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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 – – – – 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) 1. 2. 3. 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 • • • • 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 • • • • 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 – – – – 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 • • • • 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 – – – – 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 • • • • • • • 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 • Primates: – – – – – 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 – – – – 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 • • • • 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?