Evolution and Extinction

How do plants and animals adapt to different conditions? Adaptations arise through evolution, a long process of changes in a population of a specific plant or animal. An individual from that population may be born with a difference in some characteristic because of a new combination of traits passed on from its parents. Or it may have a new trait altogether that comes from a change, or mutation, in its genes, the basic chemical pattern of life. Occasionally the new behavior or body part helps the individual survive better than the other members of its species. If this individual passes the new trait on to its offspring, they may survive in greater numbers and pass it on to their offspring, and eventually a new species is formed.

What about the creatures without the new trait? Because they can’t compete or survive as well as those with the new trait, they become fewer and fewer in number, and at some point they become extinct. Extinction occurs when an entire species no longer exists.

Extinctions are important in the history of life on Earth. As less successful species die, more room is made for new species to develop. It’s hard to believe, but scientists think as many as four billion species may have come and gone during Earth’s history. That means that 99 percent are extinct! Remember, though, that if none of the plants and animals had become extinct, there would have been no opportunity for the evolution of the many newer forms of life that exist on Earth today.

Trace the path of this imaginary animal from its first appearance through evolutionary changes to the way it looks today. At each branch in the path, choose which model of the animal you think will be most successful. (If you choose a path that leads to extinction, just back up and try again.) See if you can avoid extinction and find evolutionary success!

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NOW PUT ON YOUR THINKING CAP

Think about the traits that made this animal successful and answer these questions.