Biology / Unit 13 Bio 3325 short lesson, about 20 seconds
External versus Internal Fertilization
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The idea
External fertilization releases sperm and eggs into the surrounding water for fusion outside the body; internal fertilization joins sperm and egg inside the female's body.
In practice
Salmon spawn eggs and sperm together in a stream; most land animals fertilize internally instead.
Where people slip
External fertilization needs far more eggs, since predation and environmental loss reduce offspring survival.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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