Answer: pressure changes
Valves of the heart open and close due to pressure changes
Explanation:
The veins are the blood vessels possessing valves. And because they carry blood away from the heart, the valves helps to prevent back flow of blood due to the low pressure of blood found in the veins.
Thus, Valves of the heart open and close due to pressure changes
Answer:
An organism that can provide itself with natural and nutritional substances from non-natural substances.
Example ↓
The potted plant in that window across the street.
Plankton.
Bacteria.
Evolutionary Theory of Aging describes t<span>he view that natural selection has not eliminated many harmful conditions and nonadaptive characteristics in older adults. N</span>atural selection is linked to reproductive fitness, which is present only in the earlier part of adulthood. According to evolutionary theory, possibly if some disease occurred earlier in development, it might have been eliminated many centuries ago.
