L5: Human origin and evolution

Concept of evolution

  • Definition

    • changes in the heritable characteristics/ traits of living organisms over successive generation

    • the in way in which organisms change and develop

  • it proposes that all organisms are descended from a common ancestor

  • graduate change over time due to mutations → genetic variation and diversity → biodiversity

Evidence of evolution

  • fossil records in earlier species

  • chemical and anatomical similarities of related life forms

  • geographic distribution of related species

  • recorded genetic changes in living organisms over many generations

  • genetic similarity

Darwin’s suggestion of how evolution works

  • variation already existed and was being passed onto the next generations

    • genetic variation just occurs randomly

  • nature favours the traits best suited to the given environment——Natural selection

  • survival of the fitness

    • the “fittest“ organism (with traits best suited yo the environment) are more likely to survive and reproduce

The Galapagos finches

  • origins of different finches:

    • different finches came from mainland of South America separately

    • one type came from mainland and evolved in different ways on different island

  • finches with the most suitable beak shape or other traits survive in particular island

Formation of new species

  • Definition: The process by which a new species evolves from an existing species.

  • Process

    • the “fittest“ organisms pass on the desirable characteristics to the offspring

    • species change over time: when the genetic changes are great enough → a new species is produced

Other examples of evolution

peppered moth

  • white moth vs black moth

  • colour of the tree trunk

SARS-CoV-2

  • mutation occurred by random

    • accumulation of advantageous mutations while propagating in animal hosts

  • Adaptive evolution favors mutations that enable zoonotic transmission from animal hosts to humans.

  • virus strains with mutations that allow human-to-human transmission or increased transmissibility is best fit to survive