Science 2 part 2

Key to AnswersPretest 6. d 11. d I. 7. d 12. b 1. b 8. d 13. c 2. a 9. d 14. a 3. d 10. a 15. c 4. b 5. bII. Circulatory Respiratory Blood vessels Nose Digestive Blood Air sacs Liver Heart Trachea Esophagus Arteries Diaphragm Gall bladder Veins Bronchi Stomach Capillaries larynx Mouth Small intestineIII. A. Respiratory B. Heart C. DigestiveLesson 1Activity 1.11. 700 cm – small intestine2. 20 cm – rectum and anus3. 25 cm – esophagus4. There is a difference of 550 cm between the longest yarn and the shortest yarn.Self-Test 1.11. d2. f3. c4. a5. e6. g7. b - 26 -

Self-Test 1.21. small intestines2. lined with millions of tiny hair-like projections (villi)3. the surface is so long so it makes absorption fast4. breakdown of food into simple form and removal of undigested solid food waste.Lesson 2Activity 2.1A. a. Uncomfortable because there was no air. b. Breathing is difficult c. Oxygen, carbon dioxideB. 1. Nose 2. Pharynx 3. Larynx 4. Trachea 5. Bronchi 6. Bronchioles 7. Air sacsSelf-Test 2.11. change in air pressure inside the chest cavity2. exchanges oxygen and carbon dioxide between the air and the cellsSelf-Test 2.21. lungs 5. bronchioles2. nose 6. larynx3. bronchi 7. pharynx4. trachea 8. air sacsLesson 3Self-Test 3.11. fist size, cone-shaped center of the chest2. right and left atrium right and left ventricle3. keep the blood moving in one direction - 27 -

Activity 3.1 1. carry materials to and from all parts of the body 2. right atrium right ventricle left atrium left ventricle 3. carry materials to and from all parts of the body 4. oxygenActivity 3.2Self-Test 3.2 1. Closed. Blood passes through vessels around the body. 2. Arteries, veins, capillaries 3. Transportation 4. Carry blood away from the heart 5. Carry blood towards the heart 6. Tiny vessels that connect arteries to veins 7. Exchange of materials between the blood and cells takes place here.Activity 3.3 1. C 7. A 2. H 8. K 3. B 9. G 4. J 10. I 5. F 11. D 6. E - 28 -

Posttest 6. b 11. d 7. a 12. d 1. d 8. d 13. d 2. b 9. b 14. d 3. c 10. b 15. a 4. a 5. cReferencesBooks:Daniel, L. (1994). Life science. Westerville, OH: Merill Publishing Co., Mcmillan/McGraw- Hill.Grabowski, T. (2003). Principles of anatomy and physiology. NY: John Wiley and Sons, Inc.Holo, W. (1984). Human anatomy and physiology. (3rd Ed.) Dubuque, Iowa: W. C. Brown Publishers.Hopson, J.L. & Wessells, N.K. (1990). Essentials of biology. USA: McGraw-Hill Publishing Company.Kaskel, A., Hummer, P.J. & Daniel, L. (1981). Biology on everyday experience. USA: Merill Publishing Co.Mariele, E.N. (1998). Essentials of human anatomy and physiology. (3rd Ed.) USA: Addison-Wesley Longman, Inc.Payne, H. (1995). Understanding your health. St Louis, Missouiri: Mosby Publishing Company.Pikering, W.H. (2000). Complete biology. New York: Oxford University Press.Wong, H.K. & Dolmatz, M.S. (1986). Biology: The key ideas. Eaglewood Cliffs, New Jersey: Prentice – Hall, Inc. - 29 -

Electronic Sources:Retrieved January 10, 2005 htttp//www4.tpgi.com.au/users/amcgann/body/htmlRetrieved January 10, 2005 from http//www.innerbody.comRetrieved January 10, 2005 from http/www.bartleby.comRetrieved January 10, 2005 from http//www.sirinet.ml/~jgjohnso/biologyII. - 30 -

Module 12 Making New Cells What this module is about In this module you will learn how cell division is essential to growth, repair andreproduction in eukaryotic organisms. The process of dividing the genetic material amongthe daughter cells is integral to both types of cell division. In mitosis, the daughter cellsreceive the same number of chromosomes as the parent cell. In meiosis, a reductive celldivision, the daughter cells are haploid with respect to the parent cell. This module has the following lessons:  Lesson 1 – Mitosis  Lesson 2 – Meiosis  Lesson 3 – Asexual and Sexual Reproduction What you are expected to learn After going through this module, you are expected to: 1. describe the cell cycle; 2. differentiate mitosis from meiosis; 3. enumerate the different patterns of reproduction among organisms 4. differentiate sexual and asexual reproduction of organisms; and 5. appreciate the importance of cell division and reproduction. How to learn from this module I know you are excited to start the adventure just as I am but remember to do thefollowing tips to successfully achieve the objectives of this self-learning kit. 1. Read the instructions carefully. 2. Follow the instructions carefully.

3. Answer the pretest before you start the lesson.4. Take note and record points for clarifications.5. Try to achieve at least a 75% level of proficiency in the tests.6. Work diligently.7. Answer the posttest honestly.What to do before (Pretest) Answer the pre-test to measure how much you know about the topic. You can start now.  There are 20 questions. Each question has ONLY ONE CORRECT ANSWER. Choose the one you believe to be correct.  Each question is worth 2 points.  Read each question carefully. Take your time and think.  GOOD LUCK!1. Which of the following is involved in asexual reproduction?a. mitosis d. binary fissionb. meiosis e. both a & d are correctc. oogenesis2. Which of the following is not a form of asexual reproduction?a. budding d. formation of rhizomeb. regeneration e. union of egg cell and sperm cellc. fragmentation3. Variability in the offspring is an important benefit of what form of reproduction?a. Sexual c. asexualb. Mitosis d. binary fission4. The following events are occurring in both mitosis and meiosis EXCEPTa. cytokinesis c. DNA replicationb. karyokinesis d. pairing of homologous chromosomes -2-

5. Which statement about mitosis is NOT correct?a. It makes diploid nuclei. c. The prophase is the first active phase.b. It forms four daughter cells. d. It does not affect the nuclear envelope.6. Which statement about binary fission is NOT correct?a. It occurs in prokaryotic cells. c. It produces two daughter cells.b. It exhibits five active phases. d. DNA is replicated before division.7. Polar bodies are formed during c. oogenesis a. mitosis d. spermatogenesis b. meiosisIn questions 8-14, label each statement with one of the following choices: a. meiosis I b. meiosis II___ 8. It is the synapsis of homologous chromosomes.___ 9. It involves the separation of homologous chromosomes.___10. It results in one oocyte and one polar body in human females.___11. It results in four sperm cells in human males.___12. The daughter cells have double-stranded chromosomes.___13. The daughter nuclei produced have single-stranded chromosomes.___14. The crossing-over of chromosome occurs.In questions 15-19, match the cell phase to its description. Write the letters only. a. DNA replication b. chromosomes first become visible c. chromatids separate at centromere d. chromosomes are aligned at the metaphase plate e. last phase of nuclear division___15. anaphase___16. metaphase___17. prophase___18. telophase___19. interphase20. The diploid chromosome number in an organism is 42. The number ofchromosomes in its sex cells is normallya. 21 c. 63b. 42 d. 84 Got a perfect score? Check it out! Key to answers on page 24. -3-

