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13:2 Evidence of
Evolution

Fossils provide an objective record of Evolution
Fossil = A preserved or mineralized remains (bonepetrified tree – tooth – shell) or imprint of an
organism that lived long ago.
Provide record of Earth’s past life-forms.
crinoid (800 million yrs old)
pterodactyl (140 -210 million yrs old)
3 Major Points of Scientific
Agreement

1 - Earth is about 4.5 billion years old.
2 – Organisms have inhabited Earth for most of its history.
3 – All organisms living today evolved from earlier, simpler lifeforms.

Biological Molecules Contain a
Record of Evolution

Changes in a gene’s nucleotide sequence build up over time.
PROTEINS
Analysis of amino acid sequences
Species that share a common ancestor in a more distant past
(humans/frogs) have many amino acid sequence differences.
Species that share a common ancestor more recently
(humans/gorillas) have few amino acid sequence differences.
Nucleic Acids
Scientists can directly estimate the number of
nucleotide changes that have taken place in a
gene since 2 species diverged from a common
ancestor by comparing the exact nucleotides
sequence of genes.
Cladogram
Diagram that shows evolutionary relationships among
groups of organisms.

PHYLOGENETIC TREES

Diagram that shows how organisms are related
through evolution.
Anatomy and Development Suggest
Common Ancestry

VESTIGIAL STRUCTURES
Structures in different types of organisms
that often reveal basic similarities in
anatomy, even though the functions may be
very different.
Cormorant
Homologous Structures
Structures that share a common ancestry.

Forelimbs of vertebrates contain the same kinds of bones.
Embryonic Development
 A: Gradualism – Model in which gradual change
over a long period of time leads to species
formation.
 B: Punctuated Equilibrium – Model in which
periods of rapid change in species are
separated by periods of little or no change.