CoachIn animals, making young usually takes two parents: a female and a male. The female produces egg cells; the male produces sperm cells. A young animal begins when one sperm cell joins one egg cell — that joining is fertilization. Reproduction with two parents is called sexual reproduction.
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Example 23.2 (Why the frogs sing)
The May chorus is the males calling the females to the pond. Each pair then releases its cells into the water — the female’s eggs, the male’s sperm — where fertilization happens. The black dots in the jelly a few days later are the young already growing: the song was step one of Chapter 8’s frog cycle.