Question

Identify the correct combinations :
(a) Genetic load - Existence of deleterious genes with the population - Sickle cell anaemia.
(b) Founder effect - Small group of individuals from a population that start new colony in an isolate place - Beaks of Darwin's finches.
(c) Centripetal selection - It operates when homogeneous environment changes into heterogenous type - Weight of new born in London.
(d) Directional selection - It works by removing the individuals constantly from one end and shifting fitness towards the other end of phenotypic distribution - Average value of length of Giraffe neck.

• A. (a) and (c)
• B. (a) and (d)
• C. (b), (c) and (d)
• D. (a), (c) and (d)

Answer 1

The correct option is B (a) and (d)

1. Genetic load is the reduction in the mean fitness of a population relative to a population composed entirely of individuals having optimal genotypes. It is due to the occurrence of non-beneficial alleles in heterozygous genotype.

2. The founder effect is the loss of genetic variation that occurs when a new isolated population is established by a few members of the original population. But beaks of Darwin's finches is an example of adaptive radiation.

3. Centripetal selection or stabilizing selection operates when environment is homogenous. Environment favours birth of average weight of new borns, hence their survival rate is more.

4. Long giraffe neck is an example of Directional selection since short neck of giraffe was eliminated in the course of time due to it's relative disadvantage compared to long necks.

So, the correct option is '(a) and (d)'.