Darwin's Contribution - The Theory of Evolution

Darwin's Contribution: The Theory of Evolution

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:24 PM IST

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.

Darwin's Contribution: The Theory of Evolution

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.

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.

Frequently Asked Questions (FAQs)

1. What is Darwin's theory of evolution?

Darwin's theory about evolution by natural selection describes how species adapt or evolve with time by differential survival and reproduction among individuals bearing favourable traits.

2. What is Darwin's theory of evolution?

Darwin's theory of evolution explains how species change over time through natural selection. It proposes that organisms with beneficial traits are more likely to survive and reproduce, passing those traits to offspring. Over many generations, this leads to changes in populations and the emergence of new species.

3. How did Darwin formulate his theory of evolution?

Darwin formulated this theory based on the observations he had made during the voyage onboard HMS Beagle, particularly on variation among species in the Galápagos Islands.

4. What are some of the evidence that point toward Darwin's theory of evolution?

The evidence for Darwin's theory of evolution portrays itself in the fossil record, comparative anatomy, embryology, and molecular biology.

5. What is natural selection?

Natural selection is the process whereby organisms better fitted with environmental survival traits tend to survive and reproduce more than those without these advantageous traits.

6. How has Darwin's theory of evolution impacted modern science?

Darwin's theory has profoundly influenced biology, leading to advances in genetics, ecology, medicine, agriculture, and conservation.

7. What are the key principles of natural selection?

The key principles of natural selection are: 1) Variation exists within populations, 2) Some variations are heritable, 3) More offspring are produced than can survive, 4) Individuals with favorable traits are more likely to survive and reproduce, and 5) Over time, favorable traits become more common in the population.

8. What is the significance of Darwin's finches in his theory?

Darwin's finches, observed on the Galápagos Islands, demonstrated how a single ancestral species could diversify to fill different ecological niches. The variations in beak shape and size among the finches provided evidence for adaptation and natural selection, supporting Darwin's theory of evolution.

9. How does Darwin's theory explain the concept of common ancestry?

Darwin's theory proposes that all species share common ancestors and have diverged over time through natural selection. This concept of common ancestry explains the similarities in anatomy, embryology, and biochemistry among different species, as well as the existence of vestigial structures.

10. What is the concept of gradualism in Darwin's theory?

Gradualism in Darwin's theory suggests that evolutionary changes occur slowly and continuously over long periods, rather than in sudden jumps. This idea contrasts with punctuated equilibrium, a more recent theory proposing that species remain stable for long periods, interrupted by rapid bursts of change.

11. How did Darwin's theory challenge the prevailing views of his time?

Darwin's theory challenged the widely held belief in the fixity of species and the idea of special creation. It proposed that species could change over time and that all life forms were related through common ancestry, contradicting both religious and scientific views of his era.

12. What role did Alfred Russel Wallace play in the development of evolutionary theory?

Alfred Russel Wallace independently developed a theory of evolution by natural selection similar to Darwin's. His work prompted Darwin to publish his own ideas sooner. Wallace's contributions led to the joint presentation of their theories to the Linnean Society in 1858, highlighting the collaborative nature of scientific discovery.

13. How did Darwin's voyage on the HMS Beagle influence his theory?

Darwin's five-year voyage on the HMS Beagle allowed him to observe and collect diverse plant and animal specimens from various locations, especially the Galápagos Islands. These observations of species variations and adaptations to different environments were crucial in developing his ideas about evolution and natural selection.

14. How does Darwin's theory differ from Lamarck's theory of evolution?

Darwin's theory differs from Lamarck's in that it proposes natural selection as the mechanism for evolution, while Lamarck believed in the inheritance of acquired characteristics. Darwin's theory suggests that traits beneficial for survival are passed on, while Lamarck thought organisms could pass on traits they developed during their lifetime.

15. How does artificial selection relate to natural selection?

Artificial selection is the process by which humans selectively breed organisms for desired traits, while natural selection occurs without human intervention. Darwin used artificial selection as an analogy to explain natural selection, showing how selective pressures can lead to changes in populations over time.

