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Transcript
Unit VIII: EVOLUTION
http://www.snotr.com/video/128
A. Evolution is a STRONGLY supported theory…. lots of evidence!
B. Evolution is the genetic change in a species over time.
*** occurs in a population NOT IN INDIVIDUALS!
C. Famous Theorists:
1. Jean-Baptiste Lamark (1809)
a) Organisms change their features to be
more successful in their environment.
Well hello…
b) Use and Disuse: the more something is used, the better developed
it becomes …and vice versa.
“use it or lose it”
c) Inheritance of Acquired Traits: altered traits will be passed on to
offspring.
*If you cut off your left hand… your kids won’t have one either.
2. August Weismann (early 1900s)
Well that’s just
not cool!
Well well well….
a) Disproved Lamark’s theory by cutting off the tails of mice for 50
generations.
*surprisingly… every generation grew tails.
I’m the man.
3. Charles Darwin (mid-1800s)
a) Darwin was an English naturalist.
b) Travelled around the world on the HMS Beagle (1831-1836).
c) He studied and collected many organisms
1) His theory was based on bodily differences among South American
mocking birds
2) His most well-known animals were the Galapagos finches.
What differences do you see among and mocking
birds and among the finches?
d) On The Origin of Species (1859)
* Darwin published his book more than 20 years after returning
from his voyage. Why?
Darwin’s Three Main Ideas:
1) Struggle for Existence
• Overpopulation - When most organisms reproduce, they
produce more offspring than can survive
• Competition - These offspring must compete for resources
2) Survival of the Fittest
• Variation - Slight differences occur among individuals
*caused by mutations & sexual reproduction
• Adaptation -
Variations cause some individuals to have a greater
fitness than others.
*Fitness = ability to survive and reproduce
*Offspring who are more fit for their environment
will out-compete others
So…
close…
Curse
this
short neck!
I’m better than you.
Mmm…
This tree is delicious…
3) Descent with Modification
• Transmission of Favorable Variations (“Natural Selection”) Individuals that survive to reproduce pass on their favorable traits.
Those that don’t, die and their unfavorable traits are eliminated.
• Speciation - Many changes ultimately produce new species
better adapted to their environment
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Northern
population
Early fox
population
Spreads
northward
and
southward
and
separates
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Southern
population
Gray Fox
Fig. 5.8, p. 113