Answers to Review Questions

1. The two major biological influences on the global carbon cycle are photosynthesis, which takes up CO₂ from the atmosphere, and respiration, which releases CO₂ back to the atmosphere.

2. While animals can respond to climate change by moving, their habitats cannot. Animals are dependent on plants to provide their food (or food for their prey). Climate change will be so rapid that evolutionary responses will not be possible for most species of plants, and the dispersal rates of most plant species are too slow to track the predicted climate changes. Dispersal may be inhibited by fragmentation of dispersal corridors due to land-use change. Loss of habitat will therefore result in decreased population growth for some animals. Additionally, migrating animals may respond to climate change more slowly than nonmigratory species. As a result, prey species may be less abundant or absent when these animals arrive at their destination.

3. The effect of atmospheric ozone on organisms depends on where in the atmosphere it is found. Ozone in the stratosphere acts as a shield against high-energy ultraviolet-B radiation, which is harmful to organisms. In contrast, ozone in the troposphere damages organisms that come in direct contact with it. Ozone in the troposphere also acts as a greenhouse gas, contributing to global climate change.