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Transcript
Evolution
Evolutionary change is based on
interactions between populations
of organisms and their
environments
Origin of the Species
• 1859 Darwin Published On The Origin of
Species by Means of Natural Selection.
– A convincing case for evolution
• Evolution: the process by which
populations of organisms acquire and
pass on novel traits from generation to
generation
2 points of Darwin’s book
1. Species were not created
in their present forms but
evolved from common
ancestors.
2. Natural Selection is the
mechanism for evolution
Western culture resisted
evolutionary views of life
• Darwin’s view contrasted with the
conventional paradigm of an 6000 year old
Earth, and Universe made in 7 days
– Natural theology, Creationism, or Intelligent
Design are all names for this point of view
• Others were laying groundwork for
Darwin’s view. People were talking about
evolution for years before Darwin
articulated a concise argument.
Darwin’s Predecessors
• Economist &
Demographer
Thomas Malthus’
1798 essay on
England’s population
noted that humans
increase faster than
food supplies.
Darwin’s Predecessors
• Carolus Linnaeus
– Founder of Taxonomy
– Developed 2 part naming system
• Organized the diversity of life into groups
• But believed that God created all the life,
he only organized it
Darwin’s Predecessors
• Georges Cuvier developed Paleontology
• Documented where fossils were found in
successive stratum of rock layers.
– Deeper the rock layer; the older the life
– Also noted extinctions happened
• Yet opposed evolutionary theory
• In the view of Catastrophism the layers of
fossils result because of flood or other
disasters
– Extreme views of catastrophism hold that God
wiped out all life and recreated it several times
Geologist’s
• Charles Hutton: came up with gradualism.
– Idea that erosion and continental drift slowly
shape the Earth
• James Lyell: came up with
uniformitarianism: geologic processes
happen at a constant rate
Darwin’s conclusions from Geology
• If geologic change is constant and slow,
the Earth must be much older than 6000
years
• Slow, subtle processes over long periods
can cause big changes in the Earth, so
why not in populations of living things?
– Others were already saying this
Galapagos
Jean Baptiste Lamarck
• Saw lines of descent, how older fossils
evolved into younger fossils
– Thought their were many ladders of descent
– Bacteria escalated into more complex life
forms
• His problematic mechanism: If a giraffe
stretches its neck to get more food, then
its kids will have stretched necks. Or if a
blacksmith works out only his right arm,
his children will have larger right arms.
Darwin’s Field Research
• Born on 2/12/1809 (same as Lincoln)
Darwin grows up, doesn’t really have any
direction, changes majors a couple of
times.
– Just wants to go hunting and collect bugs
– Dad’s a big time doctor and getting fed up
– Sends him to medical school, Darwin drops it
– Darwin goes into the clergy, his mentor
recommends him to be the on-board priest on
the voyage of the Beagle
On the voyage Darwin found the an
excellent Megatherium Skull
Darwin also discovered a new
species of dolphin which he named
Delphinus Fitzroyi
Voyage of the Beagle
• Captain of the Beagle: Fitzroy, really
religious, needs educated company so he
recruits the young clergyman Darwin
• They’re the original odd couple
– Fitzroy: 23y/old Creationist
– Darwin: 22y/old Liberal Evolutionist
• Both sharing a cramped cabin filled with
fossils, flora & fauna samples Darwin
collects when they go ashore
– Lots of fighting
– Much later Fitzroy slits his own throat
Beagle
• Goes around South America & Galapagos
for 5 years
• Darwin keeps bad records, who knows
where this or that bird came from.
– Takes him six years after getting back to
organize it all
– Sees unique adaptations of different species,
notably Finches.
Darwin focuses of adaptation
• New species arise as ancestral forms from
the gradual accumulation of adaptations to
different environments.
– Species fragment and get isolated
– Over a long time isolated population change
enough that they become new species
• So Darwin’s famous for his adventure and
has the idea for Evolution, then he does
something weird…
He puts away his manuscript
• He doesn’t publish for 14 years
– Has 10 kids, spends 8 years writing a book on
barnacles, writes letters to Lyell, and a young naturalist
named Alfred Wallace
• Why?
– Creationist criticism was rampant
– Darwin had a strange unidentified
illness
• Maybe Chaga’s Disease caused by a
Benchuca bug bite in South America
• Maybe Pscyhosomatic
• Maybe daddy issues
1858: Wallace
• Alfred Wallace sends Darwin a
manuscript for his ideas on
evolution.
• Darwin says Holy Crap! This
Wallace kid is going to steal the
show, I’d better get moving.
