Midterm

Spring 2002

Multiple Choice: THE CORRECT ANSWER IS IN BOLD TYPE (14 questions, 2 points each).

1.      Estimates about processes or phenomena in environmental science are difficult to make because

a.       we don’t have the proper technology to produce exact estimates.
b.      estimates are made of many interacting variables that scientists study all at the same time.
c.       the methods are not very accurate.
d.      Earth systems are large, complex, and involve many interacting variables.
e.       All of the above are true. (a, b, and c are true SOMETIMES, for some variables, so I accepted it)

2.      Consider the biosphere and the troposphere.  Choose the answer that best describes their interaction.

a.       Troposphere contains ozone, which protects the biosphere from harmful UV rays.
b.      The biosphere depends on the troposphere for energy flow.
c.       The biosphere obtains much of the inorganic carbon required for photosynthesis from the trophosphere.
d.      The troposphere is the major source of phosphate for the biosphere.

3.      Why do patterns of primary productivity relate to the distribution of terrestrial biomes?

a.       Biomes determine the amount of primary productivity that will occur.
b.      They’re not related – knowledge of biome type does not allow prediction of primary productivity.
c.       Solar energy input is the primary determinant for both biome distribution and primary productivity.
d.      Climate is the primary determinant for both biome distribution and primary productivity. (c and d both accepted)

4.      What would happen to an ecosystem if all its decomposers and detritus feeders were eliminated?

a.       Predators would have nothing left to eat.
b.      Nitrogen would remain trapped in plant material.
c.       No nitrogen would leave the atmosphere.
d.      Organic matter would build up in the ecosystem.

5.      Why are nonpoint pollution sources more difficult to control than point source pollution?

a.       Nonpoint sources cannot be easily identified.
b.      Point sources are more expensive to control.
c.       Nonpoint sources cannot be controlled.
d.      Nonpoint sources clean themselves up through natural purification methods.

6.      The sun provides

a.       all of the energy used by life on Earth.
b.      all the matter used by life on Earth.
c.       the energy to drive nutrient cycles.
d.      UV light, which is essential for photosynthesis.
e.       All of the above are provided by the sun.

7.      What determines the distribution of aquatic life zones?

a.       Temperature
b.      Nutrient inputs
c.       Light
d.      All of the above are determinants.

8.      Which of the following is most important in causing mountains to be islands of high biodiversity?

a.       Their important role in the hydrologic cycle.
b.      Their high susceptibility to erosion.
c.       A high diversity of habitats and transition zones.
d.      The snow line.

9.      What is the environmental significance of the law of conservation of matter?

a.       Waste we create never actually disappears when we throw it away.
b.      Nutrients in ecosystems cycle within that ecosystem only.
c.       Precious resources will never run out.
d.      Soot from smokestacks will be consumed by chemical reactions in the atmosphere.

10.  Climate change is primarily caused by which of the following root causes of environmental problems?

a.       Unsustainable resource use
b.      Stable human population growth
c.       Poverty
d.      Overmanaging natural systems

11.  Gene flow _______________, while genetic drift ________________ (choose the best combination).

a.       is random, is nonrandom
b.      decreases genetic variation, increases genetic variation
c.       is caused by mutation, is caused by natural selection
d.      increases genetic variation, decreases genetic variation

12.  The Columbia River system has which of the following environmental problems?

a.       Proliferation of flood control levees.
b.      Natural flow altered by numerous dams.
c.       Invasion of numerous exotic species.
d.      Depleted trout populations.

13.  Which of the following is NOT a characteristic of a species that is more extinction-prone that other species?

a.       It is a habitat specialist.
b.      It has low genetic variation.
c.       It has a low reproductive rate.
d.      It has a wide geographic distribution.

14.  Oceans

a.       have most of their biodiversity at great depths in the open ocean.
b.      provide few ecological services to humans, but many economic ones.
c.       have all of their life in the upper euphotic zone.
d.      have most productive zones near coasts.

Short answer.  Reminder: confine your answers to the space immediately below each question.

