Scientists then used microscopes to develop which of the following major scientific theories? a. the theory of thermodynamics b. the cell theory c. the theory of plate tectonics d. the big bang theory

B the cell theory. this is because the cell was so small and darwin saw plant cells using a microscope in the form of a cell that is why the smallest unit of life was called the cell.

1. tetrapods are ( four-limbed animals ) . examples of tetrapods include (extanct and extinct amphibians , reptiles , and mammals )
2. Tetrapods first appear in the fossil record ( 367.5 ) million years ago .
3. Charles Darwin predicted that tetrapods evolved from ( a finned organism that lived in the water) . What observation leads do that hypothesis?( they have “fleshy fins” and “lobe fins”) .
5. Fish use ( gills ) to breathe underwater .