Its B, i had the same test
Natural selection is the process that result in the adaptation of an organism to environment by means of selectively reproducing changes in its genotype, or genetic constitution. It is the a key mechanism of evolution. Charles Darwin popularised the term "natural selection" contrasting it with artificial selection, which is intentional, whereas natural selection is not.
To make it simple, let's have a group of beetle composing of green and some are brown as an example. here, there is a variation in traits. Since the environment could not support continuous population growth, not all species can reproduce to their full potential. Green beetles can easily be eaten by other species like birds compared to brown beetles. The surviving brown beetles will then generate brown offsprings because their trait has a genetic basis. Since more brown beetles survive and becomes more common in the population, the process continues until all individuals will eventually be brown. so basically, if you have variation, differential reproduction, and heredity, you will have evolution by natural selection as an outcome.
Answer:
The oxygen dissociation curve represents the percentage saturation of Hb with oxygen at different partial pressure of oxygen. The different partial pressures gives sigmoid shapes to the curve. When this curves shifts to right, it indicates low affinity or binding of oxygen by the Hb. it also indicates the unloading or releases of Oxygen by Hb molecules at condition of low pressure. e,g in the muscles during strenuous exercise.However, when the curve shifts to the left, this indicate high affinity for oxygen, great binding, at high partial pressure of oxygen.e,g in the lungs to take oxygen and releases CO2.
Therefore in this scenario, the statement -. <u>During strenuous exercise, the oxygen-hemoglobin dissociation curve shifts to the right.</u> is correct. because oxygen is needed by the muscles therefore ,oxygen should be less binded by Hb, decrease affinity and easily unloaded to muscles.
<u>The statement </u>This rightward shift reflects an increase in the affinity of hemoglobin for oxygen and favors loading of O2 into hemoglobin in the lungs is wrong.
As explained above the rightwards shift indicated low affinity of Hb for oxygen(unloading)and favours unloading at the muscles because during strenuous exercise the partial pressure of oxygen is very low(but that of CO2 high) in the muscles which favours low oxygen molecules binding by Hb, and easy release to respiring cells.
Explanation:
mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elementsit is of two types :- point mutation and frame shift mutation
point mutation - mutation only in a single base
frame shift - in the entire sequence or an entire set
