Answer:
Explanation:
There are many options, here are a few choices:
Fast moving water tends to be colder than slow water; some of it originates as snow melt on the sides of mountains, for example. For this, animals in fast water tend to be more cold resistant. This is why you do not see fish like freshwater trout in equatorial regions. These animals struggle and die in slow, warm water.
Fast moving water means that if the animal or plant wants to stay put, it must resist the flow. Fish tend to be far more muscular and lean in these places, while insects like stoneflies, mayflies, and other larvae have ways to secure themselves to rocks and plants while growing. Plants develop strong root systems, and algae hold fast in rocky crevices in the river. Some animals also have suction in order to stay in place where there is fast flowing water.
Some animals have to adapt their reproductive systems as well. Because finding a mate is difficult in the sweeping waters, breeding tends to happen all at one time. As an example, salmon have runs, where thousands of fish all swim upriver at once to breed, can dramatically alter the surrounding ecology of the river. Insects like mayflies have hatches, where hundreds of thousands of flies swarm into the air at once to breed and lay eggs.