Lesson 1. Mitosis Figure 1.1 Overview of the major events in mitosis Source: http://web.jjay.cuny.edu/~/acarpi/NSC/13-cell.htm How much did you weigh when you were born? How long were you? Your bodyneeded millions of new cells to become as large as you are now! It’s very likely that each time you go to the doctor, a nurse measures your height andmass. This activity gives the medical profession an idea of how people grow. Much of thegrowth happens because the number of cells in your body increases as you develop. Most of the kinds of cells in your body are constantly replacing themselves. Bonecells make new bone cells. Muscle cells make new muscle cells. The fact is that you areconstantly changing. You aren’t the same now as you were a year ago or even a few hoursago. At this very moment, as you read this page, groups of cells throughout your body aregrowing, dividing, and dying. Worn out cells on the palms of your hands are being replaced.Cuts and bruises are healing. Other organisms undergo similar processes.How does this happen? There are two ways by which cells increase in number:  Mitosis – is the process in which a cell nucleus divides into two new nuclei, each of which contains the same number of chromosomes as the parent cell. * The parent cell is the cell that undergoes division.  Meiosis – is the process in which there are two divisions of the nucleus: meiosis I and meiosis II.Cell division is controlled by the chromosomes found in each cell. -4-

Figure 1.2 A complete set of chromosomes in human. (A telomere contains bits of DNA on the ends of our chromosomes.) Source: http://www.accessexcellence.org/RC/VL/GG/human.html Study the figure below and take a closer look at what really happens during celldivision (Mitosis). Parent cell Chromatin condenses into chromosomes. Nuclear envelope disappears. Chromosomes align at the equatorial plate. Sister chromatids separate. Centromeres divide.Chromatin expands. Figure 1.3 Cytoplasm divides. Illustration of the process by which somatic cells multiply Two daughter cells and divide. Source: http://www.accessexcelence.org -5-

Mitosis is a process of cell division that results in the production of two daughter cellsfrom a single parent cell. The daughter cells are identical to one another and to the originalparent cell.Cell division is a cycle of events. The process of cell division has been divided into fivephases. These are:  Interphase: the state of a eukaryotic cell when not undergoing division. Every time a cell divides, it must first replicate all of its DNA. Because chromosomes are simply DNA wrapped around protein, the cell replicates its chromosomes also. These two chromosomes, positioned side by side, are called sister chromatids and are identical copies of one another. Before this cell can divide, it must separate these sister chromatids from one another.  Prophase: The chromatin (The total collection of DNA and proteins in a chromosome.), diffuses in interphase, condenses into chromosomes. Each chromosome has duplicated and now consists of two sister chromatids. The centrioles form asters (ray-like structures) and move toward the opposite sides of the cell. At the end of prophase, the nuclear envelope breaks down into vesicles.  Metaphase: The chromosomes align at the equatorial plate (center of the cell) and are held in place by microtubules attached to the mitotic spindle and to part of the centromere.  Anaphase: The centromeres divide. Sister chromatids separate and move toward the corresponding poles.  Telophase: Daughter chromosomes arrive at the poles and the microtubules disappear. The condensed chromatin expands and the nuclear envelope reappears. The cytoplasm divides, the cell membrane pinches inward ultimately producing two daughter cells (phase: Cytokinesis).What happens after telophase? Two new nuclear membranes form and two new nuclei are seen. Two daughtercells are produced from one dividing parent cell. Mitosis has come to an end. In animal cells, two canals (cleavage furrow) form one on each side of the cell. These canals pinch in until two new daughter cells are formed. Plant cells do not pinch in. Instead, a new cell wall (cell plate) forms between the two new nuclei. -6-

What you will doActivity 1.1Science and Math Problem If a single cell undergoes mitosis every five minutes,how many cells will result from this single cell after 30minutes?Activity 1.21. Describe the cell cycle. Key to answers on page 24. What you will do Self-Test 1.1Indicate whether each statement is true (T) or false (F) and change all false statements totrue statements.___1. Binary fission and mitosis ensure that each daughter cell is genetically identical to the parent cell. Rewrite: ___________________________________________________________ ______________________________________________________________________2. Cell division in unicellular organisms is a form of asexual reproduction. Rewrite: ___________________________________________________________ ______________________________________________________________________3. Both binary fission and mitosis are necessary to the growth and repair of multicellular organisms. Rewrite: ___________________________________________________________ ______________________________________________________________________4. Spindle formation occurs both during binary fission and mitosis. Rewrite: ___________________________________________________________ ______________________________________________________________________5. Spindle formation occurs during plant and animal cell division. Rewrite: ___________________________________________________________ ___________________________________________________________________ Key to answers on page 24. -7-

Remember:  Each cells in your skin, like most of the cells in your body, has 46 chromosomes.  Each new skin cell produced by mitosis will also have 46 chromosomes. Cell Cycle Control and Cancer As cells cycle through interphase and mitosis, a surveillance system monitors the cell for DNA damage and failure to perform critical processes. If this system senses a problem, a network of signaling molecules instructs the cell to stop dividing. These so-called \"checkpoints\" let the cell know whether to repair the damage or initiate programmed cell death, a process called apoptosis. Programmed cell death ensures that the damaged cell is not further propagated. Scientists know that a certain protein, called p53, acts to accept signals provoked by DNA damage. It responds by stimulating the production of inhibitory proteins that then halt the DNA replication process. Without proper p53 function, DNA damage can accumulate unchecked. A direct consequence is that the damaged gene progresses into a cancerous state. Today, defects in p53 are associated with a variety of cancers, including some breast and colon cancers.Lesson 2. Meiosis How are sex cells (sperm and egg cells) formed? The process meiosis (cell division)produces sex cells. In meiosis, there are two divisions of the nucleus: meiosis I andmeiosis II. The cell divides twice in this process. All human cells have forty-six chromosomes. When human cells reproduce (increasein number), mitosis ensures that each new cell will have forty-six chromosomes. There isone exception to this in the human body. Each of the sperm and egg has twenty-threesingle chromosomes.Why must meiosis take place for each sperm and egg? When a sperm unites with an egg, each of them contributes twenty-threechromosomes to the new zygote (combination of sperm and egg/the future baby). Thus, anew life begins with the normal number of forty-six chromosomes. Then the process ofmitosis begins, producing cells with forty-six chromosomes each. This is the reason whyyou are growing.If the sperm and egg did not have only twenty-three chromosomes each, the new babywould have ninety-two chromosomes rather than the normal number of forty-sixchromosomes. The number of chromosomes would double every generation if meiosis didnot occur. -8-

