Reproduction

• Reproduction


  Important for all species, can happen in two different ways
• Sexual Reproduction


  1. Genetic information from two organisms (a father and a mother) is combined to produce offspring which are genetically different to either parent

  2. Mother and father produce gametes by meiosis (e.g. egg and sperm cells in animals)

  3. Each gamete contains 23 chromosomes (half the number of chromosomes in a normal cell)

  4. Egg and sperm cell fuse together (fertilisation) to form a cell with the full number of chromosomes (half from the father, half from the mother)
• Sexual Reproduction


  Involves the fusion of male and female gametes, offspring contain a mixture of their parents' genes
• Offspring inherits features from both parents as it has received a mixture of chromosomes from its mum and dad
• Mixture of genetic information produces variation in the offspring
• Flowering plants can reproduce sexually, they have egg cells and pollen (their version of sperm)
• Asexual Reproduction


  1. Only one parent, offspring are genetically identical to that parent

  2. Happens by mitosis, an ordinary cell makes a new cell by dividing in two

  3. New cell has exactly the same genetic information as the parent cell, it's called a clone
• Asexual Reproduction


  There's only one parent, no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offspring are genetically identical to the parent, they're clones.
• Bacteria, some plants and some animals reproduce asexually
• Advantages of Sexual Reproduction over Asexual Reproduction

  • Offspring have a mixture of two sets of chromosomes
  • Variation increases chance of species surviving environmental changes
  • Individuals with desirable characteristics are more likely to breed successfully
  • Selective breeding can speed up natural selection
• Advantages of Asexual Reproduction over Sexual Reproduction

  • Only needs one parent
  • Uses less energy
  • Faster
  • Can produce many identical offspring in favourable conditions
• Some organisms can reproduce sexually or asexually depending on their circumstances
• Organisms that can reproduce both sexually and asexually

  • Malarial parasites
  • Fungi
  • Plants
• Malarial parasite reproduction


  1. Sexually in mosquito

  2. Asexually in human host
• Fungal reproduction


  • Release spores that can become new fungi
  • Asexually-produced spores form genetically identical fungi
  • Sexually-produced spores introduce variation and are often produced in response to unfavourable environmental changes
• Asexual plant reproduction


  1. Strawberry plants produce runners that form new identical plants

  2. Plants that grow from bulbs can form new bulbs that grow into new identical plants