Darwin's idea of the survival of the fittest means that certain organisms are more likely to survive with they traits in particular environments. This is because some organisms are more fit to live in a given environment whether it be due to temperature, weather, or predators.
One example is that dark moths are more fit for survival than light moths in many areas because they are able to camouflage against dark tree bark.
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Answer:
The given question is incomplete, as there is no options provided, and are not available anywhere. But in general, if a forest ecosystem has not experienced any kind of disturbances or natural disasters in the last 100 years then the various plants and animals species dwelling in that forest are reasonably stable.
Explanation:
A forest ecosystem is usually defined as a distinct ecosystem that is comprised of trees, plants and animals, and micro-organisms, in an area that interacts with the abiotic factors such as water, soil in order to survive.
If a forest ecosystem is not disturbed by any anthropogenic or natural disasters for the past 100 years, then the species living in this ecosystem becomes reasonably very stable. They will be adapting to the environment and habitat becomes permanent. There will not occur much physiological and morphological variation in these species.