"every cell has its own clock, for example, skin cells. what is the clock of the skin cells? "

Clock in the skin cells is called circadian clock.

Explanation:

Circadian clock is a system that requlates how the skin function and human physiology. The stem cells of basal epidermal harbors circadian clock.Circadian clock is found in some skin cells like melanocytes, keratinocytes and fibroblasts. Circadian clock found in skin cells may function by regulating cell proliferation.

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

voluntary muscles are controlled by the cerebellum.