How do the sizes of each population affect each other?

If one population dies out, all the populations that depend on that species for food may also die out. A change in one population affects the entire community because all the populations of a community depend on each other. A population is all the members of one type of organism living in an ecosystem.

This is what i found on google “phytoplankton, tiny organisms that live in the ocean, are autotrophs. some types of bacteria are autotrophs. most autotrophs use a process called photosynthesis to make their food.” i hope this you for what your looking for

That would be a working theory.