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W
hat do porcupines, sea urchins, and cacti have in common?
Not the environment in which they live. Porcupines live in
the forest, sea urchins live in shallow
ocean water, and cacti
live in the desert. The answer is that they all have spines. And they
have those spines for the same reason. Spines improve the organism’s
chances for survival.
Any structure or behavior that improves an organism’s chances for
survival is an
adaptation
. All organisms are able to survive, reproduce,
and grow in their environments because they have adaptations.
You already know about several adaptations that crayfish have. Having
pincers is an adaptation that helps the crayfish get food. A hard shell
is an adaptation that helps the crayfish defend itself against predators.
Molting is an adaptation for
growing. Carrying eggs under
the tail is an adaptation that
improves the chances of
raising offspring. Those are
just a few of the adaptations
that crayfish have for living
in their environment.
A porcupine
A barrel cactus
A sea urchin
Adaptations
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