Sexual Reproduction

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Sexual Reproduction

  1. 1. Sexual reproduction Life cycles and the alternation of generations
  2. 2. Sexual reproduction in animals <ul><li>Animals have diploid body cells and haploid gametes </li></ul><ul><li>The diploid body cells are made by mitosis </li></ul><ul><li>The haploid gametes are made by meiosis </li></ul><ul><li>At fertilization the haploid sperm and egg fuse to produce the diploid zygote. </li></ul><ul><li>This then divides many times by mitosis to grow into a new individual </li></ul>
  3. 4. Sexual reproduction in plants <ul><li>In flowering plants there are two distinctive phases of life cycle: </li></ul><ul><li>the diploid sporophyte and the haploid gametophyte </li></ul>
  4. 5. Sexual reproduction in plants <ul><li>The diploid sporophyte produces haploid spores by meiosis. </li></ul><ul><li>The spores develop into the haploid gametophyte, which then produces haploid gametes by mitosis </li></ul>
  5. 7. Sexual reproduction in plants <ul><li>In plants such as mosses and ferns, the main plant is the diploid sporophyte. </li></ul><ul><li>It produces (genetically different) haploid spores by meiosis </li></ul>
  6. 8. Sexual reproduction in plants <ul><li>The spore grows into the gametophyte, which produces (genetically identical) gametes by mitosis. </li></ul>
  7. 9. Sexual reproduction in plants <ul><li>In flowering plants the water dependent gametophyte stage in the life cycle is much reduced. </li></ul><ul><li>The dominant stage in the life cycle is the sporophyte </li></ul>
  8. 10. Essential terms to know <ul><li>Spore </li></ul><ul><li>A haploid cell that can be dispersed </li></ul><ul><li>It is the product of meiosis of a diploid cell </li></ul>
  9. 11. Essential terms to know <ul><li>Gamete </li></ul><ul><li>A haploid cell, produced by mitosis of haploid cells. </li></ul><ul><li>It can fuse with another gamete to produce a diploid zygote </li></ul>
  10. 12. Essential terms to know <ul><li>Sporophyte </li></ul><ul><li>A multicellular plant that is diploid and produces spores. </li></ul>
  11. 13. Essential terms to know <ul><li>Gametophyte </li></ul><ul><li>A multicellular plant that is haploid and produces gametes </li></ul>
  12. 14. Essential terms to know <ul><li>NB These terms have been defined in terms of plant kingdoms. A fungal spore is very different!!!! </li></ul>
  13. 15. Essential terms to know <ul><li>Alternation of generations </li></ul><ul><li>Terrestrial plants that have a life cycle with a multicellular gametophyte and multicellular sporophyte generation which alternates are said to have a life cycle that shows “ alternation of generations” </li></ul>

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