Question

Describe Darwin's theory of Natural Selection as a means of Transmutation of Species. Focus especially on how the struggle for life produces new species. The theory as Darwin knew it was incomplete, allowing 19th century biologists and psychologists to believe in varying theories of evolution. What do we now know about in biology that Darwin did not that makes the current “NeoDarwinist” paradigm complete?

Answer 1

• Darwin's theory of natural selection as a means of transmutation of species

This theory explains why and how the evolution have occurred. As life started on Earth the phenotype of animals was much different than it is now. These changes in the phenotypes of the animals have occurred over the period of millions of years. According to this theory the characters of animals that are best suited to the environment are retained in a particular generation and it is passed on to the next generation.

For example : When an appearance of humans was similar to ape like animals and humans required their tail, the tail was retained by humans and their generations. But as humans started walking without tail, it went on reducing and finally it remained only in the form of appendix. We consider it as a evolution in humans.

Sometimes animals adapted themselves with the changing environment. That adapted characters got inherited to next generations.

For example : Earlier giraffes were having short neck. Their food was leaves on plants. It was sufficient for them to eat the leaves upto their neck reaches. Over the period of time, the particular habitat faced scarcity of water and famine conditions. Number of trees got reduced. It was no more sufficient for the giraffes to eat the leaves upto their neck height. They needed to drag their neck to eat leaves on higher branches. In that struggle for food their necks became long. This we can call an adapted character. This adapted character is then inherited in the next generations and hence the evolution in giraffes.

This kind of changes in character are caused due to nature. "Nature selects" a particular trait that is best suited to it. That's why the name natural selection. In an actual nature doesn't do anything to change the trait but an animal make themselves to cope up with the environment. So, the "selection of trait for the nature" will be more appropriate to understand.

This was included mainly in the Darwinism.

• What was not included in the Darwinism i.e. difference in Darwinism and NeoDarwinism.

NeoDarwinism mainly differs from Darwinism in application of Medelian principles to evolution. So, it includes natural selection as well as genetics. According to the NeoDarwinism, evolution is comprised of natural selection and the changes in DNA. The concept of natural selection is already mentioned above. About the application of geneticsc is explained below.

The small changes in DNA may occur due to mutation in DNA. That DNA are transferred to next generations and the evolution have occurred. The large changes might have occurred due to recombination in genes. The best example is reproduction by mammals. The male and female gametes gets swapped and the new combination of Gene or DNA is obtained that results in evolution over the period of time.