Using an analogy of a cyclist to describe light dependent reactions, what do the downhill sections represent

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).

the correct answer is:

a population changes in response to a change in the environment.

b.

oxygen +1 most likely