Answer:
Some factors that might causes changes in the population of grasshoppers are:
1. Weather
2. Cultivation
It is useful for an ecologist to identify the keystone species in an ecosystem because the keystone species is important to maintaining the stability of an ecosystem, and any changes in the keystone species population shows that there is changes in ecosystem health.
I think it A because Cyanobacteria absorb co2 from the atmosphere and then release oxygen To the atmosphere
I think the correct answers are options C and D. Examples of science are a farmer consulting a weather almanac to decide the best time to plant a crop and a<span> drug manufacturer testing a drug to determine its safety. These things require the knowledge on science and its related subjects.</span>