Explain outbreeding, outcrossing and cross-breeding practices in animal husbandry.
Out-breeding: Out-breeding is the breeding of the unrelated animals, which may be between individuals of the same breed but having no common ancestors for 4-6 generations (out-breeding) or between different breeds (cross-breeding) or different species (inter-specific hybridisation).
Out-crossing: This is the practice of mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations. The offspring of such a mating is known as an outcross. It is the best breeding method for animals that are below average in productivity in milk production, the growth rate in beef cattle, etc. A single outcross often helps to overcome inbreeding depression.
Cross-breeding: In this method, superior males of one breed are mated with superior females of another breed. Cross - breeding allows the desirable qualities of two different breeds to be combined. The progeny hybrid animals may themselves be used for commercial production. Alternatively, they may be subjected to some form of inbreeding and selection to develop new stable breeds that may be superior to the existing breeds. Many new animal breeds have been developed by this approach. Hisardale is a new breed of sheep developed in Punjab by crossing Bikaneri ewes and Marino rams.
Organic farmers prefer the biological control of diseases and pests of the use of chemicals for the same purpose. Justify.
“India has greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.
Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?
Select and write analogous structures from the list given below:
(i) Wings of butterfly and birds
(ii) Vertebrate hearts
(ii) Tendrils of bougainvillaea and Cucurbita
(iv) Tubers of sweet potato and potato
How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in the correct sequence.
Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain.
Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation.
With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations?
