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Term Test Makeup exam 10ANSWERS-POST.doc

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Department
Environment
Course Code
ENV100Y5
Professor
Monika Havelka

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1. a. (3 marks) Environmental science is often described as being “interdisciplinary.” What does that mean? Give an example of an interdisciplinary approach to an environmental problem, based on something we discussed in our class lectures or from the readings. Answer: 1 mark for definition of “interdisciplinary,” 2 marks for an example. Note: Just listing the names of academic disciplines (Physics, Chemistry, Ecology, Geography...) is not enough for full marks – looking for a suggestion of disciplines coming together to contribute to our understanding of the environment, either in the definition or in the example. Definition (1 mark): “Interdisciplinary” refers to a situation where people from various disciplines bring differing perspectives and expertise to bear on a problem or topic. They all contribute their expertise to find a solution that is “greater than the sum of the parts”. (OR) An interdisciplinary field employs concepts and techniques from numerous disciplines and brings research results from these disciplines together in a broad synthesis. Example (2 marks; there are many possible examples – the example should show the contribution of at least two different disciplines, showing how they might come together to contribute to understanding or solving an environmental problem): An example that was mentioned in class and reading: If whales are dying in an estuary, a biologist might be able to determine what is killing the whales and how pollution is affecting them, a chemist might be able to look at the nature and source of the pollution, a hydrologist might be able to shed light on drainage patterns that affect which way the pollution-bearing runoff goes, a agricultural expert or industrial engineer might be able to look at agricultural and industrial processes and make changes to limit pollution, a politician might be able to pass laws regulating the pollution, etc. b. (3 marks) What is “carrying capacity”? What is “ecological footprint”? How are the two related? Answer: 1 mark for carrying capacity; 1 mark for ecological footprint; 1 mark for relating them Carrying capacity: The maximum population size that a given environment can sustain, without undergoing permanent damage. Ecological footprint: The amount of land and water required to provide the raw materials a person or population consumes and to dispose of or recycle the waste that is produced. (OR) The resources required to support a population, translated into terms of land. Relationship: Ecological footprint is the inverse of carrying capacity. (OR) Ecological footprint is land area need to support a population; carrying capacity is population that can be supported by a particular land area. c. (2 marks) Define sustainability. – OR – Define sustainable development. Answer: (2 marks for either definition) Sustainability: Sustainability refers to an approach to living on this planet (OR an approach to development), that: − Meets current human needs. − Leaves future generations with a rich and full Earth. − Conserves Earth’s natural resources. − Maintains fully functioning ecological systems. – OR – Sustainable development: Sustainable development is development that satisfies our current needs without compromising the future availability of natural resources or future quality of life. (OR) Sustainable development is development that maximizes economic, social, and environmental goals. d. (2 marks) List and very briefly describe any four steps in the scientific method. Answer: (0.5 marks for each, any four of the following, in any order, with very brief explanation) − Make observations: The scientific method typically starts with observations about some phenomenon in the natural world that the scientist wants to explain. − Ask questions: The scientist formulates questions about the phenomenon that was observed, such as why storms seem to be more frequent, or why a pond has turned green and mucky. − Develop a hypothesis: A hypothesis is an educated guess that the scientist develops to try to answer the questions that have been posed. − Make predictions: The scientist uses the hypothesis to generate prediction about the behaviour of the natural world under changing conditions. − Test predictions: The scientist designs tests – either laboratory experiments or natural experiments – that can be used to test the predictions. − Analyze and interpret results: The results of the tests are analyzed and interpreted, and used to re-state or modify the hypothesis is needed. − Repeat: The whole process is repeated iteratively. − Peer review, conference presentations, publications, grants/funding, repeatability: These are the follow-up steps to the scientific method. − Develop a theory: If a hypothesis is supported by many different tests and has the weight of scientific evidence behind it, it may eventually become a theory. 2. a. (3 marks) Indicate in your exam book the three major layers or zones of Earth (as labelled, A, B, C). Answer: 1 mark for each A = Mantle B = Core C = Crust (“Lithosphere” also accepted for full marks) b. (2 marks) Pick one of the layers from the above diagram, and briefly describe its fundamentally important characteristics or properties. Answer: Any ONE of the layers (core, mantle, or crust/lithosphere), brief description – probably looking for at least three or four of the points below (at about 0.5 marks each), describing the properties or characteristics of that layer or zone. Core (any two of): o metallic o very dense (or, much denser than the rest of the planet) o extremely hot and high-pressure o Fe-Ni composition o partially liquid and partially solid (or, inner solid, outer liquid) o magnetic field is generated in the liquid outer core o S waves cannot pass through the liquid outer core OR Mantle (any two of): o rocky o denser than the crust but not as dense as the core o convects o basaltic magma is generated here o top part is the asthenosphere OR Crust/Lithosphere (any two of): o two types: oceanic crust and continental crust o Earth’s outermost layer o rocky (silicate) composition o oceanic crust = basalt (dense) o continental crust = granitic (less dense) o crust + topmost portion of mantle = lithosphere c. (1 mark) Why is water such an important and unique substance? Please give two reasons. Answer: (0.5 marks for each of two reasons, any two of the reasons listed here) − supports life (OR) required for life (OR) even land-dwelling organisms need water to live − dominates Earth’s surface − unique chemical properties – polar molecule (OR) positive on one end, negative on the other end; bonds easily with other polar molecules − unique chemical properties – hydrogen bonding − stays liquid over a wide range of temperatures − occurs at Earth’s surface in solid, liquid, and vapour forms (ice, water, water vapour or steam) − strong cohesion properties (for example, this makes it possible for raindrops to fall) − participates in or acts as a medium for many biological and environmental processes − universal solvent − high heat capacity (helps stabilize systems against change) − ice (solid) less dense than water (liquid) – floating ice insulates organisms in the water below d. (2 marks) What is one important thing that scientists have learned about the history of life on this planet, through studying the fossil record? Answer: (2 marks for any one of the following) − the species living today are only a tiny fraction of all the species that have ever lived − the vast majority of Earth’s species are long extinct − earlier types of organisms changed, or evolved, into later ones − the number of species existing at any one time has increased through history (OR) biodiversity has increased through Earth history, although not evenly − there have been several episodes of mass extinctions, or simultaneous loss of great numbers of species, superimposed on background extinctions through Earth history − most of the history of life on this planet has been dominated by micro-organisms (bacteria) − There are other possible answers. e. (2 marks) What was the role of cyanobacteria in the chemical evolution of Earth’s atmosphere? Answer: (There are all kinds of things that could be said, but the following is the crucial piece; doesn’t need to be in complete sentences.) Cyanobacteria are photosynthetic, and were one of the earliest life forms on Earth. These organisms probably played the major role in oxygenating Earth’s atmosphere [i.e., they generated oxygen which eventually built up to the point where “free” molecular oxygen could be sustained in the atmosphere]. 3. a. (2 marks) What is a heterotroph? Are all consumers heterotrophs? Answer: (1 mark for “What is...” and 1 mark for “Are all...”) − What is...: An organism that consumes other organisms. − Are all...: Yes. b. (2 marks) What is a mutation? How could a mutation result in an adaptive trait? Answer: (1 mark for “What is a mutation”; 1 mark for “How could…”) − A mutation is an accidental change in DNA (OR genetic makeup) from one generation to the next. − If the trait or characteristic that is expressed as a result of the mutation is beneficial or helps the organism survive or adjust to a change in the environment, then it is an adaptive trait. c. (2 marks) Prof. Havelka told us that “the environment exerts selective pressure on organisms”. What did she mean by that? Answer: (2 marks for any reasonable explanation, fairly complete) The environment exerts selective pressure means that the existence of or, especially, changes in certain environmental factors force individuals to adapt, which then leads to natural selection. Individuals that are able to adapt to environmental changes or pressures are the ones that will be successful and will be selected for. In other words, individuals that have advantageous or adaptive traits tend to be more successful than other individuals reproductively, which means that they will pass along more of their genetic material to future generations of that population. Environmental factors that tend to cause pressure leading to natural selection include limits on resources (food, space, light, access to mates) and the existence of threats (predators, diseases, poor weather, lack of water). d. (4 marks) Choose one of the following types of natural selection. Explain what it is, and give an example of how it might work: Answer: Any one of the following (2 marks for “what it is” and 2 marks for an appropriate example/explanation, OR 4 marks overall if the example is integrated into the answer): − Stabilizing selection is natural selection that preserves the status quo. (OR) Stabilizing selection is natural selection that doesn’t favour one or the other extreme, but tends to reinforce intermediate traits. − For example, in the case of a snail that might have a thicker or thinner shell, stabilizing selection would tend to produce a shell of intermediate thickness. For an organism that might be larger or smaller (such as horses, for example), stabilizing selection would tend to produce horses of intermediate size. (OR) − Directional selection is natural selection that selects for a particular feature or trait. (OR) Directional selection is natural selection that drives a feature in one particular direction. − For example, in the case of a snail, directional selection would produce progressively thicker shells. Another example would be a giraffe selected for a progressively longer neck over the course of its evolution. (OR) − Disruptive selection is natural selection that reinforces traits that are NOT intermediate. (OR) Disruptive selection is natural selection that drives features towards more than one extreme; in other words, extreme traits are favoured. − For example, disruptive selection might favour both thin-shelled and thick-shelled snails, but not snails with an intermediate thickness of shell. 4. a. (2 marks) What is the difference between mass extinctions and background extinctions? Answer: (1 mark for each) − Mass extinction is when a large percentage (or a large number) of species all die out at once, in a very short time period (geologically speaking). − Background extinction refers to the extinctions of species that go on all the time, throughout Earth history. b. (2 marks) What is the difference between parasitism and symbiosis? Answer: (1 mark for an explanation of each term; not necessary to go into too much detail about the contrast, but the difference between the two terms should be made clear for full marks.) − Parasitism is a species interaction that has a benefit for one but harms the other participant. (OR) Parasitism is a species interaction in which the parasite depends on the host for nourishment or some other benefit, but doesn’t usually kill or consume the host (+/–). − Symbiosis is a species interaction that benefits both participants (+/+). c. (2 marks) What is a food web, and how is it different from a food chain? Answer: (Mainly looking for some suggestion of the underlined points, for 0.25 marks each.) A food web is a representation of feeding interactions within an ecological community that shows an array of relationships between organisms at different trophic levels. (OR) A food web is a “map” of feeding relationships among organisms in an ecosystem showing the many paths by which energy flows among organisms as they consume one another. (OR) A food web is the combination of a number of food chains within an ecosystem that together show the complex paths by which energy moves from one trophic level to another. d. (2 marks) What is a trophic pyramid? Why do the levels of a trophic pyramid get smaller from the bottom to top of the diagram? Answer: (1 mark for “What is…?” and 1 mark for “Why…?”) What is a trophic pyramid? (1 mark): A diagram showing the trophic levels (or energy levels or biomass) in a food chain, with autotrophs at the bottom and moving up through the heterotrophs. Why do the levels get smaller…? (1 mark): The trophic levels get smaller from the bottom to the top because they represent energy (or stored biomass or numbers of individuals), and energy is lost in going from one level to the next (and/or) numbers of individuals and amount of biomass decrease from level to level. [Also correct but not required: The lost energy is partially energy that is used by the organisms to carry out their metabolic functions, and part waste, released heat, etc.] e. (2 marks) What is primary production? What is the role of autotrophs in primary production? Answer: (1 mark for “What is primary production?” and 1 mark for “What is the role…?”) What is primary production? (1 mark): The conversion of solar energy to carbohydrates [OR sugars] during photosynthesis, performed by autotrophs. (OR) Production of biomass through the process of photosynthesis. (OR) Production of organic matter by the process of photosynthesis or chemisynthesis. (OR) Production of biomass by primary producers (bacteria, plants). (OR) production of biomass from inorganic materials, by autotrophs. What is the role of autotrophs in primary production? (1 mark): Autotrophs are the primary producers. (OR) Autotrophs carry out primary production. 5. a. (4 marks) In your exam book, draw a picture of a simple system. Portray it as a box model, with two reservoirs. Thoroughly label the various parts of the diagram. Show a system that is at steady state; define steady state, and briefly explain how your diagram illustrates a system at steady state. Answer: − Must be a box model with two connected reservoirs – not one, not three! (0.5 marks) − Definition of steady state (1 mark): A state of dynamic equilibrium or balance. (OR) A state in which the fluxes into and out of each reservoir are balanced. (OR) Homesostasis. − Brief explanation of how the diagram shows steady state (such as, “I have shown equally- sized arrows, indicating equal fluxes into and out of the reservoirs.”) (1 mark) − Required labels (0.5 marks each): o reservoir o burden (OR) content o flux (OR) flow (OR) transport process. b. (3 marks) Choose one of the following tectonic environments. Briefly describe it, and give a real, modern-day example. Answer: (1 mark for explaining divergent, convergent, or transform + 1 mark for one additional descriptive point + 1 mark for a correct example) − divergent plate boundary, oceanic: a divergent boundary is a boundary along which the plates are moving apart; an oceanic divergent boundary is one along which an ocean is splitting or