Transcript 7.2 Evidence of Evolution

7.3.c Students know how independent lines of
evidence from geology, fossils, and comparative
anatomy provide the bases for the theory of evolution.
7.4.e Students know fossils provide evidence of how
life and environmental conditions have changed.
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Key Concept: Similar body structures, patterns
of early development, molecular structures,
and fossils all provide evidence that organisms
have changed over time.
Comparative anatomy- the comparison of the
structures of different organisms
Similarities in body structure:
 Homologous structures: similar structures that
related species have inherited from a common
ancestor
All probably
inherited
similar
structure from
early ancestor
they all share
Orange
bones are
homologous
structures
Similarities in early development:
 Some species look similar in early stages of life
 Share a common ancestor
Similarities in DNA and proteins:
 If two species have similar DNA and proteins,
probably evolved from same ancestor
Most fossils form:
 Organisms that die become buried in
sediments
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Sediments = particles of soil or rock
Bird Fossil
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Most common fossils are molds and casts
Mold- a hollow area in sediment in the shape
of an organism or part of an organism
Cast- solid copy of the shape of an organism
Petrified fossil- fossils which minerals replace
all or part of an organism
Sediments cover organism, water rich in
dissolved minerals soak into spaces, over time
minerals come out of the solution and harden
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Trace fossil- provide evidence of ancient
organisms
Foot prints are an example of a trace fossil
Sediment buries footprint, sediment becomes
rock, and preserves footprint
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Preserve the remains with little or no change
Types of preserved remains- tar, amber, and ice
Tar- tar soaked into bones preserving bones from
decay
Amber- trapped on sticky resin, resin covers
organism, sealing it from the air, protecting it from
decay
Ice- freezing has preserved hair and skin too
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Paleontologistsscientists who study
fossils
Key concept: The
fossil record provides
evidence about the life
and past
environments on
Earth. In addition,
scientists use fossils to
study the rate at
which evolution has
occurred.
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Oldest rock layers contain the oldest fossils
Oldest fossils are of simple organisms like
bacteria
Fossils found in the area also gives
paleontologists an idea of what the
environment looked like
Fossils show how environment has changed
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Gradualism- is a hypothesis
that proposes that evolution
occurs slowly but steadily
Punctuated equilibria- is a
hypothesis that accounts for
the gaps in the fossil record,
species evolve quickly during
relatively short periodsperiods of rapid change are
separated by long periods of
little or no change
Most scientists think that
evolution can occur gradually
at some times and more
rapidly at others
Scientists use evidence from:
 Fossils
 Body structures
 Early development
 DNA and protein structures
to determine the evolutionary relationship
among species