Which event occurs in photosystem 1?

What do heterotrophic cells need to survive?

The following image is of a diatom. it lives in water and gets food from photosynthesis. it is encased in a hard shell made of something similar to glass or sand . a diatom is a(n) because it has a) multi-celled organism; specialized parts. b) vertebrate; a skeleton. c) insect; an exoskeleton. d) single-called organism; only one cell.

What is thought to have caused the mass extinction at the end of the cretaceous period?