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Evidence for Evolution
What was the definition
of evolution?
Biological evolution
is defined as the
genetic change in a
population of an
organism over time.
(2016)
Evidence to Support Evolution
There is an abundance of evidence from
many areas of science to support the Theory
of Evolution. This scientific evidence is
gathered by observing the world around us.
The 5 main categories of evidence are:
1. Biogeography
2. Fossil Evidence
3. Anatomy
4. Comparative Embryology
5. Molecular Biology (DNA and proteins)
1. Biogeography
In the early 1900’s
Alfred Wegner stated
that all the
continents had
originally been
joined into one super
continent called
Pangea.
Here are the
continents 300 mya.
1. Biogeography
The geology of the rocks also supports the theory.
1. Biogeography
We have found fossils from the Pangea era on the
corresponding locations of different continents.
1. Biogeography
Biogeography is
the study of the
past and present
geographical
distribution of
species.
Geographically close environments are more likely to be
populated by related species than geographically
separate species.
Animals on islands often closely resemble animals on
the closest continent.
2. Fossil Record
Fossils appear in chronological (time)
order in layers of sedimentary rock.
Fossils in young layers of rock are more
similar to species alive today.
Usually only bones form fossils when they
are buried under sediment.
Fossils are one of the strongest pieces of
evidence to support the Theory of
Evolution.
2. Transitional Fossils
Transitional fossils show links between
groups of prehistoric organisms and help
scientists better understand relationships
between group of organisms.
Vestigial structures are reduced forms of
structures that once were useful in
ancestors but are no longer needed by the
organism today. Ex. Pelvic bone in whales
• The
Archeopteryx
fossil showed
the transition
from reptile to
bird.
• This was the
first reptilian
fossil found
with feathers!
3. Anatomy
Homologous structures in mammal forelimbs.
How are the ulna and phalanges different?
3. Anatomy
Homologous structures in whale ancestors and
current whale limbs.
Homologous
structures are
structures that
have similar parts
and a common
ancestry or origin
but have different
functions now.
Ex. Bat wings and
human hands
3. Anatomy
Analogous
structures are
structures that perform
a similar function now
but do not have a
common evolutionary
origin.
Ex. Insect wings and
bat wings
4. Comparative Embryology
This is the study of structures that appear
during embryonic development.
Similarities in development are indicative of
common ancestry.
Here are
pictures
comparing
vertebrate
embryos.
4. Comparative Embryology
• For example, all vertebrate embryos have
structures called pharyngeal pouches in their
throat at some stage in their development.
• These embryonic structures develop into very
different, but still homologous, adult structures,
such as the gills of fish or the Eustachian tubes in
mammals.
5. Molecular biology
• By comparing the DNA of
different organisms,
scientists can determine
their degree of
relatedness.
• Each DNA gene controls
the production of a protein.
• Proteins control the
structure and function of
an organism.
5. Molecular biology
• By comparing the DNA or
RNA of different
organisms, scientists can
determine their degree of
relatedness.
• Each gene controls the
production of a protein.
• Proteins control the
structure and function of
an organism.
5. Molecular biology
Here scientists compare
the amino acid
sequences that make up
the hemoglobin protein
in different organisms.
The amino acid
sequence of a protein
depends on the nitrogen
base sequence in the
DNA (GCAT).
Conclusion
The major areas of evolutionary evidence
are compared to make the best theory for
evolution of a specific organism or to decide
on a family tree.
PBS – How Do We Know Evolution
Happens? Introduction to whale activity
https://www.youtube.com/watch?v=cFljTjJwy1k