Charles Darwin and Natural Selection His Ideas and What Shaped Them Chapter 10.
Charles Darwin & Natural Selection
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Transcript of Charles Darwin & Natural Selection
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Charles Darwin & Natural Selection
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Lifeline Born 1809 Study (Edinburgh and Cambridge)
1825-1831 Voyage of the Beagle 1831-36 Retired to Down 1842 The Origin of Species
1859 Died 1882
Darwin’s home at Down, near London
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Darwin’s achievements Transformed biological science
¨ Both style and content¨ Still the cornerstone of biology ¨ Now the cutting edge of psychology
Transformed attitudes of humanity to our place in the universe
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Not just an evolutionist Not even a biologist to start with Collected beetles for fun Studied geology more seriously Considered himself a geologist
throughout the Beagle voyage and for some time after
Famous for working out how coral atolls are formed
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Natural selection Developed theory in complete isolation In face of violent (religious) opposition
¨ With no knowledge of genetics¨ With no knowledge of DNA¨ With no knowledge of plate tectonics ¨ With no observations of natural selection
actually occurring
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Joining the Beagle Voyage Not paid for 5 years on Beagle. Actually, he had to pay! Was lucky to get on
¨ replaced someone who was shot in a duel
¨ his father opposed him going Mainly asked because of his class, to
keep Captain Fitzroy company It was the making of him
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Galapogos, 1835 Portrayed as a “Eureka” experience. Actually, was hugely homesick Did not recognise significance until
back in England, 1837.¨ Worked out theory much later.¨ First inkling of natural selection in 1838.
Turtles & finches were key evidence¨ On boat home, ate turtles, dumped shells¨ Thought finches different species; didn’t
even label them properly
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The Big Idea: Natural Selection
He knew about fossils Collected many for extinct animals Knew about Lyell’s theory of “evolution” of
geology Read Malthus (an economist) on population
and competition for resources. Video Clip His ideas developed steadily over 20 years
Darwin’s sand walk at Down: a daily thoughtful stroll
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Alfred Russel Wallace Thought of natural selection
independently Wrote to Darwin Darwin had been working on book Published a “letter” jointly It was Darwin who put in the hard
yards collecting and documenting evidence to support theory
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Natural Selection Process of change in populations over
many generations Individuals with certain traits survive
local environmental conditions Pass on favourable alleles to offspring Environment exerts ‘selective pressure’ This has led to biodiversity
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Assumptions of Natural Selection1. Variation
-All members of a species display a variety of characteristics in their appearance and behavior. -Many are inherited.
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Assumptions of Natural Selection2. Competition
The number of offspring produced by individuals in a species exceeds the number of offspring that will survive to adulthood
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Assumptions of Natural Selection3. Fitness
Some offspring, because of their differences, are better able to adapt to the conditions of the environment than others.
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Assumptions of Natural Selection4. Adaptation
The better-adapted organisms pass on their characteristics to their offspring and, as a result, the population changes.
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“Descent with Modification” Darwin never used
the word ‘evolution’ in his book On the Origin of Species
Used the term ‘descent with modification’ instead
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Artificial Selection Selective pressure
exerted by humans on populations
Improve or modify particular desirable traits
Eg. Selective breeding in farm animals
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Artificial Selection In food crops
¨ Wheat, corn, rice and veggies have all been selectively bred
Wild mustard plant has been modified to produce broccoli, Brussels sprouts, cabbage and cauliflower
Breed for nutritional value, as well as harvest yield and pest resistance
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Designer Dogs How many breeds
of dogs are there now?
Examples: What do you get
when you cross a Yorkie and a Poodle?
Yorkie-poo
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Designer Dogs What about a Pug
and a Beagle?
Puggle Or a Bichon Frize
and a Poodle?
Bich-Poo
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Consequences of Artificial Selection
In dogs: respiratory problems (bulldogs) and hip dysplasia (labs)
In crops: reduces genetic variation (monoculture)