Evolutionary Thought

• Evolution

  any net directional change in the characteristics of organisms or populations over many generations
• Aristotle (350 BCE)

  • species are identical.
  • they tend to remain the same and can be arranged hierarchically.
• who created the 'ladder of life'?


  Aristotle

  
• George-Louis Leclerc, Comte de Buffon (AD 1749)

  he stated that species change, they migrate to another environment resulting in their distribution

  
• Jean-Baptiste de Lamarck

  • species evolved from existing species through environmental forces. The trait can be passed to the next generation.
  • he wrote the book called Philosophie zoologique; which outlines pre-Darwinian theory of evolution

  ex: giraffe's evolution
• Charles Darwin (1874)

  • thought the idea of descent modification
  • ideas that species change over time, give rise to new species and share a common ancestor.
• He wrote the "The Origin of Species"


  Charles Darwin
• Charles Lyell (1830)

  • all changes in the environment are uniform and gradual
• Alfred Wallace (1823)

  • he realized that species evolved because the fittest individuals survived and reproduced passing their advantageous characters
  • he wrote the book called Darwinism
• Theory of Need

  • changes in the environment can raise new needs, required for species' survival.

  
• Theory of Use and Disuse

  • parts of the organism that are regularly used will undergo hypertrophy and will be developed
  • parts of the organism that are rarely used will undergo atrophy
• Survival of the Fittest

  • organisms adapt to their environment and survive.
  • descent with modification - species have descended and changed over time

  
• Thomas Malthus

  • an English economist
  • states that the supply of food cannot keep up with the growth of the human population, inevitably resulting in disease, famine, war, and calamity.
• Evolution

  • BIOLOGICAL PROCESS
  • DEVELOPS IN A LONG PERIOD OF TIME
  • ADAPT TO THE CHANGES IN THEIR ENVIRONMENT
  • SUCCESIVE GENERATIONS OF THE POPULATION
  • INHERITABLE CHARACTERISTICS
• Theory of Acquired Characteristics

  • Sometimes called the theory of inheritance of acquired traits, or “soft inheritance.”
  • Holds that an organism experiencing such a modification can transmit such a character to its offspring.