Transcript Evidence for Evolution

Evidence for Evolution
Macroevolution
Large scale
changes that
take place over
a long period of
time that create
and eliminate
species.
Microevolution
Short time scale events (generation-togeneration) that change the genotypes and
Evidence for Macroevolution
Fossils Record
 Comparative Biochemistry & Molecular
Biology
 Comparative Morphology
 Vestigial Structures
 Comparative Embryology
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Evidence for Evolution – The Fossil Record
Fossil Record
Fossils are the remains of ancient life.
 When fossils are arranged according to their
age, a progressive series of changes are seen.
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The Law of Superposition states that a layer of
rock is older than the layer above it.
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Radioactive Dating can be used to date rocks
layers rocks in which fossils occur, we can get a very
accurate idea of how old the fossils are.
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This allows fossils to be arranged by their relative age to
each other.
This allows for a time frame for when fossils formed.
Transitional forms are evidence for evolutionary
change.
Fossil Gaps
Gaps remain in the in the fossil records of
many species, although a lot of them
shrink each year as new fossils are
discovered.
 These gaps do not indicate weakness in
the theory of evolution; they point out
uncertainties in our understanding of
exactly how some species evolved.
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Dinosaur tracks are
common occurrences
in the southern and
eastern U.S.
Here is a section of
tracks that were
recently uncovered.
Can you answer the
following questions?
•What is the size and
nature of the organisms?
•Were the tracks made at
the same time?
•How many animals were
involved?
•Can you reconstruct the
events that occurred?
•In what direction did the
animals move?
•Did they change speed or
direction?
•Was the soil moist or dry?
The following summer
some more digging
revealed more of the
track. What additional
information have you
gained that allows you
to refine your answers?
•Were the tracks made
at the same time?
•How many animals
were involved?
•Can you reconstruct the
events that occurred?
•In what direction did
the animals move?
•Did they change speed
or direction?
In the final summer of
the excavation one last
part of the footprint
trail was uncovered.
Does this section
provide additional
information to refine
your hypothesis?
So what happened?
Who’s explanation is
right?
The fossil record
provides us with the
facts of what
organisms were
present but not how
they interacted with
one another or their
environment.
Evidence of Evolution –Comparative Biochemistry & Molecular Biology
Comparative Biochemistry & Molecular
Biology
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All organisms from bacteria to humans share
many of the same biochemical details.
The genetic code for protein-coding genes is nearly
universal in eukaryotes and prokaryotes.
 All organisms use ATP as an important energy carrier.
 Similarly, the plasma membranes of all organisms,
eukaryotic and prokaryotic, are structurally similar,
consisting of a phospholipid bi-layer.
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# of amino acid differences between human
hemoglobin and other organisms.
Human DNA Compared to other
Primates
If humans and chimps are more
closely related (=have had a
common ancestor more recently),
then we would expect the DNA
sequences of humans and
chimps to be more similar as
well.
 Three phylogenetic trees
were reconstructed based on
the DNA sequences of:
(a) 4700 bp of
mitochondrial DNA,
 (b) the testis specific
protein on the Y
chromosome,
 (c) noncoding regions of
the -globin gene.
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Evidence for Evolution - Comparative Morphology
Homologous Structures
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Homologous structures are parts of different
organisms, often quite dissimilar, that develop from the
same ancestral part.
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All vertebrates contain a similar pattern of organs, suggesting
that they are related to each other.
The forelimbs of all mammals contain the same pattern of
bones, although the bones now carry out a variety of functions.
Ex: horse leg, bat wing, human arm, whale flipper
Homologous structures teach us an important lesson
about evolution:
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Evolution works primarily by modifying pre-existing structures.
Even when two species function in completely different ways,
they often use homologous structures to carry out those
functions.
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All tetrapods (four legged)
have limbs with five
digits, at least at some
stage in development.
Certain tetrapods lose
some of these digits
during development, as in
the bird wing shown
here.
But if the bird wing does
not need five digits, why
do five initially develop in
the growing embryo?
The most plausible
explanation is that while
the five digits are not
functionally necessary,
they represent a genetic
artifact inherited from the
ancestors of birds.
Analogous Structures
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Analogous
structures have
similar form &
function, but are
structurally quite
different
Evidence for Evolution – Vestigial Structures
Vestigial Structures
Many organisms contain structures that
have no function but that resemble
functional structures of other organisms.
 This suggests that the structures are
inherited from a common ancestor.
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 Humans
posses a complete web of muscles
for wiggling their ears just as a coyote does.
 Humans have an appendix that seems to have
no apparent function (although we may have
needed it in the past to digest food).
 Whales & snakes contain pelvic bones just as
humans do, but they serve no function.
Evidence for Evolution - Comparative Embryology
Embryo Development
During development, organisms may
exhibit characteristics of other organisms.
 This suggests that these organisms are
related to other forms.
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 The
human embryo exhibits characteristics of
the embryos of its ancestors.
 Early in their development, embryos posses
gill slits like those of fish.
 Later in development, the embryos develop a
tail.
 Human fetuses have a fine fur (lanugo)
during the fifth month of development
Evidence for Microevolution
Evolution Observed
Evolution of pesticide resistance
in response to selection.
Evidence for Evolution – Evolution Observed
Evolution of drug-resistance in HIV