Write Darvins two major contribution with regard to evolution.
Answers
The Theory of Evolution
Darwin Darwin had the following ideas regarding the theory of natural selection:
Species keep on evolving or changing with time. As the environment changes, the requirements of an organism also change and they adapt to the new environment. This phenomenon of changing over a period of time as per the natural requirements is called adaptation.
As per Darwin’s theory, only the higher changes are naturally selected and the lower ones are eliminated. Thus, not all the adaptations contribute to a progressive evolution. For example, people living in tropical countries have more melanin in their body to protect them from the sunlight.
Almost all organisms share common ancestry with some organism. According to Darwin, all organisms had one common ancestor at some point in time and kept on diverging ever since. His evolutionary theories support the convergent theory and divergent theory of evolution with examples.
He also studied that the birds of Galapagos Island (Darwin’s finches) developed different beaks as per the availability of the food. This proved adaptive radiation. Similarly, he also observed the Australian Marsupials which showed a number of marsupials emerging from an ancestor.
According to Charles Darwin, evolution is a very slow and gradual process. He concluded that evolution took place over a very long period of time. As we talk about the time period in evolution we usually refer to billions of years. The generation of a species from another takes a long period of time. It is a very steady process as the changes and adaptation take a long time to stabilize and give rise to a new species.
Natural selection takes place in four different ways as follows:
Variation – The changes accumulated over a period of time in an organism usually gives rise to a new species.
Inheritance – It is the passing on of the variations over generations which ultimately leads to speciation.
A high rate of growth of population – This gives rise to more number of organisms being reproduced by a species than the environment can support which might lead to the extinction of that particular species.
Differential survival and reproduction – The superior variations lead to survival of a particular organism and the inferior or negative variation leads to extinction. The superior variations are the ones inherited during reproduction.
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