Exam 9: Life in the Ocean

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Most simple marine organisms have nearly the same concentration of dissolved substances in their body fluids as seawater does. They are almost isotonic to their fluid environment and experience little net flow of water through their outer membranes. In freshwater, a marine animal would be hypertonic to its surroundings; water would move into the animal through its cell membranes. If the animal had no way to eliminate the water, its cells would burst. The same kind of marine animal moved to Utah's highly saline Great Salt Lake would be hypotonic , and would flow out of its cells, causing it to dehydrate and collapse.

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The sun produces enormous quantities of energy-some of it in the form of visible light, a tiny portion of which strikes Earth. Only about 1 part in 2,000 of the light that reaches Earth's surface is captured by organisms, but that "small" input of energy powers nearly all the growth and activity of living things on Earth's surface Light energy from the sun is trapped by chlorophyll in organisms called primary producers and changed into chemical energy. The chemical energy is used to build simple carbohydrates and other organic molecules-food-that is then used by the primary producer or eaten by animals called consumers. Because light energy is used to synthesize molecules rich in stored energy, the process is called photosynthesis. The stored energy is released when the food is used for growth, repair, movement, reproduction, and the other functions of organisms.