Download Chapter 15 Evolution

15.2 Evidence of Evolution
Main idea: Multiple lines of evidence support the
theory of evolution.
Objectives:
 Describe how fossils provide evidence of
evolution.
 Discuss morphological evidence of evolution.
 Explain how physiology and biochemistry
provide evidence of evolution.
New Vocabulary
 Derived trait
 Ancestral trait
 Homologous structure
 Vestigial structure
 Analogous structure
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Embryo
Fitness
Mimicry
Camouflage
Support for Evolution
The theory of evolution states that all
organisms on Earth have descended from a
common ancestor.
The fossil record offers some of the most
significant evidence of evolutionary change.
 Fossils provide a record of species that
lived long ago.
 Fossils show that ancient species share
similarities with species that now live on
Earth.
Support for Evolution
The Fossil Record
The giant armadillo-like
Glyptodon is an extinct
animal that Darwin
thought must be related to
the living armadillos of
today.
The fossil record provides
information for
determining the ancestry
of organisms and the
patterns of evolution.
Support for Evolution
The Fossil Record
Two major classes of traits:
Derived traits are newly evolved
features, such as feathers, that do not
appear in the fossils of common
ancestors.
Ancestral traits are more primitive
features, such as teeth and tails, that
do appear in ancestral forms.
Support for Evolution
The Fossil Record
Transitional fossils provide detailed patterns
of evolutionary change for ancestors of
many modern animals, including mollusks,
horses, whales and humans.
Example:

Archeopteryx
Shares features of
both dinosaurs
and birds.
Support for Evolution
Comparative Anatomy
Homologous
structures are
anatomically
similar structures
inherited from a
common
ancestor.
The forelimbs of
vertebrates are
adapted for
different uses,
but they all have
similar bones.
Similar structure; different
function.
Support for Evolution
Comparative Anatomy
Vestigial structures are
the reduced forms of
functional structures in
other organisms.
Evolutionary theory
predicts that features
of ancestors that no
longer have a function
for that species will
become smaller over
time until they are lost.
Same structure; reduced
function
Examples: Snake pelvis,
human appendix, blind
fish and salamanders that
live in caves but have
eyes.
Support for Evolution
Comparative Anatomy
Analogous structures can be used
for the same purpose and can be
similar in construction, but are not
inherited from a common
ancestor.
Analogous structures show that
functionally similar features can
evolve independently in similar
environments.
Different structure; same function
Support for Evolution
Comparative Anatomy
Analogous structures example:

Human eye and squid eye
Similarities
 The iris to regulate light entering the lens
 Each eye is filled with fluid
 Both eyes use a lens to focus
function;
Support for Evolution
Comparative Embryology
An embryo is an early pre-birth stage of an
organism’s development.
Vertebrate
embryos exhibit
homologous
structures
during certain
phases of
development
but become
totally different
structures in
the adult forms.
Support for Evolution
Comparative Biochemistry
Common ancestry can be
seen in the complex
molecules that many
different organisms share.
Molecules are similar
because the organisms
have a common ancestor
Species
Sequence of Amino Acids in
the same part of
Hemoglobin Molecules
Human
Lys-Glu-His-Iso
Horse
Arg-Lys-His-Lys
Gorilla
Lys-Glu-His-Lys
Chimpanzee
Lys-Gu-His-Iso
Zebra
Arg-Lys-His-Arg
The genomes of humans and chimpanzees differ by
only about 1% of their genetic makeup
Scientists now use similarities in DNA and RNA
sequences to determine relationships between species
Support for Evolution
Geographic Distribution
The distribution of plants and animals that
Darwin saw during his travels first
suggested evolution to Darwin.
Rabbit in Europe
Mara in S. America
Support for Evolution
Geographic Distribution
Scientists have
confirmed and
expanded Darwin’s
study of the distribution
of plants and animals
around the world in a
field of study now called
biogeography.
Evolution is intimately linked with
climate and geological forces.
Adaptation
An adaptation is a trait
shaped by natural
selection that increases
an organism’s
reproductive success.
Fitness is a measure of the relative
contribution an individual trait makes to the
next generation. It is often measured as the
number of reproductively viable offspring that
an organism produces in the next generation.
Adaptation
Types of Adaptation
Camouflage allows
organisms to become
almost invisible to
predators. Some species
have evolved morphological
adaptations that allow them
to blend in with their
environments.
Mimicry is another
morphological adaptation
that allows one species to
evolve to resemble
another species.
Adaptation
Types of Adaptation
Can you see the peppered moth?
Adaptation
Types of Adaptation
When disturbed,
this octopus flashes
and intensifies its
stripes, resembling
a poisonous sea
snake. Unlike the
sea snake, the
octopus venom is
harmless
Adaptation
Types of Adaptation
Antimicrobial resistance
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An antibiotic is a medicine that
slows or kills the growth of
bacteria.
Bacteria originally killed by
antibiotics like penicillin have
evolved quickly into populations
of resistant bacteria.
For most antibiotics, at least one species of resistant
bacteria exists.
People infected with resistant bacteria can never get
rid of it.
Adaptation
Types of Adaptation
Traits may decrease fitness

Some features arise as a consequence of other
evolutionary changes.
• Human babies are born helpless at an earlier
developmental stage than other primates as a
consequence of the mother’s narrow birth canal.
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Narrow birth canal is an
adaptation that enables
walking on 2 legs instead of 4.
Early birth is not an adaptation
but instead a consequence of
evolution.