Inheritance, Variation and Evolution - Reproduction

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    • Cell Division
      • Mitosis
        • Results in the formation of two genetically identical daughter cells
        • Used in asexual reproduction
      • Meiosis
        • Used in sexual reproduction
        • Results in the formation of four non-identical daughter cells
        • Each cell has a pair of each chromosome (diploid cell)
          • During meiosis the pairs of chromosomes replicate and the cell splits in two
            • There are now two identical cells and the diploid cell divides again
              • This creates four genetically different gametes that have half the number of chromosomes as the parent cell (haploid cells)
                • In sexual reproduction, the male gamete fertilises the female gamete and the fertilised cell now has the correct number of chromosomes
                  • The fertilised cell then divides by mitosis until it reaches a certain size and it begins to differentiate
    • Sexual Reproduction
      • Offspring are non-identical
      • Cells divide by meiosis
      • Male and female gametes fuse to form a zygote
        • In plants this is pollen (male) and ovum (female)
        • In animals this is sperm (male) and egg (female)
      • Two parents
      • Advantages (green) and disadvantages (red)
        • Genetic variation- increases chance of servi so by natural selection because more are likely to by adapted to disease
        • Selective Breeding - boosts food production and helps breed fast horses
        • Slower reproduction
        • Requires a mate so is less efficient when it comes to time and energy
    • Asexual Reproduction
      • Cells divide by mitosis
      • One parent
      • Offspring are clones
      • No gamete fusion
      • Advantages (green)  and Disadvantages (red)
        • Clones - in the right conditions, this is favourable
        • Faster than sexual reproduction
        • No mate required - more efficient when it comes to time and energy
        • Could mean species extinction of the offspring cannot adapt fast enough
        • No genetic variation apart from with mutations


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