Several key insights led to Darwin’s idea for natural selection.
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Transcript of Several key insights led to Darwin’s idea for natural selection.
Several key insights led to Several key insights led to Darwin’s idea for natural selection. Darwin’s idea for natural selection.
Darwin noticed a lot of variation in domesticated plants Darwin noticed a lot of variation in domesticated plants and animals.and animals.Artificial selection is the process by which humans select Artificial selection is the process by which humans select traits through breeding.traits through breeding.
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– Darwin found convincing evidence for his Darwin found convincing evidence for his ideas in the results of artificial selectionideas in the results of artificial selection
The selective breeding of domesticated plants The selective breeding of domesticated plants and animalsand animals
Figure 13.2A
Hundreds to thousandsof years of breeding(artificial selection)
Ancestral dog (wolf)
Figure 13.2B
Natural selection is a mechanism by which Natural selection is a mechanism by which individuals that have inherited beneficial individuals that have inherited beneficial adaptations produce more offspring on adaptations produce more offspring on average than do other individuals.average than do other individuals.
• Heritability is the ability of a trait to be passed down.• There is a struggle for survival due to overpopulation
and limited resources.• Darwin proposed that adaptations arose over many
generations.
There are four main principles to the theory of natural There are four main principles to the theory of natural selection.selection.– variationvariation
Natural selection explains how evolution Natural selection explains how evolution can occur.can occur.
– overproduction
– adaptation– descent with modification
VARIATIONOVERPRODUCTIONADAPTATION
There are four main principles to the There are four main principles to the theory of natural selection.theory of natural selection.– VariationVariation– overproductionoverproduction– adaptationadaptation– descent with modificationdescent with modification
Fitness is the measure of survival ability Fitness is the measure of survival ability and ability to produce more offspring.and ability to produce more offspring.
Natural selection explains how evolution Natural selection explains how evolution can occur.can occur.
Natural selection can act only on traits that Natural selection can act only on traits that already exist.already exist.Structures take on new functions in addition to Structures take on new functions in addition to their original functiontheir original function..
Natural selection acts on existing variation.Natural selection acts on existing variation.
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