Dr. Reichler’s Bio 301M   MWF 9-10am    Print Name:____________KEY___________
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 pts)
A) When radioactive H gives off an electron the neutron becomes a proton changing the H to He.
B) 75

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 mutations.

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 present previously.

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 pts)
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 pts)
Many answers- must include the relationship between the ecological problem and the conflict.