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Chapter 4 Reproduction4.1 Sexual and Asexual ReproductionReproduction is the ability of living things to produce offspring or new individuals. Continuation of a species and prevents it from extinction. There are sexual reproduction and asexual reproduction. Sexual reproductionInvolves male and female gamates (called fertilisation) to produce new cells (zygote). Zygote will produce a new individual.

Male gamate(Sperm)Female gamate(Ovum)ZygoteNew IndividualFertilisationGrowthFertilisationInternal fertilisationFertilised inside the female body. Develop inside the body.

2. External fertilisationFertilised outside the female body. Develop in water.

Asexual reproductionIt does not involve the process of fertilisation. Daughter cells are identical to the parent cells.

Type of asexual reproductionBinary fissionMature parent cell divides into two to form two new organism.

2. BuddingMature parent produces a bud which will grow and finally detach itself to form new organism.

3. Rejuvenation Each piece of the parent that is detach can grow to form a new organism.

4. Vegetative reproductionCertain parts of the plants such as the leaves and stem can develop and grow into a new plant.

5. Spore formationSome non-flowering plants reproduce by the formation of spores.

Involves male and female parentsInvolves the fusion of male and female gametesInvolves the process of fertilisationInherits characteristics from both parentsProduces variation in characteristics among offspringOccurs in higher organisms

Involves only one parent

Does not involve gametes

Does not involve the process of fertilisationInherits characteristics from only one parentNo variation in characteristics offspring is identical to the parentUsually occurs in lower organismsParentsSexual reproductionAsexual reproductionProduces new organisms to ensure the continuation of speciesFertilisationHereditary characteristics of offspringVariationGametesOrganismsSIMILARITYDIFFERENCES

4.2 Male Reproduction System

Prostate gland (5)Secretes a alkaline fluid to protect sperms during sexual intercourse. Mixture of sperm and fluid is called semen. Scrotum (1)Sac that protect the testis. Penis (7)Male sexual organEjects semen containing sperms and deposits them in the vagina of the female body during sexual intercourse. Seminal Vesicles (4)Produce enzymes to activate the sperm. Semen is ejaculated through the urethra in the penis. Place where sperms are stored temporarily before ejaculation. Testis (2)Male reproductive organProduces sperms and male hormone after puberty. Sperm duct (3)Long tube that carries sperms from the testis to the urethra. Urethra (6)Carries sperm from the sperm duct to outside the body. Transport urine SpermSperm is the male reproductive cell or gamete. Sperm are produced in the testis after puberty. Fertilise the female gamete to form zygote.

Puberty Stage of growth in a young human being when the reproductive organs start to produce reproductive cells. In males, puberty occurs at the age of about twelve to fourteen. Changes in the males at puberty:Testes produce sperms.Height increases rapidly. Hair grows in the armpits.

4.3 Female Reproduction System

Fallopian tube (3)Directs the ovum from the ovary to the uterus. Place the ovum is fertilised by the sperm. Cervix (5)Widens during childbirth for the baby to come out of the uterus. Ovary (2)Female reproductive organProduce female gametes called eggs or ovumProduce female hormone after puberty.Uterus (4)Pear-shapedPlace where implantation of embryo occursPlace the embryo and foetus develop during pregnancyProtects the embryo and foetus from injuryVagina (1)Place where the semen is deposited during sexual intercourse. OvumOvum is the female reproductive cell or gamete. Produced and released by the ovary after puberty. Fertilise the male gamete to form zygote.

Layer of jellyCell membranePuberty In females, puberty occurs at the age of about eleven. Changes in the females at puberty:Ovary produce ovum.Height increases rapidly. Hair grows in the armpits. Menstruation starts. Breasts enlarge.SpermDifferencesOvumMuch smaller than the ovumThe smallest cell in the male body (0.001mm - 0.05mm)Size Larger than the spermThe largest cell in the female body (about 0.2mm)Millions of sperms are released during each ejaculationNumberUsually only one ovum is released each monthMobile has a tail that enables it to swim towards the ovumMobilityNot mobileComparison between male and female gametes4.4 Menstrual cycleThe monthly discharged of disintegrated uterine lining together with the unfertilised ovum and blood from the uterus through the vagina is called menstruation or period. 2. A menstrual cycle normally take about 28 days.

3. Menstruation occurs during the first to the fifth day. 4. During menstruation, the uterine lining breaks down. 5. After it, the repair of uterine lining begins. It becomes thick, spongy and full of blood vessel. 6. Ovulation is the release of an ovum from ovary through the fallopian tube. It occurs between the thirteenth to fifteenth day. 7. If the ovum is fertilised, a zygote will form. Menstruation stops during pregnancy and continue after the baby is born. 8. If ovum is not fertilised, the uterine lining will broken down. Menstruation starts again. 9. The fertile phase in a menstrual cycle is from eleventh to the seventeenth day. A woman who has sexual intercourse during the fertile phase may become pregnant.

4.5 Fertilisation and Pregnancy1. During sexual intercourse, the male ejaculates semen (contains millions of sperms) into vagina of female. From the vagina, the sperms swims their way through the cervis and uterus to the fallopian tube. 2. Only one sperm will penetrate the ovums membrane. 3. The nuclei of sperm and ovum will fuse together and a zygote formed. This process called fertilisation.

4. After fertilisation, the zygote moves along the fallopian tube to the uterus, the zygote divides again to form a ball of cell, called embryo.

5. When the embryo reaches the uterus, it implants itself into the thick uterine lining. This process is called implantation.

6. After implantation, embryonic membranes develop to enclose the embryo in a double-layered capsule, called the amniotic cavity. The amniotic is filled with amniotic fluid (). 7. The amniotic fluid helps to support and protects it from injury. 8. Finger-like villi will grow from the embryo into the uterine wall. The villi contain the blood vessel of the embryo. Therefore, the embryos blood vessels can come into very close contact with that of the mothers. 9. The villi together with the part of the uterus in which they are embedded form a structure known as placenta ().

4.6 Importance of Pre-natal careA pregnant mother needs a healthy diet to ensure the health and development of the foetus.

NutrientFunctionProteinsFormation of new foetus cells and tissuesCarbohydrates and fatsProvide energy for growth of the foetusCalcium and phosphorusFormation of foetus bones and cartilageIronFormation of red blood cells in the foetusVitaminsEnsures the health of the foetusStrengthens the mothers immune system against illnessFolic acidHelps to strengthen the immune system of the foetus4.7 Importance of Research in Human ReproductionSterility or infertility is the inability to have children. Sterility can involve males as well as females. Possible causes of sterility in males: Low sperm count or no sperm in semenLow quality spermsBlocked sperm ductInfection such as venereal diseases4. Possible causes of sterility of females:Ovaries do not produce ovaBlocked fallopian tubebenign uterus tumourFailure implantation of embryo into the uterusHormone imbalancesome women produce anti-sperm antibodies which kill the sperms