1
Evidence of Evolution
Based on a large amount of evidence, most scientists agree on the following three major points
1.
Earth is about 4.5 billion years old.
2.
Organisms have inhabited the Earth for most of its history
3.
All organisms living today evolved from earlier, simpler life forms.
Fossil Evidence
Fossils provide an actual record of Earth’s past life forms. Change over time (evolution) can be seen in the
fossil record.
Fossils - Remains or traces of a once-living organism
Fossil specimens found in older rocks are different from those found in newer rocks.
Darwin predicted that the “missing links” (intermediate forms) between the great groups of organisms would
eventually be found.
Since Darwin’s time, many of these links have been found.
 Example: links between fishes & amphibians, reptiles & birds, reptiles & mammals.
The fossil record is far from complete. Finding fossils is no easy task. Not all organisms lived in areas where
fossils form.
Paleontologists - scientists who study fossils.

They can determine the age of fossils using radiometric dating (fairly accurately)
How does this help us?
 When fossils are organized from oldest to youngest, orderly patterns of evolution can be seen.
 See page 284 – 285 (Whale evolution)
Biological Molecules as Evidence
Proteins
If evolution is to have taken place, then species descended from a common ancestor.
Common ancestor - species from which two or more species have diverged.
Amino acid sequences of proteins are genetically determined.
If evolution has taken place, then a species that descended from a common ancestor in the distant past
should have more amino acid sequence differences between their proteins than do species that shared a
common ancestor more recently.

This predication was tested by analyzing the amino acid sequences of similar proteins found in
several species. See Figure 13-10. Human hemoglobin compared to other species.

The data supported the prediction. Example: Humans and gorillas have fewer differences than do
humans and chickens.
Nucleic Acids (DNA/RNA)
2
Changes in a Nucleic Acid sequence are what cause changes in the amino acid sequence of a protein.
Example: Segments of DNA called GENES code for the production of a particular protein. This code is
specific directions indicating the type and order of amino acids that will be needed to assemble the protein.
Scientists can estimate the number of nucleotide changes that have taken place in a gene since two species
diverged from a common ancestor by comparing the exact nucleotide sequence of genes.
Phylogenetic trees – show how organisms are related through evolution. Pg. 286
These provide strong evidence supporting evolution because they show the same relationships indicated by
the fossil record.
Humans and Chimpanzees are 97% genetically identical. This supports the claim that chimpanzees and
humans have a common ancestor
Anatomy and Development
Homologous Structures -Structures found in organisms that share a common ancestry but have since
evolved for different functions.
Example: Structure of the forelimbs of ALL vertebrates are made from the same basic groups of bones.
See page 287 Figure 13-13
Analogous structures - Similar features of organisms that evolve independently.
Example - Wings of a butterfly and wings of a bat
Vestigial Structures -structures that are reduced in size and function.


They are considered to be evidence or an organism’s evolutionary past.
These structures have no apparent function. (Evolutionary left-overs)
Example- internal hind-leg bones in whales
Example - Pg 287 Figure 13-12. Wings of the flightless cormorant.
Early Embryological Evidence
Page 288 Figure 13-14
Early on in development, vertebrate embryos have many similarities. Each has:
 A tail
 Pharyngeal pouches (develop into gills in amphibians and fish)
 Buds that become limbs
The structures develop at different rates in different groups of vertebrates, and are homologous structures.
3
Evidence of Evolution
Based on a large amount of evidence, most scientists agree
on the following three major points
4. Earth is about 4.5 billion years old.
5. Organisms have inhabited the Earth for most of its
history
6. All organisms living today evolved from earlier,
simpler life forms.
Fossil Evidence
Fossils provide an actual record of Earth’s past life forms.
Change over time (evolution) can be seen in the fossil
record.
Fossils - Remains or traces of a once-living organism
4
Fossil specimens found in older rocks are different from
those found in newer rocks.
Darwin predicted that the “missing links” (intermediate
forms) between the great groups of organisms would
eventually be found.
Since Darwin’s time, many of these links have been found.
 Example: links between fishes & amphibians, reptiles &
birds, reptiles & mammals.
The fossil record is far from complete. Finding fossils is no
easy task. Not all organisms lived in areas where fossils
form.
Paleontologists - scientists who study fossils.
 They can determine the age of fossils using radiometric
dating (fairly accurately)
How does this help us?
 When fossils are organized from oldest to youngest,
orderly patterns of evolution can be seen.
 See page 284 – 285 (Whale evolution)
Biological Molecules as Evidence
Proteins
If evolution is to have taken place, then species descended
from a common ancestor.
5
Common ancestor - species from which two or more species
have diverged.
Amino acid sequences of proteins are genetically
determined.
If evolution has taken place, then a species that descended
from a common ancestor in the distant past should have
more amino acid sequence differences between their
proteins than do species that shared a common ancestor
more recently.
 This predication was tested by analyzing the amino acid
sequences of similar proteins found in several species.
See Figure 13-10. Human hemoglobin compared to
other species.
 The data supported the prediction. Example: Humans
and gorillas have fewer differences than do humans and
chickens.
Nucleic Acids (DNA/RNA)
Changes in a Nucleic Acid sequence are what cause changes
in the amino acid sequence of a protein.
Example: Segments of DNA called GENES code for the
production of a particular protein. This code is specific
directions indicating the type and order of amino acids that
will be needed to assemble the protein.
6
Scientists can estimate the number of nucleotide changes
that have taken place in a gene since two species diverged
from a common ancestor by comparing the exact nucleotide
sequence of genes.
Phylogenetic trees – show how organisms are related
through evolution. Pg. 286
These provide strong evidence supporting evolution because
they show the same relationships indicated by the fossil
record.
Humans and Chimpanzees are 97% genetically identical.
This supports the claim that chimpanzees and humans have
a common ancestor
Anatomy and Development
Homologous Structures -Structures found in organisms that
share a common ancestry but have since evolved for
different functions.
Example: Structure of the forelimbs of ALL vertebrates are
made from the same basic groups of bones.
See page 287 Figure 13-13
Analogous structures - Similar features of organisms that
evolve independently.
Example - Wings of a butterfly and wings of a bat
7
Vestigial Structures -structures that are reduced in size and
function.
 They are considered to be evidence or an organism’s
evolutionary past.
 These structures have no apparent function.
(Evolutionary left-overs)
Example- internal hind-leg bones in whales
Example - Pg 287 Figure 13-12. Wings of the flightless
cormorant.
Early Embryological Evidence Page 288 Figure 13-14
Early on in development, vertebrate embryos have many
similarities. Each has:
 A tail
 Pharyngeal pouches (develop into gills in amphibians
and fish)
 Buds that become limbs
The structures develop at different rates in different groups
of vertebrates, and are homologous structures.