Evolution, Part 1
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Transcript of Evolution, Part 1
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The True Story of theTheory of Evolution
Or Fitzroy, Fickle Fuegians, and Funny, Feathered Finches
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1973: “Nothing in biology makes sense, except in the light of evolution.”
-Theodosius Dobzhansky (1900-1975)
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Evolution, Pre-Darwin
Beginnings in Ancient Greece Species are changeable… Variation occurs! Selective breeding utilized already “Artificial Selection”
Widely accepted in early-1800s: Lamarck’s Theory of Acquired Characteristics
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Jean-Baptiste de Lamarck 1744-1829
1. Individuals lose characteristics they do not require (or use) and develop characteristics that are useful
2. Individuals inherit the traits of their ancestors.
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Thomas Malthus Malthus: An Essay on The
Principles of Populations (1798)
Populations grow exponentially while food supply grows linearly.
Eventually population will outgrow food supply; life is a constant struggle
What keeps a population in check? War, pestilence, famine, competition, etc.
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Charles Lyell
Principles of Geology (1830)
“The present is the key to the past.”
Geologic change is the steady accumulation of tiny changes over a lengthy period of time.
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Charles Robert Darwin Born in 1809, same day
as Lincoln
Wealthy, upper-class
Father, Robert, was a physician and anti-evolutionist
Grandfather, Erasmus, was pro-evolutionist and gifted debater
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Darwin’s Career
Robert: “You will be a disgrace to yourself and all of your family”
Eventually earned a degree in divinity from Cambridge
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The HMS Beagle
First voyage: May 22, 1826
Captain Pringle Stokes Mission: survey coast
of southern South America
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First Voyage of the Beagle
Stokes – suicide Robert Fitzroy
becomes captain: seeking a literal, biblical interpretation of creation
Boat stolen Fuegians captured as
hostages, then returned to England
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The Beagle’s Second Voyage
Darwin – captain’s companion
Fitzroy and Darwin – devoted observers of the natural world
IMPORTANT – Darwin did not SET OUT to discover natural selection
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Darwin’s Finches
Galapagos islands (Pacific Ocean)
Finches uniquely related to the individual islands
Ornithologist John Gould helped Darwin make his…
HYPOTHESIS: Modification of original group of finches that colonized islands
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Megatherium
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Darwin’s Later Life
Returned to England in 1836 and never left again
Suffered frequent illnesses, probably tropical in nature
Married his cousin, Emma Wedgewood
Son Charles fell critically ill in June, 1858
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Evolution, Post-Darwin Wallace sends his
manuscript – 1858 Darwin faces pressing
dilemma – to present or not to
Darwin and Wallace present together on July 1, 1858
Around 1900, Mendel’s papers were “re-discovered”, as many scientists attempted to merge the two theories.Alfred Russell Wallace
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On the Origin of Species (1859)
Caused controversy in religious and scientific communities
Darwin did not use the term “evolution” and did not suggest humans descended from apes
Questions remained for Darwin… “The eye to this day gives me a cold shudder...”
Theory did not gain wide acceptance until 1930s-40s
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Premises of Natural Selection1. Populations overproduce.
2. Resources are limited, so competition ensues.
3. Genetic variations directly impact the ability of organisms to survive.
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Premises of Natural Selection
4. Organisms with beneficial differences will have a better chance of survival.
5. Surviving individuals pass their traits onto future generations.
6. This results in a slow change in populations over time.
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Natural Selection
process by which individual organisms with favorable traits are more likely to survive and reproduce
IMPORTANT – Individuals do not evolve. Populations evolve.
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KEY DEFINITIONS Population: all members of a
species in one area
Species: Group of organisms that can produce fertile offspring
Variation: slight differences among organisms, often caused through genetic mutations
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KEY DEFINITIONS Adaptation: Trait that affords
organism a better chance of survival
Evolution: Gradual change in a species over time***
Natural Selection: One mechanism through which evolution occurs
Adaptive Radiation: multiple species descend from one original species because of selection
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Darwin’s Mechanisms for Evolution
1. Natural Selection
2. Whatever would cause “nature” to select for such a ridiculous tail on this peacock?