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Slide 1 - “Nothing in biology makes sense except in the light of evolution”
- -Theodosius Dobzhansky
- Evolution by Natural Selection
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
Slide 3 - Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION
- He explained how organisms changed, or adapted, to their environments over time.
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
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
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
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
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!
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.
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…….
Slide 11 - The ones that survived mated and passed their genes to the next generation. (reproduction)
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!
Slide 13 - This process came to be known as Natural Selection
- The favorable variations are called Adaptations