16. How does Darwin's theory explain the existence of cooperative behaviors in nature?

Darwin's theory can explain cooperative behaviors through concepts like kin selection and reciprocal altruism. These ideas suggest that behaviors that appear altruistic can evolve if they increase the survival and reproduction of related individuals or if they are likely to be reciprocated, thus indirectly benefiting the individual's genetic success.

17. How does Darwin's theory explain the phenomenon of convergent evolution?

Convergent evolution occurs when unrelated species develop similar traits in response to similar environmental pressures. Darwin's theory explains this as the result of natural selection favoring certain adaptations in different lineages independently, leading to analogous structures or behaviors in distantly related species.

18. How does Darwin's theory account for the existence of altruistic behaviors in nature?

Darwin's theory can explain altruistic behaviors through concepts like kin selection and reciprocal altruism. These ideas suggest that behaviors that appear selfless can evolve if they increase the survival and reproduction of related individuals or if they are likely to be reciprocated, thus indirectly benefiting the individual's genetic success.

19. How does Darwin's theory explain the phenomenon of evolutionary arms races?

Evolutionary arms races, where adaptations in one species trigger counter-adaptations in another, are explained by Darwin's theory as the result of ongoing, reciprocal natural selection between interacting species. This process can lead to extreme adaptations as each species evolves in response to changes in the other.

20. How does Darwin's theory account for the existence of parasitism?

Parasitism is explained by Darwin's theory as an evolutionary strategy that can be successful if it increases the parasite's ability to survive and reproduce. Natural selection favors parasites that can exploit their hosts effectively while avoiding elimination by the host's defenses, leading to complex adaptations in both parasites and hosts.

21. What is the significance of molecular biology in supporting Darwin's theory?

While not available in Darwin's time, molecular biology strongly supports his theory by revealing the genetic basis of inheritance and variation. It provides evidence for common ancestry through similarities in DNA and proteins across species, and allows us to track evolutionary changes at the molecular level.

22. How does Darwin's theory explain the phenomenon of exaptation?

Exaptation, where a trait evolved for one purpose is co-opted for a different use, is consistent with Darwin's theory. It demonstrates how natural selection can repurpose existing structures for new functions, explaining how complex adaptations can arise from simpler precursors.

23. What is the concept of "evolutionary lag" in relation to Darwin's theory?

Evolutionary lag refers to the delay between environmental changes and evolutionary adaptations. Darwin's theory explains this as a result of the time required for beneficial mutations to arise and spread through a population, especially in species with long generation times or small population sizes.

24. What is the significance of comparative genomics in supporting Darwin's theory?

Comparative genomics, which analyzes and compares the genetic material of different species, provides strong support for Darwin's theory. It reveals the genetic basis of evolutionary relationships, demonstrates the molecular mechanisms of adaptation, and provides evidence for common ancestry at the DNA level.

25. How does Darwin's theory explain the phenomenon of parallel evolution?

Parallel evolution, where similar traits evolve independently in related lineages, is explained by Darwin's theory as the result of similar selective pressures acting on species with a shared genetic background. This demonstrates how natural selection can produce similar adaptations in different populations facing similar environmental challenges.

26. What is meant by "survival of the fittest" in Darwin's theory?

"Survival of the fittest" refers to the idea that individuals with traits best suited to their environment are more likely to survive and reproduce. It's important to note that "fittest" doesn't necessarily mean strongest or fastest, but rather most adapted to the specific environmental conditions.

27. How does genetic variation contribute to evolution according to Darwin's theory?

Genetic variation provides the raw material for natural selection. Darwin recognized that individuals within a population vary in their traits, though he didn't know the mechanism of heredity. We now know that genetic mutations and recombination create this variation, allowing populations to adapt to changing environments over time.

28. What evidence supported Darwin's theory of evolution?

Darwin's theory was supported by evidence from various fields, including: fossil records showing changes in species over time, comparative anatomy revealing similarities among related species, embryology demonstrating shared developmental patterns, biogeography explaining species distribution, and vestigial structures indicating evolutionary history.

