Answer:
Natural selection is an adaptative mechanism that modifies gene frequencies (allele frequencies) in the whole population across generations
Explanation:
According to the evolutionary theory proposed by Darwin, natural selection is the main process that leads to evolution. Natural selection can be defined as a mechanism through which populations adapt and change. The organisms better adapted to their environment will have more chances to survive and reproduce, and therefore they will pass their genes (and favorable traits) to the next generation. This process is able to modify the allele frequencies in the whole population, thereby changing and adapting (i.e., evolving) across generations.
Divergent boundaries in the middle of the ocean contribute to seafloor spreading. As plates made of oceanic crust pull apart, a crack in the ocean floor appears. Magma then oozes up from the mantle to fill in the space between the plates, forming a raised ridge called a mid-ocean ridge.
Answer:
PVR is calculated by the formulae: 
Explanation:
Pulmonary vascular resistance may be defined as the resistance to blood through the pulmonary circulation.
PVR can be determined by the following formula:

Here, PAP is the pulmonary artery pressure, PAOP is pulmonary artery occlusion pressure and CO is cardiac output.
Four hydrogen nuclei are converted to helium nuclei in the proton-proton chain. This does not occur naturally on Earth because the process requires it. extremely high temperatures, pressures, and densities
The proton-proton chain is a series of reactions that fuses four hydrogen nuclei to form one helium nucleus. The energy is derived from the mass difference between the four hydrogen nuclei with higher masses and the single helium nucleus with lower masses. Energy is released when hydrogen is fused into helium: mass to energy conversion. Because mass is created during the proton-proton chain, energy is released. However, this is essentially the end of the story for the nuclear fusion reactions that occurred in the early Universe, known as Big Bang Nucleosynthesis.
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Answer:
Carbohydrates such as glucose, cellulose, deoxyribose, fructose, etc
Nucleic acids such as DNA, mRNA, tRNA
Proteins such as structural proteins and enzymes