Why are so many other living things dependent on plantlike protists?

Since the plant-like protists photosynthesize, they form the energy base of food chains. ... You could say life on Earth depends on the protists because they supply us with oxygen, are critical organisms in food chains, and recycle important nutrients for other life forms to use.

There are many animals on our planet, they all need plants, why? because plants are a source of food for all herbivorous animals, forests and jungles are also a habitat for animals, fish throw their eggs on algae, thanks to sea plants, many fish find refuge from predators.