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What was the land like over 500 million years ago? what was under the sea?

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

The breakdown of food is accomplished by enzymes. a. physical b. chemical c. mechanical d. none of the above