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13. succession is possible because
a. existing plants reproduce quickly.
b. new species make the environment less suitable for previous ones.
c. climates change over time.
d. it is a rapid and chaotic process that is very difficult to control.

The correct option is b. new species make the environment less suitable for previous ones.

Explanation:

In ecology, succession can be described as the changes in a species structure over a period of time. In a community, newer species tend to have better characteristics and adaptations to survive in a community as compared to the older ones. As a result, the new species begin to take over the land and the older ones gets removed. It is due to ecological succession that climax communities are formed from pioneer species.

the correct answer would be b) volume versus temperature, because they are also directly proportional.