Dr. Reichler’s Bio 301M MWF 9-10am Print
Exam #3 May 2, 2007
Read each question carefully and don’t hesitate to
ask if a question seems unclear. If possible, answer each
question in the space provided, but if needed, continue on the
back. If you use a drawing as part of your answer, be sure to
also include a written explanation. These questions have specific
answers, although for some, more than one answer is possible. To
receive full credit you must clearly and fully answer the question
being asked. This exam is worth 103 points with the points for
each question noted in parentheses.
1. Would having a lot of biodiversity also mean that there was a lot of
ecosystem diversity? Why or why not? (8 pts)
No, ecosystem biodiversity means
several different types of environments. A single area could have
many different species, but all existing in one ecosystem.
2. If rural populations decline leading to farmland being restored to
rainforest, would these restored rainforests be the same as other
rainforests that had not been disturbed? Why or why not? (8 pts)
No, many species cannot survive
during succession, and so they would not be present after secondary
succession is complete. OR Climate change would make these areas
different from what they once were.
3. If today there are 100 radioactive hydrogen atoms (half-life ~12
years), and after 12 years there are 50 hydrogen atoms and 50 helium
atoms. A) Where did the helium atoms come from? B) How many
helium atoms will there be after another 12 years (24 total years)? (6
A) When radioactive H gives off an
electron the neutron becomes a proton changing the H to He.
4. Some of the workers and firefighters at Chernobyl were killed by the
radiation in the few weeks after the accident. Were they killed
by cancer? Why or why not? (6 pts)
No, cancer takes time for mutations
and cancer cells to build up. These people died as a result of
the radioactivity killing their cells directly.
5. What are two signs that the organisms in the Chernobyl exclusion
zone are still being affected by the radiation? Describe what the
evidence is and how that evidence indicates the affects of radiation
exposure. (8 pts)
Any two of: Aquatic worms
changing from asexual to sexual reproduction- sexual reproduction gives
the worms some protection from mutations, and the increase is seen as a
response to increased mutations due to radioactive contamination.
Unusual tree growth- many of the trees that have regrown have unusual
growth such as many branches; this is likely due to mutations.
Bird survivorship- the survivorship of monitored birds is lower in the
Chernobyl area than in other similar areas probably due to increased
6. Why might restoring areas in Darfur to their previous biodiversity
be difficult? (8 pts)
Decreasing rain means that the
resources available for the ecosystem are now different from what was
7. One solution to restoring a changing ecosystem is to introduce new
species that are better adapted to the new climate. What is a
risk of doing this? (8 pts)
Introducing non-native species can
have disastrous consequences. Invasive species can disrupt
interrelationships between pre-existing species.
8. How can introducing a new predator, a secondary or higher consumer,
affect the primary producers? (8 pts)
Increases in predators can decrease
levels of primary consumers that can mean an imbalance of primary
producers due less consumption.
9. You are involved in restoring an ecosystem, and some of the native
species have been reduced to just a few individuals. Why might
you want to bring in some members of these species from other areas? (8
After a species is reduced to a small
number of individuals, the genetic diversity of that species is reduced
to a level where they cannot continue to reproduce. By bringing
in other individuals from another area the genetic diversity can be
increased allowing successful reproduction.
10. Why would large areas of farming and channelizing a river have a
similar affect on the animals in each of those ecosystems? (8 pts)
Both lead to decreased niches due to
the homogenization of the ecosystem thereby reducing biodiversity.
11. To restore a creek, would you start by restoring natural water flow
and then allowing normal succession to take place, or by introducing
native plants and animals first? Why? (6 pts)
The native plants and animals will
not survive without natural water flow. So restoring water flow
must come first.
12. What is one difference between the initial stage of primary and
secondary succession? (6 pts)
The quantity of available
resources. Bare rock has virtually no resources. An area
undergoing secondary succession may have many resources, only lacking
the species to make use of those resources.
13. Given a city of 200,000 people, would the nearby creeks be
healthier with a dense development of tall buildings or spread out
development of single story homes? Why? (6 pts)
Many single story homes will have a
large area of impervious cover thereby increasing the area of the creek
that is subjected to flash flooding and contamination after moderate
rain. A denser development will have relatively less impervious
cover, meaning that the footprint of impervious cover will be less.
14. Do you expect more or fewer future human conflicts over
resources? Why? (6 pts)
Likely more conflicts. Human
population is increasing and resources are not. Rain decreases in
some areas will lead to greater conflicts. Alt answer: Some
areas are experiencing increases in rainfall, and that may diminish
conflicts in those areas by making more resources available.
Bonus: Describe a conflict, other than Darfur, and how ecological
issues have been in some part caused the conflict. Include what
is the conflict (it can be something current or historical), and the
relationship between the ecological problem and the conflict. (3
Many answers- must include the
relationship between the ecological problem and the conflict.