Download Surprising truths about Charles Darwin

Charles Darwin
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

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 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 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

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
The Big Idea:
Natural Selection
Darwin’s sand walk at Down:
He knew about fossils
a daily thoughtful stroll
 Collected many for extinct animals
 Knew about Lyell’s theory of
“evolution” of geology
 Read Malthus (an economist) on
population and competition for
resources.
 His ideas developed steadily over 20
years

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

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

Assumptions 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 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 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 Selection
4. Adaptation
The better-adapted
organisms pass on
their characteristics
to their offspring
and, as a result, the
population changes.
Natural Selection game
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 Selection



Selective pressure
exerted by humans
on populations
Improve or modify
particular desirable
traits
Eg. Selective
breeding in farm
animals
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

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
Designer Dogs

What about a Pug
and a Beagle?
Puggle

Or a Bichon Frize
and a Poodle?
Bich-Poo
Designer Dogs

What about a Bull
mastiff and a ShihTzu?
Consequences of Artificial
Selection


In dogs: respiratory
problems (bulldogs)
and hip dysplasia
(labs)
In crops: reduces
genetic variation
(monoculture)