Transcript What is Evolution?

Evolution
Chapter 15
Student Performance Standards
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SB5. Students will evaluate the role
of natural selection in the
development of the theory of
evolution.
• a. Trace the history of the theory.
• b. Explain the history of life in terms of
biodiversity, ancestry, and the rates of
evolution.
• c. Explain how fossils and biochemical
evidence support the theory.
Lesson Essential Question
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How can we observe how species
have changed over time?
Charles Darwin (1809-1882)
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English Naturalist
Sailed on the HMS Beagle from
1831 - 1836
His job was to collect biological and
geological specimens during the
ship’s travels to S. America.
• Collected rocks, fossils, plants, and
animals
Darwin (continued)
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Influenced by:
• Charles Lyell - proposed that the Earth
was millions of years old.
• Thomas Malthus - predicted that one day,
the human population would outgrow it’s
food supply which would lead to
competition for survival. Said that those
better suited would survive.
Darwin Reached the Galapagos Islands in
1835:
• A series of islands off the coast of S. America
• Each island had it’s own slightly different variety of
animals.
• Collected mockingbirds and finches
• In 1836, John Gould classified the birds and
determined them to be new species. However, the
birds resembled species from mainland S. America.
• Darwin began to suspect populations from the
mainland changed after reaching the Galapagos.
• Hypothesized that new species could appear
gradually through small changes in ancestral
species.
Galapagos Islands – a series of volcanic
islands off the coast of Ecuador
Jean-Baptiste Lamarck (1801)
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Theory of Acquired Characteristics:
• Lamarck believed that organisms change
to adapt to their environment and that
those changes are passed on to its
offspring.
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elephant trunk length
giraffe neck length
• This theory is FALSE. Why?
Natural Selection
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Artificial Selection – Selective breeding
(dogs).
Darwin inferred that the same process
could happen in nature. Perhaps over
time, this process could produce new
species.
Natural Selection – if given enough
time, natural selection could modify a
population enough to produce a new
species.
Principles for Natural Selection
(Change Over Time):
1. Variations or differences within a
population are visible.
2. Variations can be inherited.
3. Overpopulation = “struggle for
existence” because not enough
available resources for survival.
4. Variations that increase reproductive
success (fitness) will have a greater
chance of being passed on than those
that don’t.
The Origin of Species
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1859 – Darwin compiled evidence for
evolution and published On the Origin of
Species by Means of Natural Selection
Main Points:
• The diverse forms of life have arisen by
descent with modification from ancestral
species.
• The mechanism of modification has been
natural selection working over enormous tracts
of time.
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Darwin used the term evolution only on
the last page.
What is Evolution?
- Any change in the relative
frequencies of alleles in a
population’s gene pool.
- Evolution works on populations
not individuals.
- Evolution is CHANGE OVER
TIME.
Support for Evolution
1. Fossil Record:
Glyptodonts
Armadillos
2. Comparative Anatomy
the study of similarities and differences
in the anatomy (body plan) of an
organism:
a. Homologous Structures – anatomically
similar structures inherited from a
common ancestor.
b. Vestigial Structures – structures that are
the reduced forms of functional
structures in other organisms. (see
Table 15.2, page 425)
c. Analogous Structures – not inherited
through common ancestors.
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Homologous Structures
Vestigial Structures
The wings of kiwis
are too small to be
of any use in flight.
Snake Pelvis
Appendix
Snake Pelvis
Analogous Structures
Wing of an eagle and the wing
of a beetle have the same
function but are constructed in
different ways from different
material.
3. Comparative Embryology
– vertebrae embryos exhibit homologous
structures during certain phases of
development but become totally different
structures in the adult form.
1. Head
2. Pharyngeal Pouches
3. Tail
Bird Embryo
Human Embryo
4. Comparative Biochemistry
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scientific data shows that common ancestry
can be seen in metabolic molecules:
- cytochrome c (see Fig. 15.9, page 427)
- DNA/RNA
- other proteins, as well
5. Geographic Distribution – of plants
and animals
- Darwin observed that animals on the S.
American mainland were more similar
to other S. American animals than they
were to animals living in similar
environments in Europe.
Ratite Birds
PBS Video Clips
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http://www.pbs.org/wgbh/evolution/educ
ators/teachstuds/svideos.html
Watch “Isn’t Evolution Just a Theory?”
Watch “Who Was Charles Darwin?”