Biol 304 1st EditionFinal Exam Study GuideLecture 1 (April 13)Chapter 16Mechanisms of SpeciationSpeciation- Process leading to origination of new species- Ancestral species diverges to the point where the divergent forms are considered different species- About 2 mill. Species describedFinSpecies concept – what is a species- Interbreeding pop. That are on own evolutionary trajectory- Smallest evolutionarily independent- Boundary for the spread of alleles- No clear diagnostic tool!- Morphological: group of individuals that look alikeo Sometimes organisms look the same, but can’t interbreed of have important genetic/physiologic differenceso Some things do not have a lot of morphologyo May be only option for extinct species- Biological: group of individuals that can interbreedo Difficult to know breeding habits of some thingso Plant considered different species or even different morphology often hybridize and form fertile offspringo Irrelevant for asexual specieso Bad for plants, protists, bacteria, fish- Phylogenetic: (one of many) – group of individuals that share a common ancestor, smallest diagnosable clade (DNA)o Sometimes we don’t know the phylogenyo Closely relates individuals may not interbreed, or have morphological differenceso Phylogenetic species may not fit morphological/biological species conceptso May result in recognizing more species by splitting old groups.Extinct organisms?- No DNA over 40,000 years old- No interbreeding info- Incomplete morphology- Often, chorological series define “paleospecies” or “morphospecies”Problems with species- No single clear definition of species that works for everything- Disagreements about species limits- Applying different species concepts often result in different delineations. Look at case studiesIterative process of systematics- Alpha taxonomy: newly discovered species are delineated and classified by morphology- Later, more detailed studies of phylogenetic relationships, biology, and ecology may refine by moving species to different taxa, or lumping/splitting speciesLecture 2 (April 15)Speciation- Process leading to origination of new species- Speciation may be driven by natural selection and, or, random genetic drift- Evolution happens in populationsClassic model of speciation1. Population becomes isolated2. Genetic divergence takes place (selection, or drift) 3. Populations become reproductively isolated, unable to interbreed aven if secondary contact happensAllopatric speciation ModelGenetic divergence following isolation- Genetic drifto Often bottlenecking in the case of long distance dispersal- Natural selectiono With either dispersal or vicariance, new isolated habitats may differ in climate, enemies, mutualists, resources, etc.Not so classic model of speciation1. Genetic divergence takes place (selection, or drift) without geographic isolation2. Eventually pop. Become reproductively isolated, unable to interbreed even with secondary contactSympatric speciation modelDoes occurPolyploidy and chromosome changes can cause isolation- 2-4% of plant species from polyploidy- About 50% have polyploidy in their history- Rarer in animalsSympatric speciation- Plants may spectate sympatrically by hybridization, polyploidy events, changes in breeding systems/pollinators, or combinations of this- In animals, it is most likely involving phytophagous insects- May diverge due to mutations/adaptations involving host useo Pop. Eat different hostso Pop. Mate at preferred hostso Pop. Seasonally synchronized to different hostsLecture 3 (April 17)How do new or incipient species remain genetically isolated after secondary contact?- Reinforcement: hybrids have lower fitness than either parent, selected againsto Should favor evolution of Prezygotic isolation Chapter 17Origins of Life and Precambrian evolutionNo theories only hypothesis. DNA and proteins: chicken and egg dilemma- What came 1st DNA or proteins- DNA can store information, but no cellular work- Proteins do cellular work, but cannot stop information- How can “central dogma of biology” evolve gradually?- Ribozyme: enzyme made of ribonucleic acid- Inefficient, sloppy enzyme discovered in 1980’s- This ribozyme breaks/forms bonds between nucleic acidsAn RNA world?- RNA can store info- RNA can replicate itself- RNA can do cellular work (sloppy)- RNA can evolve- Catalytic RNA were transitional molecules between non-living matter and the 1st cellsWill ribozymes change by natural selection?- Experiments with ribozymes from tetrahymena thermophile, a ciliate protest- Very weird: has 2 nuclei per cell, has 7 sexes- Model organism in genetics, epigenetics, cell biology, evolutionRibozymes can:- carry genetic info- Catalyze reactions- Evolve by natural selection and random genetic driftIn today’s world, RNA is replicated by RNA polymerase, an enzyme made of proteinsHow would it be done in the RNA World?Can we artificially select for a ribozyme that will replicate RNAHasn’t been done yet, but researchers have made a ribozyme that catalyzes formation of a phosphodiester bondLecture 4 (04/24/15)Where did the 1st living organism come from?- Panspermia hypothesis: life originated elsewhere in the universe and traveled here- ’76 viking: no evidence of microbial life on mars- ’96: meteorite with organic compounds and possible fossils of microbes or biological processesOparin-Haldane model1. Assemble simple molecules into building blocks for complex polymers2. Assemble polymers that can store info and catalyze reactions3. Add membranes and an energy sources to make a living organism Review Miller-Urey experiment 1953Earliest life- 3.7 billion years old sedimentary rocks containing carbon- 12C: 13C isotope profile suggests derivation from living organism (enriched 12C)How did LUCA evolve into modern life?- Woese’suniversal gene-exchange pool hypothesis o Lateral gene transfer was rampant in early life. The sister relationship of Archaea and Eucarya may be artifactual “Darwinian threshold” - Ring of life hypothesiso More than 1 hypothesis, bacterium may or may not be the ancestor of mitochondria. o Critics: doesn’t explain genes unique to eucaryao Neither bacteria nor archaea are phagocytes, so fusion seems unlikelyo Need a phagocyte with cytoskeleton 1st- Chronocyte hypothesis o An early eukaryote engulfs an archaean; the archaean later becomes the nucleus- 3 viruses, 3 domains hypothesiso 3 domains diversified while still RNA-based. Switched to DNA when DNA-based