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Evolutionary Scientists
Francesco Redi 1668
• First to disprove spontaneous generation
• First to be recognized for having a control
group in an experiment
John Needham 1745
• Attempted to prove spontaneous
generation with microscopic organisms
• Heated chicken broth in a flask to kill all
living microscopic organisms
• Let broth cool and sit.
• Broth became cloudy with microorganisms
• This gave Needham proof that
microorganisms came from the broth
Lazzaro Spallanzani
• Repeated Needham’s experiment
• He removed the air from the flask by creating a
vacuum after the broth was heated
• No microorganisms grew disproving
spontaneous generation of microorganisms
• Some believed that all Spallanzani proved was
that spontaneous generation could not occur
without air
Louis Pasteur 1850s
• Designed an experiment to disprove
spontaneous generation once and for all
• Performed a variation of Needham’s and
Spallanzani’s experiments by using a
special flask that allowed air but trapped
contaminants so it could not get to the
flask
• Pasteur showed that microorganisms lived
in the air but was not formed from the air
Pasteur’s other accomplishments
• First to determine that yeast is responsible
for fermentation
• Developed the germ theory
• Created vaccines for rabies and anthrax
• Created pasteurization
• Experiment led to the law of Biogenesis:
living things come from other living things
Jean-Baptiste de Lamarck
• Believed that as the environment changed,
organisms changed their behavior to survive
• As an organism used a body part to adapt, that
body part would improve over time or shrink if
not used. ‘First Law’
• Organisms passed on characteristics to their
offspring. ‘Second Law’
• He believed organisms changed over time from
simple to more complex
Example: How did Lamarck believe
giraffes acquired longer necks?
• By stretching their necks to eat leaves
from tall trees, giraffes could grow their
necks and pass on the longer necks to
their offspring.
Charles Darwin 1809-1882
• Considered the father of evolution
• Went on a 5 year journey on the H.M.S.
Beagle to study specimens
Galapagos Islands
• Studied the birds on these islands
• If the birds migrated from the mainland, then
they would be the same on the island. If the
birds were created differently then they would be
different from the mainland birds.
• Darwin found the birds were not exactly the
same nor different so he thought the birds
evolved over time in order to adapt to the island.
On the Origin of Species: Darwin’s
book of theories
1. All populations show the ability to change from
one generation to the next
2. Competition and variation lead to natural
selection (organisms that survive an
environment are more adapted. The strongest
survive) survival of the fittest
3. Descent of modification: natural selection
leads to new species or organs formed by a
steady accumulation of modifications
On the Origin of Species cont…
4. All living organisms have a common
ancestor that evolved over time that have
either become extinct or exist today.
• Both Lamarck and Darwin believed in
species changed over time but neither had
knowledge of genetics
Thomas Malthus 1766-1834
• Believed that plants and animals reproduced
more offspring than could survive (the struggle
for existence)
• For example, the rate of reproduction in humans
would one day be greater than the resources
(food supply) to sustain them.
• Darwin used Malthus’ idea to support his ideas
of natural selection and survival of the fittest
Charles Lyell 1797-1875
• Geologist and paleontologist
• Ideas were known as uniformitarianism
(geologic forces transformed the surface
of Earth over a long period of time)
• Darwin used Lyell’s ideas to support
natural selection of living organisms over a
long period of time
Alfred Russel Wallace
• Had a paper to be published on the same
ideas as Darwin. Together, they published
a paper on natural selection.
• A year later, Darwin published On the
Origin of Species. Darwin received the
recognition.
Remember…
• Natural selection choose the most
advantageous trait for an organism so
those traits are passed on to future
generations.
• The only way scientists have observed
changes in genes is by mutations.
• Random mutations with natural selection
are thought to be the driving force behind
evolution