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50 Cards in this Set
- Front
- Back
macroevolution
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large scale patterns of evolution and processes that explain them
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microevolution
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start of new variation in a population
- smaller scale changes in morphology over a smaller period of time |
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variation is caused by
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1. mutation
2. gene flow |
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2 evolutionary processes that determine the fate of those variants
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1. natural selection
2. genetic drift * these processes and our original ancestors gave rise to our present diversity |
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chance events and earth's history
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- life's history intimately correlated with with Earth's history
- ex: extinction correlates with complex changes in morphology |
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genome sequencing
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- comparative analysis
- can determine what genes have been conserved |
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example of genome sequencing
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- genetic bases for deafness in certain breeds of dogs is similar to some cases of deafness of humans
-shown by comparative analysis -provides us with animal model |
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human genome
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- our nucleotides differ by 1% with chimps
- there are 20,000 protein- coding agents in the human genome - across all mammals there are 20,000 genes which are nearly all the same as ours - why? becuase we share a common ancestor |
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complex morphological change
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result of natural selection and gene drift
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examples of macroevolutionary change
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- patterns of evolution in fossil record
-mass extinction - adaptive radiation - origin and evolution of complex morpholiogies: simple to produce hugely different morphologies - history of life on earth |
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65 million years ago
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-asteroid impact caused a NEAR extinction of dinosaurs because modern day birds are dinosaurs
-adaptive radiation allowed for diversfication of a group into a large variety of forms -7500 species of birds |
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parts to macroevolution
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-mutation
-gene flow - genetic drift -natural selection and 3.8 billin years led to macroevolution |
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first phylogenetic tree
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- came from Darwin
- Darwin said that evolution was the modification with descent from common ancestor |
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evolution in short time scale
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- evolution can happen in a such a short time scale that in the fossil record it looks instantaneous
- "evolution under natural selection is extraordinarily fast"- Schneider |
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example of evolution in short time scale
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-Anolus lizards were seeded on different islands, varying small to large
- in 20 generations these lizards evolved according to their environmental conditions - some had longer limbs on islands that had large trees requiring them to jump from tree to tree -others had developed shorter limbs on islands with scant vegetation and thin trees |
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life's history explainable by these events in Earth's history
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- origin of life
- mass extinction - adaptive radiation - biogeography |
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origin of all complex metazoans
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-metazoans- multicellular organisms
- suddenly appeared in the fossil records - table 25.1 |
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cambrian explosion
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- every phyla that exist today and others that have gone extinct appeared within those few tens of millions of years
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permian extinction
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- 245 million years ago
- 95% of all species went extinct with a few million years - had to do with continental drift |
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origin of life
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- living things require energy to survive and can reproduce themselves
- large molecules - complex chemical reactions - existing within "package" * these three are essential components to life |
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living organisms
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- share common properties
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essential components to life
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1. polymerization- large molecules
2. catalysis- complex chemical reactions stimulated by catalysts 3. all of which continained in single package- closed, ex: cells |
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hypothesis of origin of organic compounds on earth
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- miller Uray Apparatus
- undersea volancoes/volcanism -panspermia |
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The Miller Uray Apparatus
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- occured before Watson and Crick and the modeling of DNA
- this experiment replicated the conditions found in the earth's early atmosphere under which the first amino acids (building blocks of proteins) were created - water and other gases + energy run over a long period of time with excess oxygen removed leads to successful production of amino acids -gases used are methane, hydrogen, ammonia |
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necessities of Apparatus
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- must be anoxic process- early atmosphere of the earth lacked oxygen
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problem with oxygen
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-very reactive and binds with many compounds readily through oxidation
-doesnt allow for formation of large molecules because of this - therefore reduction that occrued in the early atmosphere favored large polymer formation |
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Miller Uray Apparatus run for nucleic acids instead of amino acids
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- yields are extremely high
- RNA precursors are extremely high |
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undersea volcanoes or vulcanism
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- eruptions were rich in inorganic chemicals
- head produced was high enough to drive reactions - build up of organic compounds around these volcanoes |
