Evolution - A Brief Account: Definition, Steps and Examples

Evolution is the changes in the inheritable characteristics of populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation. These result in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level.

This Story also Contains

1. What is Evolution?
2. The Big Bang Theory
3. Implications For Evolution
4. Mechanism of Evolution
5. Patterns of Evolution
6. Recommended video for "Evolution"
7. MCQs on Evolution

The scientific theory of evolution by natural selection was conceived by two Britain scientists, Charles Darwin and Alfred Russel Wallace, in the mid-19th century. It was an explanation for why organisms are adapted to their physical and biological environments. The theory was first made public in Darwin’s book “On the Origin of Species”. Evolution- A Brief Account is an important topic of the chapter Evolution. It is an important chapter in the biology subject.

What is Evolution?

Evolution is defined as the slow development of organisms over generations by mutation of their genetic material. Inherent mechanisms like mutation, natural selection, genetic drift or gene flow can bring about such changes. Over very long periods, evolution gives rise to diversity in life forms, adaptation to varied environments, and the emergence of new species.

The Big Bang Theory

The Big Bang Theory is an attempt at a cosmological model that tries to explain the origin of the universe, according to which it began with a singularity about 13.8 billion years ago and has ever since been expanding.

• The universe began in a very hot and dense state.

• It kicked off the expansion of space and created fundamental particles, which took the form of simple elements like hydrogen and helium.

• With the expansion of space, matter began to hold together by gravitation and took a star-like or galactic form as the universe expanded and cooled down.

• In billions of years, galaxies evolved through merging and interactions that shaped the large-scale structure of the universe.

Implications For Evolution

The Big Bang theory sets the scene for subsequent chemical and physical processes, which finally bring about planets and life on Earth.

Knowing the origin of the universe puts the study of life evolving within it.

Mechanism of Evolution

Several mechanisms bring about and spread genetic variations in populations. They work to propel the process of evolution in changing diversity on Earth.

Mutation

• They are changes in the DNA sequence that happen randomly, introducing new genetic variations.

• Such changes may be advantageous, neutral, or deleterious and constitute the raw material of evolution in the form of new traits.

• At increasing frequencies, some of these beneficial mutations can be incorporated into populations over time through natural selection.

Gene Flow

• Gene flow is the exchange of genetic material between different populations of a species.

• This is achieved through the migration of people from one breeding population to another, leading to the addition of new genes in a gene pool.

• Gene flow can thus be defined as a genetic process in that it contributes towards the maintenance of genetic diversity, hence reversing the processes of genetic drift.

Genetic Drift

• Genetic drift refers to random changes in the allele frequency in a population; this mostly takes place in very small populations.

• These are changes independent of natural selection and include random events that can result in the loss or fixation of alleles over time.

• Genetic drift may have impactful effects on the genetic makeup of small populations, leading to reduced genetic diversity.

Natural Selection

• Darwin’s Theory of Natural Selection propagates adaptation because the beneficial traits get more frequent in a population over generations.

• Examples include the resistance of antibiotics by bacteria and the evolution of beak shapes of Darwin's finches.

Patterns of Evolution

Evolutionary patterns depict the change and diversification of species with time. Some of such patterns include:

• Divergent Evolution: It explains how two or more related species become more different over time.

• Convergent evolution: It is through convergent evolution that the evolution of similar traits in unrelated species happens under similar environmental pressure.

• Parallel Evolution: The process of evolution of related species in similar ways over extended periods from similar environments.

• Coevolution: Evolution of two or more species that have a reciprocal effect on each other, such as predator and prey.

Recommended video for "Evolution"

MCQs on Evolution

Q1. Progenotes mainly contain:

Option 1: DNA

Option 2: mRNA

Option 3: tRNA

Option 4: None of the above

Correct answer: 1) DNA

Explanation:

Progenote - The precellular stage of organisation has been termed as progenitor. The progenitor contained DNA, most genes with introns, slow growth and heterotrophic nutrition.

Hence, the correct answer is option 1) DNA

Q2. Assertion (A): Evolution is the process through which organisms adapt over time to their surroundings.

Reason (R): The larger changes in new species are known as macroevolution, and small changes in new species are known as microevolution.

Option 1: Both, A and R, are correct and R explains A

Option 2: Both, A and R, are correct but R not explains A

Option 3: A is correct but R is wrong

Option 4: A is wrong but R is correct

Correct answer: (1) Both, A and R, are correct and R explains A.

Explanation:

The term "evolution" refers to the idea that all living things are related to one another through a common ancestor. Microevolution and macroevolution are two categories of evolution. Macroevolution refers to the larger changes that occur when a new species emerges. Microevolution refers to the small changes that occur when a new species emerges. Some biologists believe that macro-evolutionary change is controlled by different mechanisms than micro-evolutionary change.

Hence, the correct answer is Option (1) Both, A and R, are correct and R explains A.

Q3. Which of the following statements is true about the evolutionary process?

Option 1: Humans are an entirely different form of an organism.

Option 2: Nature's religion is progress.

Option 3: No real progress in the concept of evolution.

Option 4: Life forms evolved quickly in the early eras.

Correct answer: 1) Humans are an entirely different form of an organism.

Explanation:

The statement in Option 1 states that humans represent a distinct form of life separate from other organisms. It recognizes that humans have unique characteristics, traits, and capabilities that differentiate us from other species. While humans share common ancestry with other organisms and are part of the broader tree of life, the statement emphasizes the distinctiveness of the human species. It implies that humans have evolved through the process of evolution to become a specific and separate form of life. Option 1 acknowledges the uniqueness of humans as a distinct form of life among the vast diversity of organisms on Earth and hence becomes the correct answer.

Hence, the correct answer is option 1) Humans are an entirely different form of an organism.

Also Read-

• Practice MCQs on the Meaning of Evolution

• Biological Evolution

• Theories of Evolution