Answer:
<h2><u>
directional selection</u></h2>
Explanation:
This type of natural selection is referred to as . In this type of natural selection, either one phenotype is preferred or the other; therefore, there is no equilibrium between the populations of the phenotypes that are present.
Examples of organisms that have undergone directional selection are black bears during the ice ages, African chichlid and sockey salmon.
Answer:
The presence of cholesterol in the plasma membranes of some animal cells <u>enables the membranes to stay fluid when cell temperature drops</u>.
Explanation:
Cholesterol is an essential lipid in the basic structure of cell membranes. The membranes must have a fluid structure so that the proteins integrated in them can move ''horizontally'' to interact with their ligands and with other proteins. With excess saturated fat the membranes become rigid, but only with the necessary unsaturated fat the membranes are extremely fluid, and very sensitive to changes in temperature. Cholesterol stabilizes the structure of the membranes; preventing the collapse and crystallization between lipid chains that would lead to loss of fluidity and excessive rigidity in the membrane. By decreasing the temperature; as temperatures drop, fluidity decreases, an effect that partially counteracts the presence of cholesterol.
Answer:
C
Explanation:
heterotrophic oragnisms gain energy from other oragnisms and need to break down complex organic molocules to release energy.
Air rises when it is warmer
