1
Question
Read the following statement with two blanks A and B. Select the correct option given.
____A____ and _____B_____ were the two key concepts in Darwin's theory of evolution.
Read the following statement with two blanks A and B. Select the correct option given.
____A____ and _____B_____ were the two key concepts in Darwin's theory of evolution.
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Solution
The correct option is A A - Branching descent, B - natural selection
Darwin’s theory of evolution was based on the two key concepts - branching descent and natural selection.
Natural selection is defined as a process by which better adapted organisms having favourable characters lead to better survival while less adapted organisms get eliminated at successive stages. The organisms selected in this way by nature, reproduce more adapted individuals that will establish more in due course of time in nature. For example: Black peppered moth in England grew more in number than the white peppered moth because of natural selection after industrialisation.
Branching descent is the process of development of new species from a single common descendant like how branches of a tree originate from a common trunk. For example: The development of vertebrates from a common ancestor is shown in the figure. The new species developed, became geographically adapted to their respective environments and acted as the pioneer species for the development of a new species.
Darwin, in his theory of natural selection, believed that all organisms produce much more offspring than actually survive. This is called overproduction. For example: An insect like a house fly may lay thousands of eggs. Darwinism is based on some conditions or features like over production, struggle for existence, survival of the fittest, etc. So, overproduction is one of the features or conditions of Darwin’s theory, not a key concept.
Discontinuous variations are sudden and large changes called mutation in organisms. Mutation theory is proposed by Hugo de Vries. According to him, discontinuous variations occur in the organism that lead to evolution.
Darwin’s theory of evolution was based on the two key concepts - branching descent and natural selection.
Natural selection is defined as a process by which better adapted organisms having favourable characters lead to better survival while less adapted organisms get eliminated at successive stages. The organisms selected in this way by nature, reproduce more adapted individuals that will establish more in due course of time in nature. For example: Black peppered moth in England grew more in number than the white peppered moth because of natural selection after industrialisation.
Branching descent is the process of development of new species from a single common descendant like how branches of a tree originate from a common trunk. For example: The development of vertebrates from a common ancestor is shown in the figure. The new species developed, became geographically adapted to their respective environments and acted as the pioneer species for the development of a new species.
Darwin, in his theory of natural selection, believed that all organisms produce much more offspring than actually survive. This is called overproduction. For example: An insect like a house fly may lay thousands of eggs. Darwinism is based on some conditions or features like over production, struggle for existence, survival of the fittest, etc. So, overproduction is one of the features or conditions of Darwin’s theory, not a key concept.
Discontinuous variations are sudden and large changes called mutation in organisms. Mutation theory is proposed by Hugo de Vries. According to him, discontinuous variations occur in the organism that lead to evolution.
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