I know physics , but I'm not sure if that is the only one
Plankton is at the bottom of a food chain. Think of a pond. Mosquito larvae are in a pond. They eat the plankton. Small fish eat the larvae. Larger fish eat those smaller fish and the chain keeps going..BUTTT it all started with the PLANKTON. Without the plankton the whole food chain would be messed up and everything would start dying.. No plankton, no larvae, no small fish..and so on..
Answer:
Blood, the heart pumps oxygen-poor blood to the lungs to be oxygenated.
Explanation:
:) Merry Christmas!
