Transcript Evolution=change

Evolution=change
Biological evolution: change in a
species caused my changes in
genes that become common in
the population
Evolutionary change:
• Must be Inherited--must be in the genes
• Often affects an entire species…but not
always
• May cause enough change to make a new
species
• Can result from mutations in DNA that
increase the chance of survival and
reproduction
Consider
• Species: organisms that are so similar (genetically and
physically) that they can reproduce together
– Horse x donkey = mule
– Wolf x dog = dog (if the wolf doesn’t eat the dog first--they usually
do)
• Theory of Evolution: the biological, scientific, natural
explanation for why there are so many species and why
they are so well adapted. Supported by evidence.
• Other explanations are “supernatural.”
review
• Evolution is genetic: genes are the raw material for
adaptation
• Adaptive changes must help a species survive and
reproduce
• Reproductive definition of a species
• Evolution involves
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Adapting species
Creating new related species
The idea that all living things have a common ancestor
Life originated by natural rather than supernatural
processes.
Why is evolution controversial
• There are other beliefs about the origin of species
that mix science and religion
– Creationism: supernatural creation event (biblical creation).
Sometimes called “Creation Science”
– Intelligent design: life is too complex to happen without an
outside force: intelligent designer like “God.”
• “Irreducible complexity”
• Accepts evolution.
• There is little evidence about the origin of life.
• Evolution is not inherently atheistic. Biologists are no
more likely to be atheist than any other population.
Evolution is a fact!
• Species evolve in “real time”--we can
see it happen now
– Antibiotic resistant bacteria
– Pesticide resistant insects
– Sickle cell anemia gene
Can this create new species?
Does this account for all species?
“Most of what we observe in biology
makes sense because of Evolution.”
Theodosius Dobzhansky
• Fossil record
• Mass extinctions (dinosaur extinction was the fifth
mass extinction and not the largest) followed by
increasing diversity and complexity of species
• Taxonomy: classification of species
• Common genes and proteins in all organisms--”the
unity of life”
• Adaptation of critters to environment--”the diversity of
life.”
Theory of evolution is one of the oldest
and best supported scientific theories!
• Based on direct observation and tested hypothesis.
Evolution is science.
• Has never been refuted scientifically.
• New technology and evidence has always supported
the original theory:
– Species change over time by “Natural Selection”
– Existing species have common ancestors alive and extinct.
• Can be disproved because it is based on
observation--it’s “falsifiable”
Charles Darwin
Charles Darwin: 1800’s
• Discovered the Theory of Evolution
– “Descent with modification”
– Natural selection: survival of the fittest
• Studied theology: ordained minister
– He was a “Young Earth Creationist.”
– He practiced “Natural Theology”: science studies God’s
creation.
– Accepted the “Typological View”: one creation of all “types”
and “forms” of life
• Signed on as “naturalist” (biologist) on the HMS
Beagle and sailed around the world form 1831-1836
(5 years!)
• Published the book in 1859: On the Origin of the
Species--4 years later!
Artificial Selection: selective
breeding
• Farmers and breeders select individuals
depending on favorable traits
– Breeds of dogs
– Breeds of horses and cows
– Short legged sheep
– Varieties of plants
Darwin’s big idea: natural selection
(survival of the fittest)
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Genetic variation (natural)
Super fecundity: overpopulation (natural)
Competition for resources
– Survival challenge
– Environmental change: climate, predation, disease,
introduced species
4. Best adapted (fittest) survive and reproduce
The genes for adaptive traits become more common.
“Frequency of alleles increases.”
Darwin’s context: age of biology
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Mendel did his work at the same time
Cell theory formulated (Schleiden and Schwann)
Germ theory formulated (Pasteur)
Tom Malthus: overpopulation theory--some (people) won’t
survive
• Jean Baptist Lamarke: evolution by acquired characteristics
• Charles Lyell: geologist
– Old earth
– Dynamic, changing planet
– Superposition: younger layers on top of older layers
• Alfred Wallace: naturalist in Indonesia
– Came up with same theory right after Darwin!
HMS Beagle: 1831-1836
• Africa: biodiversity
• Australia: biodiversity
• S. America: fossils of dinosaurs and ice
aged animals
• Galapagos Islands off the coast of
Equador
– New land: volcanic islands
– New species: finches, tortoises, iguanas,
plants
Voyages of the HMS Beagle
3 issues
• Microevolution: change in a species
• Speciation (Macroevolution): new
species
• Origin of Life
– Inorganic chemicals being organized into
organic chemicals and the formation of
cells
Origin of Life: hard to explain
• Oldest fossils are 3.5 billion years old!
• Hypothesis
– Supernatural: “divine” creation--impossible to prove. Not
science
– Extraterrestrial
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There are hydrocarbons in space
There are even amino acids in space
But, we can’t even go to other planets in the solar system.
However, rocks from Mars have been found on Earth.
– Natural
• Inorganic chemicals form organic chemicals and cells
• Stanley Miller Experiment shows this is possible
• How can a cell membrane form?
Microevolution
• A species becomes better adapted by
natural selection
• No doubt: this can be observed in
“real” time: insects, bacteria, appendix
Examples
• Antibiotic resistant bacteria
• Industrial melanism
– Peppered moths
• Dark moths are selected when the tree bark is
sooty
• Light colored moths are “selected” when there
is less pollution
Speciation: macroevolution
• This is what people usually mean by “evolution.”
• Lots of microevolution over a long period of time
• Evidence
– Fossil record: mass extinctions followed by increasing
diversity and complexity
– New species on islands
– New species following mass extinctions
– Missing links: “evolutionary intermediates”
• Archaeopteryx: feathered dinosaur
• Walking fish
– Genes
• Shared genomes: human/ape/worm
• Nucleotide sequences in hemoglobin
Evidence for evolution: speciation
• Microevolution: observable changes in a species
caused by mutation and selection
• Fossil record
– History of life: increasing diversity and complexity
– Mass extinctions
– Intermediaries: archaeopteryx, Lucy
• Anatomy
– Homologous structures: same structure, different
function (wings, arm, fins)
– Vestigial structures: parts with no use
• Hips in whales, eyes in cave fish
– Convergent evolution: wings on bats and birds, fins on
fish and whales
– Embryology: your fetus had gills
• Genetics: everything!
– Genetics shows how change happens
• Mutation and recombination
– Molecular clocks--rate of mutation used to
date divergence and speciation
Patterns in evolution
• Gradualism: gradual, continuous change
• Punctuated equilibrium: sudden increase in evolutionary
change following mass extinctions
• adaptive radiation: like Darwin’s finches. Many species
from a “founder” species
• Coevolution: bees and flowers
• Island species--isolation
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Reproductive isolation
Geographic isolation
Ecological niche
Behavioral isolation
Population dynamics
• Evolution happens to populations rather than
individuals
• The issue is gene frequencies
• Mutations create new genes
• Genes can be imported to a population from isolated
members
• Viruses may introduce new genes
• Selection pressures affect frequencies.
• Hardy Weinberg formula is statistical analysis of gene
frequencies.
– Frequencies of alleles should not change unless something
happens.
Dates to remember
• 4.5-4.7 billion years: age of Earth
• 3.5 billion years: oldest fossils (bacterial
stromatolites)
• 2 billion years: photosynthetic cyanobacteria
• 250 million years: Permian extinction (96% of species
gone including trilobites)
• 65 million years: dinosaur extinction
• 20,000 years ago: glaciers melted, ice age (Pleistocene
period) ended
Radiometric Dating Methods:
there are more
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C-14 5700 Yr.
K-Ar (K-40) 1.25 B.Y.
Rb-Sr (Rb-87) 48.8 by
U-235 704 M.Y.
Absolute Ages: Early
Attempts
The Bible
• Add up Dates in Bible
• Get an Age of 4000-6000 B.C. For Earth
• John Lightfoot and Bishop Ussher 4004 B.C. (1584)
• Too Short
Absolute Ages: Early
Attempts
Salt in Ocean
• If we know rate salt is added, and how much salt is in
ocean, can find age of oceans.
Sediment Thickness
• Add up thickest sediments for each period, estimate
rate.
Both methods gave age of about 100 million years
• Problem: Rates Variable
FOSSILS
• Remains of past life in sedimentary rock
• Usually hard tissues are preserved: not hair or skin or
muscle or organs--usually
• Rare to form, rare to find
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Freezing: Pleistocene life (ice age)
Mummification (drying)
Tar traps: La Brea Tar Pits in California
Petrification: turned to stone (no dino bones, just bone
shaped rocks)
– Trace fossils
• Foot prints, impressions, carbon prints of leaves
• Casts and molds
– Amber--petrified sap
Famous fossils
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Lucy
Sue
Trilobytes
Archaeopteryx
Ice man
Frozen mammoths
Hobbits
Chronology of Hominid
Evolution
• The Pleistocene (2 m.y.a. to 10,000 B.P.) is the epoch of human
life.
– Lower Pleistocene (2 to 1 m.y.a.): Australopithecus and early Homo
– Middle Pleistocene (1 m.y.a. to 130,000 B.P.): Homo erectus and
archaic Homo sapiens
– Upper Pleistocene (130,000 to 10,000 B.P.): modern Homo
sapiens
Primate vs Homonid
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Opposable thumbs
Binocular vision: depth perception
Prosimians: lemurs
Monkeys: tails
Apes: no tails
• Homonids: human-like primates
– All the above plus:
• Bipedal--walk upright
• Tool making and use
– Humans
• Culture--social organization
• Language
• Abstract thought--art, religion
Skeletons
Comparison of
human and
chimpanzee
skeletons.
Primates: thumbs, binocular vision
• Prosimians: 50 m.y.a.
– nocturnal
• Monkeys: 30 m.y.a. (old world and new world)
– Tails
– diurnal
• Apes: 10 m.y. No tails
– More upright
– SMRTR
• Homonids: 4-5 m.y.a.
– Human-like
– Bipeds
– Smart ape?
Humans
• Homo sapien: “thinking man”
– 200,000 years?
– Made art
– Agriculture: 10,000 years
• Homo neanderthalis or homo sapien neanderthalis
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Occupied Europe for a long time!
Just ugly people?
No speech?
Made art
homonids
• Australopithecus: Lucy
– 4.5 m.y.
– First homonids
• Homo habilis: “Handy man”
– 2.5 m.y.
– Used tools
• Homo erectus: “standing man”
– 1.8 m.y.
– First to leave Africa
– PEKING MAN, JAVA MAN fossils
Out of Africa
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Most homonid fossils from Africa
Homo erectus is found throughout the “Old World”
mRNA studies indicate African origins
Did Homo erectus become Homo sapien in many
places or only Africa
• H. erectus seems to have become Homo
neanderthalis in Europe
• What happened to H. neanderthalis? Their extinction
corresponds to H. sapien’s arrival in Europe.
– Interbreeding?
– Hunting?
– Competition?