Download 5.1 evidence of evolution

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Evidence from Fossils
• Sequence fossils appear matches
the sequence they would evolve
• Age of fossils determined from age
of rock
• Bac t., algae, fungi , worms, land
• Bony fish, amphibians, reptiles,
birds, placental mammals
• Plants before animals, land plants
before land animals, flowering
plants before insects
• Many sequences link existing
organisms to ancestors
Evidence from selective breeding
• Large differences between modern
livestock and wild species
• Variation between domesticated
• Humans selectively breed animals
for specific traits that they consider
useful. This process is called
artificial selection
• Artificial selection causes large
changes in a short period of time.
• Selection causes evolution
Analogous Structures
• Structures that have different
origins but become similar
because they perform the same
or a similar function. Result of
Convergent evolution.
• Wings of birds and butterflies
• Tail fins of whales and fishes
• Unrelated species evolved
similar features out of necessity
Evidence of Homologous structures
• Structures that look different and
may form a different function, but
have a “unity of type.”
• Forelimbs of human, mole, horse,
porpoise, and bat
• Same bones in same positions.
• All share common ancestor that
had a pentadactyl limb.
• Limbs have become different
because they perform different
• Adaptive Radiation
Vestigial Structures
• Reduced structures that show no
particular function
• Developing teeth in whale embryos
when adult whales have no teeth
• Small pelvis and thigh bone in
whales and some snakes
• Appendix in humans.
• Structures that no longer have a
function and are eventually being
lost by evolution
Pentadactyl Limb
Bone Structure
Single bone in the proximal part
Two bones in the distal part
Radius and ulna
Tibia and fibula
Group of wrist/ankle bones
Series of bones in each of 5 digits
Metacarpals and phalanges
Metatarsals and phalanges
• Populations of a species become
separated so they cannot
• Natural selection acts differently
on each of the two populations
• Species evolve in different ways.
• Characteristics gradually diverge
and become recognizably different
• Species no longer capable of
• Often occurs if species become
geographically isolated
Charles Darwin
• Young naturalist explored the Galapagos Islands
located off the western coast of South America
• Noticed on the islands numerous different
• Finches: differences in the size and shape of
their beaks
Evidence from Patterns of Variation
• Divergence is gradual
• Organisms present at different stages of divergence
• Red Grouse of Brittain and Willow Ptarmigan of Norway
• Sometimes classified as same species, sometimes not.
• Darwins Finches
The Red Grouse and the Willow Ptarmigan where at one time classified as
two separate species. The current scientific consensus is that they are
both members of the same species (Lagopus lagopus)
Populations will gradually diverge over time
and it is natural to see continuous variation
across a geographical range.
The greater the geographical separation and the longer
the populations have been separated the greater the
Industrial Melanism
• Melanistic- dark varieties of
typically light-colored insects
• Melanistic varieties more common
in polluted, industrial areas
• In unpolluted areas, light colored
insects are better camouflaged.
• In polluted areas, dark colored
insects are better camouflaged.
• Example of evolution by natural