15.  Define two of the following terms (4 pts – 2 pts each):

a.       Element: distinctive building blocks of mater that make up every material substance
b.      Atom: smalles unit of matter unique to a particular element
c.       Molecule: combinations of two or more atoms of the same or different elements held together by chemical bonds
d.      Compound: two or more different elements held together in fixed proportions by attractive forces called chemical bonds.
e.       Ion: electrically charged atoms or combinations of atoms (gained or lost an electron)

16.  Give an example of a biological polymer.  What type of monomer makes up this molecule (4 pts)?

Protein, or polypeptide, made up of amino acids
Complex carbohydrates, starch, cellulose, or glycogen, made up of simple sugars
Nucleic acids, DNA or RNA, made up of nucleotides

17.  If warm air is less dense than cool air, then why does it expand when it cools as it rises higher in the troposphere (4 pts)?

Warm air, at the same pressure as cool air, takes up more volume, so as it cools it should not expand, but contract. However, as it rises there is less air above, and hence less pressure, and so even though it is cooling it is still expanding due to the decreased pressure it is under.

18.  Explain energy quality and use the second law of thermodynamics to explain why energy cannot be recycled (6 pts).

Energy quality is a measure of an energy source's ability to do work. High quality energy is concentrated and can perform more work than low quality energy. Energy cannot be recycled because when it is used to do work it is degraded to lower quality, less useful energy. Once given off as heat in the environment it is much dispersed and will not be easily recaptured to perform work (it will cost more high quality energy to get any work out of the low quality energy than the low quality energy is worth).

19.  What is one important aspect of the law of conservation of matter as it applies to the mercury cycle (5 pts)?

As mercury cycles in the environment it will never go away. Unlike many other pollutants that may degrade to their component elements, mercury is an element. As basic matter, it cannot be destroyed, biodegraded, or changed. It may change forms, but the mercury is always a component of the resulting molecule.

20.  What is a necessary condition for speciation to occur?  List two isolating mechanisms that are likely to be involved in species formation (6 pts).

Necessary conditions include isolation of two (or more) populations, time, and genetic variation. Isolating mechanisms are numerous, but the most important for speciation, ultimately, is reproductive isolation. Others include geographic (or spatial), temporal, mechanical, gametic, behavioral, hybrid infertility, and hybrid inviability.

21.  What is one reason for the importance of genetic variation in microevolution?  Answer using no more than one sentence (5 pts).

Genetic variation is the raw material for natural selection. It increases biodiversity and allows for adaptations to environmental change.

22.  State two reasons why streams may be sensitive to pollution (4 pts).

Because they are tied so closely to the land, streams are subject to runoff containing pollution and sediments (from erosion). Although many streams have low flow and small volume, the flow itself can help clean up the pollution (many of you stated that was what makes them more sensitive - not necessarily true). It may be that the flow can cause quick spread of pollutants, but that could also clear pollutants out of a stream. Changing land use in watersheds may also alter flow and volume characteristics of streams.

23.  Choose one of the following and list three ecological (ecosystem) services provided by that ecosystem or organism (6 pts).

a.       Trees: modify climate, provide food, materials, habitat, prevent erosion, filter pollutants from soils and air, and more.
b.      Corals: provide habitat for high biodiversity, buffer coasts from storms, absorb CO2.
c.       Estuaries: filter pollutants, provide habitat for waterbirds and marine creatures, buffer coastal habitats, and more.
d.      Oceans: moderate global climate, absorb CO2 and heat, provide food, and more.

24.  List one preventative and one cleanup control to address both of the following pollution problems (8 pts):

a.       ground-level ozone: PREV: decrease vehicle emissions; CL: filter pollutants, plant more vegetation, disperse pollutants above thermal inversions.
b.      cultural eutrophication: PREV: decrease vehicle emissions, fertilizer runoff, phosphates in detergent; CL: filter nutrients from water, remove algae and/or plants
 c. increasing carbon dioxide: PREV: decrease vehicle emissions, and fossil fuel burning; CL: plant more trees/vegetation

25.  If the world warms up in the coming century, many things are predicted to happen.  For three of the following five resources or habitats, state one thing that may change as temperatures increase.  Be specific (6 pts).

a.       Biodiversity: may decline as species that can't adapt to changing environment or migrate to new habitat go extinct.
b.      Coastal habitats: may suffer from more extreme storm events or may become aquatic as sea levels rise.
c.       Forests: may suffer same fate as biodiversity, or may suffer from more frequent fires in some regions as climates change to become drier.
d.      Human health: tropical diseases may become more frequent in temperate zones, we may suffer from food shortages and other resource depletions, which may cause more war and violence as competition for those resources increases
e.       Water resources: distribution and availability will change, as weather patterns and climate shift. Some areas will have more water, others will have less. This will affect many biomes and organisms, including humans. May contribute to forest and biodiversity effects listed above.

