Q. According to the modern synthetic theory of evolution, the factor that does not contribute to the evolution process is
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Solution:
Basic concepts of Lamarckism (Inheritance of Acquired Characters) :
- The internal forces of life tend to increase the size of an organism.
- According to Lamarck, a change in the environment brings about changes in organisms. It gives rise to new needs. New needs or desires produce new structures and change the habits of the organisms. The doctrine of desire is called appetency.
- Use and disuse of organs: Continuous use of a particular organ or structure tends to increase its size while its disuse results in its disappearance.
- Inheritance of acquired characters: Lamarck stated that all the characters, which are acquired in one's lifetime are inherited by offsprings.
Postulates of Neo-Darwinism (or Modern synthetic theory of Organic evolution):
- Over-production of offsprings: All living organisms possess enormous reproductive potential.
- Struggle for existence: Food and shelter is limited in a particular area which leads to a struggle for existence, which is of following types - A. Intraspecific struggle (the most acute type of struggle), B. Inter-specific struggle (most potent force for evolution), and C. Extra-specific struggle.
- Genetic variations: A. Gene migration and gene flow - when a section of a population migrates to another place and sets up a new population, then the gene frequencies of the original as well as the new population changes. New genes/alleles are added to the new population, while some are lost from the old population. If the above-mentioned gene migration happens multiple times, it leads to gene flow, B. Genetic drift - if the change in gene frequency occurs by chance, it is called genetic drift, C. Mutation - experiments on microbes show that pre-existing advantageous mutations help the organisms to get selected, and the result is observed in new phenotypes. This may lead to speciation over a few generations, D. Genetic recombination – this occurs during gametogenesis, and E. Hybridisation – it is the crossing of animals which are genetically different in one or more traits.
- Natural selection: Only those organisms will survive which possesses the most useful variations. This has been called 'Natural selection' by Darwin and 'Survival of fittest' by Herbert Spencer. When Darwin referred to fitness, it was ultimately and only to reproductive fitness.
- Isolation and Speciation.
- The internal forces of life tend to increase the size of an organism.
- According to Lamarck, a change in the environment brings about changes in organisms. It gives rise to new needs. New needs or desires produce new structures and change the habits of the organisms. The doctrine of desire is called appetency.
- Use and disuse of organs: Continuous use of a particular organ or structure tends to increase its size while its disuse results in its disappearance.
- Inheritance of acquired characters: Lamarck stated that all the characters, which are acquired in one's lifetime are inherited by offsprings.
- Over-production of offsprings: All living organisms possess enormous reproductive potential.
- Struggle for existence: Food and shelter is limited in a particular area which leads to a struggle for existence, which is of following types - A. Intraspecific struggle (the most acute type of struggle), B. Inter-specific struggle (most potent force for evolution), and C. Extra-specific struggle.
- Genetic variations: A. Gene migration and gene flow - when a section of a population migrates to another place and sets up a new population, then the gene frequencies of the original as well as the new population changes. New genes/alleles are added to the new population, while some are lost from the old population. If the above-mentioned gene migration happens multiple times, it leads to gene flow, B. Genetic drift - if the change in gene frequency occurs by chance, it is called genetic drift, C. Mutation - experiments on microbes show that pre-existing advantageous mutations help the organisms to get selected, and the result is observed in new phenotypes. This may lead to speciation over a few generations, D. Genetic recombination – this occurs during gametogenesis, and E. Hybridisation – it is the crossing of animals which are genetically different in one or more traits.
- Natural selection: Only those organisms will survive which possesses the most useful variations. This has been called 'Natural selection' by Darwin and 'Survival of fittest' by Herbert Spencer. When Darwin referred to fitness, it was ultimately and only to reproductive fitness.
- Isolation and Speciation.