ADAPTATIONS
A hereditary characteristic that helps an organism survive and reproduce in its environment.
FITNESSMeasure of ability to survive and produce more offspring relative to other members of a population
DARWIN’S EXPLANATIONDarwin realized that animals have many offspring and some don’t survive.
The survivors are better suited to their environment.
NATURAL SELECTION
• Mechanism by which the environment is the selective agent
• Mechanism by which evolution occurs
Darwin said that in nature, environment creates selective pressure
Darwin said that in nature, environment creates selective pressure
STEPS OF NATURAL SELECTION1. Overproduction
-organisms have many offspring, but not all will survive.
STEPS OF NATURAL SELECTION
2. Genetic Variation
--Individuals vary within a population
--New traits appear due to genetic mutations
STEPS OF NATURAL SELECTION3. Struggle to Survive
--Organisms compete for resources (food, water, shelter, and mates)
--Organisms have to get away from predators
STEPS OF NATURAL SELECTION3. Struggle to Survive
--Some adaptations allow organism to survive at higher rate and individuals are “naturally selected” to survive and produce offspring
STEPS OF NATURAL SELECTION4. Descent with Modification
--Organisms with the best adaptations will survive and reproduce passing these good traits down to their offspring
Natural Selection acts on phenotypes not genotypes
As environment changes, different traits will become beneficial.
OTHER EXAMPLES OF EVOLUTION:
Bacteria become resistant to antibiotics
Don’t take antibiotics unless you have a bacteria infection!
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