With age, the tissues making up a heart valve can lose flexibility and become stiff and narrowed while retaining their one-way closure properties. suppose a man's aortic valve is affected by this condition but his ventricles do not change their force of contraction. which of the following will likely happen?

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.

Isotopes of the same element have differ in their

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic