Natural Selection

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Natural Selection

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  1. “Nothing in biology makes sense except in the light of evolution”

    Slide 1 - “Nothing in biology makes sense except in the light of evolution”

    • -Theodosius Dobzhansky
    • Evolution by Natural Selection
  2. Evolution is a scientific theory that explains how living things have changed over time.

    Slide 2 - Evolution is a scientific theory that explains how living things have changed over time.

    • In science, theories are statements or models that have been tested and confirmed many times.
    • Evolution is a Scientific Theory
  3. Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION 

    Slide 3 - Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION 

    • He explained how organisms changed, or adapted, to their environments over time.
  4. Before Darwin, a scientist name Lamarck attempted to explain the diversity of life on Earth

    Slide 4 - Before Darwin, a scientist name Lamarck attempted to explain the diversity of life on Earth

    • Larmarck thought that you would gain or lose features if you overused or didn't use them; “Inheritance of Acquired Characteristics”
    •  PROVEN TO BE WRONG!
    • Photo courtesy of ucumari, creative commons, flickr
  5. Darwin was a naturalist

    Slide 5 - Darwin was a naturalist

    • He traveled the world and made observations and sketches of many species
    • His most famous travels were aboard the H.M.S. Beagle where he traveled to the Galapagos Islands
  6. Darwin noted that the many finches on the islands had similarities, but each had a slightly different shaped beak.

    Slide 6 - Darwin noted that the many finches on the islands had similarities, but each had a slightly different shaped beak.

    • It was later determined that the shape of the beak matched the type of food the birds ate (ex: seeds vs. nuts)
    • Cactus finch, photo courtesy of zrim, flickr creative commons
  7. Darwin published his work in a book called THE ORIGIN OF SPECIES.

    Slide 7 - Darwin published his work in a book called THE ORIGIN OF SPECIES.

    • His theory of Natural Selection explained how groups of living things adapted over time.
    • In Natural Selection, nature, or the environment “chooses” which individuals are “fit” to survive.
    • “Selected for”- fit to survive
    • “Selected against”- not fit to survive
  8. Variation exists among individuals in a species.  Variation can be observed in the many differences in physical traits (coloration, body size, etc).

    Slide 8 - Variation exists among individuals in a species. Variation can be observed in the many differences in physical traits (coloration, body size, etc).

    • There is competition for resources (food, mates, and space). Darwin referred to this competition as the “struggle to survive”.
    • Selection occurs when those individuals who are “best fit” survive, while those who are not fit die. Darwin referred to this as “survival of the fittest”.
    • Reproduction of survivors increases the appearance of best fit traits in the next generation. Reproduction causes the population to change, or evolve!
  9. Say in a species of blob….there exists blobs of all shapes and sizes (variation)

    Slide 9 - Say in a species of blob….there exists blobs of all shapes and sizes (variation)

    • Blobs eat the little purple pellets that live underground and on the surface.
  10. During a particularly hot year, food became less abundant (competition).  Blobs that had the ability to dig into the soil to get food had a better chance of survival.  Blobs without this ability died (selection).

    Slide 10 - During a particularly hot year, food became less abundant (competition). Blobs that had the ability to dig into the soil to get food had a better chance of survival. Blobs without this ability died (selection).

    • Many blobs died that year…….
  11. The ones that survived mated and passed their genes to the next generation. (reproduction)

    Slide 11 - The ones that survived mated and passed their genes to the next generation. (reproduction)

  12. The next generation inherits the same trait that allowed their parents to survive.  There are many more blobs with this feature…the population has evolved!

    Slide 12 - The next generation inherits the same trait that allowed their parents to survive. There are many more blobs with this feature…the population has evolved!

    • Variation
    • Competition
    • Selection
    • Reproduction
  13. This process came to be known as Natural Selection

    Slide 13 - This process came to be known as Natural Selection

    • The favorable variations are called Adaptations