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| Question | Answer |
| Opairin- Haldane Hypothesis | 1. Synthesis of complex organic molecules -CH3+ NH3+ H2 + H2O  amino acids, sugars, purines, pyrimidines 2. Synthesis of self-replicating molecules -Evolution by natural selection of variations of molecules that reproduced more prolifically -“RNA World Hypothesis” 3. Packaging of replicating molecules in a membrane – cell |
| Opairin Haldane Model | -prebiotic soup 1. Assemble simple molecules into building blocks for complex polymers 2. Assemble polymers that can store information and catalyze reactions 3. Add membranes and an energy source to make a living organism |
| The Panspermia Hypothesis -Case Studies | -Life originated on another planet and colonized earth -Microbes could have been dislodged from another planet by a meteor impact carried into space on a chunk of debris, and deposited on Earth 1. metro from mars in antartica: Contained organic molecules called polycyclic aromatic hydrocarbons & Found objects that resemble tiny bacteria 2. studies of meteorites in australia: Found several different amino acids in significant concentrations & The extraterrestrial amino acids were racemic (equal proportions of D- and L- stereoisomers), whereas living organisms on earth only contain L-steroisomers of amino acids. |
| Endosymbiotic Theory | -Chloroplasts and mitochondria may have originally been prokaryotic symbionts living inside primitive eukaryotic organisms. The relationship began when a large eukaryote engulfed a prokaryote but did not digest it. -Later, evidence was found supporting the theory – e.g. organelles have prokaryotic-like DNA (circular, no histones) and membrane biochemistry. |
| Cambrian Explosion -graph | -first animals with simple body plans -diverse groups present today (Annelida, Mollusca) -represents only 1% of the history of life - #phyla vs time |
| What caused the Cambrian Explosion? | -OXYGEN: increased atmospheric concentration facilitated the evolution of larger and more active animals -SEXUAL REPRODUCTION:he advent of recombination and independent assortment of chromosomes during meiosis provided the genetic variation necessary for diversification in body plans -REGULATORY GENES: evolution of genes that control the transcription of many other genes enabled animals to development diverse and complex body plans -EYES: the advent of sight enabled animals to forage many different ways leading to different body plans. = SEARCHERS -PREDATION: evolution of predators selected for adaptations in their prey that enabled them to escape predation (e.g. shells, burrowing). |
| Mass Extinctions: occurrence and extinction of species | -ORODOVICIAN:occurred 450-440 Myr ago, extinction of ~75% of species -DEVONIAN:occurred 364 Myr ago, extinction of ~75% of species -PERMIAN:occurred 251 Myr ago, extinction of ~96% of species -TRIASSIC:occurred 205 Myr ago, extinction of ~65% of species -CRETACIOUS:occurred 65 Myr ago, extinction of ~76% of species |
| What caused the mass extinctions? | -TEMPERATURE DECLINE: killed species adapted to warm temperatures in low latitude regions and glaciation killed all species in high latitude regions -SEA LEVEL DECLINE: occurred during all 5 mass extinctions. Marine species became extinct on exposed continental shelves. -VOLCANIC ERUPTIONS: bury organisms, reduce sunlight (photosynthesis), emit sulfur oxides (acid rain dissolves calcium carbonate) -PLATE TECTONICS: formation of supercontinents (Pangaea) reduced sea levels and caused volcanic eruptions. Probably largely responsible for Permian mass extinction. -ASTEROIDS: cause massive dust clouds that reduce sunlight. Probably largely responsible for Cretaceous mass extinction. -GAMMA RAY BURSTS: from far away supernovae destroy the ozone layer which protects organisms from too much UV light |
| Three Tiers of Evolution: | 1. Microevolutionary change within populations and species 2. Species selection – the differential proliferation and extinction of species during “normal” geological times. 3. Mass extinctions – elimination of groups of species, resetting the stage for new evolutionary radiations (macroevolution). |
| Wallace's Line | abrupt change in species composition on islands between Southeast Asia and Australia. The islands are part of two different plates that are moving toward each other. Islands on each plate were interconnected during Pleistocene events. |
| Case Study of Geography of Evolution | CRICKETS ON HAWAIIAN ISLANDS: -Molecular phylogenetic analysis shows that successively younger groups of species originated on successively younger islands. |
| Why are there more species in the tropics that in other areas of earth? | 1. Time Hypothesis 2. Climate Hypothesis 3. Area Hypothesis 4. Competition Hypothesis 5. Speciation Rate Hypothesis |
| Time Hypothesis -graphs | tropical communities have had more time for speciation than temperate or polar communities |
| Climate Hypothesis | more species can adapt to favorable climate in the tropics than harsh climate in other regions. |
| Area Hypothesis | tropical zones contain more area on the globe than temperate areas. More area promotes more speciation events. |
| Competition Hypothesis | species are more specialized in the tropics, allowing more species to coexist -graphs |
| Speciation Rate Hypothesis | speciation rate is faster in the tropics than in other regions. |
| Temporal Changes in Taxonomic Composition | -Competitive Displacement -Incumbent Replacement |
| Competitive Displacement | -when a later group has caused the extinction of reduction of an earlier group. The later group outcompeted the earlier group -EX: Gymnosperms and spore-bearing plants declined as flowering plants increased |
| Incumbent Replacement | extinction of an earlier group is followed by proliferation of a later group. The later group did not drive the earlier one extinct. -Ex. Extinction of dinosaurs was followed by diversification of mammals. |
| Case Study of Correlation between Origination and Extinction Rates | analysis families within orders of marine organisms -Origination rate = probability that a new family originates within the order per time period -Extinction rate = probability that a family within the order becomes extinct per time period |
| Why are extinction and origination rates correlated? | 1. Ecological Specialization 2. Geographic Range |
| Ecological Specialization | -Specialists – use a narrow range of resources -Generalists – use a broad range of resources -Origination rates are higher for specialized taxa because new species can avoid competing with other species by specializing on unique resources. -graphs -Extinction rates of specialist taxa are higher because they are more sensitive to environmental variation. |
| Tempo of Evolution | -Gradualism -Punctuated Equilibrium |
| Geographic Range Case Study | -Species with broad geographic ranges have a lower risk of extinction because they are not extinguished by local catastrophes. - Species with broad geographic ranges tend to have a higher capacity for dispersal and thereby less likely to have populations that become isolated and undergo speciation. -Snails: speciation rate vs log median geographical range |
| Gradualism: Draw Model | (Darwin) evolutionary change within lineages is slow and continuous. |
| Punctuated Equilibrium -Draw Model | (Eldredge and Gould) evolution within lineages occurs in short periods with rapid change separated by long periods with little or no change. |
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