Lamarckism (Theory of Inheritance of Acquired Characters)
This theory was proposed by French biologist, Jean Baptiste de Lamark in 1809. It was published in ‘Philosphie Zoologique’ in the year 1809. It is popularly known as “The Inheritance of Acquired Characters in Organisms’.
Definition: Lamarckism or theory of inheritance of acquired characters can be defined as “The changes [...]
The theory of organic evolution appears most plausible explanation for the occurrence of varied forms of plants and animals on this earth. But an absolute proof in this connection is lacking. The circumstantial proof is the only type of evidence available. The convincing evidences for the occurrence of descent with modification come from:
Morphology and comparative [...]
The similarities among living organisms indicate that all of them have evolved from some single common ancestor (This is called monophyletic origin). Through the process of gradual modifications, adaptations and natural selection, over a million and a half different species have evolved from a common ancestral form. This process is called evolution or organic evolution. [...]
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. Grassland [...]
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 of variations.
Deductions
Survival of the fittest or Natural Selection.
c) Hypothesis
i) [...]
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 [...]