Figure 2.1 Formation of sex cells. Source: http://www.usoe.k12.ut.us/curr/science/sciber00/7th/genetics/sciber/compare.htmMeiosis-Sex Cell Formation Figure 2.2 Overview of the major events in meiosis (Homologous chromosomes means two chromosomes that are similar in structure.) Source: http://web jjay cuny edu/~/acarpi/ NSC/13-cell htm -9-

Carefully follow the steps of meiosis shown here and look at the illustration on thenext page when studying this. Figure 2.3 Meiosis Source: http://www.accessexcelence.orgIllustration of the process by which a single parent diploid cell (Both homologouschromosomes) divides to produce four daughter haploid cells (One homologouschromosome of the pair). Meiosis is the type of cell division by which germ cells (eggs and sperm) areproduced. Meiosis involves a reduction in the amount of genetic material. Meiosis comprises two successive nuclear divisions with only one round of DNAreplication. - 10 -

Four stages can be described for each nuclear division.  First division of meiosis  Prophase 1: Each chromosome duplicates and remains closely associated. These are called sister chromatids. Crossing-over can occur during the latter part of this stage.  Metaphase 1: Homologous chromosomes align at the equatorial plate.  Anaphase 1: Homologous pairs separate with sister chromatids remaining together.  Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.  Second division of meiosis: Gamete formation  Prophase 2: DNA does not replicate.  Metaphase 2: Chromosomes align at the equatorial plate.  Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole.  Telophase 2: Cell division is complete. Four haploid daughter cells are obtained. One parent cell produces four daughter cells. Daughter cells have half the number ofchromosomes found in the original parent cell and with crossing over, are geneticallydifferent. Meiosis differs from mitosis primarily because there are two cell divisions in meiosis,resulting in cells with a haploid number of chromosomes. Figure 2.4 Crossing over Source: Morgan T.H., Sturtevant A.H., Muller H.J., and Bridges C.B. (1915). The Mechanism of Mendelian Heredity. - 11 -

Illustration of crossing-over and recombination during the formation of gametes (germ cells) or meiosis. Crossing-over is part of a complicated process which can occur during cell division. In meiosis, the primordial (primary) cells of the sperm or ova must multiply and at the same time reduce the number of chromosomes to one full set. During the early stages ofcell division in meiosis, two chromosomes of a homologous pair may exchange segments in the manner shown above, producing genetic variations in germ cells.What you will doActivity 2.1Can you do this? Write the correct answers under each column. If you find difficulty, reviewthe lesson on mitosis and meiosis.Basis of Comparison Mitosis Meiosis 1. Type of cell where the process occurs 2. Number of cell division 3. Number of chromosomes (2 sets/1 set) 4. Number of daughter cells produced per parent cell Key to answers on page 24.To further familiarize you with the process of cell division, here's another activity. What you will do Self-Test 2.1Answer these: 1. Meiosis is sometimes called reduction division. Why is this so? 2. How many cells are there at the end of meiosis II? (Refer to the discussion of meiosis II if you find difficulty in answering this question) - 12 -

3. If body cells of a horse have 64 chromosomes, how many chromosomes are there in a horse sperm cell? Key to answers on page 25. Was it quite difficult? If you did not understand it well, I would suggest that you readthe lesson on cell division again. Congratulations! Why? You’re on the final lap of the module! To be in the lastlesson means you are really very, very good. You will not reach this part if you didn’t showinterest and determination to learn. So, what are you waiting for? Go!Lesson 3. Asexual versus Sexual Reproduction Figure 2.5 Asexual reproduction (volvox) vs sexual reproduction (tadpoles) Source: Pictures copyright biodidac.bio.uottawa.caReproduction in Animals Reproduction is a marvelous activity of individual existence. Individual organismscome and go, but, to a certain extent, organisms surpass time by reproducing offspring.We'll take a look at reproduction in animals. - 13 -

 What is reproduction? Reproduction is the creation of a new individual or individuals from previously existing individuals. In animals, this can occur in two primary ways: through asexual reproduction and through sexual reproduction. Let's look at asexual reproduction. Figure 2.6 Gemmules of the freshwater sponge spongilla. Source: Image courtesy of J. Houseman; BIODIAC Asexual Reproduction In asexual reproduction, one individual produces offspring that is geneticallyidentical to itself. This offspring is produced by mitosis. There are many invertebrates,including sea stars and sea anemones for example, that produce by asexualreproduction. Common forms of asexual reproduction are the following:Budding In this form, an offspring (in the form of bud) grows out of the body of the parent. Hydras exhibit this type of reproduction. Hydra Budding Image courtesy of BIODIACGemmules (Internal Buds) In this form, a parent releases a specializedmass of cells that can develop into an offspring. Internal buds (gemmules) Sponges exhibit this type of reproduction. Sponge Gemmmules Image courtesy of BIODIAC - 14 -

Fragmentation In this form, the body of the parent breaks into Planarian distinct pieces, each of which can produce an offspring. http://www.mrothery.co.uk/module2/ mod2trimmednotes.htm Planarians exhibit this type of reproduction.Regeneration Oral surface of a star fish. In this form, if a piece of a parent is detached, it Image courtesy of BIODIAC can grow and develop into a completely new individual. Echinoderms exhibit this type of reproduction.Reproduction in Animals: Sexual Reproduction Sexual Reproduction In sexual reproduction, two individuals produce offspring that have genetic characteristics from both parents. Sexual reproduction introduces new gene combinations in a population. Image credit: U.S. Fish and Wildlife Service - 15 -

 Gametes : Sex Cells In animals, sexualreproduction encompassesthe fusion of two distinctgametes to form a zygote.Gametes are produced bya type of cell divisioncalled meiosis. Thegametes are haploid(containing only one set ofchromosomes) while thezygote is diploid(containing two sets ofchromosomes). In mostcases, the male gamete, called the spermatozoon, is relatively moving and usually hasflagella. On the other hand, the female gamete, called the ovum, is not moving andrelatively large in comparison to the male gamete. Types of Fertilization Human Ovum(Egg) and Sperm Image credit: Copyright Dennis Kunkel There are two types by which fertilization can take place. The first is external (the eggs are fertilized outside of the body); the second is internal (the eggs are fertilized within the female reproductive tract). Patterns and Cycles Reproduction is not a continuous activity and is subject to certain patterns andcycles. Oftentimes these patterns and cycles may be linked to environmental conditionswhich allow organisms to reproduce effectively. For example, many animals haveestrous cycles that occur during certain parts of the year so that offspring can typically beborn under favorable conditions. Likewise, these cycles and patterns can be controlledby hormonal cues as well as other seasonal cues like rainfall. All of these cycles andpatterns allow organisms to manage the relative expenditure of energy for reproductionand maximize the chances of survival for the resulting offspring. Asexual reproduction does not involve sex cells or gametes (produced throughmeiosis). Rather, it is reproduction by mitosis allowing a new, genetically identicalindividual to be produced. Both methods of reproduction have advantages anddisadvantages. Sexual reproduction allows genetic variation and allows thedevelopment of a population that is specifically adapted to its surroundings (and istherefore more likely to survive). However, when a very desirable combination of traits isfound, sexual reproduction risks losing them in the randomness of the process. Asexualreproduction does not allow genetic variation, but guarantees reproduction (nodependence on others). It rapidly increases numbers of an organism and keeps its - 16 -

