Charles Darwin & Natural Selection. LifelineLifeline n Born 1809 n Study (Edinburgh and Cambridge)...
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Transcript of Charles Darwin & Natural Selection. LifelineLifeline n Born 1809 n Study (Edinburgh and Cambridge)...
Charles Darwin & Natural SelectionCharles Darwin & Natural Selection
LifelineLifeline 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
Darwin’s achievementsDarwin’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
Not just an evolutionistNot 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
Natural selectionNatural 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
Joining the Beagle VoyageJoining 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
CHARLES DARWINCHARLES DARWIN Video: Who Was Charles Darwin?
Galapogos, 1835Galapogos, 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
The Big Idea: Natural Selection
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
Alfred Russel WallaceAlfred 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
Natural SelectionNatural 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
Assumptions of Natural SelectionAssumptions of Natural Selection
1. Variation
-All members of a species display a variety of characteristics in their appearance and behavior.
-Many are inherited.
Assumptions of Natural SelectionAssumptions of Natural Selection
2. Competition
The number of offspring produced by individuals in a species exceeds the number of offspring that will survive to adulthood
Assumptions of Natural SelectionAssumptions of Natural Selection
3. Fitness
Some offspring, because of their differences, are better able to adapt to the conditions of the environment than others.
Assumptions of Natural SelectionAssumptions of Natural Selection
4. Adaptation
The better-adapted organisms pass on their characteristics to their offspring and, as a result, the population changes.
“Descent with Modification”“Descent with Modification” Darwin never used
the word ‘evolution’ in his book On the Origin of Species
Used the term ‘descent with modification’ instead
Artificial SelectionArtificial Selection Selective pressure
exerted by humans on populations
Improve or modify particular desirable traits
Eg. Selective breeding in farm animals
Artificial SelectionArtificial 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
Designer DogsDesigner Dogs How many breeds
of dogs are there now?
Examples: What do you get
when you cross a Yorkie and a Poodle?
Yorkie-poo
Designer DogsDesigner Dogs What about a Pug
and a Beagle?
Puggle Or a Bichon Frize
and a Poodle?
Bich-Poo
Consequences of Artificial Selection
Consequences of Artificial Selection
In dogs: respiratory problems (bulldogs) and hip dysplasia (labs)
In crops: reduces genetic variation (monoculture)