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The ‘Theory of Evolution’ is a short term for ‘theory of evolution by natural selection and was proposed by Charles Darwin. Charles Darwin, also known as the father of evolution, was an English naturalist who developed various theories in the area of biological evolution. The theory of evolution is also known as Darwinism theory. According to the Darwinism theory of evolution, living species experience changes and modifications in their physical characteristics over time. These changes and modifications in the physical characteristics are the causes of the evolution of species.
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Keyterms: Evolution, Natural Selection, Darwinism theory, Environment, Living species, Adaptation, Adaptive Radiation, Branching Descent
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Theory of Evolution
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Species evolve over time. These evolutions happen due to changes in the environment. This process of continuous change to adapt to changes in the environment is called adaptation.
The species that adapt more quickly to the environmental changes tend to survive compared to those that do not adapt to the change in the environment. This process of the fitter species getting selected by nature to survive is also called Natural Selection. Natural Selection is an essential component of the theory of evolution. Only the more evolved species are selected by nature that survives the test of changes in the environment.
It is also worthwhile to mention that according to the observations made by Charles Darwin, all the species that exist today have a very shared history. All the living species in the present-day world are reported to share a common ancestry.
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Adaptive Radiation
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Darwin observed that in a particular geographical area, the evolution of different species had a common ancestry or starting point. This process is called Adaptive Radiation. Further, in his stay at Galapagos islands, Darwin made a very significant observation.
Darwin observed a particular kind of bird that was later named Finches. The finches were a highly diverse class of birds and were of many types with different characteristics. Later, Darwin concluded that these birds of so many varieties evolved in the island and are bonded with common ancestry.
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Biological Evolution
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Branching descent and natural selection form the basis of Darwin’s theory of evolution. The process in which new species evolve from common ancestry or a starting point is called Branching Descent. The term is called so because, in this concept, an ancestor species is called a descendant, and new species branch out or evolve from them.
Whereas natural selection is the process in which the species with robust and robust evolutionary systems are selected by nature to outlive other species with weaker evolutionary systems. Therefore, only the fittest species out survive the weaker ones.
Therefore, natural selection and branching descent form the crux for the concept of biological evolution.
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Mechanism of Evolution
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The mechanism of evolution is a very complex concept. The reason is that there are different opinions on the process of evolution. For example, some naturalists believe that the process of evolution is very gradual and continuous, while others believe that the process of evolution happens by a drastic mutation and that evolution is a single-step process.
However, Darwin believed that the mechanism of evolution is a continuous and gradual process.
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Things to Remember
- Darwin was an English naturalist who developed the theory of evolution
- According to the theory of evolution, species constantly evolve with time due to environmental changes.
- According to adaptive radiation, in a particular geographical area, the evolution of different species happens from common ancestry.
- Branching descent and natural selections are the concepts that form the basis of Darwin’s theory of evolution.
- Branching descent is when an ancestor species is called a descendant and from them, the new species branch out or evolve.
- Natural Selection is the process in which nature selects the species with a more robust evolutionary system rather than species with a weaker evolutionary system.
- According to Darwin, the mechanism of evolution is a continuous and gradual process.
Read Further: Living Fossil
Sample Questions
Ques: What is adaptive radiation and how is it related to the theory of evolution? (2 Marks)
Ans: According to Darwin, all the species evolve from a common ancestry in a specific geographical area. This process of evolution of the ancestral species to the species with different features in a particular location is called adaptive radiation. Adaptive radiation is one of the essential concepts of the theory of evolution. In accordance with the theory of evolution, the process of adaptive radiation explains the evolutionary process of the species in a particular geographical location
Ques: What are divergent and convergent evolution? Explain with an example. (2 Marks)
Ans: Divergent evolution is the process of evolution in which the development and modification of features occur in the later species compared to their ancestral species. An example of divergent evolution is the finch bird that Darwin observed in Galapagos Islands. The island has many varieties of birds with common ancestry.
Convergent evolution is the evolution in which new features and structures are developed in different groups of organisms. The wing of the bird and bat is an example of convergent evolution.
Ques: What are analogous organs and homologous organs? Explain them in detail with an example. (3 Marks)
Ans: The birds and the bats have wings to fly. But, the structure of their wings is different. Therefore, analogous organs are those organs whose structures are different from species to species, but their functions and uses are the same.
But the homologous organs are those organs in which the structures of the organs are similar amongst the species, but their functions are different. Common examples of homologous organs are the arms of the chimpanzees and the front legs of the horses.
Ques: What are acquired and inherited traits. Explain the difference between the two. (3 Marks)
Ans: Acquired traits are the traits that an individual develops due to constant interaction with the environment, habits and other external factors. Some of the examples of acquired traits include losing weight by exercising.
Inherited traits are those traits that cannot be affected by any external factors. Furthermore, these traits are transmitted from parents to their off-springs. Here, genes play a vital factor in determining inherited traits. Some of the examples are eye-ball colour, hair colour and basic body structure.
Ques: What is meant by the process of speciation? What are the factors that lead to speciation? (3 Marks)
Ans: Speciation is the process in which new species of organisms evolve from the pre-existing ones but the features of the evolved species do not have any similarities with the previous ones.
The factors that lead to speciation are:
- Genetic Drift
- Natural Selection
- Severe DNA mutation
Ques: What is the difference in opinion between Darwin and Hugo de Vries on the mechanism of evolution? (3 Marks)
Ans: The mechanism of evolution is a very complex process with diverse opinions from different naturalists and biologists. According to Darwin, the evolution of species is a very gradual and constant process. In fact, Darwin believed that evolution happens every moment and there is no time when evolution is not happening. Darwin also believed that due to constant interaction with the minor environment changes, all the living species face evolution to some degree.
Whereas Hugo de Vries believed that evolution is a one-step process. Furthermore, Hugo de Vries was of the opinion that a drastic mutation in the cellular or DNA structure could facilitate the evolution phenomena.
Ques: What is the process of classification and how is it related to evolution? (3 Marks)
Ans: Classification is the process of grouping different species based on their similarities and differences. In fact, classification is very important to understand the different living species and their evolution. For e.g., bats and birds have wings. But bats are not classified under the bird grouping. In fact, bats have mammalian features and are grouped under the mammal category.
Therefore, classification is of paramount importance because it facilitates the correct grouping of different species and helps us understand the process of evolution by presenting us with correct examples.
Ques: Explain the concept of Genetic Drifting. (4 Marks)
Ans: Genetic drift is the process in which there is a change in the frequency of genetic variation. The genetic variation, in this case, is also called an allele. Generally, genetic drifts have the highest probability of occurrence in areas with smaller population sizes. Furthermore, the process of genetic drifting can cause permanent changes in the genes of the species. The changes might be harmful or beneficial.
Genetic drift takes place due to the following reasons:
- Bottleneck Effect: In this process, there is a large decline in the population due to natural disasters. These can cause genetic drift.
- Founder Effect: When a small group of the population migrates away from the main population, that can also facilitate genetic drift.
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