BY2 - Reproductive Strategies

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  • BY2 - Reproductive Strategies
    • Asexual Reproduction
      • Produces offspring genetically identical to the parent.
        • Offspring are clones.
        • One Parent
        • Mitosis
      • Disadvantage
        • If conditions change individuals in the species may die because they are unable to adapt.
        • No genetic variation
      • e.g. Amoeba
    • Sexual Reproduction
      • Produces offspring genetically different to the parents.
        • Genetic variation
        • Two parents
        • Gametes produced by meiosis.
      • Advantage
        • Seeds/sperm/larvae allow dispersal.
        • Genetic variation allows a species to adapt to and survive an environmental change.
        • Development of a resistance stage in the life cycle which allows a species to survive adverse conditions.
      • Disadvantage
        • Slower than asexual reproduction.
    • Gamete Production
      • Diploid (2n)
        • Full chromosome number.
        • Body/Somatic cells.
      • Haploid (n)
        • Half the chromosome number.
          • Found in the gametes (sex cells)
        • Produced by meiosis.
      • Adult Diploid (2n)
        • Meiosis
          • Gametes (n)
          • Gametes (n)
            • Zygote (2n)
              • Mitosis
                • Adult Diploid (2n)
                  • Meiosis
                    • Gametes (n)
                    • Gametes (n)
                      • Zygote (2n)
                        • Mitosis
      • Ferilisation
        • 1. Haploid sperm cell fuses with the haploid egg cell.
          • 2. Produces diploid fertilised egg.
            • 3. Mitosis takes place.
              • 4. Zygote forms.
        • Internal Fertilisation
          • Terrestrial organisms
            • Male gamete becomes independent of the need for water.
          • DEFINITION: The joining together of gametes.
            • OR: The fusing together of sperm and eggs inside the females body.
          • Advantages
            • Less gametes produced (greater chance of them meeting)
            • Less chance of gametes being wasted.
            • Gametes independent of water.
            • Egg remains nourished and develops inside female because its enclosed in a protective layer.
        • External Fertilisation
          • Aquatic organisms release their gametes directly into the sea/fresh water.
          • Disadvantages
            • Large wastage of gametes.
            • Large numbers of gametes produced.d
            • Less chance of gamete fusion.
      • How flowering (Angiosperm) plants colonise the land.
        • Development of a seed which contains the embryo, roots and shoots.
        • Seed contain a foodstore.
          • Enables it to survive for long periods of time.
        • Large numbers of seeds are produced.
        • Pollen can survive without water (except ferns and mosses).
        • Relationship with animals and insects for pollination and seed dispersal.
        • Seed Coat (Testa)
          • Protects the embryo and prevents it from drying out.
        • Water carrying xylem vessels.
    • Advantage
      • Allows rapid increase number/out competes sexual reproduction.
      • Asexual Reproduction
        • Produces offspring genetically identical to the parent.
          • Offspring are clones.
          • One Parent
          • Mitosis
        • Disadvantage
          • If conditions change individuals in the species may die because they are unable to adapt.
          • No genetic variation
        • e.g. Amoeba

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