Evidence of Evolution
Chapter 15
Part II
1. Fossil Record
 Are able to observe links between modern forms and
ancestors (ex. transition species)
 Relative age- age compared to other fossils by
referring to the geologic time scale and records of
known fossils
 Absolute age- use of radiometric dating to date rocks
2. Biogeography
 Geographical distribution of species
 New organisms arise in same geographic
area where similar forms already lived

Example) Australia – has native wolves, cats,
mice, moles, and anteaters. Most mammals are
marsupials (animals evolved in isolation)
Ex) Ancient Irish Elk
Ex) European Elk
3. Anatomy and Embryology
 Homologous structures- anatomical structures
that occur in different species that originated
in most recent common ancestor

may have different functions but look similar
Common Ancestor:
Human
Bat
 Analogous Structuresa body part similar in function to another
organism due to environmental pressures
Ex) the wings of a fly, a moth, and a bird developed
independently as adaptations to a common function –
flying
Analogy vs. Homology
 Vestigial structures- a part of an
organism with little or no function but
which had a function in an ancestral
species
 Comparative Embryology- Study of
structures that appear during embryonic
development

Ex)All vertebrate embryos go though a stage in
which they have gill pouches on the sides of
their throats
4. Molecular Biology (DNA and Proteins)
 Comparison of DNA, RNA, and amino acid
sequences
 Greater the number of similarities, the more closely
the species are related through a common ancestor
 Shows the common descent of the most diverse
organisms.
Amino Acid Chart
Evidence of Evolution:
fossil evidence, homologous structures, embryology,
vestigial organs, biochemical
 Bones in bird’s wing and human’s arm are similar in
structure.
 All organisms use ATP to transfer energy.
 There are similarities in structure among the early
stages of fish, birds and humans.
 Humans, unlike rabbits, have no known use for
their appendix.
 Horses have increased in size and decreased in
number of toes since the Eocene.
Phylogeny
 The relationships by ancestry among
groups of organism
 Represented by the “Tree of Life”
 Different evidence supports different
“trees”
Patterns of Evolution
 1. Coevolution
 2. Convergent Evolution
 3. Divergent Evolution
1. Coevolution
 When two or more species have evolved
adaptations that influence each other
(evolutionary “arms race”)
 Examples:




Predator-prey
Parasite-host
Plant-animal pollinator (bee and flower)
Humans have developed and used
antibiotics to kill bacteria, bacteria have
evolved to become antibiotic resistant
2. Convergent Evolution
 Organisms appear to be similar but are not
closely related at all
 The environment selects similar traits
 Result in analagous structures

Ex) dolphin and shark
3. Divergent Evolution
 Two or more biological characteristics
become more and more dissimilar in
response to different habitats
 Adaptive radiation- a new population in a
new environment (island) will undergo
evolution until the population fills many
parts of the environment
Ex) Galapagos finches
Caribbean Anole Lizards
Artificial Selection
 The intentional breeding (by humans) of certain
traits, or combination of traits, over others