What is Evolution?

Evolution is the gradual changes occurring over generations after generations, during which different species of plants, animals, birds and insects gradually change some of their physical characteristics. These changes include the different aspects of life like genetic drift, mutation, natural selection, thought and technology.The main factors responsible for the evolutionary changes are certain environmental changes and predation pressures

What is Darwin’s Theory of Evolution?

Charles Darwin, an English biologist, was the first person to propose the theory of evolution. In his book, On the Origin of Species (1859), he noted that all living organisms change their physical and anatomical structure over a long period of time to adapt to the changing environment. He also proposed that this change is by natural process and those organisms which do not adhere to it will find difficulty in their survival and named it as ‘Survival of the fittest.’

In other words, Evolution can be simply defined as the progressive modification in inherited traits over a huge span of time (usually over generations). This definition covers not only small-scale evolutions but also large-scale evolutions. Small-scale evolutions refer to the changes in gene frequency and large-scale evolutions refer to different species having a common ancestor.

Evolution helps us in better understanding about how the species became extinct, about their habitats and how new species are produced. It can also be observed that there is an inbuilt tendency to variation during reproduction process and these are mainly caused by the combining of genetic material from two parents and error in DNA copying during sexual reproduction.


Difference between Change and Evolution

Let us try and understand this in better detail.

For example, changes can be of several types. The falling of leaves from trees, a human losing weight, hair fall, melting of ice, etc.

These do not play any sort of role in evolution. One must clearly understand only the changes that are passed down during genetic inheritance play a hand in this transformation.

The basic idea of the theory of evolution leads us to the conclusion that all life on Earth shares a common ancestor. The common ancestor who probably lived millions of years ago gave rise to the immense diversity that we see around us today. Evolutionary theory suggests that we are all somehow related to the trees, humans, dolphins and everything else on this diverse planet.

Causes and Mechanism

The mechanisms of evolution occur due to various reasons that focus on:

  • The heritable genetic differences which are carried to the next generation.
  • Four fundamental forces of evolution include natural selection, genetic drift, mutations, migration and gene flow.
  • Variation, differential reproduction, and heredity result in evolutions by natural selection.
  • Different species affect each other evolution through co-evolution.

It can be clearly understood that evolution can occur due to various reasons.Natural selection is an advantage for survival that altered certain shared characteristics of the population, as the population might not have been exponential. So, near-fatal accidents in a small group of organisms can change some of their genetic frequency, even when those offer no advantage for their survival. This is the concept of genetic drift, a process that causes diversity but not any survival adaptations.

However, Darwin’s theory was slightly flawed since it did not explain much about genetic theory. Charles Darwin observed and noted the grand pattern of evolution, but he could not have known about the exact mechanism. Darwin’s theory of evolution, along with the concepts of genetics, is known as “modern evolutionary synthesis.”

To know more about evolution and its mechanisms, visit BYJU’S.

Practise This Question

Assertion 1: Wings of a bat and a bird are analogous organs.

Assertion 2: Forelimbs of a bat and a bird are homologous organs.

Reason : Wings of a bat and a bird do not share a common origin.

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