Problemset
Title
Essay Questions
Introductory
Text
Question 1
Type:
Senescence is due to both genetic and environmental factors. Give at least three obvious
examples of evidence in support of this statement.
Hint:
Do all animals in the same environment live for the same amount of time?
Essay
Feedback: pp. 66-68 There are many obvious examples: Do turtles and fish in the same
environment live equally long? They certainly have different genes. Do cats in
France live about as long as cats in your town? They certainly have different
environments.
Question 2
Type:
Essay
What is the difference between programmed and unprogrammed theories of senescence?
Give two examples of each type of theory.
Hint:
What is a "program"?
Feedback: pp.68-72 and 73-77 The many programmed theories and unprogrammed
theories are discussed in this chapter so it should be easy to come up with
examples.
Question 3
What is the current biological clock theory based on? What does the evidence show?
Hint:
Think of telomere strands.
Type:
Feedback: pp. 69-70 The theory is largely based on the upper limit on cell division which
Essay
is governed by telomere length so you should explain how this works. As will
all theories, the evidence is, at best, mixed and indirect. In support of the
theory is the work on immortal cancer cells but, on the other side, is the finding
of long telomere strands in senescent tissues.
Question 4
Describe free radical theory, evidence, and impact.
Hint:
Why do people take anti-oxidants?
Type:
Feedback: pp. 74-75 You should explain what free radicals are where they come from.
Essay
You could then present evidence in support (e.g., the presence of SOD in all
living organisms) and the difficulties in testing the theory (e.g., anit-oxidants
suppress appetite so it could be eating less that is beneficial). You might show
its impact by describing the plethora of products that promote the anti-oxidants
they contain and/or the free radical damage they prevent.
Question 5
Why is immune system theory hard to place as programmed or unprogrammed? What
problems does this theory have?
Type:
Hint:
Essay
Feedback: p. 73 One version of this theory (leaky defense) is very much like a
programmed theory if you assume the thymus is programmed to disappear
while the other version (autoimmune) is unprogammed if you think the system
attacks body tissues that have been changed by environmental (e.g., free
radical) damage. A major problem is explaining the initial damage to the
immune system (also free radicals?).
Question 6
Type:
Describe one other programmed (not biological clock) and one other unprogrammed (not
free radical) theory.
Hint:
Not immune system theory since it's a middle category.
Essay
Feedback: You could choose evolution (pp. 70-71) or hormone (pp. 71-72) for your
programmed theory and garbage accumulation (pp. 76-77) or DNA damage
and repair (p. 77) as your unprogrammed theory to describe.
Question 7
Type:
Essay
Why does the text conclude that none of these programmed and unprogrammed theories
will be able to explain all forms of senescence? Describe possible interactions between the
presented theories that may explain senescence.
Hint:
Think of the problems that each theory has encountered.
Feedback: pp. 77-78 and Figure 4-2 The problem for any one theory can be found in the
evidence against it (e.g., long teleomere strands in senescent tissue). You
should enjoy creating and describing possible interactions and Figure 4-2
should be fairly helpful.