Evolution of Life Forms- A theory

Evolution of Life Forms- A theory

Evolution theory:

Evolution theory based on the observation made during the sea voyage by Charles Darwin in sail ship H.M.S Beagle around the world. He was appointed as a naturalist for this voyage to study the vast flora and fauna of the different continents and islands. He said that every living organism, whether animal or plant has its characteristics.

Characteristics are the details of appearance or behavior. For example, we have four limbs, and bearings four limbs are one of our characteristics that is the reason we are called tetrapods. While moving from one place to another on his voyage he (Darwin) observed that even differently looking and differently behaving organisms share some similarities among them.

The similarities can either be in the body structure or their behavior. He also observed that living organisms share similarities not only among themselves but also with those organisms which became extinct from earth.

Based on his observations, Darwin concluded that all the existing life forms share similarities to varying degrees and may share common ancestors. More are the similarities, more closely they are related, and more recently they shared common ancestors. Hence, we can say that if two organisms share common ancestors in recent history, it would be present in the same epoch, period, or era. And if they share common ancestors in distant history, it would be present in the different epoch, period, or era; depending upon how distantly they share it. Hence, we conclude from it that the geological history of the earth closely correlates with the biological history of the earth. There had been extinctions of different life forms in the years gone by just as new forms of life arose at different periods of the history of the earth. There has been a gradual evolution of life forms.

Concept of Natural selection-

Darwin talked not only about the similarities but also the differences or variations among the organisms. He said that every population has its own characteristics feature that differs from the characteristics of other populations.

Nature poses the same challenges to all living organisms in the form of harsh climate, food scarcity, natural disasters like floods, droughts, etc. The characteristics that enable some organisms to survive better than others in the same environment are said to be selected by nature. Some used the word ‘fitness’ for this capability to survive better, but Darwin called it “reproductive fitness” which means those organisms who are a better fit in the environment produce more offspring than others or we can say their reproductive rate is higher than the others. These, therefore, will survive more and hence are selected by nature. He used the phrase “natural selection” for this and said that this is the natural selection that is responsible for the evolution. Another naturalist named ‘Alfred Wallace’ worked in the Malay Archipelago and led to the same conclusion as that of Darwin.


  • Charles Robert Darwin (1809-1882) was an English naturalist who published his work on the evolution in his book “on the origin of species” in 1859. He set out on sea voyage when he was only 22 years old. The five-year voyage took him to South America and the islands off its coast.
  • Alfred Russel Wallace (1823-1913) was also a British naturalist and geographer. He is best known for indecently proposing a theory of evolution due to natural selection that probably prompted Charles Darwin to publish his theory.
  • Malay Archipelago: Archipelago means the chain or cluster of islands. Malay here comes from the Malay race (or brown race) of humans. The Malay Archipelago is the Archipelago between mainland Southeastern Asia and Australia.

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