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Term Test 10ANSWERS-POST.doc

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University of Toronto Mississauga
Monika Havelka

1. a. (3 marks) In class we defined “environment” to include biotic and abiotic components, the built environment, and social/cultural institutions. How do social/cultural institutions influence the natural environment? Please mention three ways. Answer: (1 mark for each of three reasonable ways that social/cultural institutions influence the natural environment. Specific examples are not necessarily required, but how each of them is connected to the natural environment needs to be clear.) Social/cultural institutions influence the natural environment through: − the establishment of laws (OR) regulations governing the use of the environment or withdrawal of resources (just saying “laws” would only be good for ½ mark) − laws or regulations that govern our impacts on the environment, such as limiting pollution − government policies, such as setting aside protected land or subsidizing resource extraction − economic incentives, such as carbon taxes − economic drivers such as poverty, which might lead a country to exploit its natural resources, for example − cultural values, such as holding a certain natural location to be sacred or important − traditional ecological knowledge − religious values that might lead us to view or relationship with the environment in a certain way, such as the Christian ethic of dominating the environment − aesthetic values that might lead us to value one part of the environment differently from another − universities and other research institutions that contribute to our understanding of natural environmental processes − There are other possible examples; the connection to the natural environment should be clear. b. (1 mark) Name one biotic and one abiotic component of the natural environment. Answer: (0.5 marks for biotic; 0.5 marks for abiotic – not necessary to define them, just give an example. They need to be examples from the NATURAL environment, not from the BUILT environment, so “buildings” is not an appropriate example of an abiotic component, for example.) − Biotic: (anything living) possible examples include tree, bird, moss, deer, fish, etc. − Abiotic: (nonliving components of the environment) possible examples include water, sunlight, minerals/rocks (Note soil is not a good example, since so much of soil is alive; 0.25 marks for soil as an example, either for biotic or abiotic) c. (2 marks) What is the difference between environmental science and environmentalism? Answer: (1 mark for each; not absolutely necessary to have a long statement contrasting them, as long as the difference is made clear) − Environmental science is a scientific undertaking that explores the interactions between humans and the physical/biological world. (OR) Environmental science is the pursuit of knowledge about how the natural world works, how natural resources and processes support life, and the impacts of our activities on the natural world. − Environmentalism is a social movement aimed at protecting the natural environment. (OR) Environmentalism is advocacy on behalf of the natural environment. − The contrast: Science is a systematic approach to learning about the world and testing our knowledge; in principle, science (and therefore environmental science) strives to remain an objective source of knowledge about the world. By definition, in contrast, advocacy (and therefore environmentalism) is biased and not objective; this is the main contrast with environmental science, which strives to remain objective. d. (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. e. (2 marks) What is the difference between a hypothesis and a theory? Answer: (1 mark for reasonable explanation of each term; not necessary to have a detailed statement contrasting them, as long as the difference is clear) − A hypothesis is an educated guess that explains a phenomenon or answers a scientific question. − In contrast, a theory is a widely accepted, well-tested explanation that has been extensively validated by a great amount of research. 2. a. (3 marks) Please list three characteristics that make Earth unique as a planet. Answer: (1 mark for each of three characteristics from the following list) − nitrogen-and oxygen-rich atmosphere (OR) particular composition of Earth’s atmosphere (it is NOT sufficient to just say “atmosphere”) − existence of water in three forms (solid, liquid, gas) at the surface (it is NOT sufficient to just say “water”) − ecosphere (OR) conditions that support life (OR) life-supporting sphere − biosphere (OR) existence of life − dynamic nature of rock weathering − dynamic, multi-component nature of soil − dynamic nature of the lithosphere (OR) plate tectonics b. (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 c. (2 marks) Name and briefly describe one of the main hypotheses that have been proposed to explain the origin of life on Earth. Answer: (1 mark for name, 1 mark for brief description; any one of the following) − Heterotrophic hypothesis (or “primordial soup” hypothesis): life