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IGCSE Biology - Sexual and Asexual Reproduction

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IGCSE Biology - Sexual and Asexual Reproduction

  1. 1. IGCSE Biology – 4BI0 MAKING SENSE OF Copyright©2015HenryExham Icons CC – The Pink GroupIcons CC – The Pink Group Copyright©2017HenryExham
  2. 2. This PowerPoint is protected under copyright. It is designed for educational use. Either personal study or to be presented to a class. It may be edited or duplicated for these purposes only. It must not be shared or distributed online in any format. Some images used are under a separate creative commons license, these are clearly marked. Copyright © 2015 Henry Exham Brought to you by MrExham.com TERMS AND CONDITIONS 2
  3. 3. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Objectives 3 • Can you describe the differences between sexual and asexual reproduction? • Do you understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo?
  4. 4. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Reproduction 4
  5. 5. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Asexual Reproduction 5 • Cells in one part of the body divide by mitosis and then break off from the parent to form a new organism. • All the offspring are genetically identical. • These organisms all reproduce asexually. http://commons.wikimedia.org/wiki/User:Dietzel65
  6. 6. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual Reproduction 6 • Sex cells called gametes are produced. • There are two types, a male gamete and a female. • The male gamete must move to the female gamete and fuse. • This is called fertilisation. • The new cell formed is called a zygote.
  7. 7. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual Reproduction 7 • This cell will then divide many times by mitosis to form the new organism. Zygote Embryo Egg Sperm
  8. 8. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual Reproduction - Gametes 8 • The male gamete sperm are produced in the testes. • In the female the ova are produced in the ovaries. • The cells inside these organs divide by meiosis. • Meiosis produces cells that are not genetically identical.
  9. 9. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual Reproduction - Meiosis 9 • In meiosis four cells are made from the original cell. • These cells are called haploid cells as they each have half the compliment of chromosomes. • This process is covered in more detail in section 5.2 along with mitosis.
  10. 10. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual Reproduction - Sperm 10 • Sperm cells have a tail for swimming. • The head contains the genes from the father in the nucleus. • The acrosome digests its way into the egg for fertilisation.
  11. 11. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Cell Division 11 • The whole of asexual reproduction happens using mitosis. • This is when a cell with the full number of chromosomes (diploid) copies itself to become two identical cells. • In sexual reproduction, the gametes are made using meiosis. • This produces haploid cells with only half the full number of chromosomes. • Once they combine to make a zygote they will once again be up to the full number of chromosomes and the new cell can continue dividing using mitosis.
  12. 12. Copyright © 2015 Henry Exham 2.7 Reproduction in Humans – Sexual and Asexual Sexual and Asexual 12 Asexual Sexual Produces genetically identical organisms Produces genetically different organisms Only needs one parent Needs two parents Uses mitosis Uses meiosis to make gamete and then mitosis to grow in size after fertilisation Very quick but no variation so susceptible to disease Slower but produces variation
  13. 13. This PowerPoint is protected under copyright. It is designed for educational use. Either personal study or to be presented to a class. It may be edited or duplicated for these purposes only. It must not be shared or distributed online in any format. Some images used are under a separate creative commons license, these are clearly marked. Copyright © 2015 Henry Exham Brought to you by MrExham.com TERMS AND CONDITIONS 13

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