic organisms.21. Cloning is a method that scientists use to produce a genetic copy of another individual. PosttestI. Multiple Choice. Choose the letter of the correct answer. Write the chosen letter on aseparate sheet of paper.1. Who is considered as the father of Genetics?a. Darwin c. Gregor Mendelb. Linnaeus d. Hugh de Vries2. Punnett squares are used to ________ the outcome of crosses of traits:a. assure c. numberb. dominate d. predict3. Which of the following are located in chromosomes?a. Carbohydrates c. Pedigreesb. DNA codes d. Zygotes4. A codon is composed of: c. 3 bases a. 1 base d. 4 bases b. 2 bases5. A nucleotide is composed of: c. sugar only a. base only d. sugar, phosphate and base b. protein only6. The science that deals with the study of how traits are inherited from parents tooffsprings is calleda. Economics c. Politicsb. Genetics d. Polygenic - 26 -

7. The component in the nucleus of a cell that codes and stores genetic information iscalled:a. DNA c. Nucleoplasmb. Nucleolus d. RNA8. An organism with two identical alleles for a trait is called:a. heterozygous c. homozygousb. homologous d. polyploid9. Which refers to the different forms of genes representing a certain trait?a. allele c. hybridb. chromosome d. locus10. What do you call a combination of the dominant and recessive genes present in the cellsof an organism?a. genotype c. neotypeb. lectotype d. phenotype11. Which of the following is NOT a Mendelian law of inheritance? a. In every organism, there is a pair of factors that control the appearance of a particular trait. b. The first filial generation does resemble either parent. Therefore no allele is dominant over the other. c. During gamete formation, the pair of factors segregates or separates from each other. d. During fertilization, the genes come together again to form new combinations.12. What is a monohybrid cross? b. A cross using a single factor or character. c. A cross using two factors or characters. d. A diagram that determines the possible combinations of traits. e. None of the above.13. All are Non-Mendelian laws of inheritance EXCEPT,a. codominance c. incomplete dominanceb. multiple alleles d. law of segregationc. incomplete dominance14. Which of the following describes DNA replication?a. parallel c. conservativeb. anti-parallel d. semi-conservative15. What is genetic engineering? a. It involves transcription and translation. b. A process of altering the genes, which you find in all living things. c. A method that scientists use to produce a genetic copy of another individual. d. None of the above. - 27 -

II. Problem Solving (5 points each)1. Show the given cross below: a. Axial flower (A) in peas is dominant over terminal flowers (a) in peas. A homozygous axial pea plant is crossed with a homozygous terminal pea plant. What will be the genotypes of all the possible offspring? b. In man, brown eyes (B) is dominant over blue eyes(b). If a homozygous brown- eyed man marries a blue-eyed woman, what percent of their children will be blue- eyed? Key to answers on page 32.Key to AnswersPretest II. 1. Result: I. Genotypes of all possible offspring: All Yy 1. c Phenotype of offspring: All yellow 2. d 3. b 2. Result: 4. c Genotypes of all possible offspring: LL, Ll, and ll 5. d Phenotypes of all possible offspring: LL and Ll = long wings 6. b ll = short wings 7. a 8. c 9. a 10. a 11. b 12. a 13. d 14. d 15. b - 28 -

Lesson 1 Again Try this: TT X ttTry this: RR X rr Tt (self- fertilized) red yellow TT, Tt, tT and tt Rr All redDo this: Dominant Recessive Dominant Recessive (letters (letters Tall Short only) only) Curly hair Straight hair Brown eyes Blue eyes TT tt Unattached Attached CC cc earlobe earlobe BB bb AA aaSelf-Test 1.1 1. Dominant trait - a form of a trait that appears to dominate or mask another form of the same trait, while recessive trait is a form of a trait that appears least often in offspring. 2. Monohybrid cross involves a cross using a single factor or character trait, while dihybrid cross involves a cross using two factors or character traits. 3. Homozygote - an organism that has two identical alleles for a trait while heterozygote refers to an organism that has two different alleles for a trait. 4. When two different pure breed parents are crossed, the first generation shows only one trait (the dominant) the other trait is hidden (recessive). 5. In the second generation he got plants that showed the dominant trait to everyone plant that showed the recessive trait - 29 -

