4. You are looking at a layer of rock. The rock contains a fossil seashell. How do you know that this area of land was once covered by an ocean?

Cells tend to have a relatively small and uniform size. why aren’t cells larger?

Variety of living organisms; includes genetic, species, and ecological types.

Use the phylogenetic tree to the right to determine which statement below is true. organisms a and f are not related. organism e is more closely related to organism b than organism f. organisms c and d are more closely related than organisms a and b. phylogenetic trees