Theory of Evolution

  • Evolution refers to the progressive change of organisms as they descend from ancestral species.
  • Important names in the history of theory of evolution are:
    • Jean Baptiste Lamarck
    • Charles Darwin
    • Alfred Russell Wallace
  • There are four common mechanisms of evolution.
    1. Natural selection
    2. Genetic drift,
    3. Mutation,
    4. Gene flow
Jean Baptiste Lamarck
  • Lamarck developed the fist comprehensive theory of evolution.
  • Lamarck, a French Zoologist, proposed that organisms increased in complexity through time because of an innate tendency.
  • He proposed that interactions of organisms and environment drove the process of evolution.
  • He proposed that patterns of use and disuse drove the evolution of adaptations. 
  • His theory states that every organism was continually striving for greater complexity.
  • Lamarck’s theory was an important step to the studies on evolution, eventhough it was proved that acquired characters cannot be passed to offspring.
Charles Darwin
  • Charles Darwin was born in 1809 – Shrewsbury, England.
  • He was graduated in medicine from Cambridge University.
  • Darwin used the term “descent with modification” for “evolution.”
  • His theory states that all organisms – animals, plants, fungi, all organisms – are descended from a remote common ancestor.
  • He stated that all species evolved from earlier species.
  • Organisms change in time, usually very slowly, or evolve overtime to become a new species.
  • He explained the mechanism of natural selection as members of a species possessing more desirable traits will have more offspring and survive to reproductive maturity.
  • Other mechanisms of evolution include genetic drift and mutation, which were discovered after Darwin.
  • The famous idiom Survival of The Fittest refers to:
    • Individuals whose characteristics are well suited to their environment survive.
    • Individuals whose characteristics are not well suited to their environment either die or leave fewer offspring or extinct.
  • The term artificial selection refres to the intervention of humans ensures that only individuals with the more desirable traits produce offspring.
  • He explained his theory in his publication On the Origin of Species - 1859.
  • Darwin received several scientific awards in his life time.
  • He died in April 1882.
Alfred Russell Wallace
  • Alfred Russell Wallace, was naturalist and explorer lived in Europe during the time of Darwin.
  • He developed the same theory of evolution by natural selection as Darwin.
  • The idea of evolution has remained controversial for a long time.
  • Lamarck proposed the fist comprehensive theory of evolution, which was a prelude to Darwin's theory.
  • Darwin's theory has had tremendous impact on science, philosophy, and the way humans viewed the world.
  • Alfred Russell Wallace was a contemporary of Darwin who also explained the same theory of evolution by Darwin.
  • Antibiotic resistance is an evolutionary phenomenon of tremendous clinical significance.
  1. Dr John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online (


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