Download Evolution - Effingham County Schools

Descent with Modification
•
Natural Selection – A population can
change over time if individuals have
heritable traits that leave more offspring
than others
• Natural selection results
in evolutionary adaptation
– enhancing an organism’s
survival and reproduction
• Evolution is biological
change over time
The Historical Context
for Evolutional Theory
• Charles Darwin’s book, The Origins of
Species, rocked the world!
– It challenged prevailing scientific views
– It challenged a worldwide view that had been
taught for centuries, such as
• The Earth is only a few thousand years old
• The Earth is populated by unchanging
forms of life that has been individually
made during the single week in which the
Creator formed the entire universe.
Theories of Geologic Gradualism
• Study of fossils – in sedimentary rock, fossil
species that are deeper in the stratum are
more dissimilar from modern species
• Gradualism – profound change in the
cumulative product of slow but continuous
processes.
– Darwin concluded Earth must be very old
– Several slow and subtle processes can add
up to substantial change
Early Theories of Evolution
• Jean Baptiste Lamarck
– Theory of use and disuse – body parts that were
used more grew bigger and stronger; those that
were not would deteriorate. Ex. giraffe’s neck and
fiddler crab’s claw
– Inheritance of acquired
characteristics – modifications
and organism acquired during
its life could be passed down to
its offspring. Ex. with much use,
the giraffe’s neck grows longer
and this long neck is passed
down to its offspring
Scientists who influenced
Darwin
Lyell
• Principles of Geology
• Plant and animal
species emerged,
developed variations
and then became
extinct
Scientists who influenced
Darwin
• Malthus- populations outgrew their
food supplies causing competition
Essay on the
Principle of
Population
(1798)
The Darwinian Revolution
• Charles Darwin (1809 – 1882)
• At age 16 Darwin went to medical school, but
found it “boring and distasteful”
• In 1831, Darwin set sail around the world on
the HMS Beagle as the ship’s naturalist
The Darwinian Revolution
• Darwin noted that animals living on the
Galapagos Islands live nowhere else in the
world – although they resemble those on
South American’s mainland.
– Origin of new species and adaptation to
environment are closely related
The Darwinian Revolution
• By the 1840s, Darwin had already established
his theories of natural selection
• In 1859, he published “The Origin of
Species”
– He did not use the word evolution → instead he
used “descent with modification”
– Evolution is an explanation for life’s unity and
diversity
– Natural selection is the cause of adaptive
evolution
– 99% of all species that ever lived are extinct
The Darwinian Revolution
Darwin’s Main Ideas
• Natural selection is differential success in
reproduction
– Tendency towards overproduction
– Not all offspring survive (struggle for survival)
– Variations exist and are inherited
– Those best suited to their environment will live
longer and leave more offspring
– Favored traits disproportionately represented
in the next generation – thus the population
changes as a whole
Artificial selection supports these claims
Some Subtleties of Natural Selection
• Populations evolve, not individuals
• Heritable variations are amplified or
diminished (must be a heritable
variation)
• Situational – some adaptations may be
advantageous in one environment and
detrimental in another
More Examples of
Natural Selection
• Evolution of
insecticide
resistance in
hundreds of insect
species
• Evolution of
antibacterial
resistance in bacteria
species
Evidence for Evolution
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1. Fossils
2. Comparative anatomy
3. Comparative embryology
4. Biochemistry
5. Genetic evidence
6. Direct evidence
Fossils
FOSSILS
• mold or cast
of organism
left in rock,
fossilized
bone and teeth
• life becomes
more complex
over time
• record is
incomplete
Evidence for
Evolution
RELATIVE
DATING
• layers in
rock bed
used to date
organisms
Evidence for Evolution
• PHYLOGENYdescription of the
lines of descent of
organisms as they
lived through
history.
Other Evidence of Evolution
• HOMOLOGY – similarity in characteristics
resulting from common ancestry
1. Anatomical
– Homologous structures – have the
same structure, but different functions
– Vestigial organs – structures of marginal,
if any, importance to the organism
2. Embryological
– All animals have similar embryonic stages
3. Molecular
– Comparing DNA and RNA to determine how
Comparative Anatomy:
Homologous structures
Vestigial Organs
Vestigial Remains of a Pelvic Girdle in a Whale
Comparative Embryology
• the study of developing plants
and animals
Below is the pictures of embryos for a CHICKEN, FISH,
HUMAN, RABBIT, and TORTOISE . Can you guess
which one is each type of organism?
1
2
3
4
5
Comparative Embryology
Comparative Embryology- The complete picture
Evidence for Evolution
• Genetic Evidence
• Mutations- mistakes in the genetic code
– Causes changes in populations over
time
• Population genetics- researchers use
mathematical descriptions of genetic
make ups to help them trace
evolutionary trends within populations
• Selective Breeding- humans choose
plants/animals with most desirable
traits and breed them to pass those
traits to offspring
Evidence for Evolution
• Direct Evidence
• Rapid Evolution
– Strains of bacteria becoming resistant to
antibiotics
– Weeds and herbicides
– Insects and insecticides
Biogeography
• The geographic distribution of a species
• Species tend to be more closely related to
other species from the same area than to
other species with the same way of life but
living in different areas
Final words
• “Absence of evidence is not
evidence of absence.” Charles
Darwin