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Charles Darwin
Born 1809
 Study (Edinburgh and Cambridge)
 Voyage of the Beagle 1831-36
 Retired to Down 1842
 The Origin of Species
 Died 1882
Darwin’s home at Down, near London
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
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
Natural selection
Developed theory in complete isolation
 In face of 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 Voyage
Not paid for 5 years on Beagle.
 Actually, he had to pay!
 Was lucky to get on
his father opposed him going
Mainly asked because of his class, to
keep Captain Fitzroy company
 It was the making of him
Video: Who Was Charles Darwin?
Galapagos, 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
Darwin’s sand walk at Down:
a daily thoughtful stroll
He knew about fossils
Collected many for extinct animals
Knew about Lyell’s theory of “evolution” of
geology (uniformitarianism)
Read Malthus (an economist) on population
and competition for resources.
His ideas developed steadily over 20 years
Alfred Russel Wallace
Thought of natural selection
 Wrote to Darwin
 Darwin had been working on book
 Published a “letter” jointly
 It was Darwin who put in the hard
years collecting and documenting
evidence to support theory
Natural Selection
Process of change in populations over
many generations
 Populations have genetic diversity
 Environment exerts ‘selective pressure’
(food, climate, predators, etc.)
 Individuals with certain traits survive
local environmental conditions
 Pass on favourable alleles to offspring
Assumptions of Natural Selection
-All members of a
species display a
variety of
characteristics in their
appearance and
-Variation among
individuals is (at least
in part) heritable.
Assumptions of Natural Selection
2. Competition
number of offspring
produced by
individuals in a
species exceeds the
number of offspring
that will survive to
Assumptions of Natural Selection
3. Fitness
Some offspring,
because of their
differences, are
better able to adapt
to the conditions of
the environment
than others and be
more successful at
surviving and
Assumptions of Natural Selection
4. Adaptation
Individuals with
most favourable
variations (those
who are better at
surviving and
reproducing) are
naturally selected.
“Descent with Modification”
Darwin never used
the word
‘evolution’ in his
book On the Origin
of Species
Used the term
‘descent with
Natural Selection
Artificial Selection
Selective pressure
exerted by humans
on populations
Improve or modify
particular desirable
Eg. Selective
breeding in farm
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
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
Breed for nutritional value, as well as
harvest yield and pest resistance
Designer Dogs
How many breeds
of dogs are there
What do you get
when you cross a
Yorkie and a
Designer Dogs
What about a Pug
and a Beagle?
Or a Siberian
Husky and German
Gerberian Shepsky
Yorkshire Terrier and Maltese?
Mr. Alex Ander Dickie
Consequences of Artificial
In dogs: respiratory
problems (bulldogs)
and hip dysplasia
In crops: reduces
genetic variation