Activity 1.2 Ovum T T t t sperm G g G g T TTGG TT Gg Tt GG Tt Gg G TT gG TT gg Tt gG Ttgg T g t tT GG tT Gg tt GG ttGg G t tT gG tT gg ttgG ttgg g1. There are 9 tall and green peas; 3 short green; 3 tall yellow, and 1 short yellow peas.2. The phenotypic ratio is 9:3:3:1Self-Test 1.2 Ovum A A a a B b B b sperm AABb AaBB AaBa A AAbb AabB Aabb B AABB A b AAbB a AaBB AaBb aaBB aaBb B a aAbB aAbb aabB aabb b1. The genotypic ratio of the cross is 4:2:2:2:2:1:1:1:1:1 or 4 AaBb; 2 AaBB; 2 AABb: 2 aaBb: 2Aabb: 1 aaBB: 1 AABB: 1AAbb: and 1aabb - 30 -

Lesson 2Activity 2.1 Answer for Incomplete DominanceIf BB – black P1 BB x bb bb - white Bb (gray) Bb x Bb F1(self-fertilized) F2 BB Bb Bb bb (black) (gray) (gray) (white)Lesson 3Activity 3.1DNA replication Split DNA New DNA Split DNA New DNA (old strand) strand (old strand) strand A (Answer) T (Answer) T T A A T A A T A A T T G T C A G C C G C C G G A G T C T T A A G A C T C C G G A G T C T T A A T A A T G A C T C C G G C G G C G CSelf Test 3.11. DNA contains four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A and G are double-ring structures called purines; T and C are single-ring structures called pyrimidines. The nucleotide is the building block of DNA. It is made up of four bases, a five-carbon sugar deoxyribose, and a phosphate group. - 31 -

The double helix DNA is like a winding staircase. The two sugar-phosphate backbones make up the sides and the base pairs make up the rungs or steps of the winding staircase.2. The DNA replication is known as semi-conservative replication, because one of the old strands is conserved in each daughter molecule. In step 1, an enzyme breaks the bond between the nitrogen bases. The two strands of DNA split. In step 2, the bases attached to each strand then pair up with the free nucleotides found in the cytoplasm. In step 3, the complementary nucleotides join to form new strands. Two new DNA molecules, each with a parent strand and each with a new daughter strand, are formed.Self-Test 3.2Possible answers:1. Genetic engineering is a process of altering the genes which you find in all living things. Yes, because it can improve the economic condition of the people in one way, but may also cause some harm in the future.2. Some of the issues related to biotechnology are related to the outcome of this technology on the health and environmental condition of the people in the near future. It is said that only God can modify his creations. We are not supposed to play GOD.PosttestI. 6. b 1. c 7. a 2. d 8. c 3. a 9. a 4. c 10. a 5. dII. Given the following cross:1. AA X aa Aa (All heterozygous axial flowers)2. BB X bb Bb ( All or 100% brown-eyed) - 32 -

ReferencesBooks:Johnson, G. (1998). Biology visualizing life. Austin, USA: Holt, Rinehart and Winston Co. Inc.Lewis, R. (1998). Life. (3rd Ed.) USA: WCB McGraw- Hill Co Inc.Mader, S. (1998). Biology. (6th Ed.) USA: WCB McGraw- Hill Co. Inc.Merril. (1994). Life science. Ohio, USA: Glencoe Division, Macmillan/McGraw-Hill Publishing Co.Wong, H. K. & Dolmatz, M.S. (1990). Biology: The key ideas. Englewoods, NJ: Prentice Hall.Electronic sources:Retrieved March 15, 2005 http://www.mcrel.org/compendium/Benchmark.asp?SubjectID =2&StandardID=4Retrieved March 16, 2005 http://www.accessexcellence.org/Retrieved March 20, 2005 http://sciencespot.net/Pages/classbio.htmlRetrieved March 25, 2005 http://www.accessexcellence.org/AE/AEC/index.htmlRetrieved April 4, 2005 http://gslc.genetics.utah.edu/units/cloning/ - 33 -

Module 15 Evolution What this module is about Welcome to Evolution self-learning kit! This module will take you to a historic voyage that has changed our view of lifehistory. Come and join me in this exploration and discover what Charles Darwin has writtenabout how species evolve through the course of time! To open the state-of the-art capsulethat will allow us to understand how organisms evolve to what they are today, you must saythis password: I Evolve, You Evolve, and They Evolve! The module includes the following lessons:  Lesson 1 – The Origins of Evolutionary Thought  Lesson 2 – Evidences for Evolution  Lesson 3 – Process of Evolution What you are expected to learn After going through this module you should be able to: 1. Describe evolution by natural selection. 2. Define direct and indirect evidence for evolution. 3. Describe the different agents for evolutionary change. 4. Differentiate allopatric and sympatric speciations. How to learn from this module Before getting started, I have here some tips for you to successfully achieve theobjectives of this self-learning kit. 1. Read and follow instructions carefully. 2. Answer the pretest before you start the lesson.