29. How does Darwin's theory explain the origin of new species?

Darwin proposed that new species arise through a process called speciation. This occurs when populations of the same species become isolated and adapt to different environments over time. Eventually, these populations may become so different that they can no longer interbreed, forming separate species.

30. What is the role of adaptation in Darwin's theory?

Adaptation is central to Darwin's theory, explaining how organisms become better suited to their environment over time. Through natural selection, traits that enhance survival and reproduction become more common in a population, leading to adaptations that help organisms thrive in their specific habitats.

31. How does Darwin's theory explain the diversity of life on Earth?

Darwin's theory explains biodiversity as the result of descent with modification from common ancestors. Over millions of years, natural selection has led to the diversification of species as they adapted to different environments, resulting in the wide variety of life forms we see today.

32. What is the significance of homologous structures in supporting Darwin's theory?

Homologous structures are anatomically similar structures in different species that share a common evolutionary origin. These structures, such as the forelimbs of mammals, provide strong evidence for common ancestry and support Darwin's theory by demonstrating how different species have evolved from a shared ancestor.

33. How does Darwin's theory account for the existence of vestigial organs?

Vestigial organs are structures that have lost their original function through evolution. Darwin's theory explains these as remnants of structures that were useful in ancestral species but became reduced or functionless in descendants due to changes in selective pressures, providing evidence for evolutionary history.

34. What is the concept of "descent with modification" in Darwin's theory?

"Descent with modification" is a key principle in Darwin's theory, proposing that all species have descended from common ancestors and have been modified over time through natural selection. This concept explains both the diversity of life and the similarities between different species.

35. How does sexual selection fit into Darwin's theory of evolution?

Sexual selection, a concept Darwin introduced, explains the evolution of traits that increase mating success rather than survival. It occurs through competition for mates (usually among males) and mate choice (usually by females), leading to the development of elaborate features like peacock tails or complex mating behaviors.

36. What is the role of genetic drift in evolution, and how does it relate to Darwin's theory?

Genetic drift is random changes in gene frequencies in a population, especially in small populations. While not part of Darwin's original theory (as he didn't know about genes), it complements natural selection in explaining evolutionary change. Unlike selection, drift is not adaptive and can lead to the fixation or loss of traits regardless of their benefit.

37. What is the concept of "tree of life" in relation to Darwin's theory?

The "tree of life" is a metaphor used by Darwin to illustrate the branching pattern of evolution from common ancestors. It represents how species are related through evolutionary history, with the trunk representing a common ancestor and branches representing different lineages that have diverged over time.

38. What is the significance of the fossil record in supporting Darwin's theory?

The fossil record provides crucial evidence for Darwin's theory by showing the progression of life forms over time. It demonstrates the gradual changes in species, the existence of transitional forms, and the emergence and extinction of different groups, all supporting the idea of descent with modification.

39. How does Darwin's theory account for the geographical distribution of species?

Darwin's theory explains the geographical distribution of species through the processes of migration, isolation, and adaptation. It accounts for why similar environments in different parts of the world often have different but related species, and why islands often have unique species closely related to those on nearby mainlands.

40. What is the concept of "fitness" in Darwin's theory, and how is it often misunderstood?

In Darwin's theory, "fitness" refers to an organism's ability to survive and reproduce in its environment. It's often misunderstood as physical strength or intelligence, but it actually means how well an organism's traits allow it to pass on its genes to the next generation in a specific environment.

41. How does Darwin's theory explain the existence of complex organs like the eye?

Darwin proposed that complex organs like the eye could evolve through a series of small, incremental changes over many generations. Each small improvement would be favored by natural selection if it provided even a slight advantage in survival or reproduction, gradually leading to the development of complex structures.

42. What is the role of competition in Darwin's theory of evolution?

Competition plays a crucial role in Darwin's theory as a driving force of natural selection. Competition for limited resources (food, mates, territory) means that individuals with advantageous traits are more likely to survive and reproduce, passing these traits to their offspring and driving evolutionary change.

43. How does Darwin's theory explain the phenomenon of coevolution?

Coevolution, where two or more species reciprocally affect each other's evolution, is explained by Darwin's theory through the concept of interacting selective pressures. As one species evolves, it creates new selective pressures on other species it interacts with, leading to mutual evolutionary changes over time.

44. What is the significance of Darwin's concept of population thinking?

Darwin's concept of population thinking shifted the focus from individual organisms to populations as the unit of evolution. This perspective recognizes the importance of variation within populations and how this variation allows for evolutionary change through natural selection.

45. What is the concept of adaptive radiation in relation to Darwin's theory?

Adaptive radiation is the rapid diversification of a single ancestral species into many descendant species, each adapted to different ecological niches. This concept, exemplified by Darwin's finches, demonstrates how natural selection can lead to the evolution of diverse forms from a common ancestor when new environmental opportunities arise.

46. How does Darwin's theory explain the existence of mimicry in nature?

Mimicry, where one species evolves to resemble another, is explained by Darwin's theory as an adaptation that increases survival. Natural selection favors individuals that more closely resemble the model species, whether for protection (as in Batesian mimicry) or to share the benefits of warning coloration (as in Müllerian mimicry).

47. What is the significance of biogeography in supporting Darwin's theory?

Biogeography, the study of the distribution of species across geographic locations, provided crucial evidence for Darwin's theory. It explains patterns such as why islands often have unique species related to those on nearby mainlands, and why similar environments in different parts of the world often have different but related species.

48. What is the concept of "struggle for existence" in Darwin's theory?

The "struggle for existence" is a key concept in Darwin's theory, referring to the competition among organisms for limited resources necessary for survival and reproduction. This struggle, combined with variation within populations, drives natural selection and evolutionary change.

49. How does Darwin's theory account for the existence of sexual dimorphism?

Sexual dimorphism, where males and females of a species differ in appearance, is explained by Darwin's concept of sexual selection. Traits that increase mating success, even if they don't enhance survival, can be favored by selection, leading to the evolution of distinct male and female characteristics.

50. What is the significance of embryology in supporting Darwin's theory?

Embryology provides evidence for Darwin's theory by showing similarities in early developmental stages among related species. These similarities suggest a common ancestry and support the idea of descent with modification, as proposed by Darwin.

51. How does Darwin's theory explain the phenomenon of island endemism?

Island endemism, where species are unique to a particular island or archipelago, is explained by Darwin's theory through the processes of isolation and adaptation. Species colonizing islands evolve in response to the unique environmental conditions, often resulting in forms distinct from their mainland ancestors.

52. What is the concept of "evolutionary trade-offs" in relation to Darwin's theory?

Evolutionary trade-offs occur when a trait that is beneficial in one aspect comes at a cost in another. Darwin's theory explains this as the result of natural selection optimizing traits within the constraints of an organism's biology and environment, often leading to compromises rather than perfect adaptations.

53. How does Darwin's theory account for the existence of symbiotic relationships?

Symbiotic relationships, including mutualism, commensalism, and parasitism, are explained by Darwin's theory as the result of coevolution. Natural selection favors individuals that benefit from these interactions, leading to the evolution of complex interdependencies between species.

54. What is the concept of "evolutionary novelty" in relation to Darwin's theory?

Evolutionary novelty refers to the emergence of new traits or structures that have no clear precursors. While challenging to explain, Darwin's theory accounts for this through the accumulation of small modifications over time, potentially leading to significant innovations when combined in new ways or exposed to new selective pressures.

55. How does Darwin's theory contribute to our understanding of human evolution?

Darwin's theory provides the framework for understanding human evolution as part of the broader process of biological evolution. It explains how humans have evolved from earlier primates through natural selection, adapting to changing environments and developing unique traits such as bipedalism, increased brain size, and complex social behaviors.