Darwin's Contribution: The Theory of Evolution

Charles Darwin's theory of evolution has changed the whole course of people's understanding of life on Earth. Darwin postulated that species evolve through time based on something he called natural selection, where survival and reproduction-enhancing traits increase in population. According to Charles Darwin's theory of evolution, all living organisms are related and descended from a common set of ancestors with species gradually adapting to an environment. This is one of the important topics of Biology in chapter Evolution class 12th.

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History of Darwin's Theory of Evolution

The theory of evolution by Darwin changed the understanding of life on Earth. Most of the previous pre-Darwinian views held species as immutable and separately created, whereas Darwin's theory proposed that species evolve through natural selection.

In 1831, Charles Darwin joined the HMS Beagle as the ship's naturalist and undertook specimen collection and made crucial observations on this voyage throughout South America up to the Galápagos Islands. His experiences, especially on the Galápagos Islands, were very formative in the development of his ideas.

He became attentive to the changes in species, especially finches and tortoises, whose beak shapes and sizes vary according to the food they eat. These observations motivated Darwin to think of how species may evolve to become a better fit for their environment over time. In doing so, he eventually framed his theory of evolution through natural selection.

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Darwin's Theory of Evolution

Darwin's theory of evolution by natural selection describes how species vary and change over generations in function of traits that cause different survival and reproduction. Some of the key features of Darwin's theory are as follows:

• Variation- Individuals of a species vary in size, colour, behaviour, etc, mainly because of changes at the level of genes as mutation

• Inheritance-Some of these variations get passed to the generation. Traits favouring survival can be inherited and will be highly probable to thrive in the next generations.

• High Birth Rate- Species generate greater numbers of offspring than can survive, hence the competition for resources, such as food and shelter.

• Differential Survival and Reproduction - Traits that help survive and reproduce, such as excellent camouflage or thicker fur, are shared and thus more common in the population.

• Adaptation and Speciation- With time, favourable traits add up to help the species adapt. It later results in the formation of new species, especially with populations that are separated and have different environments.

• Fitness and Adaptation- Fitness is defined as how well traits in an organism help survive and reproduce in the environment it is in. Adaptation is the accumulation of traits that increase fitness.

• Coevolution- An instance of two or more species evolving together, like the flowering plants and their pollinators.

• Natural Selection- The mechanism in Darwin's theory of evolution whereby traits that give an advantage become common in a given generation due to selective pressures such as predators or changes in climate.

This process brings about evolutionary change, whereby favourable traits should be passed throughout the population and may eventually lead to new species according to the theory of evolution by Charles Darwin.

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