Download Evolution 1

Evolution Part 1
The Evidence
Evolution Outline
I. What is evolution?
II. Evidence of Evolution
A. Evidence from the past (Fossils)
B. Evidence from living organisms
-Comparative anatomy
-Comparative embryology
-Comparative biochemistry
III. Early Hypotheses Origin of Life
A. Spontaneous generation
B. Atmosphere of early earth – Stanley Miller
experiment
C. Heterotroph hypothesis
Evolution Outline (Con’t)
IV. Theories of Evolution
A. Early Theories
1. Lamarck: Theory of acquired traits
“Use and disuse”
2. Darwin and Wallace:Theory of evolution by
natural selection
B. Synthetic (Modern) Theory of Evolution
1. Population Genetics
2. Genes, Variation and Evolution
3. Hardy-Weinberg Law and Genetic Equilibrium
V. Adaptations and Natural Selection
A. Structural Adaptations
B. Behavioral Adaptations
Evolution Outline (Con’t)
VI. Types of Natural Selection
A. Directional Selection
B. Stabilizing Selection
C. Disruptive Selection
VII. Speciation and Adaptive Radiation
A. Geographic and reproductive isolation
B. Convergent evolution
C. Coevolution
VIII. Classification and Evolutionary Histories
A. Phylogenetic trees
B. Taxonomy
What is evolution?
• Evolution is the central and unifying theme in
biology.
• “Nothing in biology makes sense unless cast in
the light of evolution” – Theodozius Dobzhonski
• Evolution is the gradual change in a population
of organisms over time.
• Geologic evolution: Refers to the gradual
changes in the Earth over the last 4.5 billion
years
• Organic evolution refers to the changes in life
forms as they adapt to their changing
environments.
Is evolution real?
• There is no doubt that evolution has
occurred, is occurring, and will continue to
occur as organisms constantly adapt to
changing environments.
• Convincing evidence comes from the
fossil record.
• Fossil: any trace or remains of an
organism that has been preserved by
natural processes.
Transitional Fossils – Evidence of
Evolution Part 1
• Archeaopteryx:
• Had teeth and a long
tail like a dinosaur,
but feathers like a
bird.
• This fossils
demonstrates how
birds are modern
descendents of
dinosaours.
Transitional Fossils
• Tiktaalik: 375 million
year old fish whose fins
appear to be “limbs in
the making”
• The figure below shows
bones in the fins that are
homologous to bones
that make up the fingers,
wrists, and elbows of
terrestrial (land dwelling)
vertebrates.
Transitional fossils
• Evolving from life in
the sea to life on land
required some major
limb adjustments
• Tiktaalik is a long
awaited piece of the
puzzle of how life
transitioned from sea
to land
Sealing up “gaps” in the fossil record.
• Opponents of
evolution often point
to a “lack of evidence”
or “gaps in the fossil
record” to justify their
position.
• …but rarely change
their positions when
confronted with the
real evidence.
But surely this evolution stuff doesn’t
apply to humans.
Question to Ponder
• Why aren’t there more, lots more,
transitional fossils out there? Most fossils
are of organisms in their “complete” state.
Evidence for Evolution Part 2:
Comparative Anatomy
• What traits would you
use to classify:
-Birds
• Feathers, lay eggs
-Mammals
• Fur, milk, live young
-Reptiles
• Scales, cold-blooded,
lay eggs
• Scales, gills, fins
-Fish
Comparative Anatomy: Homologous
Structures
• Homologous Structures: are characteristics which are shared
by related species because they have been inherited in some
way from a common ancestor.
• For example, although the arms of four-limbed vertebrates
externally appear quite different, all have the same basic
underlying skeletal and muscular pattern. Such shared patterns
are best explained by the inference that they were inherited
from a common ancestor that also had this pattern.
Homologous Structures and Wing
Development
• The wings of
flies, moths and
butterflies, and
beetles are
homologous
structure
derived from a
four winged
common
ancestor.
There is also homology in gene
expression
• Similarities in
gene
expression
between
mammals
and insects
demonstrate
the common
ancestry of
ALL animals.
Comparative Anatomy: Analogous
Structures
• Would you say that a
butterfly is more
closely related to a
bird or an ant?
• But birds and
butterflies both have
wings.
• True, but the
underlying structure of
those wings are
completely different.
• Insect wings and bird wings are
considered Analogous Structures.
• Insect wings and bird wings have
evolved independently of each
other.
• They illustrate two different
evolutionary pathways to the same
result – wings.
• This is called convergent evolution
• Analogous structures do not
demonstrate common ancestry
between organisms.
Analogous Structures
• Here we can see why
vertebrate forelimbs
are considered
HOMOLOGOUS –
reflecting the common
ancestry of all
vertebrates.
• And why the wings of
insects and birds are
considered
ANALOGOUS –
reflecting the
convergent evolution
of bird and insect wings.
Comparative Anatomy:Vestigial Organs
• Some of the most
compelling evidence
supporting evolution
comes from vestigial
organs.
• Vestigial organs:
Structures that were
functional in early
ancestors, but are now
useless in present day
organisms.
• Ex. Hind-limb bones in
whales and snakes,
human appendix and
nictitating membranes
• Why does this early whale
fossil have non-functional
leg bones?
• They were used by a land
dwelling ancestor similar
to modern hippos
Vestigial leg bones found in snake fossil
• This fossil demonstrates the
evolution of snakes from
lizards.
• The loss of limbs enables
snakes to exploit new areas
in search of prey, that would
not be accessible to lizards.
• The only sensible
explanation as to why a
snake fossil would have
functionless leg bones is an
evolutionary explanation
Vestigial Eyes in Cave Dwelling
Salamanders
• Grotto salamander
Typhlotriton spelaeus
• This lizard lives in
caves with absolutely
no light.
• Rather than invest
precious resources
for unnecessary eye
development, these
blind creatures have
functionless bulbs of
tissue rather than
eyes.
Evidence for Evolution Part 3 –
Comparative Embryology
• Comparative
embryology:
Refers to the
similarities and
differences between
organisms during
embryological
development.
• Vertebrate embryos
develop in very
similar ways.
Evidence for Evolution Part 4:
Biochemical Similarities
Comparative Biochemistry
• Just as DNA
can be used to
demonstrate
paternity, it can
also be used to
demonstrate
common
ancestry
between
species.
We don’t just look like other primates, we
share most of our DNA with them too!
Evidence for Evolution Part 6:
Artificial Selection
• Artificial Selection and
Selective breeding has
enabled humans to
develop a variety of
dog, horse, livestock,
and agricultural breeds.
• Darwin argues that
humans are simply
playing the part of the
environment in the
selection of desired
traits.
• All of these
vegetables come from
the same mustard
plant!
Artificial selection in dogs
• All dog breeds
(Canis familiaris)
are derived from
domesticated
dogs very similar
to wolves.
• Artificial
selection gives
us tremendous
diversity within
the species.