Darwin's Contribution: The Theory of Evolution

Charles Darwin was an English naturalist of the 19th century who made an extensive contribution towards the world of evolution for over 20 years. He made many observations on animal distribution and the relationship between living and extinct animals. He found that the living animals share some similarities with them, and with other species that were present millions of years ago.

This Story also Contains

1. What is Darwin's Theory of Evolution?
2. History of Darwin's Theory of Evolution
3. Darwin's Theory of Evolution
4. Evidence for Darwin's Theory
5. MCQs on Theories of Evolution: Darwinism or Natural Selection

He was also known as the father of evolution because of his contribution to the theory of evolution. His theory helped to remove certain old beliefs about the formation of various species, that it was a supernatural phenomenon or an act of the Almighty. His theory gave a more rational explanation regarding the formation of species. In natural selection, various species originate from a single species and also adapt to their environment. Darwin's Theory of Evolution is an important topic in the chapter Evolution. It is an important chapter in the biology subject.

What is Darwin's 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 a 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.

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. But 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 important 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.

Darwin's Theory of Evolution

Darwin's theory of 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 genetic mutations.

• Inheritance- Some of these variations get passed to the next 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, leading to the process of pollination.

• 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.

Evidence for Darwin's Theory

Darwin's theory of evolution is supported by a huge amount of evidence from many very different fields of science. Evidence can be fossil records, comparative anatomy, embryological and molecular evidence.

Fossil Record

• Fossils offer a chronological record of the life of the past.

• Fossils show changes in species over time and transitional forms that link major groups.

• Archaeopteryx, a transitional fossil between dinosaurs and birds (class Aves), and the many hominid fossils tracing human evolution.

Comparative Anatomy

• Homologous organs (e.g.-forelimbs of vertebrates) have similar structures but serve different functions.

• Analogous organs (e.g, wings of insects and birds) have the same functions but different structures.

Embryological Evidence

• Embryos of different species show similar early embryo development stages, showing a similar origin.

• Structures like pharyngeal gill slits on vertebrate embryos hint at common ancestry.

Molecular Evidence

• Similar DNA sequences and proteins across various species indicate evolutionary relationships.

• The genetic code is universal, indicating they come from a common ancestor.

MCQs on Theories of Evolution: Darwinism or Natural Selection

Q1. Which of the following refers to the correct example(s) of organisms which have evolved due to changes in the environment brought about by anthropogenic action?

A) Darwin’s Finches of Galapagos islands.
B) Herbicide-resistant weeds
C) Drug-resistant eukaryotes
D) Man created breeds of domesticated animals like dogs

Option 1: only (a)

Option 2: (a) and (c)

Option 3: (b),(c) and (d)

Option 4: only (d)

Correct answer: 3) (b),(c) and (d)

Explanation:

Anthropogenic actions are due to the direct or indirect effects of human actions on the environment. Resistance due to antibiotics, use of herbicides and artificial breeding of domesticated animals are examples of anthropogenic actions. Deforestation, industrial pollution, and excessive carbon emissions contribute to climate change and habitat destruction. Overfishing and intensive agriculture disrupt natural food chains and reduce genetic diversity in wild populations. These human-induced activities have long-term consequences, affecting both natural ecosystems and human societies.

Hence, the correct answer is option 3) (b),(c) and (d)

Q2. Which of the following is a mismatch?

Option 1: Charles Darwin – Branching descent and natural selection

Option 2: Lamarck – Theory of use and disuse

Option 3: Hugo de Vries – Mutation theory

Option 4: A.R Wallace – Theory of Panspermia

Correct answer: (4) A.R Wallace – Theory of Panspermia

Explanation:

Svante Arrhenius proposed the panspermia theory, which suggests that there is life everywhere in the universe and that it can spread using heavenly bodies. According to him, microorganisms can survive space travel and can seed life on the earth. Alfred Russel Wallace and Charles Darwin supported the concepts of "struggle for existence" and "survival of the fittest" within the framework of natural selection. Thus, the correct answer is that Arrhenius proposed panspermia, while Wallace and Darwin contributed to evolutionary theory.

Hence, the correct answer is Option (4) A.R Wallace – Theory of Panspermia

Q3. Which of the following best explains the concept of fitness in the context of natural selection?

Option 1: The physical strength and size of an individual

Option 2: The reproductive success of an individual relative to others in the population

Option 3: The ability of an individual to learn and adapt to new environmental conditions

Option 4: The total number of offspring produced by an individual over its lifetime

Correct answer: (2) The reproductive success of an individual relative to others in the population

Explanation:

Fitness is not about physical strength and size, ability to learn and adapt, or the total number of offspring produced by an individual, but about the reproductive success of an individual relative to others in the population. The fittest individuals are those that have the greatest number of offspring that survive and reproduce in subsequent generations, passing on their advantageous traits.

Hence, the correct answer is Option (2) The reproductive success of an individual relative to others in the population

Also Read:

• MCQs on Darwin’s Theory of Natural Selection

• Lamarckism and theory

• Evolution by Stages