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.
Define two ways in which genetic recombination occurs during meiosis. Genetic recombination happens during crossing- over and independent assortment.
Q. Explain nutrient requirements during hypertension? In order to meet the above objectives, we need to understand the nutrient requirements during hypertension. Let us start w
P r o c esse d Chicken Products Preparation of comminuted meat products is the best way to salvage meat from spent hens and broiler parent stock. Incorporation of whole eg
Q. What is the difference between obligate anaerobic beings and facultative anaerobic beings? Obligate anaerobic beings are those that cannot survive when oxygen is present. So
Antimicrobial prophylaxis Antimicrobial prophylaxis is generally not indicated for cardiac catheterization, varicose vein surgery, most dermatologic and plastic surgery, arteri
Various structures are seen in two-dimensional planes; hence mental conceptualization is still required because the heart is three-dimensional. Now, newer technology has evolved
Heat Exchangers : This is an integral part of cardio pulmonary bypass and is designed to cool and warm the perfusate. non-sterile water from ice bath or warm water passed through
DIFFERENCES BETWEEN MITOSIS AND MEIOSIS EVENTS MITOSIS MEIOSIS Occurrence In all the body cells including
Define essentiality of Sulphur for growth of micro-organism? Sulphur is a part of some amino acids, some carbohydrates, biotin and thiamine. It is obtained either as elemental
Explain The concentration of a solution The concentration of a solution is the amount of solute dissolved in a specified amount of solvent or solution. When the concentration
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: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd