Transcript Section 17-2

Concept Map
Section 17-2
Evolution of Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.
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Figure 17-8 Miller-Urey Experiment
Section 17-2
Mixture of gases
simulating
atmospheres of
early Earth
Spark simulating
lightning storms
Condensation
chamber
Water
vapor
Cold
water
cools
chamber,
causing
droplets
to form
Liquid containing
amino acids and
other organic
compounds
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Figure 17-12 Endosymbiotic Theory
Section 17-2
Chloroplast
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Plants and
plantlike
protists
Photosynthetic
bacteria
Mitochondrion
Primitive Photosynthetic
Eukaryote
Ancient Anaerobic
Prokaryote
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Primitive Aerobic
Eukaryote
Animals, fungi, and
non-plantlike protists
Geologic Time Scale with Key Events
Section 17-3
Era
Cenozoic
Mesozoic
Paleozoic
Precambrian
Time
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Period
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Time
(millions of
years ago)
1.8–present
65–1.8
145–65
208–145
245–208
290–245
363–290
410–363
440–410
505–440
544–505
650–544
Key Events
Glaciations; mammals increased; humans
Mammals diversified; grasses
Aquatic reptiles diversified; flowering plants; mass extinction
Dinosaurs diversified; birds
Dinosaurs; small mammals; cone-bearing plants
Reptiles diversified; seed plants; mass extinction
Reptiles; winged insects diversified; coal swamps
Fishes diversified; land vertebrates (primitive amphibians)
Land plants; land animals (arthropods)
Aquatic arthropods; mollusks; vertebrates (jawless fishes)
Marine invertebrates diversified; most animal phyla evolved
Anaerobic, then photosynthetic prokaryotes; eukaryotes,
then multicellular life
Patterns of Evolution
Section 17-4
Macroevolution refers to large-scale
evolutionary patterns and processes that
occur over long periods of time. Includes
extinction, adaptive radiation, convergent
evolution, coevolution, punctuated
equilibrium, and changes in developmental
genes.
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Extinction
• More than 99% of all species that have every lived are now
extinct.
• Occur because species compete for resources and
environments change (natural selection).
• Mass extinctions wiped out entire ecosytems. Food webs
collapsed and disrupted energy flow through the biosphere.
– Most mass extinctions caused by several factors.
– Large volcanoes erupting, continents moving, sea levels changing.
– Leads to burst of evolution as species fill niches.
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Adaptive Radiation
• A single species or a small group of species has evolved,
through natural selection and other processes, into diverse
forms that live in different ways.
– Darwin’s finches – more that a dozen species evolved
from a single species.
– Dinosaurs – ruled earth for about 150 million years.
– Mammals – disappearance of dinosaurs lead to adaptive
radiation of mammals.
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Convergent Evolution
• Process in which unrelated organisms come to resemble
one another.
• Groups of different organisms, such as mammals and
dinosaurs, undergo adaptive radiation in different places or
at different times but in ecologically similar environments.
Face similar environmental pressures. Natural selection
molds different body structures into modified forms (arms
and legs into wings and flippers).
• Analogous structures – look and function similarly but are
made up of parts that do not share a common evolutionary
history.
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Coevolution
• Organisms that are closely connected to one another by
ecological interactions evolve together.
– Flowers and pollinators
• As evolutionary change in one organism may also be
followed by a corresponding change in another organism.
• Analogous structures – look and function similarly but are
made up of parts that do not share a common evolutionary
history.
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Punctuated Equilibrium
• Fossil records show that some organisms evolved gradually
over time.
• Others are in equilibrium – have changed little over time.
• Long, stable periods are interrupted by brief periods of
more rapid change – punctuated equilibrium. May occur
when
– a small population becomes isolated from the main part of the
population or a small group migrates to a new environment.
– a mass extinction occurs.
– Organisms evolve rapidly to fill available niches.
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Flowchart
Section 17-4
Species
that are
Unrelated
form
Related
in
under
under
in
in
Interrelationshiops
Similar
environments
Intense
environmental
pressure
Small
populations
Different
environments
can undergo
can undergo
can undergo
can undergo
can undergo
Coevolution
Convergent
evolution
Extinction
Punctuated
equilibrium
Adaptive
radiation
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Videos
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Geologic Time
Evolution of Cells
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Career links on fossil preparators
Interactive test
For links on the fossil record, go to www.SciLinks.org and enter the
Web Code as follows: cbn-5171.
For links on eukaryotic cells, go to www.SciLinks.org and enter the Web
Code as follows: cbn-5172.
For links on extinction, go to www.SciLinks.org and enter the Web Code
as follows: cbn-5174.