NS Foldable
Process of Natural
Selection Foldable
Natural Selection =
NS
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NS – individuals better adapted to their environment survive and reproduce more successfully than less well-adapted organisms do.
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Overproduction
egg sac
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• Overproduction: organisms in a population produce more offspring than their environment can support.
Many die through predation or starvation
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Example:
• Tarantula’s egg sac holds 500 to
1,000 eggs.
• Some eggs survive and develop into adult spiders and some die.
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The moulting process
Genetic Variation Within
A Population
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• Variation:
Differences in a population of organisms of the same species.
Variations/Genetic Adaptations passed to offspring from parents through genes/alleles.
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Example:
• Every individual has its own combination of traits.
• Each tarantula is similar, but not identical, to its parents.
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Struggle to Survive
(adaptation)
Newly inherited traits help organisms survive and reproduce in their environment.
Some variations are favorable and help organisms compete to survive and reproduce.
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Example:
• Some tarantulas have traits that make it more likely they will survive.
•better able to fight off predators
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Adult female
Brachypelma smithi , showing a bald patch after kicking hairs off of her abdomen.
Successful Reproduction
(natural selection)
Over time, offspring with helpful variations increase and become a larger percentage of the population.
The organisms with favorable variations become plentiful. The ones without favorable variations become rare or extinct.
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Example:
• Tarantulas best adapted to their environment are likely to survive and reproduce.
• Offspring may inherit traits that help them survive.
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