1.1 Compare this food chain: algae to this food chain: trees, water fleas, catfish, green herons, tent caterpillars, red-eyed vireos, hawks.

Both water fleas and tent caterpillars are:
a. Carnivores
b. Primary consumers
c. Detritus feeders
d. Both a and b are correct

1.2 Consider the components of a food chain: producers - herbivores - carnivores - top carnivores. Which level contains the most energy?
a. Producers
b. Herbivores
c. Carnivores
d. Top carnivores

1.3 Which of the following contributes to the carbon cycle?
a. Respiration
b. Photosynthesis
c. Fossil fuel combustion
d. All of these are correct

1.4 A natural food web
a. Contains only grazing food chains
b. Contains several trophic levels
c. Is usually unstable
d. All of these are correct

1.5 How do plants contribute to the carbon cycle?
a. When they respire, they release carbon dioxide into the atmosphere
b. When they photosynthesize, they consume carbon dioxide from the atmosphere
c. They do not contribute to the carbon cycle
d. Both a and b are correct

1.6 How do nitrogen-fixing bacteria contribute to the nitrogen cycle?
a. They return nitrogen to the atmosphere
b. They change ammonium to nitrate
c. They change nitrogen to ammonium
d. They withdraw nitrate from the soil

1.7 In what way are decomposers like producers?
a. Either one may be the first member of a grazing food chain
b. Both produce oxygen for other forms of life
c. Both require a source of nutrient molecules and energy
d. Both supply organic food for the biosphere