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REPRODUCTION

Learn about somatic cells and gametes, the process of fertilisation, and the differences between internal and external fertilisation. Explore the male and female reproductive systems and their functions. Understand asexual and sexual reproduction, and the journey from fertilisation to implantation.

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REPRODUCTION

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  1. REPRODUCTION Haileybury IGCSE Biology

  2. Learning objectives • Distinguish between somatic cells and gametes • Outline the process of fertilisation • Compare internal and external fertilisation • Draw and label the male and female reproductive systems

  3. Somatic Cells Most of the cells in our bodies are SOMATIC cells They contain two sets of chromosomes We describe it as being DIPLOID One set from each parent Our cells contain 46 chromosomes 23 from each parent

  4. Gametes Sex cells are called gametes They contain one set of chromosome Our gametes contain 23 chromosomes They will be a mixture of chromosomes from each parent

  5. Gametes • Ova Pollen • Sperm • Ovum

  6. Fertilisation gamete gamete Somatic cell Gametes are produced by meiosis Meiosis is a type of cell division that halves the chromosome number Fertilisation is a fusion of gametes This restores the chromosome number

  7. External fertilisation • Suitable for animals that mate in water • Many eggs • The sperm are able to swim through the water to fertilise the eggs • The eggs do not have shells

  8. Internal fertilisation • Suitable for animals that mate on land • Few eggs • The sperm are placed inside the female • The eggs have shells

  9. External vs Internal

  10. Reproduction Learning objectives • Distinguish between asexual and sexual reproduction and give example of both • Draw and label the structure of the human male and female reproductive systems • State the functions of the organs of the male and female reproductive systems

  11. ASEXUAL REPRODUCTION Asexual reproduction requires just one parent and does not involve the production of gametes

  12. Can human’s reproduce asexually?

  13. SEXUAL REPRODUCTION • Sexual reproduction requires two parents and the production of GAMETES

  14. Male Reproductive System Sperm duct

  15. Male Reproductive System Draw and label the diagram above

  16. Male Reproductive System Penis Testis (pl. testes) Sperm duct

  17. Sperm cell

  18. Female reproductive system Oviduct Ovary Ovary

  19. Female Reproductive System Draw and label the diagram above

  20. Female reproductive system

  21. Ovum

  22. Sexual Intercourse • The biological purpose of sexual intercourse is to place the sperm as close as possible to the ovum to optimise the chance of fertilisation. • The ovum is wafted down the fallopian tubes (oviducts) by small hairs called cilia. • The sperm have to swim through the cervix, uterus and part of the way up the fallopian tubes. • Only a very small proportion of the sperm will reach the ovum. • Barrier methods of contraception such as condoms prevent the sperm from reaching the ovum

  23. Fertilisation The membrane of the head of the sperm fuses with that of the ovum. Changes to the zonapallucida prevents the entry of another sperm. The male nucleus containing 23 chromosomes fuses with the female nucleus which also contains 23 chromosomes. The fertilised ovum is now called a zygote and it contains 46 chromosomes. Half the sperm contain a Y chromosome, resulting in a boy and the other half contain an X chromosome resulting in a girl.

  24. Fertilisation to Implantation

  25. Questions • Where does fertilisation occur? • Define the following words: • Zygote • Blastocyst • Fertilisation

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