In many small populations completely random fluctuations in the frequencies of certain alleles or gene combinations may occur, even under constant environmental conditions. These fluctuations constitute genetic drift or Sewall Wright effect. The potential role of drift in microevolution is considerable. Dunker religious community in Pennsylvania (U.S.A.) comprises a small population. The gene frequencies at [...]
1. What do you mean by climatic background to human evolution? Ans. Towards the end of the Miocene, between seven to five million years ago, an abrupt drop in global temperature coincided with the formation of the West Antarctic ice sheet, Sea levels fell, the tropical belt shrank residing widespread extinctions of primates throughout Eurasia. [...]
1. What are the propositions of Darwin’s theory? Ans. According to the book “Origin of Species by means of Natural Selection” (1859) the Propositions of Darwin concept may be summarized as follows: a) Hypothesis: i) Prodigality of Production. ii) Resources are constant. Deductions: Struggle for existence. b) Hypothesis: i) Struggle for existence. ii) Universal occurrence [...]
Evolution from one kind of organisms to another occurs through sequential steps or stages. In case of the evolution of many organisms one or more stages of the sequence are yet to be discovered. These stages were constituted by such organisms which connected two large and distinct groups of organisms. These undiscovered or suddenly discovered [...]
Fossils are the geological remains of impressions or traces of organisms that existed in the past. They were preserved in the rocks of earth. Their structure and nature give an idea of organic evolution such as: 1. How the organisms have gradually evolved from their ancestors. 2. The time of evolution of organisms. 3. They [...]
