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!
It is generally believed that genetic drift occurs as a result of sampling error. As we said earlier it occurs in small populations such as peripheral isolates. We may demonstrate genetic drift by a small experiment. Take beads of same size but different colours, say blue, red, green and yellow. Take a thousand of each colour and mix them well in a bag or mug. The 4000 beads now constitute a population. Now put your hand in without looking, pick up just four beads with your finger tips. Let us say that you get two blues, one red and one green. This will mean that the blues have increased from 25% to 50% but the yellows are reduced to zero. You could see that the random drifting or large scale changes in the frequencies of coloured beads is a result of sampling error. Just as the frequencies of coloured beads drift randomly in the experiment, in small populations or peripheral isolates gene frequencies may drift due to sampling error. Hence the phenomenon is known as genetic drift.
Can such drift be observed in natural populations? The answer appears to be yes. Let us take a small population of mice living in the rice barn of a farmer as four or five extended families. The farmer tries a variety of methods like setting up of traps, use of a shot gun, surprise visits, cats etc, to eradicate them. Such acts of the farmer ,' exert a severe selection pressure on the mice. Under such circumstances the trails that would be selected are the swiftness, short tail, hearirig acuity, cautiousness etc. Naturally the frequencies of the alleles that control thcsc traits would tend to be high in the population as only those mice which possess such traits can survive in an hostile environment. After a couple of months, let us say there is an environmental change and a severe winter sets in. The farmer confines himself to a fire place and as a result the selection pressure on those traits we mentioned earlier is now liftcd. And in order to survive in a changed environment, the mice need to possess totally a different set of traits and essentially mice with such traits would be selected for. Thus swiftness and visual acuity are no more the trails that would be selected for, but the mice with a thick fur on them and similar such traits which would protect them from the severity of the winter would be selected. The net result is that the frequencies of the alleles that controlled the traits in the earlier environment undergo a drift (i.e.) their frequencies become significantly low in the new environment. It should be emphasised that such a drift is characteristic of only small populations.
What are likely to be (a) the coldest, (b) the warmest parts of the body? The extremities of the body (hands and fingers, feet and toes, ears and nose) are likely to be the col
Q. How is the striped pattern of the striated muscle cells formed? The functional units of the muscle fibers are the sarcomeres within the sarcomeres blocks of myosin and actin
which organism are called primitive and how are they different from the so-called adavnced organisms
Slight or no Metamorphosis In primitive wingless insects (Apterygota) such as spring tails, silver fish etc. and in secondarily apterous insects the young ones which hatch fr
Enumerate about the Luria Nebraska battery Luria Nebraska battery will be based on the assumption that the only connecting link between Luria and that procedure is the set of
Q. What are the angiosperms, the flowering plants? What is the major feature that distinguishes them from the gymnosperms? Flowering plants have seeds and flowers (phanerogamic
State the series of stimuli ERPs a series of stimuli such as tones or light flashes are presented to the participant, and the raw EEG for a precise one or two second period fol
In 2003 nearly 70 million hectares globally were planted in genetically modi?ed crops. Of these, 73% were plants such as soybean, corn and cotton, which were modi?ed to be he
Question 1: Describe the process of hearing. The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Discuss the process of hearing
Planning the Nursing Care The goals of nursing care are: Identify the causative factor of megaloblastic anaemia. Administer appropriate vitamins depending on
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