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50 Cards in this Set

  • Front
  • Back
macroevolution
large scale patterns of evolution and processes that explain them
microevolution
start of new variation in a population
- smaller scale changes in morphology over a smaller period of time
variation is caused by
1. mutation
2. gene flow
2 evolutionary processes that determine the fate of those variants
1. natural selection
2. genetic drift
* these processes and our original ancestors gave rise to our present diversity
chance events and earth's history
- life's history intimately correlated with with Earth's history
- ex: extinction correlates with complex changes in morphology
genome sequencing
- comparative analysis
- can determine what genes have been conserved
example of genome sequencing
- 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
human genome
- 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
complex morphological change
result of natural selection and gene drift
examples of macroevolutionary change
- 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
65 million years ago
-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
parts to macroevolution
-mutation
-gene flow
- genetic drift
-natural selection
and 3.8 billin years led to macroevolution
first phylogenetic tree
- came from Darwin
- Darwin said that evolution was the modification with descent from common ancestor
evolution in short time scale
- 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
example of evolution in short time scale
-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
life's history explainable by these events in Earth's history
- origin of life
- mass extinction
- adaptive radiation
- biogeography
origin of all complex metazoans
-metazoans- multicellular organisms
- suddenly appeared in the fossil records
- table 25.1
cambrian explosion
- every phyla that exist today and others that have gone extinct appeared within those few tens of millions of years
permian extinction
- 245 million years ago
- 95% of all species went extinct with a few million years
- had to do with continental drift
origin of life
- 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
living organisms
- share common properties
essential components to life
1. polymerization- large molecules
2. catalysis- complex chemical reactions stimulated by catalysts
3. all of which continained in single package- closed, ex: cells
hypothesis of origin of organic compounds on earth
- miller Uray Apparatus
- undersea volancoes/volcanism
-panspermia
The Miller Uray Apparatus
- 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
necessities of Apparatus
- must be anoxic process- early atmosphere of the earth lacked oxygen
problem with oxygen
-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
Miller Uray Apparatus run for nucleic acids instead of amino acids
- yields are extremely high
- RNA precursors are extremely high
undersea volcanoes or vulcanism
- eruptions were rich in inorganic chemicals
- head produced was high enough to drive reactions
- build up of organic compounds around these volcanoes
Panspermia
- 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
recent breakthroughs supporting Panspermia
- recent studies have found such organic compounds in comet debris as it travels through space
- martian meteors show signs of bacterial life
Importance of RNA
- 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
new evidence with micro RNA
- micro RNA help turn on and off sections of genomes
- regulation of micro RNA can lead to manipulations of gene expressions
Packaging the first cells
- packaging must happen
- must be differentiation of internal and external environments
Early cell theory: Oparin's Coacervate theory
- 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
coacervates
- droplets in theory
- represent one way cells may have developed
formation of coacervates
- 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
Boston Globe Article
- 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
Early Prokaryotes
- 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
undersea volcanism
- 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
Darwin's idea of descent with modification
- 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
Rock Eating Bacteria
- 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
early bacteria
- many were photosynthetic but most used sources of hydgrogen such as H2S that did not release oxygen when it was metabolized
The Oxygen Revolution
- 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
Cyanobacteria
we have cyanobacteria- bacterial photosynthesizers to thank for our oxygenated atmosphere
Stromatolites
- build ups of blue-green algae (cyanobacteria) which becomes layered between sediments
- usually in salt lagoons
- cyanobacteria are responsible for algal blooms
oxygen revolution and origin of cellular respiration
- the change in oxidizing atmosphere created serious problems for anaerobic bacteria
beginning of aerobic respiration
- 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
Timeline
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
simple life forms
evolved at first until oxygen build up enouh to support more complex forms of life
Tree of life
- 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