Evolution Of Life Forms – A Theory

Evolution is a process of gradual changes in the heritable characteristics of a biological population, over successive generations, over a long period. (Population: – It is a group of individuals of the same species who live in the same area and can interbreed) 

Theories of Evolution

Till now, several theories have been proposed by several groups of religious persons, philosophers, and scientists. These things make this topic more interesting and generate curiosity about ourselves and the world. 

Theory of Special Creation

It is a conventional religious theory that comes with three significant aspects.

1.  All the living organisms that we see today were created as it is.
2. The diversity among the communities (groups of populations) was always the same as in past and will remain the same in the future.
3. Earth came into existence around 4000 years ago. 

Darwin’s theory of Evolution

Charles Darwin was a famous English naturalist, biologist, and geologist. He is famously known for his contribution to evolutionary biology. 

• He gave his theory based on his observations on a sea voyage worldwide. (H.M.S. Beagle was the name of the ship on which Darwin roamed around the world)
• In the conclusion of the theory, he talked about the similarities among species.
  • All the existing life forms share similarities with varying degrees among themselves. 
  • Not only the existing species but all those species that existed millions of years ago.

Darwin’s Theory of Natural Selection

Natural selection talks about the survival of the fittest. It is a widely accepted theory which tells about the selection of a natural fit or, more precisely, reproductively fit organism by the nature. (Note: –On the Origin of Species, published on 24 November 1859, was the scientific literature of Charles Darwin).

   Theory of natural selection talks about the variation in characteristics of a population which enable an organism/population to survive better in natural conditions, i.e., climate, food, physical factors etc. Another thing that Darwin emphasised in his book was fitness which ultimately refers to reproductive fitness because the better-fit organism will have more progenies as compared to the less-fit organism. Hence better-fit organisms get more chances to be selected by the nature.

Example of Natural Selection

Industrial Melanism is a famous example of natural selection. 1850 was the time when England did not have industrialization. The trees of England were populated by two major species of moths; white-winged and dark-winged moths. 

 

Before Industrial melanism, the environment was populated with both the type of white-winged and dark-winged moths. But the population of white-winged moths always dominate the dark-winged moth. Due to their lighter body colour, the white moths get an advantage over dark moths; they can camouflage with the tree trunks. But the dark-coloured moths were easily visible to the predators, which resulted in the death of dark-coloured moths and ultimately lowered the population. After the 1850s, when industries came to England, the level of pollution started increasing, and pollutant got settled down on the bark of trees. Now, this has become an advantage for dark-winged moths. It becomes easier for them to camouflage in the dark-coloured background. But white-winged moths got suffered due to this; they became readily available/visible to the predators. This resulted in a drastic decrease in the white-moth population. 

How does natural selection work in the example of industrial melanism?

Industrial melanism, as explained above, acted as a natural force for the selection of dark-winged moths. Before industrialization, the white-winged moths were supported by nature as they could camouflage with the environment. But after industrialization, the environment became more suitable for dark-winged moths, and this is how the environment favoured, or nature selected, the dark-winged moths.)

Alfred Wallace supported Darwin’s theory

Alfred Wallace was a famous naturalist. He worked on the Malay Archipelago and came up with a similar solution to Darwin at the same time (which further supported Darwin’s theory). 

In his theory, he explained that all the existing species share similarities and common ancestors. The ancestors were always present at different periods in the history of the earth (epochs, periods, and eras). The history of the earth, which we call geological history, runs parallel to the history of life forms that came into existence. 

Both these theories (Darwin’s theory and Wallace’s theory) come to a common conclusion that the earth is billions of years old. The ancestors always existed with similar characteristics to today’s organisms. 

FAQs on Theory of Evolution

Question 1: What was the name of the book in which Darwin published his work?

Answer: 

On the Origin of Species, published on 24 November 1859

Question 2: How Industrial melanism supported the selection of dark-winged moths?

Answer:

Industrial melanism acted as a natural force for the selection of dark-winged moths. Before industrialization, the white-winged moths were supported by nature as they could camouflage with the environment. But after industrialization, the environment became more suitable for dark-winged moths, and this is how the environment favoured, or nature selected the dark-winged moths.

Question 3: How do Darwin’s and Alfred Wallace’s theories support each other?

Answer:

Both these theories come to the common conclusion that the earth is billions of years old. The ancestors always existed with similar characteristics to today’s organisms. 

Question 4: Write the two conclusions of Darwin’s theory. 

Answer:

In the conclusion of the theory, he talked about the similarities among species.

• All the existing life forms share similarities with varying degrees among themselves.
• Not only the existing species but all those species that existed millions of years ago.

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