desired combination of traits. Many plants reproduce using a combination of sexual and asexual reproduction to get the benefits of both methods.Types of Asexual Reproduction in Plants Among the many ways that plants produce asexually are the following:  Formation of stolon: Stolon is an above ground runner from which plants roots can grow to start off a new plant. Wild strawberry plants connected by stolons Epiphyllum has roots that are preformed at the nodes along the stem. As the heavy stems bend over or break off coming in contact with the soil, the preformed roots will penetrate the soil and form a new attachment for the plant.  Formation of rhizome: Rhizome is an underground runner that gives rise to new plants. This grass species is a good example of a rhizome. Paul displays a sample of weed, a notorious invader of gardens due to its habit of sending long underground stems.  Formation of tubers: Tubers are underground storage stems (e.g. potato) from which new plants can grow after a dormant season. Reka holds a clump of artichoke. The tubers are displayed up close.  Development of bulbs: Bulbs are underground storage units that divide by mitosis allowing many new plants to form new bulbs. A hybrid amaryllis is a good example of a bulb that can reach up to 12 cm in diameter. - 17 -

This species of garlic also produces flower-like headswith small bulbs developing in the head.Nono checks out the garlic bulbs. Shown here are thebulbs that divided underground, after one season’sgrowth. Formation of \"bulblets\": This is a form of asexual reproduction which is quite unique. Some types of garlic will form small bublets in the place of a flower head. Schizostylus is a late flowering garden ornamental from the iris family. It produces small bulbs with a shoot preformed on its stem after flowering. These small bulblets drop off and produce new plants. A week or so after the flowers have dried up, on the flower stem small bulbs begin to form They send out a shoot while on the stem and then they easily break away from the stem. Falling on moist soil, they start to grow and resemble a plant like one that grows from a creeping rootstock, as shown here in the photo. Formation of corms: Corms are bulbousunderground stems that lie dormant during the winter,just as rhizomes do. They also produce new plants thenext growing season. The gladiolus in this photo is atypical representative. Gabi also develops corms. - 18 -

 Fragmentation: Parts of a plant break off and grow into a new plant. It may also include vegetative reproduction in which a part of the plant, not specialized for reproduction, breaks off and grows into a new plant. Opuntia Cactus has very brittle stems and leaves that often break off when animals walking by brush into them. Any piece of leaf tissue touching the ground will form roots and grow into a new plant when conditions are right. These are some samples that have grown from the receptacles of flowers. Lucas works with another Xerophytic plant (a plant that can live in hot environment) Crassula. When dropped on moist soil, each leaflet will produce a tiny plant at the point of attachment.  Budding Plantlets: several plants bud off tissue that develops into a miniature version of the parent plant. This tissue may even develop roots while still attached to the parent plant. Bits of the plants are specialized for breakaway and dispersal (look like tiny plants with very small leaves and roots already visible). Katakataka plant produces plantlets along leaves. Another species of katakataka produces completed plantlets at the ends of its leaves.Artificial Asexual Reproduction Economically speaking, it is very beneficial to reproduce plants asexually. Itguarantees a \"perfect\" product every time because once the desired combination of genesis found, there is no need to risk losing it through sexual reproduction. - 19 -

One of the most common methods of asexualreproduction is by cuttings. In this method, a piece of theplant (a cutting) is removed, usually dipped in rootinghormone, and then left in water or moist soil allowing newroots and therefore a new plant to form. Another methodoften used is grafting where a cutting or a scion is takenfrom one plant with desirable characteristics and graftedinto a rootstock. The rootstock will keep its traits and allow the scion to grow, enablingdisease resistant varieties of high quality crop plants to be produced. In the photo, thestudents are preparing cuttings of Ribes Sanguineum, a local native species of floweringplant that flowers or blooms very early in the spring, in February or early March. They willplant these on our campus. Their bright red blossoms are one of the first food sources formigrating hummingbirds. (All photos/pictures are courtesy of www.pearson-college.uwc.ca/pearson/biology/asex/asex.htm) What you will do Activity 3.1Share your opinions. What do you think? What are the advantages and the disadvantages of asexual reproduction and sexual reproduction? Share your thoughts, opinions and feelings. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ Activity 3.2 1. Give five examples of asexual reproduction in organisms (animal or plant) Key to answers on page 25. What you will do Self-Test 3.1Label each of the following as describing asexual reproduction (A) or sexual reproduction(S).___ 1. Budding is an example of this type of reproduction.___ 2. Gametes are produced by the same or different individuals. - 20 -

___ 3. Offspring has a different combination of genes than either parent.___ 4. It produces an offspring that may be better adapted to a new environment.___ 5. Regeneration is an example of this type of reproduction.___ 6. Usually, a large number of offsprings are produced.___ 7. Strawberry plants grown from the nodes of stolons___ 8. Potato plants grown from the eyes of a potato___ 9. Gametes of gumamela flower fuse___10. Ornamental plants grown from stem cuttings Key to answers on page 25. Let’s Summarize 1. The cell cycle is a process of cellular division consisting of five phases: interphase, prophase, metaphase, anaphase and telophase. 2. Each cell must have a set of chromosomes similar to the set in the mother cell. This ensures that the baby will look like the parent. 3. To produce duplicate sets of chromosomes, the processes of mitosis and meiosis take place. 4. In mitosis, each new cell formed has the same number of chromosomes as the parent cell. 5. In meiosis, each new cell formed has half the normal number of chromosomes. 6. A cell with 46 chromosomes at the beginning of meiosis I divides to produce cells each having only 23 single-stranded chromosomes at the end of meiosis II. 7. The two nuclear divisions result in four cells. 8. Each of these four cells is a sex cell (sperm and egg cells). 9. Each sex cell has half the number of chromosomes of the original cell. 10. Reproduction is the creation of a new individual or individuals from previously existing individuals. In animals, this can occur in two primary ways: through asexual reproduction and through sexual reproduction. 11. Animals reproduce sexually and asexually (budding, regeneration, fragmentation). 12. Plants reproduce sexually and asexually (formation of bulbs, formation of rhizome, formation of corm, formation of tubers). 13. Reproduction ensures the existence of organisms.Whew! That was a tough job. At last! You have finished studying the module. But, beforeyou completely exit from this module, let us find out how much you learned from thislearning material. - 21 -

