Sex Determination: More Complicated Than You Thought

Sex Determination: More Complicated Than You Thought

How is sex determined? In humans, it’s a matter of genetics, and it begins the moment a sperm cell fertilizes an egg, thereby producing a certain combination of sex chromosomes. Throughout the animal kingdom, though, sex determination varies widely and isn’t always genetically based, as biologist Aaron Reedy explains in the TED-Ed video below. For example, in some species—such as alligators and turtles—sex is actually determined by the environment. Specifically, the sex of these reptiles depends upon the temperature of their eggs at a critical point in development (cooler = male; warmer = female). Check out the video below to learn more about  other fascinating variations in how sex is determined throughout nature.

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