What is an easy way to memorize the word ecology

Okay, the word ecosystem means (from google) "A biological community of interacting organisms and their physical environment."

The definition of ecology  (from google) "Is the branch of biology that deals with the relations of organisms to one another and to their physical surroundings."

So some types of studies of science end with -logy. So just remember ecosystem and studies.

Explanation:

A)death rate

B)mass of plant

C)number of plants

D)amount of fertilizer