Posttest  There are 20 questions. Each question has ONLY ONE CORRECT ANSWER. Choose the one you believe to be correct.  Each question is worth 2 points.  Read each question and carefully. Take your time and think.  GOOD LUCK!1. Which of the following is involved in asexual reproduction?a. mitosis d. binary fissionb. meiosis e. both a & d are correctc. oogenesis2. Which of the following is not a form of asexual reproduction?a. budding d. formation of rhizomeb. regeneration e. union of egg cell and sperm cellc. fragmentation3. Variability in the offspring is an important benefit of what form of reproduction?a. Sexual c. asexualb. Mitosis d. binary fission4. The following events are occurring in both mitosis and meiosis EXCEPTa. cytokinesis. c. DNA replication.b. karyokinesis. d. pairing of homologous chromosomes5. Which statement about mitosis is NOT correct?a. It makes diploid nuclei. c. The prophase is the first active phase.b. It forms four daughter cells. d. It does not affect the nuclear envelope.6. Which statement about binary fission is NOT correct?a. It occurs in prokaryotic cells. c. It produces two daughter cells.b. It exhibits five active phases. d. DNA is replicated before division.7. Polar bodies are formed during c. oogenesis a. mitosis - 22 -

b. meiosis d. spermatogenesisIn questions 8-14, label each statement with one of the following choices: a. meiosis I b. meiosis II___ 8. It is the synapsis of homologous chromosomes.___ 9. It involves the separation of homologous chromosomes.___10. It results in one oocyte and one polar body in human females.___11. It results in four sperm cells in human males.___12. The daughter cells have double-stranded chromosomes.___13. The daughter nuclei produced have single-stranded chromosomes.___14. The crossing-over of chromosome occurs.In questions 15-19, match the cell phase to its description. Write the letters only. a. DNA replication b. chromosomes first become visible d. chromatids separate at centromere e. chromosomes are aligned at the metaphase plate f. last phase of nuclear division___15. anaphase___16. metaphase___17. prophase___18. telophase___19. interphase20. The diploid chromosome number in an organism is 42. The number ofchromosomes in its sex cells is normallya. 21 c. 63b. 42 d. 84 Got a perfect score? Check it out! Key to answers on page 25. - 23 -

Key to AnswersPretest1. b 6. b 11. b 16. d2. e 7. e 12. a 17. b3. a 8. a 13. b 18. e4. d 9. a 14. a 19. a5. b 10. a 15. c 20. aLesson 1Activity 1.1The number of cells that would result from the division of a single cell after 30minutes is 64. In mitosis, one dividing cell produces two daughter cells.Activity 1.2 The cell cycle is a process of cell division divided into five phases namely:interphase, prophase, metaphase, anaphase and telophase. Different events/activities takeplace in each phase.Self-Test 1.11. T2. T3. F Mitosis is necessary (multicellular organisms do not undergo binary fission).4. F Spindle formation occurs only during mitosis5. TLesson 2Activity 2.11. Body cells such as bone, skin and muscle cells divide by mitosis. Reproductive cells such as sperm and egg cells are formed by meiosis.2. The dividing cell in mitosis divides once. In meiosis, the dividing cell divides twice.3. The number of chromosomes in the parent and daughter cells is the same which are two sets in mitosis (46). In meiosis, the number of chromosomes in the daughter cells is one half the original number (23).4. Since the dividing cell in mitosis divides once, the number of daughter cells produced is two. In meiosis, the dividing cell divides twice producing four daughter cells. - 24 -

Self-Test 2.11. Meiosis is sometimes called reduction division because the number of chromosomes is reduced by half. The cell here also divides producing four daughter cells.2. There are four cells at the end of meiosis II.3. Since sperm cell is a sex cell, it will have half the number of chromosomes which is 32.Lesson 3Activity 3.1Asexual reproduction versus sexual reproductionAdvantages of Asexual: no cost of meiosis; no cost of males; no cost of findingmates.Advantages of Sexual: genetic recombination; offspring have a different combinationof genes than either parent; offspring may be better adapted to a new environment;usually, a large number of offspring are producedActivity 3.2 1. budding 2. regeneration 3. fragmentation 4. formation of rhizome 5. formation of bulbSelf-Test 3.1 1. A 6. A 2. S 7. A 3. S 8. A 4. S 9. S 5. A 10. APosttest1. b 6. b 11. b 16. d2. e 7. e 12. a 17. b3. a 8. a 13. b 18. e4. d 9. a 14. a 19. a5. b 10. a 15. c 20. a - 25 -

ReferencesBooks:Alexander, G.; Balzer, L.; Collins, A.; Goodson, P.; Lauer, L.; Slesnick, I. (1984). Introduction to biology. Glenview, Illinois: Scott Foresman And Company.Biggs, A.; Daniel, L. Ortleb, P. (1994). Life science. Westerville, OH: Merrill Publishing Co., Mcmillan/McGraw – Hill.Campbell, N.A. (1996). Biology. California: The Benjamin/Cummings Publishing Company.Miller, K.R. & Levine, J. (1991). Biology. New Jersey, Massachusetts: Prentice Hall.Hopson, J.L. & Wessells, N.K. (1990). Essentials of biology. USA: McGraw-Hill Publishing Company.Wong, H.K. & Dolmatz, M.S. (1986). Biology: The key ideas. N.Y.: Globe Book Company, Inc.Electronic Sources:Retrieved January 8, 2005 from http://biology.about.com/library/weekly/Aa090700a.htmRetrieved January 8, 2005 from http://www.biology.arizona.edu/cell_bioTutorials/meiosis/ page3.htmlRetrieved January 8, 2005 http://www.accessexcellence.org/RC//VL/GG/index.htmlRetrieved January 8, 2005 from http:www.usoe.k12.ut.us/curr/science/sciber00/7th/ genetics/sciber/compare.htmRetrieved January 8, 2005 from www.pearson-college.uwc.ca/pearson/biology/asex/ asex.htm - 26 -

Module 13 The Human Reproductive System What this module is about This module is about the human reproductive system. It will familiarize you with theparts, functions, growth and development of the human embryo. This topic will be ofinterest to you as it deals with the beginning of human life. There are four lessons prepared for you in this module and they are as follows:  Lesson 1 - The Female Reproductive System  Lesson 2 - The Male Reproductive System  Lesson 3 - From Fertilization to Birth  Lesson 4 - Human Reproductive and Developmental Concerns What you are expected to learn As you go over the lesson, you are expected to: 1. Identify the parts of the male and female reproductive systems. 2. Describe the jobs of the parts of the male and female reproductive systems. 3. Compare the stages of the menstrual cycle. 4. Explain the stages of human growth and development. 5. Describe some reproductive technologies. How to learn from this module In order to achieve the objectives of this module successfully, you have to rememberthe following: 1. Read and follow the instructions carefully. 2. Answer the pretest. 3. Take down notes and record points for clarification.

