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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Photography of Egg sack - Poecilotheria pederseni

                                                                                                                                                       

                 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.GLE 0807.5.3 - GLE 0807.5.4 - SPI 0807.5.2 - SPI 0807.5.3GLE 0807.5.3 - GLE 0807.5.4 - SPI 0807.5.2 - SPI 0807.5.3

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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