1. Which of the following is a biotic factor?

A. sunlight
B. worms
C. water
D. climate

2. Nitrogen is used by ____.

A. plants
B. animals
C. both a and b
D. neither a or b

3. As you move from level to level in an energy pyramid, energy ____.

A. decreases
B. increases
C. stays at the same level
D. is destroyed

4. The part of Earth that supports life is a(n) ____.

A. biome
B. ecosystem
C. biosphere
D. organism

5. Population ____ can be even, random, or clumped together.