an organism is resistant to a chemical if it has a gene that protects it from the chemical.
This property allows fish living in lakes and ponds to survive the winter. The ice that freezes on the surface insulates the water below so it stays warmer! In general, it is extremely unusual for the solid phase of a substance to be less dense than its liquid phase, but lucky for aquatic life it is!
Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. At the first trophic level<span>, </span>primary producers<span> (plants, algae, and some bacteria) use solar energy to produce organic plant material through photosynthesis. Herbivores—animals that feed solely on plants—make up the second trophic level. Predators that eat herbivores comprise the third trophic level; if larger predators are present, they represent still higher trophic levels. Organisms that feed at several trophic levels (for example, grizzly bears that eat berries and salmon) are classified at the highest of the trophic levels at which they feed. Decomposers, which include bacteria, fungi, molds, worms, and insects, break down wastes and dead organisms and return nutrients to the soil
I got this passage from Annenberg Learner
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