Darwin & Natural

  • Who was Darwin?
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  • What were some of the views of the world at the time that Darwin was studying at the university?
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  • What were some competing ideas of descent during (and before) Dararwin, and why?
    - Jean-Baptiste de Lamarck - the forerunner of evolution, hypothesized that the environment can influence genetic traits in natural populations, and the soft inheritance of acquired characteristics. His theory was later discredited.
    - George Cuvier - developed the study of comparative anatomy, compared living animals with fossil remains, and established the concept of extinction
    - Charles Lyell - uniformitarianism - Wrote Principles of Geology which argued the formation of Earth’s crust took place over vast periods and influenced Darwin’s ideas.
    - Thomas Malthus - populations - well-known economist contemporary of Darwin, argued that as populations increase, resources decrease → the struggle to live intensifies, and he influenced Darwin by providing a frame of reference for his developing ideas.

  • Cite Darwin's observations that lead him to conclude that populations have changed over time.
    - Observation 1: species have great reproductive potential
    - most organisms produce a surplus of offspring.
    - exponential growth but there are always environmental limitations:
    - resources become limited like food, shelter, and mates, reproduction decreases, and mortality increases
    - Observation 2: Variation
    - all populations exhibit variation in traits
    - some traits convey an advantage
    - Observation 3: Some variation is heritable

  • What is natural selection, and what are the fallacies in how many people without scientific training perceive it?
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  • What are the essentials for natural selection?
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  • Artificial selection - how does this work? What are some examples of this, and how does it lead to beneficial (and often harmful) outcomes?
    - humans consciously select for or against particular features in organisms
    - a trait was desired, it was bred into the next generation
    - domesticated plants and animals

Perfect organisms – evolution is not “goal-oriented”
• Natural selection results in organisms that are best adapted to current environment. Because the environment is dynamic, there is no such thing as a “perfect” organism.

Adaptations arise in response to need
• The mechanisms that cause diversity are random (eg. mutation, gametogenesis). Organisms cannot “urge” the appearance of an advantageous trait.

Individuals evolve – “soft inheritance”
• physical changes that occur during an organism's lifetime are not passed to offspring. Evolution occurs at the population level, not the individual level.

Evolution and Natural Selection are one and the same
• Evolution is defined as the genetic changes that occur in a population over time. Natural selection explains some of these changes (i.e mutation, accepted, rejected and many more). Therefore N.S. is a mechanism of evolution.