B1b 6 Variation

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B1b 6 Variation

• 6.2 Types of reproduction

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Learning objectives

• Understand the differences between and products
  of different types of reproduction

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Pass it on

• Essential for species
• Genetic info passed from parents to offspring
• Two types of reproduction
• Asexual reproduction
• Sexual reproduction

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Asexual reproduction

• Most common in plants and very small
  animals/bacteria
• Also in humans at cellular level
• Only needs one parent
• Completely identical offspring produced
• Clones
• No variation in genetic material
• No joining of sex cells
• No need for a mate

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Asexual reproduction

• Why is there no variation in offspring produced
  asexually?

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Sexual reproduction

• Joining of male and female sex cells (gametes)
• Genetic info from both parents
• Characteristics of both, identical to neither
• Introduces variety into a species
• Gametes in plants ovules and pollen
• Gametes in animals egg and sperm
• More risky needs 2 cells
• Worth the risk to gain variety

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Sexual Reproduction

• Genetic info passed down in genes through
  gametes
• Gametes contain 23 chromosomes each
• Fertilisation - gametes fuse together to make a
  single cell called a ZYGOTE
• Zygote has 46 chromosomes
• 23 pairs
• contains information from each parent

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Sexual reproduction

• Why does sexual reproduction produce variety in
  organisms?

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Variation

• Whats the benefit?
• Greater chance of survival when the going gets
  tough
• Less chance of inherited genetic disorders
• Inbreeding

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How does variation work?

• Genes affect characteristics
• Each pair of genes has different forms
• Alleles (A lee-els)
• Most things controlled by combination of loads of
  genes
• Some things controlled by just one pair with 2
  different alleles
• Dimples, ear lobes and thumbs
• We all get a random mixture

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The spice of life

• Why is variety important?

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• Define the key words
• a) asexual reproduction b) sexual reproduction
• c) gamete d) variety
• Name one advantage and one disadvantage of sexual
  reproduction
• Daffodils reproduce both sexually and asexually.
• How does this make them successful plants?
• What are the genetic differences between an
  asexually produced daffodil and a sexually
  produced one?