Answer:
B) There is an increase in the number of giraffes with long necks in areas of Africa where low-growing trees have died
Explanation:
The directional selection is one of the ways of the natural selection in which the natural selection selects or favours the most extreme trait of the species and the extreme trait show higher fitness than the normal or average trait.
In the given question, the case of Giraffe necks shows directional selection as the normal length of the neck is not favoured by the environment but the extreme trait that is long neck is favoured by the environment and the selection shifted to that level.
Thus, Option-B is the correct answer.
Tyrosine is listed as a non-essential amino acid because it can be synthesised from the essential amino acid phenylalanine.
<u>Explanation:</u>
Amino acids are classified as essential and non essential according to whether they can be synthesized in the body itself or should be supplied by the diet. Essential amino acids cannot be synthesized in the body of the organism and thus can be obtained only from the diet. In the case of human beings, valine, phenylalanine, methionine etc are examples of essential amino acids.
Non essential amino acids can be synthesized within the body of the organism. Thus they need not be supplied by the diet. Alanine, aspartic acid etc are some of the non essential amino acids in human beings. It is given here that animals cannot synthesize tyrosine from shikimate-3p due to the lack of EPSP synthase.
But the amino acid tyrosine can be synthesized from the amino acid phenylalanine which is an essential amino acid. Thus tyrosine will be a non-essential amino acid.
fall & rise.. The initial compensating response to an acute respiratory alkalosis is a modest decline in ECF bicarbonate concentration as the result of cellular buffering. Subsequent renal responses result in decreased ECF bicarbonate concentration through reduced renal bicarbonate reabsorption.
What disaster, do you mean and aretalking about.
