Transcript Evolution….After Darwin…

Bellwork: 02/24/2012
Collect the following data:
• Chlorine
Salt Water Tanks Only:
• DO
- Phosphate
• Turbidity
- Salinity
• Nitrate
- Calcium
• Nitrite
- Water Hardness
Make sure to clean out any excess food
• Ammonia
from your filter and gravel/sand. Scrub
off
• pH
the inside of the glass & clean the
• Temperature outside
(Fresh water only)
with Windex once you are finished.
Before we start:
What is a scientific theory?
– It makes falsifiable predictions with consistent accuracy across a
broad area of scientific inquiry
– It is well-supported by many independent strands of evidence,
rather than a single foundation
– It is consistent with pre-existing theories and other experimental
results
– It can be adapted and modified to account for new evidence as it
is discovered, thus increasing its predictive capability over time.
– It is among the most parsimonious explanations, sparing in
proposed entities or explanations.
Other Scientific Theories:
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The Atomic Theory
Theory of Matter and Energy
Theory of Plate Tectonics
Theory of Quantum Mechanics
Theory of of Molecular Bonds
Theory of the States of Matter
Theory of Homeostasis
Theory of Gravity
Theory of Evolution (we are the only Westernize
country that argues about this)
Keep In Mind:
• The theory of evolution and:
– Creationism
– Neo-creationism
– Intelligent design
– Creation science (“science”)
• Are not equal on an intellectual and rational level
Evolution….After Darwin…
Fossils
Conditions that Favor Fossilization:
• Having Hard parts – shells, bones, cysts
• Get buried, trapped
– Marine species
– Marsh, flooding areas
• Abundant species (with many individuals)
• Long lived species (as a species)
• Avoid eroding away
Fossil Record
• Fossil any preserved remnant or impression
of an organism that lived in the past
• Most form in sedimentary rock, from
organisms buried in deposits of sand and
silt. Compressed by other layers.
• Also includes impressions in mud
• Most organic matter replaced with minerals
by Petrification
• Some fossils may retain organic matter
• Encased in ice, amber, peat, or dehydrated
• Pollen
Fossil Formation
Conditions that Favor Fossilization:
• Having Hard parts – shells, bones, cysts
• Get buried, trapped
– Marine species
– Marsh, flooding areas
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Abundant species (with many individuals)
Long lived species (as a species)
Avoid eroding away
Get discovered
Limitations of Fossils record
• Has to die in right place under the right
conditions. Most things don’t get into the fossil
record
• Biased: Highly favors hard parts, abundant, long
lived species organisms.
• Lots of missing organisms
• Hard to find, only certain areas highly
researched (NA. Europe)
Biogeography
Biogeography
Biogeography
Biogeography
• Study of geographic distribution
• Use to study how lineages of animals
evolved
• History of earth
• Patterns of adaptations for different
environments
Comparative Anatomy
• Comparison of body structures
among taxa to understand
evolutionary relationships/ history
– Homologous vs analogous
Homology
• Similarities in body structures due to common
ancestry
– Ex. Forelimbs in animals
Analogy
• Structures with similar function that do NOT
share common ancestry
Comparative Embryology
• Compare developmental
patterns to understand
common ancestry
Molecular biology
• Study of DNA sequences to understand
evolutionary relationships
• Quantifiable relevant means of comparison
• Compare degree of similarity
• Uses conserved sequences of DNA
• Mitochondrial DNA, RNA, proteins
• Revolutionized our understanding of
evolutionary biology
Population Genetics
• The study of genetic changes in populations over
time
• Quantify molecular differences within and among populations
– Traits exhibit variation
– Traits we have identified genes for
• Population= group of individuals of the same species
living in the same area at the same time
• Gene pool= Genetic composition of a population (all alleles in
a population at a given time)
Microevolution
How does it happen?
• Mechanisms:
• Gene flow
• Genetic drift
–Bottleneck effect
–Founder effect
• Mutations
• Natural Selection
Gene Flow
• The loss or gain of alleles (genes) in a
population due to migration of fertile
individuals or gametes between populations
• Migration
– Immigration
– Emmigration
Genetic drift
• Gene pool contains alleles available for the next
generation
• Genetic drift is a change in allele frequency due to
random chance
• Affect small populations
• Limits alleles available to subsequent generations
• Two types
– Bottleneck
– Founders effect
Bottleneck Effect
Genetic drift resulting from the reduction of a population, typically
by natural disaster, surviving population does not represent the original
population’s gene pool
Bottleneck: 19th Century
The northern elephant
seal bottleneck
Microunga angustirostris
• large US California and Baja California
populations were hunted for oil and skins
• by end 1800’s, ~ 20 individuals remained on
Guadalupe Island off Baja California
• population rebounded to ~120,000 by 1980
Inbreeding in California Sea Otters
• Sea otters, once abundant along the west
coast of the U.S., were almost wiped out by
fur hunters in the 18th and 19th centuries.
Inbreeding in California Sea Otters
• California population reached a low of 50
individuals (now over 1,500). As a result of
this bottleneck, the population has less
genetic diversity than it once had.
Inbreeding in California Sea Otters
• Population is still at a low density and Lidicker
and McCollum (1997) investigated whether
this resulted in inbreeding.
• They determined genotypes of 33 otters for
PAP locus, which has two alleles S (slow) and F
(fast)
Bottleneck: 88,000 years ago
Bottleneck: 43,000 years ago
Bottleneck: dermal immunity
Founder Effect
• Genetic drift attributed to colonization by a
limited number of individuals from a parent
population
Founder Effect
• Examples
– Islands
– Mayflower
– Amish
Figure 18.5
Before You Go: Groups of 2 or 3
1) What is potentially problematic about a combination
of the bottleneck effect & polygyny?
