Transcript 10.3 Theory of Natural Selection

10.3 Theory of Natural Selection
KEY CONCEPT
Darwin proposed natural selection as a mechanism for
evolution.
10.3 Theory of Natural Selection
Charles Darwin - Biography
• Born – England, February 12 1809
• Sailed around the world as a naturalist
(scientist who studies nature)
• Well educated and interested in natural history
• Curious with an analytical nature
• Made observations and collected evidence
which later supported his hypothesis about how
life changes over time
10.3 Theory of Natural Selection
Charles Darwin - Travels
• Sailed on the ship H.M.S. Beagle in 1831
– From Europe to South America, the Galapagos
Islands, New Zealand, Austrailia, the southern tip of
Africa, back to South America, and then home to
England
• The Galapagos Islands
– Islands are close together; climates are very different:
hot, dry and barren vs. more rainfall and vegetation
10.3 Theory of Natural Selection
Darwin observed differences among island species.
• Variation is a difference in a physical trait.
– Galápagos tortoises that live in areas with tall plants
have long necks and legs.
– Galápagos finches that live in areas with hard-shelled
nuts have strong beaks.
10.3 Theory of Natural Selection
Several key insights led to Darwin’s idea for natural
selection.
– Darwin observed 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
10.3 Theory of Natural Selection
Artificial selection in dogs
10.3 Theory of Natural Selection
Artificial selection in horses
10.3 Theory of Natural Selection
• Natural selection is when individuals that have inherited
beneficial adaptations produce more offspring on
average than do other individuals.
10.3 Theory of Natural Selection
• Heritability is the ability of a trait (beneficial
adaptations) to be passed down.
– There is a struggle for survival due to overpopulation
and limited resources.
•Darwin proposed that adaptations arose over many generations.
10.3 Theory of Natural Selection
Natural selection explains how evolution can occur.
• There are four main principles to the theory of natural
selection.
• Variation – differences in organisms
VARIATION
10.3 Theory of Natural Selection
Natural selection explains how evolution can occur.
• There are four main principles to the theory of
natural selection.
• Adaptation – changes caused by evolution
in an organism to better survive in their
environment
ADAPTATION
10.3 Theory of Natural Selection
Natural selection explains how evolution can occur.
• There are four main principles to the theory of
natural selection.
• Overproduction – producing more offspring than
will survive
OVERPRODUCTION
10.3 Theory of Natural Selection
Natural selection explains how evolution can occur.
• There are four main principles to the theory of
natural selection.
DESCENT with
MODIFICATION
Traits that are
heritable and
beneficial (like big
jaws and teeth)
will be passed
down to further
generations.
10.3 Theory of Natural Selection
• Fitness is the measure of survival ability and ability to
produce more offspring.
10.3 Theory of Natural Selection
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