• Publishes Origin of the Species. It
sells out and everybody goes
crazy with logic
• Wallace is cool, goes on to be a
good thinker & naturalist, but gets
weird ideas about spirits and life
on other planets
• Darwin didn’t call it evolution
until the sixth printing of the
book. He called it “Descent with
Modification”
• We’re all descended from some
unknown ancestor
– Like an tree. Species at the
leaves and the ancestor at the
trunk. Closer related species
share branches. Forks in
branches are common ancestors
– Lots of dead ends: 99% of
species that have ever lived are
extinct
• The Linnean hierarchy of classification fit
nicely with the branching genealogy of
species
• Kingdom>phylum>class>order>family>
genus>species>sometimes race or breed
• Kids Playing Chicken On Freeways Get
Smashed
• King Philip came over for good spaghetti
Darwin’s Sweet Logic
• Observation #1: All species have such
great potential fertility that population size
would increase exponentially if all
individuals born had maximum
reproductive rates
• Observation #2: populations are stable
• Observation #3: Natural resources are
limited
• Inference #1: Production of more
individuals than the environment can
support leads to struggles for existence,
and only a fraction survive.
• Observation #4: Individuals of a population
vary in characteristics
• Observation #5: Much of this variation is
heritable
• Inference #2: Survival in the
struggle for existance is not random,
but depends in part on the
hereditary constitution of surviving
individuals. Those individuals
whose characteristics fit them best
to the environment are likely to
leave more offspring than less fit
individuals
• Inference #3: The unequal survival
and reproductive ability will lead to a
gradual change in a population with
favorable characteristics
accumulating over generations
Natural selection
• Natural selection is the differential success
in reproduction and its product is
adaptation of populations of organisms to
their environment.
• Though we didn’t know it Mendel’s work
published ~ 1868 explained this but no
one recognized that for ~ 30 years
Evidence
• Artificial Selection: We
breed domesticated
animals for certain traits.
Humans modify species.
• Cauliflower, Cabbage,
Brussels Sprouts,
Broccoli, Kale, and
Kohlrabi are all modified
Wild Mustard
Unintentional Artirficial Selection
• We don’t always want
things to adapt
• Drugs have evolved
resistance to
Antibiotics
• Pests have evolved
resistance to
pesticides
Year
Year Resistance
Pesticide
mark
first observed
eted
DDT
1943
1950
2,4 D
1945
1954
Delaphon 1953
1962
Atrazine
1958
1968
Picloram
1963
1988
Trifluralin
1963
1988
Triallate
1964
1987
Diclofop
1980
1987
Palumbi, S.R. 2001.
Humans as the World's Greatest
Evolutionary Force.
Science 293: 1786-1790.
Subtleties
• It takes a population to evolve, not an
individual
• The best adaptations depend on place and
time. Just because you’ve got a great
mutation that lets you survive at -100
degrees it won’t do you any good if you
live in Brazil
Evidence
• Biogeography: Why are animals of South
American tropics more closely related to
South American deserts than African
tropics? Why are most marsupials in
Australia? Armidillos are only in America,
fossils that look like Giant Armidillos are
only in America.
• Go America!
Biston moth
• industrial melanism tree bark either light in
color (covered with
lichens) or dark in
color (because of
industrial soot). Light
moths favored when
most trees have
lichens (no pollution)
and dark moths
favored when tree bark
is dark from pollution.
Fossil Record
• Biochem, Cell bio, and
molecular bio all predict
that prokaryotes should
be the oldest organisms,
and the oldest fossils are
prokaryotes
– Stromatalite: Blue
Green Algae that
trapped sediments and
makes fossils that
show evidence of
biological activity, 500
-4500 million years old
– Transitional evidence. A
criticism of evolution by some.
However a series of skulls exist
in the strata that show the
transition from reptiles to
mammals.
• Also Archaeopteryx was found
just in 1861
– Saltationists like T.H.Huxley
(Darwin’s Bulldog) thought
evolution happened suddenly
– What good is ½ an eye?
– Paley’s argument from design
likened it to finding a pocket
watch, so complex it must have
had an intelligent creator.
• Comparitive anatomy: the same skeletal
elements make up the forelimbs of all
mammals even though these appendages
have different functions.
• Hands, paws, whale fins, bat wings, all
have the same basic bones because they
have a common ancestor. These bones
are homologous structures
• Also why have vestigial organs? Some
snakes have a simpilfied hip bone.
Homologous as opposed to
analagous structures
Comparitive embryology
• Closely related organisms go through
similar stages during development.
• All vertebrates go through a stage of
development when they have gill slits.
• “Ontogeny recapitulates Phylogeny”
• The development of an individual replays
the evolutionary history of the species
Molecular Biology
• Similar DNA and proteins indicate a closer
relationship.
– Who has the DNA most similar to yours?
• We’ve got cytochrome C, a respiratory
protein, and so do bacteria.
• There is a global common genetic code
Is it just a theory?
• Depends on what you mean by theory.
• Theories are more than hypothesis. They
account for many facts and explain a
variety of phenomena.
• Its not Dogma. Evolution can be
challenged, but you’ve got to come up for
a better explanation for the evidence.
• You can debate gravity, but objects keep
falling