1. Sexual Reproduction in Animals

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

4. 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

5. Large number of sperm and egg are released to overcome hazards • Hormones control behavior to have sperm and egg released at the same time.

6. Internal Fertilization*within the female body • Land animals • Some aquatic animals • Shark • Octopus

7. Requires specialized sex organ to carry sperm to body of female • Watery environment needed for sperm to swim to the egg

8. After fertilization, zygote is enclosed in a protective shell and released OR remains and develops in female body Zygote Turtle laying eggs

9. Internal Fertilization • Fewer eggs needed • Well protected • Increased chance of fertilization Parthenogenesis – development of unfertilized egg into an adult.- Bees & Wasps

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