Explain how passive transport works

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.

case study case study case study case study case study case study case study case study case study case study case study

What was the land like over 500 million years ago? what was under the sea?