4. Take the posttest and check your answers against the key at the end of the module.5. Try to obtain at least a 70% level of proficiency in the tests.What to do before (Pretest)Test 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 26. -2-

Lesson 1. The Female Reproductive System Humans have many body systems but the system involved in the production ofoffspring is called the reproductive system. Most organ systems of the body show littledifference between male and female except in the case of the reproductive system. Thereis a striking difference between the male and the female reproductive systems, althoughthey also share a number of similarities. For example, the reproductive organs of male andfemale are developed from the same embryological structures, and some hormones are thesame for the male and female although they produce different responses.The female reproductive system has the following functions:1. Production of female sex cells2. Reception of sperm cells from the male3. Nurturing the development of and providing nourishment for, the new individual Try to examine the diagram on Figure 1a. The figure shows a cut away view of thefront of the female reproductive organ. Now, study the job of each part. Part Job Ovary Produces egg cellsOviduct Passageway of eggs from the ovary to the uterus (also the same place where the egg is fertilized.Uterus Place where fertilized egg developsVagina Receives penis of male during mating The female reproductive organ consists of the ovaries, uterine tubes (fallopian tubes),uterus, vagina, external genitalia, and mammary glands. The internal reproductive organsof the female are located within the pelvis, between the urinary bladder and rectum. Theuterus and the vagina are in the middle line, with an ovary on each side of the uterus. Figure 1.The Parts of the Female Reproductive System -3-

The Ovaries There are two ovaries each comparable to the size of an almond nut. It is suspendedin the pelvic cavity by a ligament. The ligament extends from each ovary to the lateral bodywall, and the ovarian ligament. The mesovarium is the mesentery that suspends the ovaryto the body wall. The ovary contains ovarian follicle, which contains an oocyte, the femalegerm cell.Ovulation When follicles mature, they expand and rupture to release the egg and the process iscalled ovulation. After ovulation, the remaining cells of the ruptured follicle becometransformed into a glandular structure called the corpus luteum.Fallopian Tubes This part extends from the area of the ovaries to the uterus. Long, thin processescalled fimbriae surround the opening of each uterine tube. Fertilization usually occurs inthe part of the uterine tube near the ovary.Uterus This is as big as a medium-sized pear. The larger rounded part is directedsuperiorly. The part of the uterus superior to the entrance of the uterine tubes is called thefundus. The main part is called the body, and the narrower part is the cervix, directedinferiorly. Internally, the uterine cavity continues through the cervix as the cervical canal,which opens into the vagina.Vagina This is the female organ for copulation and functions to receive the penis duringintercourse. It also allows menstrual flow and childbirth. The vagina extends from theuterus to the outside of the body. In young females, the vaginal opening is covered by a thin mucous membrane calledthe hymen. This can completely close the vaginal opening, in which case it must beremoved to allow menstrual flow. The hymen can be perforated or torn at some earlier timein a young female’s life during a variety of activities including strenuous exercise. Thecondition of the hymen is therefore not a reliable indicator of virginity. -4-

External Genitalia The female external genitalia consists of the vestibule and its surrounding structures.The vestibule is the space into which the vagina and urethra open. A pair of thin,longitudinal skin folds called the labia minora borders the vestibule. A small erectilestructure called the clitoris is located in the anterior margin of the vestibule. The two labiaminora unite over the clitoris to form a fold of skin called prepuce skin. Figure 2. The Female External GenitaliaMammary GlandsThese are the organsof milk production and arelocated in the breasts. Themammary glands aremodified sweat glands.Externally, each breast ofboth males and females hasa raised nipple surroundedby a circular, pigmented,areola. Each breastconsists of around 15-20glandular lobes covered bya considerable amount of fattissue. It is this fat thatgives the breast its form. Figure 3. Mammary Gland -5-

The Menstrual Cycle Figure 4. The Menstrual Cycle We have just discussed that normally, an ovary releases only one egg every 28 days.Now, what controls this timing? Hormones control many of the changes in the reproductivesystem. Remember that hormones are chemicals that affect certain body organs. Themonthly changes that take place in the female reproductive system are called menstruation.This cycle occurs every month starting when a female is 10 to 13 years old. The monthlycycle continues for about 40 years. Refer to figure 4 and figure 5 for a clearer explanationof the different events that take place. Just follow 1-10 in proper order. -6-

Figure 5. A graph of the menstrual cycleIn a nutshell, the important events during the menstrual cycle are as follows:1. The pituitary gland starts the cycle.2. The pituitary releases hormones that cause the egg in the ovary to mature. The luteinizing hormone (LH) initiates the maturation of the follicles, converts ruptured follicle into corpus luteum and caused the secretion of progesterone. The other hormone, follicle stimulating hormone (FSH) assists in the maturation of the follicles and caused the secretion of estrogen from the follicles.3. Meanwhile, the ovary itself releases a hormone called estrogen. Estrogen is a hormone that causes changes in the female reproductive system. This hormone also causes the uterus to increase in thickness. The uterus becomes thicker so that the fertilized egg can attach to it.4. The ovary releases an egg on day 14. Assume that no sperm was present.5. The egg moves through the oviduct and enters the uterus.6. Meanwhile the uterus continues to thicken.7. The egg has not been fertilized, therefore, it will not attach to the uterus.8. The thick uterus is no longer necessary, so it begins to break apart. The cells of the thickened uterus break off and leave the vagina. The unfertilized egg is lost. Some blood is lost too. This loss of cells from the uterus lining, blood and egg is called menstruation.9. After menstruation, the cycle starts again. -7-

What you will do Activity 1.1 What is the Menstrual Cycle?Materials: 2 calendar charts diagrams of the male and female reproductive system scissors tape or glueProcedure: Part A - For no fertilization: 1. Get a calendar. It must be marked by the day-to-day changes in the menstrual cycle. 2. Note that certain events are marked on certain days. 3. Make a copy of the diagrams of the menstrual cycle like those found below. Some of the diagrams will show events in the ovary, and some will show events in the uterus. They are not in proper order. Cut out each square. 4. Place the diagram in the space to the right of the corresponding description. 5. Tape or glue your diagrams in right places/dates where they occur. 6. Make sure that they are correctly placed. Part B – With fertilization of Egg 1. Get another calendar marked by the day-to-day changes in the menstrual cycle. 2. Again you will be given a set of diagrams to place on the calendar. The diagrams will not be in proper order. You may not need all the diagrams that show the uterus.Questions: 1. How long does a menstrual cycle last if fertilization does not take place? 2. Describe what happens to an egg during the first 14 days of the cycle in part A. 3. Describe what happens to the egg and the uterus during the last 14 days of the cycle in part B. 4. What takes place after fertilization? Key to answers on page 26. -8-

