Download Darwin`s Ideas

Intro to Evolution
Darwin and Natural Selection
Biology AP Todeschini
Darwin’s Ideas
• When Darwin published The
Origin of Species in 1859 he
was not the first to suggest the
idea of evolution.
• He merely suggested a
mechanism under which it
would function: natural selection
• He suggested that the diversity
of life resulted from descent
with modification from previous
ancestors.
Darwin’s Influences
Scientists that influenced Darwin
• Carolus Linnaeus,
the founder of
taxonomy, said every
creature had a
purpose.
• Thomas Malthus
predicted that
populations were all
grow exponentially
and then crash.
• Paleontology, the
study of fossils, was
largely developed by
French scientist
Georges Cuvier
Scientists that influenced Darwin
Lamarck was correct in identifying that traits
are passed on but didn’t know they must be
genetic in nature NOT acquired.
• Geologists James
Hutton and Charles
Lyell perceived that
changes in Earth’s
surface can result from
slow continuous actions
still operating todayVERY OLD EARTH!
• Lamarck hypothesized
that species evolve
through use and disuse
of body parts and the
inheritance of acquired
characteristics
Darwin’s Journey
• After graduating with a degree in theology, he took an
unpaid position as naturalist and companion to Captain
Robert FitzRoy for a 5-year around the world voyage on
the Beagle
Darwin’s Journey
• He observed adaptations of
plants and animals that
inhabited many diverse
environments, most influential
stop being the Galapagos
Island
“The natural history of these islands is eminently curious, and well deserves
attention. Most of the organic prof\ductions are aboriginal creatures, found
nowhere else, there is even a difference between the inhabitants of the different
islands; yet all show a marked relationship with those of America, though
separated from that continent by an open space of an ocean, between 500 and 600
miles in width. …Hence, both in space and time, we seem to be brought somewhere
near to that great fact- that mystery of mysteries- the first appearance of new
beings on this earth.” Darwin (Journal entry)
What did Darwin See?
• Giant land tortoises,
will great diversity oh
shells, neck length
• Sea iguanas that eat
algae, only ones on
planet
• Finches, finches,
finches!
The Origin of Species
• Darwin developed two main
ideas:
• Descent with modification
explains life’s unity and
diversity
• Natural selection is a cause of
adaptive evolution
• Natural selection acts on
adaptations organisms have
• In the Darwinian view, the
history of life is like a tree with
branches representing life’s
diversity
How it Works
1. Overproductions of offspring (Malthus)
-not all offspring will survive, there will be competition and
varying chances of survival
How it Works
2. Variation among individuals
- no two organisms are exactly the same
How it Works
• 3. Competition for limited resources
• Struggle for existence is real!
How it Works
• 4. Successful competitors survive, reproduce, &
pass on their traits
• The more traits you pass on the higher your Fitness!
How it Works
5. Repeat 1-4 for millions of years and life will adapt
to the environment.
Artifical Selection
• Darwin was influenced by the artificial selection
he saw happening because of the
“fitness”determined by human wants and
needs.
https://www.youtube.com/watch?v=WseH479iOM0
Pesticide/Antibiotic
Resistance
• Life will always adapt if it
can.
• Spraying of pesticides kills
all the pests who are not
resistant.
• Because of variation
present some pests will
have a natural defense
and survive to reproduce.
• Similar mechanisms drive
antibiotic resistance in
bacteria and viruses.