a. Define the terms ‘Deme’ and ‘Selection pressure’ as they relate to evolution.

Question

a. Define the terms ‘Deme’ and ‘Selection pressure’ as they relate to evolution.

b. Write the equation for calculating ‘covariance’ between two traits.

c. In a closed breeding population under selection can we breed for a particular selected trait indefinitely? Briefly describe why or why not.

d. Name two fixed effects taken into account when calculating EBV’s.

e. What is the genetic value of an animal and what is the breeding value of an animal and why might these be different?

f. The bonus in value of a trait obtained from a cross which is over and above that of the average effect of the parents is, (1 or 2 words)?

g. Write the formula for calculation of ‘effective population size’ and briefly describe why it may be different for breeding populations with exactly the same number of animals in them.

Explanation / Answer

Answera): Deme is a group of subpopulation of individuals who are freely inbreeding, often very homogeneous . Deme is used for local population that actively inbreed but have a same gene pool. When we use demes for a long time then they will become distinct subspecies .

Selection breeding or artificial breeding results in deme formation. We know that there are generally four different types of selection pressure as 1) over production of offspring, 2) environmental pressure, 3) competition and 4) human interference these all led to natural selection and hence to develop subpopulation or deme.

Answer b)Covariance measures how two variables move together. Covariance indicates the relationship of two variables whenever one variable changes. Both are directly related as increase in one variable results in an increase in the other variable. It can be calculated by the formula as:

Answer c) No, In a closed breeding population under selection can we breed for a particular selected trait indefinitely, because No population can increase indefinitely all population have the capacity to increase in number. Again here is action of natural selection pressure that is fittest will survive.

For example.. In some grains the increase in feed size results by certain plowing practices rather then from intentional collection of larger seeds which is most likely the result of inbreeding practices..

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