Which is not a major similarity or difference between freshwater and marine ecosystems? i believe its b
a. both support a large number of plants and animals adapted for aquatic living
b. ocean and freshwater system conditions generally remain constant throughout the year
c. freshwater ecosystems have a very low salt concentration, and include ponds, lakes, streams, wetlands, and rivers
d. saltwater ecosystems have a high salt concentration and include oceans, coral reefs, and estuaries

The correct answer is:

b. ocean and freshwater system conditions generally remain constant throughout the year .

Explanation:

ocean and freshwater system requirements frequently remain constant completely the year. This is not true because they are very inconsistent. For examples, freshwater rivers can completely freeze during the winter while oceans can't freeze entirely, not even a bit. Also, the animals inside have radically changed body structures to fight these changes.

when it is at an intermediate population density

if you listed your answers right then i believe your answer is b.