16. A "greenhouse gas" is one that absorbs infrared radiation (heat) and traps that heat in the atmosphere. The greenhouse
effect is a naturally occurring effect that is important to life on
the planet. Without this effect, the earth would be too cold for life
to exist.
How does an excess amount of CO2 in the air contribute to
Earth's warming? Use the diagram for reference.

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.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

The equation shows cellular respiration. during cellular respiration, glucose combines with oxygen to form carbon dioxide, water, and atp. what happens to the energy in the bonds in glucose? the energy is transferred to oxygen. the energy is transferred to carbon dioxide. the energy is transferred to water. the energy is transferred to atp.