Selective permeability, made possible in cells by the phospholipid bilayer that makes up the plasma membrane, is basically monitoring and regulating what can and can't enter the cell. It is carried out by a series of membrane proteins that act as channels to polar molecules, opening to allow them in and closing to prevent their entry. This is possible because the hydrophobic tails of the phospholipid molecules repel polar molecules and so prevent their entry unless through a channel.
The answer is B. This the systolic pressure of a giraffe in comparison
to that of a human that is 100 mm Hg. This
high blood pressure ensures that the giraffe maintains 100 mmHg in the brain.
Since a high BP impairs gas exchange and increases transpulmonary filtration,
the pulmonary circulation must be separated. Therefore, in the giraffe, there
is a relatively great difference between the right ventricular and left ventricular
maximal rates of pressure ascent, the left ventricular rate of ascent being 5
times that calculated for the right ventricle.
Answer:
An index fossil is a fossil used to determine the age of the sediments in which it is found. When quickly approximating the age of new finds, an archaeologist looks at the rocks in which it is buried, as those sediments would have been on the surface at the time of the death of the pre-historic creature.
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