Natural selection under different environments condition, Biology

In the absence of any large scale envirorrmental change that is, in more or less uniform environments, populations often maintain a stable genetic constitution with respect to many traits. Natural selection in the absence of environmental change maintains a genetic homeostasis. This phenomeon is known as normidising selection Several of the phenotypic, traits of individuals can be arranged on a linear scale. The distribution curve of the traits usually takes a bell shape, so that the number of individuals is greater at intermediate values and gradually decrease towards the extremes. Ja. As stated earlier, normalising selection occurs when individuals with intermediate phenotypes are favoured and those with extremes are under selection pressure. This tendency continues generation after generation. If there is a strong selection pressure against the phenotypes occupying the extremes of normal curve, then the population may show less variability although the mean remains the sarne. Natural selection has more often a normalising or stabilising effect on populations with mid-values for the traits and individuals with intermediate values for their traits have better chances of survival. For instance, new born infarits which weigh very less or very more than the average weight have high rate of mortality. Contrarily infants of intermediate weight have less problems of survival. We discuss two examples below, one from nature and the other from the experiments of Dobzhansky and Spassky to explain the concept of normalising selection.

Posted Date: 4/6/2013 1:25:00 AM | Location : United States







Related Discussions:- Natural selection under different environments condition, Assignment Help, Ask Question on Natural selection under different environments condition, Get Answer, Expert's Help, Natural selection under different environments condition Discussions

Write discussion on Natural selection under different environments condition
Your posts are moderated
Related Questions
What is Infra-diaphragmatic Type of TAPVC? Initial stages of operation are the same as for supracardiac type of TAPVC. The heart is lifted out of the pericardial cavity and c

a) How would you destarch the leaves of a potted plant? b) How would you check that the destarching had been effective?   a) If a potted plant is kept in darkness for

Kinds of Matter On basis of its chemical organization, matter id of three categories elements, compounds and mixture An element is composed of obviously, earth similar atoms

Euthenics : It is the study of improvement of human races by providing better conditions. Euthenics means human improvement by altering external factors like as education or the co

characteristics of class mamalias

Define about the term Indicators? The easiest way to determine when the reaction is complete is by using indicators. An indicator is a compound that has a physical property (us

Phylum coelenterata

State the Variety of chemical and biological reactions Variety of chemical and biological reactions takes place leading to the formation of the solution phase. If we analyse th

Ethylene - Dormancy Ripening of fruits involves a chain of cellular events like: Rise in the rate of respiration, Breakdown of higher carbohydrates into carboxylic

A fifth member of the monoamine transmitter group is histamine. That release histamine as their neurotransmitter is located in the hypothalamus and project to cerebral cortex, lim