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I. Variation
A. Variation is the difference in traits because of
difference in genes
1. Example: Things that vary in humans
2. What are some things that vary in humans?
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Height
Eye color
Hair color
Leg length
Arm Length
Skin color
B. Variation can:
1. Hurt an organisms chance of survival
• Example: A slow cheetah
2. Help an organisms chance of survival
• Example: A fast cheetah
3. Not effect an organisms chance of survival
• Example: A fast male cheetah that does not
hunt
C. Cheetah speed
• How did the cheetah become so fast?
• http://www.youtube.com/watch?v=P1QxdSTrwwE
• With a twist: http://www.youtube.com/watch?v=WiLT-l97FHg
II. Adaptation
A. Adaptation is an inherited
genetic characteristic that
improves an organism’s ability
to survive in a particular
environment
B. Cheetah Adaptations
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Spotted
Sharp claws
Long spine
Speed
C. Polar Bear Adaptations
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Big claws
White fur
Big, sharp teeth
Strength
D. Seal adaptations
• Blubber
• Long, slick body
• Fins
III. Fitness
A. Fitness is the ability of an organism to
survive and reproduce, passing their genes
to the next generation
B. Why are faster cheetahs
more fit?
1. Some cheetahs are slower and some are faster
(variation)
2. Fast cheetahs could catch food better than
slow cheetahs
3. More fast cheetahs survived than slow
cheetahs (because caught more food)
4. Fast cheetahs passed genes to baby cheetahs
5. Fast cheetah babies
IV. Natural Selection
A . Natural Selection – the process
in nature in which organisms with
favorable variations survive,
reproduce, and pass their
variations to the next generation.
1. Favorable traits survive
2. Unfavorable traits die out
B.
How Natural Selection Occurs
1. Organisms have variation of traits
• Similar organisms are not exactly the same
• Example:
• Some cheetahs are slower and some are
faster
How Natural Selection Occurs
2. Organisms struggle to survive
a. Struggle with other organisms
b. Struggle because of the environment
• Example:
• Cheetahs need to catch prey (food) to
survive
How Natural Selection Occurs
3. Some variations help organisms survive
such as adaptations
• Example:
• Faster cheetahs can catch more food
than slower cheetahs
How Natural Selection Occurs
4. Organisms with best adaptations are most likely
to survive to reproduce
• Example:
• Faster cheetahs are more likely to survive and
reproduce (because they catch more food)
How Natural Selection Occurs
5. They will pass their genes to next generation
• Example:
• Fast parent cheetahs will pass their genes
on to baby cheetahs
How Natural Selection Occurs
6. Over time, there will be more organisms with
best adaptations for the environment
• Example:
• More fast cheetahs survive to have baby cheetahs
than slow cheetahs
• More fast baby cheetahs are born than slow baby
cheetahs
How Natural Selection Occurs:
Summary
1. Organisms have variation of traits
• Similar organisms are not exactly the same
2. Organisms struggle to survive
• Struggle with other organisms
• Struggle because of the environment
3. Some variations help organisms survive
• Adaptations
4. Organisms with best adaptations are most likely to survive to
reproduce
5. They will pass their genes to next generation
6. Over time, there will be more organisms with best
adaptations for the environment
V. Evolution
A. Natural Selection causes species to
change over time.
B. Common WRONG Ideas
1. You can acquire the trait if you need it to survive – NO; if you
don’t already have the trait, you die! Populations can and do
become extinct.
2. One organism can evolve – NO; evolution is change in a
population over time (it may be thousands of years)
3. Evolution is only a theory – NOT entirely; evolution is a
SCIENTIFIC theory which means it is supported by mountains
of evidence, experimentation, and observations. All of the
SCIENTIFIC evidence supports evolution. There is NO
scientific evidence that does not support evolution.