Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
In this section, we shall discuss a classic example of natulal selection in action. In the preceding unit, it was stated that natural selection always aims at eliminating alleles, which are less adapted to the environment. Conversely selection indirectly aims to promote those alleles or individuals that are well adapted to a given environment.
The promotion and establishment of an allele and the resultant phenotype may take several hundreds of years in natural populations. But there are indeed instances where the selective forces have brought changes in the character of individuals within historical times.
The peppered moths Biston betillaria occur in two forms, the melanic and non-melanic. As shown in Fig. the melanic forms are black in colour and non-mel?nic ones are mottled grey. Until the early part of the 19th century, the melanic forms were regarded as rare and prize collections by insect collectors, and the light non-melanic forms were abundantly present in natural populations. The rarit.? of black forrns was essentially due to the higher rate of predation by birds. The black forms resting on light coloured and lichen encrusted trees were the easy targets for the birds. The light coloured non-melanics blend with their background, and therefore, are not easily visible to the predators. With the onset of the industrial revolution the distribution of melanic forms particularly in the industrial centres underwent a great change. An examination of museum collection of insects over the past 100 years showed that the melanic forms increased in numbers and the non-melanics were becoming rarer and rarer. What could be the possible reason for such an occurrence? In industrial regions, the sooty smoke emanating from factories blackened the bark of the trees and prevented the growth of lichens. This resulted in the black coloured forms resting on such trees becoming invisible to the p~edators and the light coloured ones being increasingly susceptible to the predator attack because of their contrast with the background. In industrial areas the birds predated upon non-melanics in extremely large numbers whereas in other areas melanics were preferentially caten. Since the proportion of melanics increased due to industrial activity, the examplc is often referred to as industrial melanism.
what is the mode of nutrition in tape worm
How is the large size of some cephalopods related to the type of circulatory system they present? In cephalopods the circulatory system is closed and this gives more speed and
Explain Procedure for Analysis of Air of Processing Facility? Now conduct the experiment following the steps enumerated herewith: 1. Label the Petri plates with nutrient aga
M e t h ods of curing Curing ingredients are applied in dry form or as a solution of curing ingredients in water (pickle or brine). The combination cure is applied in the i
The synthesis of the three fundamental polymers of life, DNA, RNA and protein, is template-directed. This means that - Answer A. the monomers are assembled one by one in a sequence
Infectious laryngotracheitis (ILT) Infectious laryngotracheities, caused by fowl Gallid Herpesvirus 1 belonging to the family Herpesviridae, is a quickly spreading acute res
Define Sugar as a type of Carbohydrates? This group includes monosaccharide and disaccharides. List down the names of sugars under both these groups and check it out with those
Explain the periodic table of the elements ? Periodic Table of the Elements : An element is a pure substance composed of atoms all of a single kind. It cannot be broken down
How are genetic diseases classified? The Genetic diseases classify into chromosomal abnormalities and genetic mutations. Between chromosomal abnormalities there are the aneu
Define Formula Concentration and Supplementation - Calorie Density? Formula Concentration can be done by decreasing the amount or water added in the mixing of the formula. Sta
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd