We can rule out small fish and grasses. My guess is that zooplankton get their energy from phytoplankton, because phytoplankton use photosynthesis to get their energy.
The first land plants appeared around 470 million years ago, during the Ordovician period, when life was diversifying rapidly. They were non-vascular plants, like mosses and liverworts, that didn't have deep roots
The main function of the cell membrane is that regulates and monitors the movement of specific substances into and out of the cell, permitting only some substances to move across and not allowing others.
Kin selection, I think this is right, but I am not sure
