(a) Explain Darwinian theory of evolution with the help of one suitable example. State the two key concepts of the theory.
(b) Mention any three characteristics of Neanderthal man that lived in near east and central Asia.
Answers
Answer:
Principle: Electric generator works on the principle of electromagnetic induction. It converts mechanical energy into electrical energy. Construction: A loop ABCD is rotated in a permanent magnetic field. Its ends are connected with two semi-circular rings as shown in the figure below.
Explanation:
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Answer:
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Charles Darwin gave the theory of evolution in his book 'Origin of species'. Adaptive radiation and natural selection are two key concepts of this theory. The main points of this theory are as follows:
1) New forms keep on gradually evolving with time in the history.
2) There is always variation in characteristics of populations which help them to adapt better to the surroundings.
3) Those organisms which adapt themselves better to the surroundings survive and reproduce while others die. This is known as the survival of fittest.
4) The organisms which adjust to the changing environments are selected by nature and thus can survive. This is called natural selection.
5) There is an inheritance of adaptability and the consequence of adaptability is fitness.
Natural selection takes place due to the following reasons:
* Limited natural resources
* Variations in the characters of members of the population
* The inheritance of variations to the next generation.
Example of natural selection
Industrial melanism: There were a large number of white moths before the industrial revolution in England. These moths could easily camouflage against the background of the trees and so were protected from the predators. Thus their numbers increased as a result of reproduction. But after the industrial revolution, soot deposited on the bark of trees and thus white coloured moths became susceptible to the predators and their number started decreasing. The deposition of soot on the trees was advantageous to dark coloured moths as now they were not easily visible to the predators and thus their population started increasing. Thus with the change in the environment, nature selected only on those individuals which were fit to survive in that environment.