Sample First Hour Exam --- from October 1996
Answer all questions. 5 points each.
1. If every country in the world were to set aside 30% of their land area as nature preserves (and allow the rest of their land to be developed), in which countries would the most extinction continue to occur? Why?
- tropical - more species with more small ranges
- can argue that third world countries with overpopulation provide little protection for preserves.
- size of country is not a real issue unless its a tiny island.2. What is a keystone species? Are they most likely to be high or low on a food chain?
keystone = a species which if eliminated, would affect many other species.
Its position on food chain is not the issue - keystone species are often a large component of a tropic level - ponderosa, oak, coyote, etc.3. What is a possible mechanism for a chemical that is useful to the body at low dosage becoming poisonous at high dosage?
- at high dosage it clogs an enzyme active site and prevents a vital reaction from occurring, CO vs CO2.
- at high dosage, bady can't break it down fast enough to prevent above.4. What is biological magnification and why is it a problem?
- increase in concentration of a substance as it passes through a food chain, usually due to fat soluibility. - animals at top of chain get high dose; which can be poisonous as with DDT
5. If you visited an area (like a large island) with only a few species, what would you expect to find (and why) in terms of:
a) rates of evolution?
few species = low competition. If no change in habitate, then very low rate of evolution
b) rate of extinction
- if few species - then low competition = low extinction but, if colonists from outside; rats, dogs, humans, then high rate as island forms loose competitive edge.
6. How can we be affected by the use of DDT in Argentina?
all substances in food chains eventually enter the air and water which can spread a substance anywhere. - Note that migratory birds and importation of crops were given some credit.
7. Describe two ways in which forest fires can be beneficial to the health of the forest.
- cause sucession- allow pioneer species to live.
- prevent fuel accumulation and more severe future fires.
- ash acts as a nutrient.8. If snow leopards were native to the United States instead of Asia, would they be in danger of extinction? Why or why not?
native = naturally accuring
1. since ESA only passed in 1973- maybe they would have gone extinct from hunting, fur trade, etc. before then
2. If survived until 1973- then ESA would protect them as high profile (people like cats, etc.)
3. As a predator and large, would run into problems, but so have grizzley bears and mt. lions which survive.9. If you could revise the endangered species act, how would you:
a) make it a more "rational" way of protecting unique genotypes?
- protect only full species and not populations or subspecies.
- don't protect species common in other countries but rare here.b) make it more effective?
- appropriate more money - protect habitats - start protedting when threatened - don't wait until endangered.
10. A meteor wiped out most of the life on earth 65 million years ago. After this event, would you expect the number of species to increase more rapidly on an island or on the mainland? Why?
speculation requires isolating mechanismas and different possible ways of life. A mainland area with mountains, rivers, etc. and lots of climatic sones has both much more than an island.
11. What is meant by the term "sustained yeild" when applied to a forest? How has this worked as a policy in the national forests?
SY = harvest only the annual growth of the forest. national forests don't do this on a forest by forest base and often exceed SY for political reasons. Don't spend the money to replant.
12. What is meant by the term "carrying capacity" when applied to biological systemms? How can the carrying capacity of an area be increased?
CC = when birth rte = death rate in a species; when the environment is full. Can increase it by supplying more of the one limiting factor (Leibig's law of the minimum); food, space, etc.
13. Can two different species live in the same niche? Why or why not?
If niche is defined on the needs of an organism, every organism has different needs and therefore a different niche. No two are alike and need exactly the same conditions. However, the overlap can be great enough for a needed resource that one goes extinct.
14. Is human activity increasing or decreasing the rate of speciation? Explain.
- we create more barriers - housing tracts- isolating areas of habitat; more barriers = more chances for speciation. - we move animals around across barriers; more contact- less speciation.
15. Mt. Blady just north of us has had the same climatic conditions (temp and rainfall) for the last 8000 years. How would you expect the number of species on Mt. Baldy to have changed during this time? Why? (Assume no impact of humans).
The number of species in a given area through time remains very constant (extinction = colonization). I would expect no change.
16. Present 3 problems that make it nearly impossible even after testing to fully quarantee the safety of a drug or food additive.
- synergism - the reaction with all other chemicals a person might take
- human differences - some of us might be allergic, etc.
- delayed effects - can't test for a 30 year period or future generations
- cumulative effects - what if ong term exposure?17. What in the rationale behind the way we decide who owns organisms in the United States?
- if it can cross state lines or lives in the ocean the federal government owns it. Otherwise the state owns it.
18. In New England fully 70 percent of the natural vegitation is left intact when people develope homes in the forest. Despite this, the numbers of wildlife, both birds and small mammals, are decreasing. What might account for this?
- more edge effect - change in the structure of the woods.
- more cats, dogs and kitds.
- for birds - effects elsewhere during migration, etc.