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EAS25_Exam2_Key.doc A) Multiple choice -­‐ circle the letter of the best answer. (1 point each): 1) Vicariance can best explain a) allopatric speciation b) sympatric speciation c) parapatric speciation d) all of the above 2) Linnaeus’ contribution to taxonomy included:
a) the concept of evolution by natural selection
b) the introduction of the species concept c) a hierarchical system of classification d) the concept of endosymbiosis 3) Lynn Margulis contributed to: a) the concept of evolution by natural selection
b) the introduction of the species concept c) a hierarchical system of taxonomy d) the concept of endosymbiosis 4) In the past few decades, the primary cause of endangerment and extinction of terrestrial species has been: a) hunting b) habitat destruction c) climate change d) invasion by exotic species. 5) Clausen Keck and Heisey’s work on transplant gardens helped establish the notion of a) the ecotype b) genetic drift c) gene flow d) endosymbiosis 6) What drives the approximately 100 KY cycle of Earth’s temperature in the past 800,000 years? a) eccentricity b) tilt c) precession d) sunspot activity 1 EAS25_Exam2_Key.doc 7) Compared to the Eocene Optimum, Earth’s Pleistocene climate would best be described as a a) hot phase b) cold phase c) similar temperature state d) warmer or colder state (depending upon whether we are in a glacial or interglacial phase) 8) Behaviorally, Homo sapiens became “fully human” approximately a) 5,000,000 years ago b) 1,000,000 years ago c) 200,000 years ago d) 40,000 years ago 9) Evidence for a climate contribution to megafaunal extinctions is strongest in: a) Australia b) North America c) Africa d) Europe 10) A “natural” classification would be a) paraphyletic b) polyphyletic c) monophyletic d) all of the above B) Short Answer (proposed point count in parentheses before each question): 1) Describe a geological process that can cause vicariance, and define the time scale involved. (1 point)[Continental drift due to plate tectonics can cause vicariance over periods of millions (hundreds of millions) of years] [Also accepted answers discussing changes in sea level creating/removing land bridges, flooding and stream changes separating species, and bolide impact – if they specified secondary processes causing extinction, new niches etc…] 2) Describe a limitation of using molecular sequences to reconstruct phylogenies. (1 point) [largely limited to extant organisms, different clocks (e.g. mitochondrial vs. nuclear DNA) operate at different speeds and on different time scales] [Part marks for things like time consuming, expensive, etc. or incomplete answers – ie. limited ability to reconstruct phylogenies (why?). Did not accept morphological differences or environmental changes] 2 EAS25_Exam2_Key.doc 3) Briefly contrast and compare the biological and morphological species concept. Your answer should include a brief explanation of an advantage and disadvantage of each concept. (2 points) The biological concept indicates individuals interbreed and provide fertile offspring; this concept does not work with species that reproduce asexually (e.g. vegetative reproduction). The morphological species concept implies that species can be identified by phenotype; however phenotype is “plastic” and can change with environmental conditions, making this a difficult criterion for defining species. [For full point you needed to discuss the concepts and compare advantages/disadvantages. DNA sequencing is not an advantage for the biological concept – that is a methodology for recreating phylogenies and defining species.] 4) According to the Broecker Hypothesis, what caused the Younger Dryas and why was it more pronounced in the Greenland than Antarctica? (2 points) The breaking of an ice dam and the flooding of the North Atlantic with freshwater from Lake Agassiz presumably altered the ocean’s thermohaline circulation, reducing the transport of heat to the northern Atlantic. This would have affected Greenland more than Antartica. 5) Contrast the current climate of the Southwestern US to that during the Wisconsin glaciation. What evidence exists for this climate change? (2 points) The southwestern US was cooler and wetter during the glaciation. Evidence exists in remnants of forests at lower altitudes, and in the abundance of former lakes (now lake beds) that date to this period. Cold (partial marks); covered in ice was not accepted; saying a change in fossils was evidence was partial marks – but indicating that there are more species now is not – there was migration up slopes as the climate dried. 6) Do species migration since the Pleistocene best fit the Clementian or Gleasonian model of community structure and dynamics? Explain your answer using evidence discussed in class or your book. (2 points) Species migrated not in lock step, but in an individualistic way (migrating in different directions and at different speeds), suggesting communities were not obligate associations (as Clements suggested), but were chance associations the (Gleasonian view). 7) Briefly discuss a proxy record used in reconstructing climate over the past 400,000 years. Your answer should specifically explain how this record is used to derive temperature. (2 points) 3 EAS25_Exam2_Key.doc Possible answers include: oxygen isotopes in the ice core (or foram) record – delta 18O vs 16O is used to estimate prevailing temperature during that time. [Also took arguments for CO2 concentration changes and the link it has to temperature.] 8) Describe an event in the past history of Earth (not the Holocene) where the advent of a new type of organism fundamentally changes the Earth system, including the climate. Name the type of organism involved, and explain how it changed the atmosphere or climate. (2 points) The advent of photosynthesis (cyanobacteria) altered the atmosphere and the climate, by reducing atmospheric carbon dioxide levels and increasing atmospheric oxygen and ozone levels. The advent of terrestrial plants led to further declines in atmospheric carbon dioxide and to the buildup of stable soil carbon (and fossil carbon) pools. 9) According to Dr. Alex Wolfe, what is the proposed year of the start of the Anthropocene Epoch, and (from a stratigraphic perspective) why was this date chosen? (2 points) 1945, the date of atomic bomb tests, which placed radioactive elements into the Earth’s sedimentary layers of the time, which provided a convenient stratigraphic marker. 10) Describe two contrasting types of genetic change, one gradual and one abrupt, that lead to new phenotypes and possibly new species. Briefly explain the mechanism of change for each case. (4 points) Gradual – evolution by natural selection, genetic drift, gradually change the frequency of alleles/genes in a population. Evolution involves variation, selection, inheritance, and changing gene frequencies over time. Genetic drift involves random changes in gene frequency and is particularly prevalent in small, isolated populations. Abrupt – transposition, polyploidy are all abrupt changes. Bits of DNA can move to a new location (transposition) or chromosome number can be multiplied (polyploidy), causing new phenotypes and often reproductive isolation and the formation of new species. 4