Sexual Reproduction in Animals

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Sexual Reproduction in Animals

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Fertilization

Sperm nucleus enters the egg and moves to the egg nucleus. The 2 nuclei join together and then form a zygote.

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External Fertilization outside the body

Animals that breed in the water

Many hazards in the environment

Sperm and egg may not meet

Eggs or offspring may be eaten

May die due to environmental conditions

Temperature

Oxygen level

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Large number of sperm and egg are released to overcome hazards

Hormones control behavior to have sperm and egg released at the same time.

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Internal Fertilization within the female body

Land animals

Some aquatic animals

Shark

Octopus

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Requires specialized sex organ to carry sperm to body of female

Watery environment needed for sperm to swim to the egg

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After fertilization, zygote is enclosed in a protective shell and released OR remains and develops in female body

Zygote

Turtle laying eggs

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Internal Fertilization

Fewer eggs needed

Well protected

Increased chance of fertilization

Parthenogenesis – development of unfertilized egg into an adult.- Bees & Wasps