Data and Observations : Did you know? Menstrual cramps are the results of the strong contractions of the uterine wall that occur before and during menstruation. The cramps can result from excessive secretion of prostaglandins. Sloughing of the endometrium of the uterus results in the inflammation in the endometrial layer of the uterus and prostaglandins are produced as part of the inflammation. In some women, menstrual cramps are extremely uncomfortable. Some women take aspirin-like drugs to avoid prostaglandin secretion just before menstruation. These drugs can reduce the pain. -9-

What you will doSelf-Test 1.1Concept Mapping: Fill-in the concept map of egg release (start with the ovary).Ovary OvaryReleases an egg in a process calledThe egg travels through theTo theIf the egg is not fertilized, the uterine walls Zygoteslough off and blood comes out in the processcalledIf egg is fertilized, it is called a Key to answers on page 26. - 10 -

Lesson 2. The Male Reproductive System Examine the diagram on thenext page. Shown are the parts of themale reproductive system. Figure 6 shows the main partsof the male reproductive system.Notice that this figure is a cut-awayview from the side. Also notice thatcertain parts of the male reproductivesystem are also part of the urinarysystem. Figure 6. The Male Reproductive SystemBe familiar with the specific functions of the parts using the table below: Part Job Testis Produces sperm cells Scrotum Sac that holds the testis Penis Places sperms into the vagina during matingTube (vas deferens) Carries sperm from testes to urethra Urethra Carries sperm out of the body Glands Provide liquid in which sperm can swima. seminal vesicle Secretes one of the components of the semenb. prostate gland Secretes a milky fluid that is discharged into the urethra as part of the semenc. Bulbourethral gland Mucous secreting glands located at the base of the penisDid you know?…that some males do not have descended testes? Ideally,during the seventh and the eighth month of fetal developmentor in some cases shortly after birth the testes descends.However, in some cases the testes fails to descend into thescrotal sac in a condition called cryptorchidism. It results tosterility because of the inhibiting effect of normal bodytemperature on sperm cell development. - 11 -

Scrotum Externally, the scrotum consists of skin. Beneath the skin are a loose connectivetissue and a layer of smooth muscle called dartos. In cold temperatures, the dartosmuscles contract, causing the skin of the scrotum to become firm and wrinkled, reducing theoverall size of the scrotum.Testes The testes are oval organs within the scrotum each about 4-5 cm long. Each testesis composed of cone-shaped lobules that contain seminiferous tubules, in which sperm cellsdevelop.Epididymis This is a tightly coiled series of thread-like tubules that form a comma-shapedstructure on the posterior side of the testes. The sperm cells continue to mature along thistube.Vas deferens The vas deferens emerges from the epididymis and ascends along the posterior sideof the testis to become associated with the blood vessels and nerves that supply the testes.From the epididymis, sperms move to this tube up to the ampulla of the ductus deferens.The wall of this tube is composed of smooth muscles.Ejaculatory Duct The ejaculatory duct extends into the prostate gland and ends by joining the urethrawithin the prostate gland.Urethra The male urethra extends from the urinary bladder to the distal end of the penis. Theurethra is a passageway for both urine and male reproductive fluids. The two, however, donot exit the urethra at the same time. So, there is no mixing. While seminal fluid passesthrough the urethra, a reflex causes the urinary sphincter muscles to contract tightly to keepurine from passing the urinary bladder through the urethra.Penis The penis is the male organ of copulation and functions in the transfer of sperm cellsfrom the male to the vagina of the female. It is only an accessory organ of reproduction andnot the reproductive organ as most people think of. It is composed of erectile tissues andthe engorgement of this erectile tissue with blood causes the penis to enlarge and becomefirm in a process called erection. - 12 -

Where Are Sperms Formed? Each testis is partitioned into as many as 300 wedge-shaped lobes. Each containstwo to three highly coiled tubes, the seminiferous tubules, and this is where spermsdevelop. Although a testis is only about 5 cm long, 125 meters of tubes are packed in it! When sperms move out of the testis, they enter a long, coiled duct, the epididymis.The sperms are not fully developed at this time, but secretions from the duct walls help themmature. When they are about to leave the body, they pass through a thick-walled tube thevas deferens, the ejaculatory ducts, and finally, the urethra, where they are ejected. Figure 7. Cross-section of the testis Did you know? …..that prostate cancer is the second most common cause of male deaths from cancer in the United States? - 13 -

What you will do Self-Test 2.1Answer the following questions: 1. Why are so many sperms released if only one is needed to fertilize the egg? 2. Trace and label the pathway of the sperm as it moves from the testes to the outside (use arrows). Key to answers on page 27. What you will do Activity 2.1 Collect clippings or articles regarding the effect of alcohol and smoking on the malereproductive system. Summarize your work and you can put this in a clear book or portfolio.Lesson 3. From Fertilization to Birth Now that you knowthe parts and functions ofthe human reproductivesystem, let us trace whathappens to the ovulatedegg. Figure 8 shows theorderly sequence ofevents from the time anegg is ovulated. It isnumbered 1-7. Just followthe numbers and you willbe guided accordingly.Figure 8. Fertilization andImplantation in the Uterus - 14 -

Below is a summary of the stages of reproduction that can serve as your guide: 1. Egg cells are formed in each ovary. 2. Each month, one ovary releases an egg. Usually, only one egg is released about every 28 days. The ovaries usually take turns releasing the eggs. 3. Once released from the ovary, the egg moves into a tube called oviduct. Oviducts are tube-like organs that connect the ovaries to the uterus. The uterus is a muscular organ in which the fertilized egg develops. 4. Sperms are released into the vagina during mating. The vagina is a muscular tube that leads from outside of the female’s body to the uterus. Sperms swim from the vagina into the uterus and into the oviducts. If an egg is present, fertilization takes place. The fertilized egg moves down the oviduct into the uterus. 5. The fertilized egg then attaches itself to the wall of the uterus implantation. Once attached it will remain there for nine months as it develops into a baby. Did you know? ... that ectopic pregnancy results if implantation occurs anywhere other than the uterine cavity? The most common site of ectopic pregnancy is the fallopian tube. Implantation in the fallopian tube can be fatal and can cause the tube to rupture. In some cases, implantation can occur in the mesenteries of the abdominal cavity, and the fetus can develop normally, but must be delivered by caesarian section.Ovulation This refers to the release of a mature egg from the ovary. It usually takes place onthe 14th day from the first day of menstruation if the cycle is a 28-day cycle.Fertilization When a sperm encounters an egg cell in the fallopian tube, it releases digestiveenzymes. Those enzymes clear the path for the sperm nucleus to fuse with the nucleus ofthe ovum or egg cell. A zygote is now formed.Implantation This occurs before the end of the first week. By this process, the zygote attaches tothe uterine lining, and some of its cells send out projections that has been part of thematernal tissue. The inner cell mass becomes the embryonic disc. This disc will give rise tothe embryo proper during the week following implantation. - 15 -