rifting, and widening; new crust is created by magma welling up along the rift; Example: mid-Atlantic rift (or) mid-Atlantic ridge (or) the Red Sea − convergent plate boundary, continent-continent: a convergent boundary is a boundary along which the plates are coming together; continent-continent will be a collision zone where the two continents collide and crumple up into large mountain ranges; earthquakes but no volcanism; Example: Himalayas (or) India-Asia − convergent plate boundary, continent-ocean: a convergent boundary is a boundary along which the plates are coming together; continent-ocean boundary there will be subduction – the oceanic plate will subduct under the continent; earthquakes + volcanism; Example: the Andes (or) Juan da Fuca − transform fault plate boundary: a transform or strike-slip boundary is one along which the plates are sliding laterally or horizontally past one another; earthquakes but no volcanism; Example: San Andreas Fault, California c. (3 marks) What is the difference between a “source” and a “sink”? Can a source ever be a sink? (Briefly explain.) Answer: 1 mark for each definition + 1 mark for “Can a source ever be a sink?” A source is a reservoir from which material [or energy] flows from another reservoir [that is, where the inputs come from]. (OR) A source is a reservoir that gives out more than it takes in. A sink is a reservoir into which material [or energy] flows from another reservoir [that is, where the outputs go]. (OR) A sink is a reservoir that takes in more than it gives out. [Looking for something like the following]: A source can be a sink, because typically matter flows both into and out of reservoirs. A reservoir functions as a sink when it receives matter, but then if matter leaves the reservoir to go to a different reservoir, it functions as a source. 6. a. (2 marks) Why is the carbon cycle so complicated, and relatively poorly understood? Please mention and very briefly discuss at least two reasons. Answer: (1 mark each, for any two reasons) − Fluxes vary a lot, both in time and space − There are many carbon species involved in the cycle − Carbon changes from oxidized forms to reduced forms − Carbon changes from organic to inorganic forms − Many reservoirs are involved – carbon cycles among biotic and abiotic reservoirs − Hard to measure fluxes on a global scale − Cycle is changing as a result of anthropogenic impacts − Hard to take local measurements of fluxes and scale them up to a global scale − There may be other possible answers but I can’t think of them. b. (4 marks) What distinguishes a biogeochemical cycle from any other type of cycle (such as, for example, the sodium cycle)? In your answer, discuss the basic differences and mention at least two specific characteristics. Give two examples of major biogeochemical cycles. Answer: 1 mark for generally “how they are different from other cycles” + 2 marks for two specific characteristics that make biogeochemical cycles different (1 mark each). Two examples of major biogeochemical cycles = 1 mark (at 0.5 marks each). (How they are different) Any two of the following: Biogeochemical cycles are different from other cycles because: o they involve materials that are crucial for the support of life and biological processes o they involve materials that change from organic to inorganic form o they usually involve all of the major Earth reservoirs – atmosphere, hydrosphere, geosphere, biosphere o the materials in them are transferred from biotic to abiotic reservoirs o they are typically considered on a global scale, although they often have local aspects o “involve chemical transformations” is only good for ½ marks (Examples) Any two of the following: o Carbon o Sulphur o Oxygen o Nitrogen o Phosphorus o Water/Hydrologic c. (4 marks) The total carbon content in the atmosphere is approximately 730 billion tons, in the form of carbon dioxide gas. Plants remove 100 billion tons 2f CO from the atmosphere through net primary production each year. How long would it take the atmosphere to run out of carbon dioxide as a result of this process, if there were no means of replenishing it? For half of the marks for this question, please provide a clearly labelled sketch of a simple box model illustrating this transfer of material from one reservoir to another. For the remaining marks, do the simple calculation and provide the answer. Answer: (2 marks for sketch + 1 mark for brief explanation or math set-up + 1 mark for correct answer): Explanation/Answer: Removing 730 billion tons from the atmosphere at a rate of 100 billion tons/yr: 730 billion tons = 100 billion tons/yr x (? yrs) 730 billion tons ÷ 100 billion tons/yr = 7.3 yrs 7. a. (2 marks) What is one characteristic that humans have in common with apes? What is one fundamental way in which humans differ from apes? Answer: (1 mark for each correct answer – one needed for each, similarity and difference) Characteristics humans have in common with apes (any one of the following, at 1 mark): − strong [or broad] shoulders with wide range of movement (adapted for life in trees) − [“body structure” is vague; 0.5 mark] − more reliance on sight than smell − overlapping fields of vision; 3-D sight − ability to grasp and manipulate small objects; opposable thumb − relatively large brain in relation to body size − complex social lives (OR) live in large, complex social groups − form longlasting social relationships − participate in social bonding activities − form strategic coalitions with each other
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