Answer:
fast moving mountain streams which flow over rocks and waterfalls are high in oxygen due to the amount of surface area of the water that is exposed to the air.
Fast moving mountain streams are high in nutrients. Organisms have adaptations to hold on in fast moving water, resulting in a large diversity organism.
Slow moving flood plain rivers are high in oxygen due to the amount of surface area of the water that is exposed to the air.
Slow moving flood plain rivers are low in nutrients. These rivers move too slow for plant growth and other organisms to survive.
The answer is either A, the bottleneck effect or C, natural selection. The answer is most likely A because it is hinted that the predator fish was placed in the isolated stream. The predators eating the darters less than 5cm is natural selection though.
Option C, animals moved from the sea to the land is the right answer.
The Paleozoic Era in the history of the earth was a time of major change on Earth. This was the period that ran about 542 to 251 million years ago. The period commenced with the split of a single super-continent and the development of another. Plants grew extensively. Moreover, the primary vertebral animals conquered the land.
