Define and give reasons that the following can constrain sel

Define and give reasons that the following can constrain selection and so affect the “perfection of adaptations.\"

a. Gene flow

b. Time lags

c. Trade off

d. Constraints (ignore discussion of asexual and sexual mammals and frog)

Solution

Gene flow is transfer of alleles into or out of a population due to immigration or emmigration of fertile individuals or their gametes. Since alleles can be exchanged between different population gene flow decreases variation in between different populations. When too much gene flow occurs the effects of selection is overshadowed by the entry of several duch genes or alleles whivh may be responsible for not being able to adapt to a particular environment. This might thus interfere with perfection of adaptation.

There are several genes present in organisms which have multiple effects also known as pleiotropy of genes. Thus selection for a increase or decrease of a particular gene will favour a set of underlying allelic changes that impact other characters. These simultaneous effects influence characters responsible for reproductive fitness in opposite directions. For example in insects there is a trade off between development time and reproduction because alleles which increase fast development leads to early reproduction by adults but there is a cist which is paid as the adults have a smaller body size and a reduced reproductive capacity. This kind of trade off can constrain selection as it decreases the reproductive fitness among the individuals.

Constraints usually promote species level diversity. Many tropical animals have low evolutionary potential to adapt to colder and drier conditions when compared to the other widespread species. Many ecologically specialised species have low adaptive potential because of low genetic variation or presence of pleiotropic effects that prevent them from easily adapting or both thus interfering with perfection of adaptation.