Transcript Several key insights led to Darwin’s idea for natural

Several key insights led to
Darwin’s idea for natural selection.
Darwin noticed a lot of variation in
domesticated plants and animals.
Artificial selection is the process by which
humans select traits through breeding.
neck feathers
crop
tail feathers
– Darwin found convincing evidence for his
ideas in the results of artificial selection
The selective breeding of domesticated
plants and animals
Hundreds to thousands
of years of breeding
(artificial selection)
Ancestral dog (wolf)
Figure 13.2A
Figure 13.2B
Natural selection is a mechanism by
which individuals that have inherited
beneficial adaptations produce more
offspring on 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.
Natural selection explains how evolution
can occur.
There are four main principles to the theory of natural
selection.
– overproduction
– variation
– adaptation
– descent with modification
ADAPTATION
VARIATION
OVERPRODUCTION
Natural selection explains how evolution
can occur.
There are four main principles to the
theory of natural selection.
– Variation
– overproduction
– adaptation
– descent with modification
Fitness is the measure of survival ability
and ability to produce more offspring.
Natural selection acts on existing variation.
Natural selection can act only on traits that
already exist.
Structures take on new functions in addition to
their original function.
five digits
wrist bone
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