Transcript Natural Selection

NATURAL SELECTION
Unit 3-2 Notes
Mr. Hefti – Pulaski Biology
1. OVERPRODUCTION
A.
B.
C.
Potential to produce more
offspring than can possibly
survive
Populations remain stable
Not all offspring survive to
adulthood
EXAMPLES
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Insects
Fish
Amphibians
Puppies
2. STRUGGLE FOR SURVIVAL
A.
B.
Overproduction leads to
competition for limited resources
Best adapted most likely to
survive and reproduce
EXAMPLES
Long cold winter
 Forest fire
 Certain baby birds aggressive feeders
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3. VARIATION
A.
B.
New traits from natural
variations
Trait helps organism survive
and reproduce = adaptive
value
EXAMPLES
Fur lengths
 Colors of moths
 Antibiotic resistance or non-resistance
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4. SELECTION BY THE ENVIRONMENT
A.
B.
C.
Adaptive value = competitive
advantage
The proportion of individuals with
favorable traits increases (they are
the better competitors)
Adapting to change brings about
evolution
EXAMPLES
Giraffes’ long necks
 Drought tolerant cacti
 Omnivores eat a variety of foods
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