3. Take note and record points for clarifications.4. Try to achieve at least a 75% level of proficiency in the tests.5. Answer the posttest.6. Work diligently and honestly.What to do before (Pretest)Before we proceed, let us see if you can answer these simple questions about our lesson.Multiple Choice. Choose the letter of the correct answer. Write the chosen letter on aseparate sheet of paper.1. Which idea stems from the theory of evolution? a. The earth is relatively young. b. Each organism is specially created. c. Species are related by common descent. d. A mix of fossils in a region indicates that a local catastrophe occurred.2. An adaptation promotes c. the chance to survive and reproduce a. the chance to reproduce d. none of the above b. the chance to survive3. Vertebrate forelimbs are most likely to be studied inc. biogeography c. ecologyd. comparative anatomy d. embryology4. Which is NOT true of fossils? a. They indicate that life has a history. b. They are evidences of life in the past. c. The older the fossils, the less they resemble modern day species. d. They look exactly like modern-day species, regardless of their age.5. During the usual process of speciation, a species is first isolateda. behaviorally c. geographicallyb. genetically d. reproductively6. Which type of speciation requires a geographical barrier?a. allopatric c. divergenceb. convergence d. sympatric7. The criterion used to distinguish between two species is based ona. geography c. reproductionb. physical traits d. time -2-

8. Which of the following statements does NOT describe Darwin’s theory of natural selection? a. Members of a population will compete. b. Populations tend to reproduce in small numbers. c. Members of a population have heritable variations. d. Some members of a population have adaptive traits.9. Which of the following describes indirect evidences for evolution? a. consists of actual observation b. is actually observed or seen c. is something that does not involve actual observation of evolution but for which we can infer that evolution has taken place d. None of the above.10. Which of the following mechanisms will cause the gene pool of two populations tobecome similar?a. gene flow c. mutatione. genetic drift d. natural selection11. Which of the following describes mutation? a. A result of inbreeding. b. Any change in the structure of chromosomes. c. Change in gene pool due to unpredictable situation. d. Differential survival and reproduction of organisms.12. What agent of evolutionary change can result to a population whose members are alikein appearance, fitness and lifestyles?a. inbreeding c. genetic driftb. gene flow d. mutation13. What is genetic drift? a. a change in gene pool due to chance alone. b. A mechanism that increases variations in the population. c. The differential survival and reproduction of organisms. d. A change in the structure of chromosomes and gene composition.14. Which type of speciation does not require a geographical barrier?a. allopatric c. divergenceb. convergence d. sympatric15. What does it mean by direct evidence for evolution? a. consists of observations of actual evolution b. does not involve direct observation of evolution c. is something that is not actually observed or seen d. None of the above. Key to answers on page 21. -3-

Lesson 1. The Origins of Evolutionary ThoughtHow did life forms occur? There are many different theories which explain how different life forms exist. In themid- 18th century, most people believed in creationism. Creationism held the idea that allforms of life were created in its present form and they remain unchanged since thebeginning. Do you know that even the famous Carl von Linnaeus, the Father of Taxonomy,believed in the fixity of species? George Louis Leclerc, known as Count Buffon, was a French naturalist who firstdescribed descent with modification such as environmental influences, migration,geographical isolation and the struggle for existence. However he was hesitant in sharinghis idea to the public. In the late 18th century, Georges Cuvier, a vertebrate zoologist and paleontologistproposed the theory of catastrophism. One day he had observed that a particular regionshowed a succession of life forms in the soil layers. His observation seemed to contradictwith his belief in special creation of each species. Cuvier explained that there might havebeen violent and sudden natural catastrophes such as great floods, tectonic earthquakes,and rapid formation of mountain chains, which resulted to death and extinction of mostplants and animals. After each catastrophe, God created new sets of life forms. In contrast to catastrophism, James Hutton and Charles Lyell believed that naturalforces now changing the shape of the earth’s surface have been operating in the past muchthe same way. This idea is known as uniformitarianism - large geological changesoccurred not in catastrophic events but by gradual accumulation of small geologicalchanges over long period of time. Jean Baptiste de Lamarck was the first biologist to believe Jean Baptiste Lamarckthat life forms evolve. He proposed the Inheritance of Acquired www.victorianweb.org/scieCharacteristics, which is also called Lamarckian Evolution. He nce/Lamarck1.htmlbelieved that every organism has the will to survive, and that willhas allowed us to change to more advantageous traits that suit usto the environment. The acquired traits are then inherited by thenext generation. One example that Lamarck gave is theelongation of giraffes’ necks over time because animals stretchedtheir necks to reach for food and then passed on a long neck totheir offspring. Today, Lamarck’s idea was proven to beincorrect. Phenotypic changes acquired during an organism’slifetime cannot pass onto next generations. Cutting the cat’s tailwill not produce kittens without tail! In 1859, Charles Darwin published his book, On the Origin of Species by Means ofNatural Selection. Contrary to creationism, Darwin believed that organisms evolve from -4-

