Two species of hummingbird want the same flowers. This is an example of what kind of ecological pressure?

Describe the iron sulfide hypothesis and the lipid membrane hypothesis.

Name the organs of humanelemintary canal.

What is the main function of the central vacuole in a plant cell? a. absorbs energy from the sun to produce food b. holds water and maintains turgor pressure c. breaks down molecules to release energy d. contains the cell's genetic material