An enzyme is a protein that-A. increases the rate of a chemical reaction b. transports nutrients across a membrane
C. provides structure for the cell's organelles
D. receives and sends signals across a cell

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands