Question

The inherited character long neck in giraffe is an example of
A. Genetic variation
B. Natural selection
C. Gene drift
D. All the above

Answer 1

Hint: Jean-Baptiste Lamarck proposed that acquired characteristics were inheritable. A giraffe stretches its neck to feed on higher trees, the continuation of that habit for a long period which results in a gradual lengthening of the limbs and neck.

Complete answer:
-Genetic variation explains the difference in gene frequencies. Genetic variation can refer to differences between individuals or populations. The mutation is the ultimate source of genetic variation.
-According to Darwin’s natural selection theory nature poses the same challenges to organisms in the form of harsh climate, food scarcity, natural disasters like flood, droughts, etc. the characteristics that enable some organisms to survive better than others in the same environment are said to be selected by nature. Like in giraffes' case for eating leaves of long trees they had to stretch their neck. Ancestors of giraffes were bearing a small neck and forelimbs. But in an attempt to eat the leaves on tall trees, they had to stretch their neck. Lamarck proposed that this acquired character, i.e., stretching of the neck was passed on to the next generation resulting in the present time long necks. Therefore the inherited character long neck in giraffes is an example of natural selection.
-Genetic drift is a change in allele frequency in a population, due to a random selection of certain genes. These changes in genetics can increase and decrease in a population, simply due to chance.
So, the correct option is (B).

Note: Natural selection is proposed by Charles Darwin and Alfred Wallace in 1858, and genetic drift was coined by Sewall Wright in 1929. British geneticist R.A. Fisher mathematically demonstrated a direct relationship between the amount of genetic variation in a population and the rate of evolutionary change by natural selection.