Which is not a major similarity or difference between freshwater and marine ecosystems?

The correct answers is this: OCEAN AND FRESH WATER SYSTEM CONDITIONS GENERALLY REMAIN CONSTANT THROUGHOUT THE YEAR.
It is not possible for the conditions in the ocean and the freshwater environment to be constant throughout a year, this is because these water bodies respond the changes in their environment on a daily basis.

Molecules called lipids have long hydrocarbon chains that determine the way they act. they can be fats, oils, or hormones, and even exist in our cell membranes