Chapter 13 Meiosis and Sexual Life Cycles

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Chapter 13Meiosis and Sexual Life Cycles
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Chapter 13Meiosis and Sexual Life Cycles

• Why
• sex?

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Chapter 13Meiosis and Sexual Life Cycles

• Diversity

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Chapter 13Meiosis and Sexual Life Cycles

• Four organisms

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Chapter 13Meiosis and Sexual Life Cycles
This mutation protects against disease

• Four organisms

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Chapter 13Meiosis and Sexual Life Cycles
This mutation protects against disease
This mutation protects against cold

• Four organisms

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Chapter 13Meiosis and Sexual Life Cycles

• They reproduce asexually

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Chapter 13Meiosis and Sexual Life Cycles

• They reproduce asexually

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Chapter 13Meiosis and Sexual Life Cycles

• They reproduce asexually

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Chapter 13Meiosis and Sexual Life Cycles

• A disease comes

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Chapter 13Meiosis and Sexual Life Cycles

• A disease comes

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Chapter 13Meiosis and Sexual Life Cycles

• Then it gets cold

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Chapter 13Meiosis and Sexual Life Cycles

• Then it gets cold

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Chapter 13Meiosis and Sexual Life Cycles

• What if they reproduced sexually?

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Chapter 13Meiosis and Sexual Life Cycles

• What if they reproduced sexually?

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Chapter 13Meiosis and Sexual Life Cycles

• What if they reproduced sexually?

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Chapter 13Meiosis and Sexual Life Cycles

• What if they reproduced sexually?

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Chapter 13Meiosis and Sexual Life Cycles

• What if they reproduced sexually?

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Chapter 13Meiosis and Sexual Life Cycles

• A disease comes

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Chapter 13Meiosis and Sexual Life Cycles

• A disease comes

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Chapter 13Meiosis and Sexual Life Cycles

• Then it gets cold

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Chapter 13Meiosis and Sexual Life Cycles

• Then it gets cold

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Chapter 13Meiosis and Sexual Life Cycles

• The population with the most diversity is the
  most likely to leave survivors after
  unpredictable changes.

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Chapter 13Meiosis and Sexual Life Cycles

• Each gene has a specific location on a specific
  chromosome.

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Chapter 13Meiosis and Sexual Life Cycles

• We inherit one set of chromosomes from our father
  and one set from our mother.

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Chapter 13Meiosis and Sexual Life Cycles

• Asexual
• Sexual

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Chapter 13Meiosis and Sexual Life Cycles

• Asexual reproduction produces genetically
  identical offspring by mitosis.
• Sexual reproduction produces genetically diverse
  offspring.

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Chapter 13Meiosis and Sexual Life Cycles

• In humans,
• 2n 46
• n 23

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Chapter 13Meiosis and Sexual Life Cycles

• In humans,
• 2n 46
• n 23
• 22 pairs are homologous, the 23rd pair is either
  XX or XY.

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Chapter 13Meiosis and Sexual Life Cycles

• Gonads (testes and ovaries) produce haploid
  gametes by meiosis

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Chapter 13Meiosis and Sexual Life Cycles

• Gonads (testes and ovaries) produce haploid
  gametes by meiosis.
• Sperm and ovum unite to form a diploid zygote,
  which grows and develops by mitosis.

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Chapter 13Meiosis and Sexual Life Cycles

• Sexual life cycles differ in the timing of
  meiosis in relation to fertilization

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Chapter 13Meiosis and Sexual Life Cycles

• Sexual life cycles differ in the timing of
  meiosis in relation to fertilization.
• Multicellular organisms may be diploid or haploid
  or may alternate between haploid and diploid
  generations.

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Chapter 13Meiosis and Sexual Life Cycles

• Meiosis differs from mitosis in three ways

1. Synapsis
2. Crossing over
3. Separating homologous pairs (not sister
   chromatids) during anaphase I.

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Chapter 13Meiosis and Sexual Life Cycles
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Chapter 13Meiosis and Sexual Life Cycles
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Chapter 13Meiosis and Sexual Life Cycles
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Chapter 13Meiosis and Sexual Life Cycles
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Chapter 13Meiosis and Sexual Life Cycles

• Genetic variation is the raw material for
  evolution

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Chapter 13Meiosis and Sexual Life Cycles

• Genetic variation is the raw material for
  evolution.
• Mutations create variation

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Chapter 13Meiosis and Sexual Life Cycles

• Genetic variation is the raw material for
  evolution.
• Mutations create variation.
• Sexual reproduction promotes variation.

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Chapter 13Meiosis and Sexual Life Cycles

• Sexual reproduction promotes variation three ways

• Independent assortment of chromosomes during
  meiosis
• Crossing over during metaphase I
• Random fertilization of egg cells by sperm.
• .