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Evolution: Scientists and Theories

Evolution: Key Scientists and Concepts

Definition of Evolution

  • Evolution is change over time, driven by the environment.
  • It involves changes in species.
  • Natural selection is the primary driver of evolution.

Charles Darwin

  • Charles Darwin introduced his theory of evolution approximately 160 years ago.
  • His publication, Origin of Species, was released in 1859.
  • Darwin's work emphasized natural selection as a key mechanism for evolution.

Pre-Darwinian Ideas

  • Before Darwin, there were various inaccurate ideas about the origin and development of species.

George Louis Buffon (1749)

  • Observed similarities between species, particularly humans and apes.
  • Proposed that planets, including Earth, were formed through collisions involving the sun and comets.

Georges Cuvier

  • Pioneer in examining fossils.
  • Recognized that some species existed in the past but are now extinct.
  • Established that lower fossil layers correspond to older fossils.
  • Proposed that species can become extinct and new species can emerge over time.

Charles Lyell

  • Geologist who studied fossils.
  • Suggested Earth is millions of years old, contradicting biblical timelines.
  • Contributed to the understanding of Pangaea, the ancient supercontinent.

Jean-Baptiste Lamarck & Lamarckian Evolution

  • Proposed Lamarckian evolution, suggesting species can acquire new traits during their lifetime.
  • His theory posited that acquired traits could be passed on to offspring.
  • Example: Giraffes stretching their necks to reach taller trees, with this longer neck being inherited by offspring; this is incorrect.

Charles Darwin's Voyage and Discoveries

  • Traveled to the Galapagos Islands on the HMS Beagle.
  • Observed diverse bird species on different islands with distinct characteristics.
  • Theorized that these island species originated from a common ancestor bird.

Darwin's Theory Highlights

  • Diverse groups of animals evolve from one or a few common ancestors.
  • Evolution is driven by natural selection.
  • Darwin performed experiments with pigeons. These pigeons with weird shapes or sizes can still be seen today in the UK.

Birds and Dinosaurs

  • Birds are descendants of dinosaurs.
  • Evidence includes hollow bones, nest-laying behavior, and structural similarities.

Modes of Evolution

  • Gradualism: Gradual changes in species over time.
  • Punctuated Equilibrium: Rapid, sudden changes in traits. Very similar to genetic drift.

Punctuated Equilibrium Mechanisms

  • Punctuated equilibrium involves rapid trait changes. It happens because of founder effect and bottleneck effect.
  • Founder's Effect: A small group of individuals becomes geographically isolated and founds a new population. These founders will evolve and after time, they will not be able to reproduce with the individuals from the island or mainland. Geographic isolation leads to reproductive isolation.
  • Bottleneck Effect: Following a catastrophic event (e.g., earthquakes, floods, disease), the surviving individuals adapt differently to the altered environment.
  • Catastrophic event drastically affects population. Only a few individuals survive.

Speciation

  • Speciation: The formation of two species from a single population.