Biology 106 Dr. Dudash

Study Questions Fall 1999

Study Questions Set #7 - Handed out Nov. 1, 1999.

Due: In Lab the following week.

All answers MUST be TYPED unless mathematical computation is needed.

Use no more than one of a page of single spaced typed text. (5 points)

Please answer 3 of the following questions:

1. What is the presumed role of the massive extinctions in our earth's history?

Mass extinctions result in the presence of many unfilled niches that are often filled through adaptive radiations following mass extinctions.

2. Explain how the " Tree of Life " helps us to understand the relationship among organisms? What was the major "take home message" from lab on Systematics and Phylogenetic Reconstruction?

The tree of life provides insights to the relatedness among organisms, i.e., the presence or absence of common recent ancestry. The major "take home" message from lab was that "only derived similarities identify branches of the evolutionary tree".

3. Who are the "Masters of Metabolism" and why?

Bacteria are the Masters of Metabolism because they evolved alone for 2 billion years and are ancient.

1. Photoautotrophs = harness light energy to synthesize organic comps from CO2

ex.'s, cyanobacteria, algae, plants

2. Photoheterotrophs = use light to generate ATP, but obtain carbon in organic form (not synthesized) ex., restricted to Prokaryotes

3. Chemoautotrophs = need CO2 as a carbon source, but obtain energy by oxidizing inorganic substances such as H2S, NH3, FE ++ or some other chemical

ex., unique to Prokaryotes

4. Chemoheterotrophs = must consume organic molecules for both energy and carbon

ex. Prokaryotes, protists, fungi, animals and MOST bacteria are in this group

And others from lecture, i.e., thermophiles, acidophiles, alkalinophiles.

Another category used to divide Prokaryote Metabolism is the Effect of Oxygen on the Organism

a. Obligate Aerobes = use O2 for respiration and cannot grow without it

b. Facultative Aerobes = use O2 if present, but can also grow by fermentation

c. Obligate Anaerobes = poisoned by O2

4. Why is the capsid such an important structure in the structure of a virus?

A basic virus is a nucleic acid molecule containing a viral genome. The capsid is a protein coat that surrounds the viral genome.

The capsid:

a. protects genetic material in passage from one host cell to another

b. is responsible for host specificity

c. has a # of protein subunits that determines virus particle's shape

d. shape aids in classification of viruses

5. How do viruses differ from living cells?

Researchers can crystallize them since they have a simpler chemical structure than a cell. They lack the metabolic machinery of a living cell (are parasitic on others metabolic machinery). They are dependent on a host for reproduction.

6. How does "rapid generation time" influence the role of viruses and bacteria in our society?

Rapid generation time allow these cellular organism to reproduce quickly thus having the potential to evolve rapidly, they may mutate often, and they may also move genes from one organism to the next in a number of different ways. This level of genetic recombination at such a fast rate owing to rapid generation time make s it difficult to track changes in their genetic makeup.