common ancestor. Because we all share a common ancestor, we are all related to oneanother no matter how different we are. The relationships among organisms can beillustrated on a family tree. Look at the illustration below. Figure 1Living organisms sit like leaves at the tips of the branches of the Tree of Life. Living things share a common ancestor. All organisms are related to one another no matter how different they seem. www.sirinet.net/-jgjohso/tree.htmlWho is Charles Darwin? How did he think species evolve? Charles Darwin was only 22 years old when he got a chance to set sail aboard theBeagle, to travel around the world and map the coasts of South America. He was anassistant for Captain Robert FritzRoy. His Beagle voyage allowed him to develop a theorythat would contradict the special creation of every organism andimply that all species evolve from common ancestors through aprocess called natural selection. While on his visit to Galapagos Islands, he had observed Charles Darwinthat organisms are geographically distributed and isolated on the Yahoo.com imagesseparate islands. He noted that similar animal types show distinctdifferences in body form and functions from island to island. Heexplained that these differences represent adaptations to differingenvironment. Darwin believed that over the course of time isolatedgroups of animals had become reproductively isolated, and then-5-

gradually they become separate species.Iguana Turtle FinchBut what is adaptation? Adaptation is a set of genetically acquired traits that make the organism better suitedto its environment. Individuals with advantageous adaptations are more likely to survive andreproduce than those individuals lacking the adaptations.Do organisms simply change to fit or adapt to their environment? No, since adaptation is a set of inherited traits, you Polar Bearcannot change yourself just to suit to certain environmentalchanges. Adaptation is not something you can do http://ceso.netfirms.com/homework%202.htmpurposively or intently. For example, bears and wolves areadapted to live in extremely cold places like polar region.Their thick fur gave them an advantage over animalswithout fur. Other animals without fur, including humans,are not adapted to live in such places. No matter howmuch we want to have fur to suit to that environment wesimply cannot. Remember that any modification or changeduring your lifetime is not an adaptation. If you cut the tailof a mother mouse, do not expect her to produce taillessmittens.What is Natural Selection?Natural selection is the mechanism Darwin proposed for how evolution comes about. Natural selection refers to the differential survival and reproduction of organisms. Hestressed that in a population, the fittest organisms are those possessing characteristics thatallow them to acquire more resources, survive, and reproduce more than the less fit. Darwin’s argument for natural selection is based on a series of five observations andthree inferences: Observation 1 – Organisms have great potential fertility. -6-

 Observation 2 – Natural populations normally remain constant in size, except for minor fluctuations.  Observation 3 – Natural resources are limited.  Inference 1 – There exists a continuing struggle for existence among members of a population.  Observation 4 – All organisms show variation.  Inference 2 – There is differential survival and reproduction among varying organisms in a population.  Inference 3 – Over many generations, differential survival and reproduction generate new adaptations and new species.What does the phrase “survival of the fittest” mean? The phrase survival of the fittest relates to fitness. Fitness depends on how wellcertain traits can function in their specific environment. It includes the organism’s ability tosurvive, to mate, and to reproduce successfully. It does not necessarily mean biggest,fastest, or strongest. A trait may have high fitness in one environment and low fitness inanother.How are the concepts of natural selection and survival of the fittest related? Because some survive better than others, natural selection tends to eliminate less fitcharacteristics. The fittest are those with favorable traits adapted to a specific environment.For example, camels and cactuses are adapted to live in dry places like desert. This isbecause camels are capable of storing large amount of water on their back. Similarly,cactuses store water on their fleshy tissues that prevent them from dehydration. Otherplants and animals which lack traits similar to camels and cactuses cannot live as well insuch excessively dry places.Frog Cactus Camel Do the following activity to find out how adaptation can give an organism areproductive advantage over other organisms. -7-