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Panspermia
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- molecules arrived on earth via comets, meteors and other interplanetary debris
- collisions with the early earth were high enough in frequency to bring a large amount of molecules and water to earth |
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recent breakthroughs supporting Panspermia
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- recent studies have found such organic compounds in comet debris as it travels through space
- martian meteors show signs of bacterial life |
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Importance of RNA
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- early self replicating molecules
- likely to be first genetic material - every molecule acts as its own template for additional molecules and ** can catalyze its own polymerization - formed inorganic precursors - in reducing environment (i.e without oxygen) the monomers can form chains - precise copies can be made so that the information can be passed on genetically |
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new evidence with micro RNA
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- micro RNA help turn on and off sections of genomes
- regulation of micro RNA can lead to manipulations of gene expressions |
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Packaging the first cells
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- packaging must happen
- must be differentiation of internal and external environments |
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Early cell theory: Oparin's Coacervate theory
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- found that a solution of large proteins and polysaccharides (sugars) when shaken would produce droplets that were stable and contained higher internal concentration of compounds than external solutions
- droplets are in effect primitive cells - essential for early life and consistent with anoxic environment |
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coacervates
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- droplets in theory
- represent one way cells may have developed |
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formation of coacervates
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- proteins and polysaccrides combine to form droplet
- these internal concentrations allowed for simple chemical reactions to take place within coacervate - products could be released into external environment |
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Boston Globe Article
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- author of article stated that there were 37,000 different RNAs in the human cell in contrast to the 22,000 coding genes
- this suggests that a greater importance may lie within RNA rather than DNA and that RNA may be running the cell |
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Early Prokaryotes
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- simple single celled organism
- first Prokaryotes arived between 4 to 3.5 bya - for more than 2 million years the only organisms were anaerobic prokaryotes - most were probably sulfur bacteria - bacteria that use H2S as their source of hydrogen for metabolizing organic compounds -didnt use water so oxygen wasn't a byproduct |
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undersea volcanism
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- hydrothermal vents- undersea volacanoes
- these produce H2S and heat that allow the bacteria to metabolize organic compounds on ocean floors - this environment resembles early earth surface and atmosphere |
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Darwin's idea of descent with modification
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- in discussing old age applicability- proves true and holds true throughout Earth's history
- Schnedier points out that once a molecule can replicate itself it becomes subject to natural selection - once RNA began self- replicating variations occured- hence the beginning of evolution of species as some suggested |
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Rock Eating Bacteria
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- trapped inside rocks nearly 1000 meters under earth's surface in hot environment
- due to pressure water remains in a liquid state eventhough it is an environment twice that of boiling point - these bacteria live in this aqeous environment and metabolize minerals from rocks that surround them - resemble early Prokaryotes in terms of the environmental conditions in which they lived in |
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early bacteria
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- many were photosynthetic but most used sources of hydgrogen such as H2S that did not release oxygen when it was metabolized
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The Oxygen Revolution
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- Cyanobacteria evolved about 3.5 bya
- differed from other bacteria in one very important way: they had the ability to split water as a source of hydrogen - instead of resulting in biproduct of sulfur, there was a byproduct of oxygen - BUT oxygen didn't build up in the atmosphere for another 1 billion years due to the iron in the earth's ocean and crust - Iron binds to oxygen and extracts it from atmosphere - this was a key step in evolution of life on earth |
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Cyanobacteria
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we have cyanobacteria- bacterial photosynthesizers to thank for our oxygenated atmosphere
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Stromatolites
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- build ups of blue-green algae (cyanobacteria) which becomes layered between sediments
- usually in salt lagoons - cyanobacteria are responsible for algal blooms |
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oxygen revolution and origin of cellular respiration
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- the change in oxidizing atmosphere created serious problems for anaerobic bacteria
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beginning of aerobic respiration
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- some species of photosynthetic bacteria are able to use oxygen to pull electrons from organic molecules down to electron transport chains
- purple non-sulfur bacteria still use an electron transport system that is a hybrid of photosynthetic and respiratory pathways |
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Timeline
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Earth formed- 4.5 bya
Life orginates- 3.8 bya oldest fossils of prokaryotic life- 3.5 bya oxygen begins accumulating in the atmosphere- 2.5 bya becomes plentiful- 2.0 bya * still less than 5% of current levels Eukaryotic organisms- 500 mya |
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simple life forms
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evolved at first until oxygen build up enouh to support more complex forms of life
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Tree of life
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- 3 main branches
-- common ancestor 1. Prokaryotes- bacteria, Arcahe bacteria 2. Eukarya: protists (1.5 bya) 3. Fungi, animalia and plantae- 500 mya (Eukaryotes) ** oxygen wasn't plentiful enough to support larger eukaryotic organisms until 500 million years |