What do you call the part of the experiment that stayed the same?

The fish shown above is a tarpon. it is a fast-swimming and powerful open-water fish. its closest relatives, oddly, are burrow-dwelling conger eels that stay on the bottom. both eels and tarpon developed from snake-like larvae that float in the plankton during the first stages of life. once they mature, tarpon and eels are not found near one another in the ocean. the tarpon and the eel illustrate all of the following except

What is the primary function of the nervous system?

This is a situation in which genes are attached to an organism's sex chromosomes; the sex of an organism influences the expression of a gene.