Chapter 15.3, Problem 1NV

Summary Introduction

To fill:

The correct terms in the given blanks according to given description.

Answer to Problem 1NV

The given blanks can be filled as follows:

S. no.	Correct term
1	Hardy Weinberg Principle
2	Founder effect
3	Bottleneck effect
4	Prezygotic isolation
5	Genetic drift
6	Stabilizing population
7	Postzygotic isolation
8	Directional selection
9	Disruptive selection
10	Sexual selection
11	Allopatric speciation
12	Sympatric speciation

Explanation of Solution

Hardy Weinberg principle states that the allelic and the genetic frequency of a population remain the same over a generation in absence of evolutionary forces.

The founder effect represents a condition on which a small number of individuals are isolated from a large population and evolve to form new traits that are different from other members.

Bottleneck effect is a phenomenon that reduces the size of the population due to some accidental changes in the population, but when the situation becomes favorable, the population flourish once again.

Prezygotic isolation is a mechanism of reproductive separation of two species, in which the formation of a zygote is prevented.

Genetic drift is a sudden change in allele frequency in several generations which results in more number of individuals having a certain allele and a decline in the number of individuals with another allele.

Stabilizing population is a group of individuals, in which the existence of average individuals is preferred over the extreme ones.

Post zygotic barrier is a reproductive barrier that operates after the formation of a zygote. It prevents implantation and further embryological development.

Directional selection is a type of natural selection, in which individuals having one allele is preferred, which eventually results in shifting of the population toward an extreme end.

Disruptive selection is a natural selection, in which the average individuals are considered as not fit and result in shifting of the frequencies towards extreme ends.

Sexual selection is an evolutionary change, which arises from the choice of mates for the purpose of reproduction.

Allopatric speciation occurs, when the individuals of a population are separated by a barrier and after certain generations, they become reproductively isolated from one another.

Sympatric speciation occurs when a group of individuals of a population forms reproductive isolation without the presence of any barrier.