26.  Consider two mountain ranges, one at 10oN latitude and the other at 50oN latitude.  Assuming that both ranges have the same average elevation, which would you expect to have more habitat and biotic diversity?  Which would have habitats more affected by north/south facing slopes (4 pts)?

10N will have higher biodiversity, as it will have more biomes represented and more ecotones. 50N mountains will have habitats more affected by north/south facing slopes, especially in winter when the tilt of the Earth points that hemisphere more away from the sun.

Essays.  Use only the space provided below each question to answer.

27.  Choose one of the following to answer (10 pts):

a.       Distinguish between perpetual resources, renewable resources, and nonrenewable resources.  List one example of each. Perpetual are constantly renewed and will never be used up (at least in the lifetime of the human species). Examples are the sun, wind, tides. Renewable resources will be sustainable as long as we use them at a rate lower than that at which they are renewed. Examples are forests, fisheries. Nonrenewable resources are not replenished, at least within a time scale similar to the our use of them. Metals and fossil fuels are nonrenewable (the latter are renewed at a time scale of millions of years).
b.      Explain upwelling.  Then briefly state how ENSO (El Niño-Southern Oscillation) affects upwelling off the coast of South America. Upwelling occurs when winds blow off a continental coast, moving warm water away from the coast. Cold bottom water must come up to replace the moving water. This cold water often brings nutrients that have sunk to the continental shelf back up, making them available to organisms, especially phytoplankton, at the surface of the ocean. Upwelling areas, therefore, are incredibly productive, accounting for many of our fisheries. When ENSO occurs, for some unknown reason, the winds slow down or cease or reverse direction. That keeps the warm, nutrient poor water near the coast of Peru and other South American countries, keeps upwelling from occuring, and decreases fish catches and causes changes in regional and global weather patterns.
 c. List evidence for and against the current extinction crisis. Provide two pieces of evidence for and two against the proposition that we are in another mass extinction caused by humans. Evidence for a mass extinction includes estimates of background and current extinction rates, along with estimates of total numbers of species. Many species' populations are declining, and some have not been observed for years (and are suspected to be extinct). For taxa that we know well, there is documented evidence of declines of many species, and if their habitat is destroyed, then they have nowhere to live. The root causes of extinction are increasing, so those species that are endangered and threatened now are likely to go extinct within a matter of decades. Evidence against is that all those estimates are just that: estimates. They are not reliable, we've observed few actual extinctions, and the actual number of species may be so high that the few extinctions we've observed are not indicative of a higher extinction rate than background. Documented declines do not mean a species is extinct, and it is difficult to prove a negative (that a species no longer exists). It is also difficult to show that a species we don't even know about is no longer with us.

28.  Select one biogeochemical cycle and discuss or diagram that element’s movement through three of four of Earth’s life support spheres.  Use at least two processes and two forms of the element to illustrate the cycle, and state one way that humans are disrupting the cycle (10 pts).

For full credit, you must address all the requirements above. Show how a nutrient moves through biosphere, hydrosphere, atmosphere, and lithosphere (three of these), what forms they take in those spheres (physical states of gas, liquid, solid, or chemical states (e.g., CO2 and carbohydrate are two forms of carbon)), and what processes cause these changes. Processes can cause changes in physical state (e.g., evaporation changes liquid to vapor) or chemical state (e.g., respiration changes carbohydrate to carbon dioxide and nitrification changes ammonia to nitrite or nitrate). A mention of two processes and two forms are necessary. Finally, any way that humans disrupt the cycle is the last requirement to earn full credit.

29.  Select one type of grass-dominated biome and one type of tree-dominated biome (forest).  Identify your choices.  Compare the climates of those biomes and the adaptations of the dominant vegetation to those climates.  Compare energy flow and productivity within the two biomes and illustrate any connections to other biomes (10 pts).

You must identify the biomes you chose and accurately compare climates. Then at least one adaptation of each major vegetation type that allows them to survive in the climate indicative of that biome must be discussed. Energy flow and productivity can be discussed in general terms, such as mentioning which biome is more productive and how that affects energy flow and numbers of trophic levels. Connections to other biomes may include energy flow connections or physical connections to neighboring biomes.

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Page last modified by Chris Paradise, July 18, 2002