Transcript Evidence for Evolution

The Fossil Record
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The fossil record provides
physical evidence about
history of life on Earth. It
shows how different
groups of organisms,
including species have
changed over time.
Fossils of insects,
mammoths, and footprints
are just a few examples of
the different remains
paleontologists have found.
WHAT ARE FOSSILS?
– Fossils are
preserved remains
or trace remains of
ancient life forms
that once lived on
Earth.
– Scientist use fossils
to infer what the
past life form and
environment were
like.
The Fossil Records
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Here we see the fossil
record of modern
horses.
As you can see the
forefeet and teeth of
the horse have changed
over time.
American Beaver: Lives in North America
Coypu: Lives in South America
Muskrat: Lives in the North and Central America
Capybara: Lives in South America
Geographic Distribution of Organisms
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Darwin noticed that organisms in different
regions of the world had similarities in physical
appearance and structure.
As you can see these 4 different species have
similar characteristics such as teeth, limbs, hair,
nose, diet and habitat.
Scientists hypothesize that a common ancestor of
these species settled in different regions and
evolved to suit the different habitats. The result
being the 4 different species seen here.
Geographic Distribution of Organisms
Even though these species are separated by thousands of miles of land and water you
can see similarities in characteristics that have allowed them to survive. Perhaps an
ancient ancestral group of organisms with similar traits evolved into these 4 species
changing to suit their different environments.
Similarities in Embryology
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Embryology is the study of development of an embryo, or fertilized egg. As the
embryo grows it follows a pattern of changes. Scientists compare this pattern of
growth between different species.
Since the fish, turtle, salamander and human have similar first stage of development
we can see they may have had a common ancestor at some point in the distant past.
But, if we compare the salamander and fish we see more similarities, leading us to
think they shared a common ancestor more recently.
Comparing Patterns of Embryology in
different species
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Here we can see more patterns of
development. Scientists call similarities
in patterns of development
homologies.
You can see homologies between all 4
species at the first stage of
development.
But when you look at the 2nd stage you
only see homologies within the reptile
group (lizard and tortoise) and mammal
group (pig and human).
Homologous Structures in Different Species
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Structures that have different mature forms but develop from the same embryonic tissues
are called homologous structures.
Here we can see the homologous arm structures of 4 different species. Since they possess
homologous structures they may have a common ancestor. Each arm has adapted in ways
that enable organisms to survive in different environments. Therefore changing into
different species.
Homologous Structures in Different Species
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Here is another excellent example of
homologous structures as evidence for
evolution.
The similarities are obvious but it’s the
differences that really support evolutionary
theory.
Each species has adapted to suit its
particular environment.
The Tarsier leaps and clings to rocks. Its
large finger pads helps it do this.
The gibbon swings from tree to tree and has
elongated strong fingers to do so.
The chimpanzee may be able to manipulate
crude tools with its stubby thumb, but the
human thumb faces the forefinger. This
provides the dexterity for countless
purposes.
DNA Sequences
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Scientists look for similarities
and differences in the
sequences of nitrogen bases
from samples of DNA in
different species.
Based on similarities they
draw conclusions about
common ancestry.
Here we can see the Pax6
gene in several different
species.
The pax6 gene is the master
gene for the early
development of the eye.
In all 4 species there is a large
similarity in gene structure
leading us to believe the gene
was also in their common
ancestor.
DNA Sequences
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This diagram shows the
number of amino acid
differences between the
hemoglobin proteins in
different species.
The Macaque and Human
have only 8 amino acids
different making them more
closely related compared to
the Dog.
But, the Dog is more related
than a bird because the Dog
has only 32 amino acids
different compared to 45 for
the bird.
Finally the Lamprey is least
related because it has 125
different amino acids, more
than any of the other
organisms.