Module 5.3 – Productivity and Food Chains (Possible Written Questions)

What is the difference between gross primary productivity and net primary productivity?

GPP is total energy captured by producers, while NPP is the energy remaining after respiration.

Why is NPP important to consumers?

NPP represents the energy available to higher trophic levels.

Why are food chains usually limited in length?

Most energy is lost between trophic levels, leaving less energy available to support additional levels.

Why do aquatic ecosystems often have longer food chains than terrestrial ecosystems?

Aquatic producers such as phytoplankton are consumed more efficiently, allowing more energy transfer.

Explain the 10% rule.

Only about 10% of energy at one trophic level is transferred to the next trophic level.

Describe a trophic cascade.

Changes in one trophic level cause indirect effects throughout the food web.

What is a keystone species?

A species whose effect on community structure is much greater than expected from its abundance.

Explain how wolf reintroduction affected Yellowstone.

Wolves reduced elk populations, allowing vegetation and other species to recover, increasing biodiversity.