2) What are four conditions that favor fossilization?
3) How is homologous structures different than
analogous structures? Give an example of each.
4) What is the driving force behind human founder
effects? What aspects of human founder effects is
incompatible with the definition of genetic drift?
5) What is adaptive radiation? During which time
period would you expect the largest radiation event
& why? (Keep in mind that extinction events end
time periods)
Mutations
Mutation
• An error in replication of a nucleotide
sequence (DNA), or any other alteration of the
genome that is not due to recombination
• Mutagens
Natural Selection
• Differential success in the reproduction of
different phenotypes resulting from the
interaction of organisms with their
environment
• Results in adaptations
Adaptation
• A feature or characteristic that increases
reproductive success (including survival)
• Increases fitness relative to an alternate trait
Natural Selection
How Does it Happen?
• Directional selection
– 1 extreme is favorable
• Diversifying selection
– 2 extremes favorable
• Stabilizing selection
– Intermediate favored
Mechanisms of Natural Selection
Bellwork: 02/23/2012
1) What is a mutagen & how are they
associated with natural selection?
2) What is the importance of mitochondrial
DNA to molecular biologists?
Macroevolution
• Grand scale
• Form new species- speciation
• Existing species go extinct- extinction
Speciation
• The origin of new species in evolution
• Speciation is the process of forming new
species
– While many take place slowly over generations
– some events can be observed in our life times
• Species= biological species concept
– Members of a group of populations that interbreed or
potentially interbreed with each other, under natural
conditions, and produce viable offspring
Rate of Evolution
• Punctuated equilibrium
• Gradualism
Adaptive Radiation
• Speciation as a result of new or novel
environment
• Occurs at a relatively rapid rate
• Must have:
– Resource
– Selection pressure
• New environment or massive extinction
• Ex islands
Figure 18.14
Reproductive
barriers
Pre-zygotic
Post-zygotic
How distinct species
are maintained
Reproductive Barriers
• Lead to speciation by blocking gene flow
• Pre-zygotic barriers prevent successful
fertilization between species.
– Habitat, behavior, temporal, mechanical, gametic
isolation
• Post-zygotic barriers allow fertilization but
prevent successful development / reproduction
of hybrid.
– Reduced hybrid viability
– Reduced hybrid fertility
– Hybrid breakdown
Habitat Isolation
• Two organisms that use different habitats
even in the same geographic area are unlikely
to encounter each other to even attempt
mating.
– Two species of garter snakes occur in the same
areas but because one lives mainly in water and
the other is primarily terrestrial, they rarely
encounter each other.
Behavioral Isolation
• Many species use elaborate behaviors unique to that species
to attract mates.
Temporal Isolation
• Two species that breed during different times
of day, different seasons, or different years
cannot mix gametes.
– The western spotted skunk and the eastern
spotted skunk ranges overlap, yet they do not
interbreed because one mates in late summer and
the other in late winter.
Temporal Isolation
Mechanical Isolation
–Physical/ structural mechanism that
prevents reproduction
–Flower structure forms a mechanical
barriers to pollinated by insects or other
animals.
–many insects have elaborate reproductive
organs (lock and key) that if they do not fit
together sperm transfer between closely
related species is prevented.
Mechanical Isolation
Post- Zygotic
• Reduced hybrid
viability:
– Miscarriage, early death
• Reduced hybrid fertility:
– Sterile
– Unattractive to opposite
sex
• Hybrid breakdown:
– 1st generation is viable &
fertile
– 2nd generation is
unviable or infertile
– Occurs in plants
Reduced hybrid fertility: Liger
Reduced hybrid fertility: Zebroid
Reduced hybrid fertility: Grolar Bear
Modes of Speciation
• Allopatric speciation
– A mode of speciation induced when the ancestral population
becomes segregated by a geographic barrier
• Peripatric speciation
– A mode of speciation that occurs when neighboring
populations with modest gene flow diverge
• Sympatric speciation
– A mode of speciation occurring as a result of a radical change
in the genome of a subpopulation, reproductively isolating the
subpopulation from the parent population
Allopatric Speciation
• Takes place in separate areas.
• Populations become
separated by a geologic
barrier, blocking gene flow
• Mountains rise up, rivers cut
canyons.
• Populations accumulate
differences, diverge
genetically
Antelope squirrels of the Grand
canyon rim
Parapatric Speciation
• Takes place in large
range
• Variable environmental
• Variable selection
pressure
• Non-random mating
Parapatric Speciation
Peripatric Speciation
Sympatric speciation
• Takes place within habitat
of parent species
• Reproductive barrier forms
within a subset of
population
• Maybe genetic that
immediately blocks
reproduction
• Maybe behavioral
Behavioral Sympatric Speciation
Understanding Evolution
• Phylogeny
– Technique to understand evolutionary
relationships
– Phylogenetic trees
Shared Derived Characteristics
• Trait uniquely shared by a taxonomical group
Convergent Evolution
• Evolutionary pattern where two or more non
related taxonomical groups independently
evolved same/similar characteristics
• Similar structures evolve under similar
environmental conditions
Convergent Evolution
Ocotillo
North America
Allauidia
Madagascar
Convergent Evolution
Convergent Evolution
Spiny Anteater, Australia
Armadillo, North America
Giant Pangolin, Africa
Giant Anteater, South America
Convergent Evolution
In a group no larger then 3
• For each of the following terms, make up a
short story & a picture that describes the
reason & the change of your species that
demonstrates the term’s definition.
1)Founder Effect
2)Bottleneck Effect
3)Habitat Isolation
4)Behavioral Isolation