evolved from a “primordial soup” of simple inorganic chemicals (based on experiments on early atmosphere) − Panspermia hypothesis (or “seeds from space”): microbes or organic precursors from elsewhere were delivered to Earth on meteorites − Chemoautotrophic hypothesis (or “life from the depths” hypothesis): life originated at deep-sea hydrothermal vents, in a high-temperature environment where organisms created their food from chemicals (sulphur) rather than by photosynthesis − There are other possibilities, not discussed in detail in class or in the readings, and these would be valid answers; for example, one hypothesis suggests that life originated in “sea foam,” and another hypothesis suggests that the first RNA was patterned on inorganic molecules found in clay minerals. 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 are two characteristics of Earth’s early atmosphere that made it very different from our modern atmosphere? Answer: (1 mark for each of two from the following list) Unlike the modern atmosphere, Earth’s early atmosphere was: − Reducing (oxygen-poor) − Different composition (need to list at least two of these for one mark) – rich in C2 , CO, SO ,2CH ,4NH , 3O , x O 2 (vapour) − Dense (OR) high atmospheric pressure − Hot − Not hospitable for life as we know it 3. a. (2 marks) Contrast the concepts of habitat and niche. – OR – Contrast the concepts of fundamental niche and realized niche. Answer: (1 mark for acceptable explanation of each term; not necessary to have a detailed statement contrasting them, as long as the difference is clear) Habitat vs. niche: − Habitat is the specific environment in which the organism lives. − Niche is its use of resources and functional role in the community – in other words, habitat is where it lives, whereas niche is what it does – its “job” or role. – OR – Fundamental niche vs. realized niche: − Fundamental niche is the niche (role) that an organism would fill in the absence of any competition; its full niche. − Realized niche is a portion of the fundamental niche, the part of the fundamental niche that an organism is able to fill if there is competition. b. (2 marks) What is the difference between a species and a population? Answer: (1 mark for acceptable explanation of each term; not necessary to have a detailed statement contrasting them, as long as the difference is clear) − A species is a group of organisms that shares certain characteristics and is biologically able to breed and produce fertile offspring. − A population is a group of organisms of the same species that live in the same area and have reproductive access to each other. − Therefore, a species would typically be composed of numerous populations living in different areas. 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 1 mark for an appropriate examples, OR 3 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 interspecific competition and intraspecific competition? Answer: (1 mark for each) − Interspecific competition refers to competition for resources that occurs among individuals of different species. − Intraspecific competition refers to competition for resources (or, for example, for mates) that occurs among individuals of the same species. b. (2 marks) What is the difference between predation and parasitism? 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.) − Predation is a species interaction in which one species (the predator) hunts, captures, kills, and consumes the other (the prey). − 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. − Killing and consuming the prey is part of predation; in parasitism, killing the host can happen but it is not usually the goal and is generally not beneficial to the parasite because it ends the parasitic benefit. c. (1 mark) What is a food web? Answer: (Mainly looking for some suggestion of the underlined points, for 0.25 marks each. Note: a definition that applies to “food chain” is insufficient; a food web is different from a food chain.) 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. (5 marks) This diagram illustrates a trophic pyramid with three levels. Please draw a similar diagram in your exam booklet and label all parts thoroughly. Why do the trophic levels get smaller from the bottom to top of the diagram? Answer: (0.5 marks for each label – there are ten possible labels shown here (and some more possibilities are listed below; awarding 0.5 marks each, for any eight of them = 4 marks for the labelling; 1 mark for answering the question) Why do the trophic levels get smaller…: The trophic levels get smaller from the bottom to the top because they represent energy (or stored biomass), and energy is lost in going from one level to the next. The lost energy is partially energy that is used by the organisms to carry out their metabolic functions, and part waste, released heat, etc. (Note: “Tertiary” also acceptable as a label on the diagram. Level one, level two, level three are not really very informative as labels. Examples are acceptable – such as “Grass, Cow, Human” for the three levels.) 