Pond and Lake Life
Still water, in general much warmer than rivers and streams, can support many different kinds of plant and animal life. The silty bed of ponds and the shallower parts of lakes support rooted plants and burrowing larva, food for free-swimming animals such as fish and frogs. In deeper zones, where oxygen is less abundant, only animals adapted to the cold environment exist. Plankton develops at all levels.
(Left): At the stream’s source, animals must be able to withstand both the cold and the rapid current of the strong headwater. Some organisms, especially the smaller ones, have hooks and suckers to help them cling to the rocks; most have streamlined bodies that minimize drag. (Right): Free-swimming organisms populate the lower, slower areas of the stream.
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