Evidence of
Evolution
Main Types of Evidence
1. Fossils
2. Homologous structures
3. Embryology
Fossil record
• Layers of rock contain fossils
o new layers cover older ones
• creates a record over time
o fossils show a series of organisms have
lived on Earth
• over a long period of time
Fossils tell a story…
the Earth is old
Life is old
Life on Earth has changed
Fossil Record
• Fossils are evolutionary evidence
• Fossils show that ancient species share similarities
with species that now live on Earth.
• Fossils records provide evidence that living things
have changed over time.
Glyptodont
Armadillo
Comparing Anatomy
• Homologous structures
• Analogous structures
• Vestigial structures
Compare the bones
• The same bones under the skin
o limbs that perform different functions are built from the same bones
How could these
very different animals
have the
same bones?
Homologous structures
• Structures that come from the same origin
• homo- = same
• -logous = information
• Anatomically similar structures inherited from a
common ancestor
• These structures can be similar in arrangement
and/or function.
Homologous structures
• Forelimbs of human, cats, whales, & bats
o same structure
• on the inside
o same development in embryo
o different functions
• on the outside
o evidence of common ancestor
Analogous Structures
• Structures that do not have a common evolutionary
origin but are similar in structure.
• Shows that functionally similar features can evolve
independently of each other
• Ex: wing of an insect and wing of bird
Analogous Structures
Vestigial Structures
• A body structure that has no function in a presentday organism but was probably useful to an
ancestor.
• This shows a change over time
• Hind leg bones on whale fossils
Why would whales
have pelvis & leg bones
if they were always sea
creatures?
Because they
used to
walk on land!
Chapter
15
Evolution
Comparing Embryos
• Embryo: the earliest
stage of growth and
development of both
plants and animals
• Vertebrate embryos
exhibit homologous
structures during certain
phases of development
but become totally
different structures in the
adult forms.
Comparing Embryos
• Similar embryo development may suggest a
common ancestor
Biochemical Evidence
• Common ancestry
can be seen in the
complex metabolic
molecules that many
different organisms
share.
• Comparison of the
DNA or RNA of
different species
produce biochemical
evidence for evolution
Biochemical Evidence
• Comparisons of the similarities in amino acids and
other molecules across species reflect evolutionary
patterns seen in comparative anatomy and in the
fossil record.
Knowledge Check
True or False
Organisms with similar anatomy share
similar DNA sequences.
Knowledge Check
Which of the following best explains how the fossil record
provides evidence that evolution has occurred?
A
B
C
D
It indicates the exact cause of structural and
behavioral adaptations of organisms.
It shows that the form and structure of groups of
organisms have changed over time.
It shows how the embryos of many different vertebrate
species are very similar.
It indicates that forms of life existed on Earth at least
3.5 billion years ago.
Knowledge Check
The occurrence of the same blood protein in a group of
species provides evidence that these species
a. evolved in the same habitat.
b. evolved in different habitats.
c. descended from a common ancestor.
d. descended from different ancestors.