Identical twins in humans, which are deuterostomes, are formed when cells at the four-cell
stage are separated. a grasshopper, which is a protostome, will die if the cells are separated at
the four-cell stage. what does this indicate about when the cells are differentiated in the
zygote? why might deuterostomes differentiate their embryonic cells later than the
protostomes?

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