5. a. (2 marks) What are the two fundamentally different types of crust in Earth’s lithosphere? Briefly describe their characteristics. Answer: (0.5 marks for naming them; 0.5 marks for saying a couple of things about each of them) − Oceanic crust: dense; made of basalt; relatively thin − Continental crust: less dense; made of granite; relatively thick 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) Is Earth a closed system? Why (or why not)? Your complete answer should include the definition of a system, and the definition of a closed system. Answer: (1 mark for system definition; 1 mark for closed system definition; 1 mark for discussion of “Earth as a closed system”): − System (1 mark): A network of relationships among a group of parts, elements, or components that interact with and influence one another through the exchange of energy, matter, and/or information. (OR) A portion of the universe that can be separated by boundaries, for the purpose of studying changes that occur within the system under changing conditions. − Closed system (1 mark): A system that is self-contained with regard to exchanges of matter (but not energy) with its surroundings. (OR) A system in which energy but not matter can pass through the boundaries. (OR) A system whose boundaries are non- porous with regard to matter, but which allow energy to pass. − Earth as a closed system (1 mark; must mention both energy and matter for full marks. NOTE that the answer can be either “YES” or “NO” – the important thing is the discussion.) Technically, Earth is not a closed system because both energy and matter can pass through the boundaries. However, Earth is a close approximation of a closed system because energy comes in [solar energy] and goes out [heat], but extremely little matter (in comparison to the total mass of the planet) enters or leaves the system. [Meteorites come in, space ships and hydrogen atoms leave; that’s about it.] d. (2 marks) What does it mean if a system demonstrates “emergent properties”? Give an example. Answer: (1 mark for “emergent properties”; 1 mark for an example. OR 2 marks overall, if the example is integrated into the description): − A system is said to portray emergent properties when the system as a whole portrays characteristics that are not evident in the individual components of the system on their own. “The whole is greater than the sum of the parts.” − For example, the individual components of a tree might be a leaf, a twig, an insect, a root, etc. Together, as a tree, they display emergent properties that none of the individual components possess on their own, such as providing shade, providing habitat, producing oxygen via photosynthesis, sequestering carbon, etc. (Other examples are possible.) 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. (2 marks) Most of Earth’s nitrogen exists as gaseous nitrogen in the atmosphere. Name one other major biogeochemical cycle in which the atmosphere is an important reservoir, and one major biogeochemical cycle in which the atmosphere is not an important reservoir. Answer: (1 mark for each) − Atmosphere is an important reservoir in: o carbon cycle (OR) o sulphur cycle (OR) o oxygen cycle (OR) o water cycle or hydrologic cycle − Atmosphere is not an important reservoir in: o phosphorus cycle o sodium cycle (OK for ½) c. (2 marks) What is a positive feedback cycle? How does it differ from a negative feedback cycle? Answer: (1 mark for each; not necessary to have a long explanation of the differences, as long as the difference is clear enough from the definitions) − Positive feedback cycle (or loop): a feedback loop in which output of one type acts as input that moves the system in the same direction (OR) the input and output drive the system further toward one extreme or another (OR) a self-reinforcing, self- perpetuating, or “vicious” cycle − Negative feedback cycle (or loop): a feedback loop in which output of one type acts as input that moves the system in the opposite direction (OR) the input and output essentially neutralize each other’s effects, stabilizing the system (OR) a homeostatic, self-regulating, or “equilibrium” cycle d. (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 of CO from th2 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) 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 − genetic similarity, especially with chimpanzees Fundamental differences (any one of the following, at 1 mark): − language (OR) ability to speak (OR) throat structure that allows speech − bipedal − brain is more complex and larger relative to body size − complex reasoning ability and intellectual capacity − elaborate culture and communications − Someone might answer “genetic difference from apes”; I think this is only good for 0.5 marks, because in the grand scheme of things it is actually more of a “similarity” than a difference, unless the extent of the difference is specified. b. (2 marks) Today we know that competition for scarce resources can cause conflicts and other problems, as predicted by Thomas Malthus. What is one important thing that Malthus got wrong in his predictions about human population growth? Answer: (2 marks for one of the following) − He did no
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