Answer:
The pressure differences on either side of the valve.
Explanation:
The heart valves open and close passively because of pressure differences on either side of the valve. When pressure is greater behind the valve, the leaflets are blown open and the blood flows through the valve. However, when pressure is greater in front of the valve, the leaflets snap shut and blood flow is stopped.
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If the birth rate in a population is 40, and the death rate in that population is 15, then the population will be experiencing growth. The growth will be 25 on every 1,000 people. If this trend continues for longer period, then the population will start to become younger and younger, making the basis of the population pyramid wider, while the top part of it smaller and smaller. This demographic situation in modern times seems to be present only in the less developed countries, with the majority of the transitioning countries having much decreased population growth, and the more developed countries having more deaths than births, thus being aging populations.
I would say that the answer is C, since variations in crop restore the nitrogen in the soil from certain bacteria growing on the root of beans, including legumes.
It is the biosphere, which is all the ecosystems of the earth
In biosphere, it is the total organismic life and their entire species on which how they interact with the co-organisms. While biodiversity, is the different and varied living organisms and creatures across the ecosystem or the biosphere, on which is the composed the biotic environment. This may include now the hierarchy and organization among the species of the autotrophs and heterotrophs.<span> </span>