Embryonic and Fetal Development Three weeks after fertilization, almost one fourth of the inner surface of the uterushas become a spongy tissue composed of endometrium and embryonic membranes, thechorion. Through this tissue, the placenta and the embryo receive nutrients and oxygenfrom the mother and send out wastes in return.First trimester The first trimester of the nine months of humandevelopment extends from fertilization to the end of the thirdmonth. The picture below shows how the embryo looks likeduring this period. This is the most critical period of embryonicdevelopment. Figure 8. First Trimester Embryo http://images.google.com.ph/images?hl=tl&lr=&q= images+of+the+first+trimester+embryo&btnG=HanapinSecond Trimester This extends from the start of the fourth month to the endof the sixth month. All major organs have formed, and thegrowing individual is now called a fetus. Movements of the facialmuscles produce frowns. The sucking reflex is also evident.There are already fetal movements of arms and legs. Theheartbeat of the fetus can also be heard from a stethoscope onthe mother’s abdomen. Figure 9. Second Trimester Embryo http://images.google.com.ph/images?hl=tl&lr=&q= images+of+the+second+trimester+embryo&btnG=HanapinThird Trimester This extends from the seventh month until birth. By themiddle of the third trimester, the fetus will be able to survive onits own, if born prematurely or removed surgically from theuterus. The advancement in medical science has allowedfetuses as young as 23-25 weeks to survive early delivery.Survival chances increase to about 95 percent on the 9th month. Figure 10. Third Trimester Embryo http://images.google.com.ph/images?q=images%20of%20a%20third%20 trimester%20fetus&hl=tl&lr=&sa=N&tab=wi - 16 -

Birth or Parturition “Happy birthday!” is a very common greeting to mark the anniversary of a person’sbirth. Birth takes place about 39 weeks after fertilization. The birth process begins whenthe uterus starts to contract. For the next two to eighteen hours, the contraction becomesstronger and more frequent. The cervical canal dilates fully and the amniotic sac ruptures.Birth typically occurs less than an hour after full dilation. Immediately afterward, uterinecontraction forces fluid, blood and the placenta from the body. The umbilical cord is nowcut, and the newborn embarks on its nurtured existence in the outside world. What you will do Self-Test 3.1 1. What happens when an egg is fertilized? 2. Differentiate ovulation from fertilization. 3. Describe the first, second and third trimester of embryonic and fetal development. 4. What is ectopic pregnancy? 5. Describe the uterus during parturition Key to answers on page 27.What you will doActivity 3.1 Measuring the Growth Rate of the Embryo Use the data below to make a graph showing the day of development versus the sizeof the embryo. When is the fastest period?Week after Fertilization Size 3 3 mm 4 4 mm 6 12 mm 7 20 mm 8 40 mm 9 50 mm Key to answers on page 27. - 17 -

Lesson 4. Human Reproductive and Developmental Concerns Have you heard about test tube babies and artificial inseminations? Are youinterested to learn more about these topics? Read on. One of the goals of reproductive Biology is to understand human development and toprovide new medical technologies. The human reproductive system is unique in that it doesnot start to function actively until several years after birth. It is also unique because we cansurvive without it! Isn’t that amazing? As medical science advances, scientists learn moreabout the complex biological interactions that form a newborn from a fertilized ovum, which,in turn, leads them to discover more ways to prevent conception and treat birth defects, andto heal the fetus or newborn baby.What is Infertility? Infertility is the inability of the sperm nucleus to merge with the egg nucleus. Almostone out of six couples are infertile. What are the causes of infertility? There are several factors that cause infertility butthe most common are: 1. Physical difficulties 2. Irregular menstrual cycle 3. Low sperm count in malesInfertility in Males Infertility in males is caused by hormonal imbalance. This hormonal imbalanceresults to lower sperm count. Sometimes man’s immune system produces antibodies thatcover the sperm and prevent them from binding to the egg cell. A varicose vein in thescrotum can also cause infertility. This enlarged vein can overheat the developing spermsso they cannot mature. Sperm quality is also a factor. Some sperms are not very motileand so, they could hardly reach the egg cells. Hormone therapy can sometimes solvesperm motility.Infertility in Females Infertility in a woman can arise from abnormalities in any part of the reproductivesystem. Many women who are infertile have irregular menstrual cycle. A tumor in theovary or in the brain’s pituitary gland can cause hormonal imbalance that usually results toirregular ovulation. Another could be the abundance of prolactin in non-pregnant women,which prevents ovulation, and therefore, cannot conceive. Fertility drugs can stimulateovulation but sometimes they may also cause women to “superovulate” and produce morethan one egg a month, which could result to triplets, quadruplets, or multiple births! - 18 -

Another problem could be a blocked fallopian tube.This is a common cause of infertility in females. Blockage canprevent the sperms from reaching the egg cell, or keep thefertilized egg from descending into the uterus, resulting in anectopic pregnancy in the tube. Figure 11. Ectopic Pregnancyhttp://images.google.com.ph/images?hl=tl&lr=&q= images+of+ectopic+pregnancy&btnG=Hanapin An excess tissue growing on the uterine lining can also cause female infertility.Benign fibroid tumors or endometriosis can make the uterus not pleasant to the embryo.In endometriosis, the excess tissue bleeds during menstruation causing painful cramps. Itcan make conception difficult. Infertility is common among older women. They are morelikely to produce oocytes with abnormal numbers of chromosomes.Assisted Reproductive Technologies Do you know that some infertility problems are no longer a problem these days?Yes! Certain technologies can help women conceive. What are these technologies?Artificial InseminationThis is the oldest reproductive technology, where thedoctor places donated sperms in a woman’s reproductivetract. This is needed especially when the partner is infertileor carries a gene for an inherited illness or if she decides tobe a single parent. More than 250,000 babies have beenborn worldwide as a result of this procedure. The firsthuman artificial insemination was born in 1890’s. In 1953,they started to use frozen and stored sperms for later use.Now these are called sperm banks. They freeze and storedonated sperms and provide it to physicians who performartificial insemination. Figure 12. Artificial Insemination http://images.google.com.ph/images?q= images+of+artificial+inseminationA Donated Uterus - Surrogate Mothers &hl=tl&lr=&start=20&sa=N A woman can be both a genetic parent and a gestational parent (or uterus provider).This happens when a man produces healthy sperms but his partner’s uterus is absent orcannot maintain pregnancy. A surrogate mother can help them become parents. This ishow it happens. A surrogate mother is artificially inseminated with the man’s donated spermand carries the pregnancy, but the couple raises the child. In this situation, the surrogate isboth the genetic and gestational mother. - 19 -