Structure and function
Another topic which underlies all aspects of biology is the correlation between structure and function. If the structure is known, often the function can be determined, and vice versa.For example, knowing the amino acid sequence of a protein (the structure) can help predict how that protein functions in a cell. Or, as another example, if an animal has the ability to see (the function), then it must have the structures necessary to support that function (eyes, optic nerves, a region of the brain to interpret nerve impulses, etc.).