Question

1. Describe the differences between bottleneck effect and founder effect. What are their impacts on genetic diversity in a population? How is their impact on a population reversed over time?

2. Define sympatric and allopatric speciation and give an example of each type

3. Describe three key differences between phyletic gradualism and punctuated equilibrium.

Answer 1

1.Founder effect : If a small group of individuals from a population start a new colony in an isolated area,those individuals are called the founders of the new population.The allelic frequencies of their descendants are similar to those of the founders rather than to their ancestral parent.It doesn't affect the parent population.Result of migration.

Bottleneck effect:Natural calamities such as earthquakes,volcanic erruptions,floods etc.reduce the size of the population.After the calamities the lucky survivors may be genetically different from their original population in genetic makeup.This condition is called Bottleneck effect.It affects the parent population.Result of habitat fragmentation.

Both Founder effect and Bottleneck effect leads to dramatical reduce in genetic variation.

In founder effect there is no change or very minor change in the population size,whereas in bottleneck effect the size of the population is drastically reduced.

2.Sympatric speciation:If speciation takes place in the organisms which live in the same habitat capable of interbreeding but do not interbreed due to some isolation mechanisms.

Ex.Orca whales in Pacific ocean.Two types of orcas live in the same habitat but do not interbreed or mate with each other.

Allopatric speciation:If speciation takes place due to geographic isolation it is called Allopatric speciation.

Ex.Darwin's finches

3.Phyletic gradualism occurs over a long period of time and Punctuated equilibrium occurs within short period of time.Phyletic gradualism describes evolution as a slow process,whereas punctuated equilibrium speeds up slow evolution.In phyletic gradualism small variation to a particular species occurs,whereas in punctuated equilibrium consistent and cumulative changes are seen.