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Transcript
Lamarck
• Early theory of evolution
• Theory of “acquired characteristics”
• He said:
–the more an animal uses a body part
the more developed that part gets
–the characteristics an animal develops
can be passed on to its offspring
Lamarck
• Problems with this idea?
–Development does not affect
genes
–Only genes are passed on
–What if an animal were to lose a
leg?
Charles Darwin
• Worked on developing a theory
of evolution for most of his life
• Started as a naturalist on the
HMS Beagle
• Sailed to South America and the
South Pacific
Galapagos Islands
• Especially
important in his
travels
• Saw animals that
were unique, but
similar to animals
elsewhere
Darwin (cont’d)
•He thought that animals could
change over time but didn’t
know how
•Did lots of reading, studying,
collecting and experimenting
Thomas Malthus
•A sociologist friend of Darwin’s
•Figured out that the human
population could grow faster
than the food supply
•Therefore, some people
wouldn’t get enough food and
would not survive
An idea is born…
•Darwin expanded Malthus’s
idea to all living things
An idea is born…
•Darwin expanded Malthus’s
idea to all living things
•He said that all individuals
must struggle to survive
An idea is born…
•Darwin expanded Malthus’s idea
to all living things
•He said that all individuals must
struggle to survive
•This must be true or we’d be
overrun with creatures that
produce large numbers of
offspring
The struggle
•Food
•Space
•Shelter
•Mates
•Escape from
predators
The struggle
•Food
•Space
•Shelter
(Key idea!)
•Mates
•Escape from
predators
• Only those that
are successful go
on to produce
offspring and
NOT ALL ARE
SUCCESSFUL
Darwin’s
Experiments
• Pigeon breeding
• Saw that there was variation in the
populations
Variation means individuals were
different in their characteristics
• He could create offspring with a
certain trait by breeding two birds
with that trait
• This is artificial selection
Darwin’s Theory
•Hypothesis: there was a force
in nature that worked like
artificial selection
Darwin’s Theory
•Hypothesis: there was a force
in nature that worked like
artificial selection
–It allowed only individuals with
certain traits to reproduce and
they produced offspring with
those same traits
Darwin’s THeory
•Combining this with the idea of
struggle you get natural selection:
Darwin’s THeory
•Combining this with the idea of
struggle you get natural selection:
–Organisms vary in their traits which
makes them vary in their ability to
be successful in the struggle
Darwin’s THeory
•Combining this with the idea of
struggle you get natural selection:
–Organisms vary in their traits which
makes them vary in their ability to
be successful in the struggle
–Those traits that make you
successful are passed on and are
more common in the next
generation
Alfred Wallace
• came to the
same
conclusion as
Darwin after
studying the
islands of
Indonesia
Evolution is a
theory
•In science, this means there is
overwhelming evidence to
support it
Evolution is a
theory
• In science, this means there is
overwhelming evidence to support it
• Very slow, so hard to observe because
humans don’t live very long
–Evolution can take thousands or millions
of years
–Though, for some organisms we can see
it
Evolution is a
theory
• Most scientists accept evolution
as true
• Some people disagree because of
their faith and offer alternative
interpretations of the data
Evolution
1.
2.
There is variation in the population
More offspring are produced than
can survive
3. Those individuals with the better
traits survive and have more
offspring
4. Those offspring inherit the good
traits
5. The good traits becomes more
common in the population
What does evolution look like?
•Let’s start with a population
that is equally blue and green
The green dots are more
successful than the blue
All the green reproduce and
have 2 offspring then die
Only 1/5 of the blue reproduce
and have 2 offspring then die
The next generation looks like
this…..
If the same thing happens
again…the next generation
looks like this….