Fertilization

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Fertilization

• After Meiosis

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Gonads

• Reproductive organs
• Males have testes
• Females have ovaries

Gametes

• Reproductive cells
• Males have sperm
• Females have eggs

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Variation in Offspring

• You receive 23 chromosomes from your father and
  23 chromosomes from your mother
• Since you are a combination of two different
  individuals you are different from your parents
• This is sexual reproduction the combination of
  two haploid cells (23 in a human) to produce a
  diploid cell (zygote which contains 46
  chromosomes)

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Sexual Reproduction

• Gametes are produced via meiosis
• The male gamete combines with a female gamete
• A zygote is produced and develops into an embryo
• The embryo develops through mitosis into a mature
  offspring (gestation varies from organism to
  organism)

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• Fertilization only occurs if a sperm
• meets an egg from the same species.

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Mating Patterns

• Some animals only mate once a year
• Timed so that when offspring are born, the
  environmental conditions are favourable
• Some fish mate only when the tides are high and
  during a full or new moon
• Honeybees only mate once in a lifetime

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External Fertilization

• External fertilization is when the gametes met
  outside of the parents
• Sperm and eggs will dry out, so they must be kept
  in a moist environment
• Sperm can only swim in a wet environment
• Common in fish and amphibians

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Internal Fertilization

• Common in most animals that live on land
• Special reproductive structures are required for
  this
• Intromittent organ in most birds
• Cloaca
• Sperm is transferred to the female via the males
  reproductive structure
• Sperm travels inside of the female to reach the
  egg

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Laying Eggs or Internal Development

• Some mammals will lay eggs and the foetus will
  develop outside of the female
• Other mammals will continue to have the foetus
  develop inside of the female until is has
  developed into a mature offspring
• This is called gestation

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Gestation of Various Mammals In Months
Rabbit 1
Cat 2
Dog 2
Lion 3.5
Pig 4
Sheep 5
Human 9
Cow 9.5
Horse 11
Elephant 22
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Pros vs. Cons

• List some advantages of internal fertilization
• List some advantages of external fertilization
• List some disadvantages of internal fertilization
  
• List some disadvantages of external fertilization

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Advantages of Internal Fertilization

• Provides more nutrient investment into a single
  egg
• Sexually selected physical traits
• Provides a wet environment for the sperm and the
  egg
• Temperature regulation
• Fewer gametes are required to ensure
  fertilization occurs

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Advantages of External Fertilization

• Requires very little effort as the sperm and egg
  can randomly meet
• Female does not have to look after offspring once
  they are fertilized
• A specialized structure is not required to have
  gametes meet

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Disadvantages of Internal Fertilization

• Complex courtship and mating behaviours
• Parents (usually female) must care for the young
  throughout gestation or until the eggs hatch
• Specialized structures are required to ensure the
  meeting of gametes

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Disadvantages of External Fertilization

• Large number of gametes must be produced to
  ensure mature offspring survive
• Seasonal due to the delicate nature of the
  gametes
• Many zygotes are produced but only a few survive