Evidence for Evolution
Comparative Anatomy (Homology)
– Similarity resulting from common ancestry
• Homologous structures
– anatomical resemblances that represent variations
on a structural theme that was present in a common
ancestor
Human
Figure 22.14
Cat
Whale
Bat
Comparative embryology
– Anatomical homologies not visible in adult
organisms
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Figure 22.15
Human embryo
Molecular Homologies
• Genes and proteins that are shared among
organisms inherited from a common ancestor
• Anatomical resemblances among species
– Reflected in their molecules, genes, and gene
products
Species
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
100%
Human
Rhesus monkey
95%
Mouse
87%
Chicken
69%
Frog
Figure 22.16
Lamprey
54%
14%
Biogeography
• Similar mammals that have adapted to similar
environments, have evolved independently from
different ancestors
NORTH
AMERICA
Sugar
glider
AUSTRALIA
Flying
squirrel
Figure 22.17
• The Darwinian view of life
– Predicts that evolutionary transitions should leave
signs in the fossil record
– Fossils of many such transitional forms have been
found
Figure 22.18
• In science, a theory (e.g. evolution)
– Accounts for many observations, facts, laws, and
data and explains and integrates a great variety of
phenomena