Large molecules move across cell membrane with the or assistance of protein carriers. this type of transport is generically called

amber has allowed scientists to study dna that has been preserved over millions of years.

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