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Transcript
Evidence for Evolution

Biogeography

Fossil Records



Comparative
anatomy
Comparative
embryology
Molecular biology

Evolution is
consistent with all
scientific
observations!
Biogeography



Species are most closely
related to those near
them
Rain forests in different
parts of the world have
very different species
Species tend to be very
similar to the fossils found
in there area – but with
some changes
Fossil Records
The age of
different fossils
matches what we
would expect
 I.e. we find that
brain size has
increased over
time

Fossils Con.


Oldest vertebrate
fossils are fish, then
amphibians, reptiles,
mammals and birds
Many hypothesized
intermediate species
have been found, i.e.
Artie, Lucy, fish with
legs
Comparative Anatomy



The anatomies of
related species are
similar, even if they are
used differently
i.e. bones of humans,
cats whales and bats
are similar
It seems unlikely a
designer would make a Homologous Structures
bat's wing similar to a
whale's fin
Vestigial Organs



Leftover body parts
that do not help a
species
i.e. whales still have
pelvises and remnants
of leg bones
These structures serve
no purpose in the
modern animal
Comparative Embryology


Similar species develop in very similar ways
Especially early in development, before lots of
specialization has occurred
Molecular Biology


Closely related species
are closely related in
their genetic codes
Also supports idea that
all species are relatedall species share DNA
and some proteins
The “Theory” of Evolution



The closely related
nature of all life is
really not debatable
Natural selection is
really the theory
Well documented
and thoroughly
supported- like the
“Theory” of Gravity
Macroevolution and Speciation
•Microevolution
explains how
populations can
change over time
•But how do new
species or other
taxonomic groups
arise?
Geographic Speciation
•The formation of new species usually occurs
when 2 populations are separated and evolve
differently
•Eventually the species have changed so much
that they can no longer reproduce
Reproductive Isolation
•A byproduct of genetic
differences
•Different:
•Mating behaviors
•Mating times
•Mating locations
•Mating “structures”
•Gametes
•Or offspring that are
infertile- no mixing of genes
Reproductive Isolation 
Speciation
•With no gene flow
between the
population, they
become more and
more different
•This usually takes
thousands to
millions of years
Exception - Polyploidy
•Occasionally plants end
up combing their full
genomes (instead of
half) leading to a
doubling of the
chromosome #
•Instantly forms a new
species
•Extremely significant in
plant evolution
Biological Definition of Species
•2 populations that
cannot naturally
mix genes
•Due to any of the
reproductive
isolation methods
•Not a perfect
system
Evolution is Always Occurring
•Usually just slowly
•Bacteria and
viruses change
over time – we
must constantly
come up with new
antibiotics and new
vaccines
Changing Environments
Accelerate Evolution
•New habitats open up opportunities for evolution
•Leads to adaptive radiations – where many
groups evolve from a single ancestor
•i.e. after the fall of dinosaurs- many mammal
groups evolved
One Major Change leads to many
New Adaptive Radiations



Imagine the first
species that could
breath in air
Many new species
would quickly evolve
– lots of territories to
take over!
Then evolution would
slow down once there
is competition for
space
Extinction
•Is the norm
•Most species go
extinct- but new
ones survive
•There have been
at least 5 major
mass extinctions
Phylogeny and Taxonomy
Tracing Evolutionary History
Phylogenetic Trees



Show how each
species is related to
other closely related
species
Shows common
ancestors
Use fossils and other
evidence to reconstruct
an organisms history
Monophyletic Taxa


We want to trace
species to a single
common ancestor for
each taxa, and include
every species that
descended from that
ancestor
i.e. all mammals can be
traced to a single
mammalian ancestor
Monophyletic Taxa
•Includes a species
and every single
one of it’s
descendents
•I.e. Primates –
include the primate
ancestor and all of
it’s descendents
(including us!)
NOT a Monophyletic Taxa
•Plants and Animals
(because fungi and other
species share the same
common ancestor)
•Grouping all
monkeys/apes together
BUT not including humans
•Reptiles (birds share the
same common ancestor
and should be included in
reptiles!)
How Do We Make Trees?
•Comparing DNA
•Comparing
fossils/anatomies/structure/devel
opment
Molecular Biology Provides Great
Evidence for Classification



Similarities in DNA
sequence
Comparison of
proteins
The more DNA
changes/protein
differences, the
less closely related
the species
Molecular Analysis
Advantages
•Most accurate
Disadvantages
•Individuals of the
same species differ in
•Large numbers of
traits/proteins to analyze DNA
•Allows us to
•Can be confusing
differentiate between
closely related species
that appear very similar
DNA Base Pair Differences
1
2
3
4
5
1
x
10
20
30
40
2
10
x
10
20
30
3
20
10
x
10
20
4
30
20
10
x
10
5
40
30
20
10
x
1
2
3
4
5
1
x
10
20
30
40
2
10
x
10
20
30
3
20
10
x
10
20
4
30
20
10
x
10
5
40
30
20
10
x
Practice
(# of base pair differences in a gene)
Cat
Dog
Wolf
Skunk
Otter
Cat
x
28
26
15
14
Dog
28
x
2
10
9
Wolf
26
2
x
9
8
Skunk
15
10
9
x
2
Otter
14
9
8
2
x
Phylogenetic Tree
Time
Homology/Anatomy Analysis


Find an
adaptation that is
present in one
lineage, but not
in another
The phylogenetic
tree branches
when these new
features evolved
Cladistic Tables
Different Species
1
2
3
4
5
Character A?
Yes
Yes
Yes
Yes
Yes
Character B?
No
Yes
Yes
Yes
Yes
Character C?
No
No
Yes
Yes
Yes
Character D?
No
No
No
Yes
Yes
Character E?
No
No
No
No
Yes
1
2
3
4
5
Character A?
Yes
Yes
Yes
Yes
Yes
Character B?
No
Yes
Yes
Yes
Yes
Character C?
No
No
Yes
Yes
Yes
Character D?
No
No
No
Yes
Yes
Character E?
No
No
No
No
Yes
Practice
DNA
Organelles
Cell Walls
Amnion
Hair
Reptiles
Y
Y
N
Y
N
Plants
Y
Y
Y
N
N
Mammals
Y
Y
N
Y
Y
Bacteria
Y
N
N
N
N
Amphibians
Y
Y
N
N
N
Time
Ancestral reptile
Ancestral fish
Ancestral animal
Anatomy Analysis
Advantages
Disadvantages
•Homologous
structures show
relationships
•Analogous structures
do not and can be
confused
•Allows us to
determine when
changes occurred
(using fossils)
•Not all species leave
fossils
•The fossils we have
collected are
•Best way to analyze incomplete
extinct species
Homology vs. Analogy

Homology means two
features are similar
due to ancestry



Wings in bats,
arms in humans,
fins in whales
Called homologous
structures
Caused by divergent
evolution




Analogy is when two
organisms have
similar features but
are not closely related
Wings in bats and
birds
Caused by
convergent
evolution
Evolved the same
solution
Embryology Analysis
Advantages
Disadvantages
•Allows us to see
similarities even
when adults of the
species look very
different
•Often similarities are
lost later in
development
• i.e. We have gills
early on in
•I.e. reptiles and birds development
look more closely
related
We did not evolve from
chimpanzees!