Charles Darwin through his book "The origin of species" in 1859, has been credited with giving the first systematic and comprehensive spproach in the perspective of evolutionary development.
In the book, he presents his theory based on 3 factors
-The reproductive capacity of all plants and animals is very high.
-The population of plants and species remains more or less the same through generations.
-Variations secure Universally
Based on these he arrived on the following inference
-Survival of the fittest/natural selection.
Under the above observations he made the following conclusions-
As a result of struggle for existence, variability and inheritence, the successive generations tend to become better adapted to their environment. These adaptations are preserved and accumulated in the individuals of the species and ultimately lead to the origin of new species from the old ones.
The environment is ever changing and it leads to further changes and the appearence of new adaptations in the organism. As natural selection continues, the latter descendants after several generations become markedly distinct from ancestors. Furthermore certain memebrs of a population with one group of variations may become adapted to environmental changes in one way, while others with differnt set of variations may become adapted in a different way. As a result, tho or more species may arise from a single ancestral species.
Darwin's Theory of Artificial selection-
According to Darwin, the commonest method of producing new race of individuals is that of selection under human control. The man selects only the useful variety of plants and animals and breeds them together expecting htat offspring will have beneficial characters, Thus, various new races of plants and animals are produced which are more useful, viable and domestic value to common man.
A good example of this is the development of gaze following in Dogs and horses; a trait missing even in apes.
Darwin's Theory of Sexual selection-
There is always a contest among males for possession of beautiful female. During this contest, inferior males are eliminated and superior males dominate. Thus sexual dimorphism becomes marked in highly developed individuals.
Example would be development of huge horns in male stags, while missing in females.
He was however now able to explain how heridity of trains occurs in nature. For this he used the concept of Pangenes; All somatic cells produce minute particles called pangenes which are included in sperm cells. These pangenes dictate development in a zygote.
In the book, he presents his theory based on 3 factors
-The reproductive capacity of all plants and animals is very high.
-The population of plants and species remains more or less the same through generations.
-Variations secure Universally
Based on these he arrived on the following inference
-Survival of the fittest/natural selection.
Under the above observations he made the following conclusions-
As a result of struggle for existence, variability and inheritence, the successive generations tend to become better adapted to their environment. These adaptations are preserved and accumulated in the individuals of the species and ultimately lead to the origin of new species from the old ones.
The environment is ever changing and it leads to further changes and the appearence of new adaptations in the organism. As natural selection continues, the latter descendants after several generations become markedly distinct from ancestors. Furthermore certain memebrs of a population with one group of variations may become adapted to environmental changes in one way, while others with differnt set of variations may become adapted in a different way. As a result, tho or more species may arise from a single ancestral species.
Darwin's Theory of Artificial selection-
According to Darwin, the commonest method of producing new race of individuals is that of selection under human control. The man selects only the useful variety of plants and animals and breeds them together expecting htat offspring will have beneficial characters, Thus, various new races of plants and animals are produced which are more useful, viable and domestic value to common man.
A good example of this is the development of gaze following in Dogs and horses; a trait missing even in apes.
Darwin's Theory of Sexual selection-
There is always a contest among males for possession of beautiful female. During this contest, inferior males are eliminated and superior males dominate. Thus sexual dimorphism becomes marked in highly developed individuals.
Example would be development of huge horns in male stags, while missing in females.
He was however now able to explain how heridity of trains occurs in nature. For this he used the concept of Pangenes; All somatic cells produce minute particles called pangenes which are included in sperm cells. These pangenes dictate development in a zygote.
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