STUDY GUIDE A2 (76-108) and 2 (76-111), SELF TEST 2

© Department of Physics, University of Guelph.

Select the problem number or part you wish.

1. Cell culture A has a population of 1.00X103; culture B has a population of 1.50X103. Culture A has a growth constant of 0.0500 day-1. Culture B doubles in size every 3.00 days. How long will it be until culture B has p times as many cells as culture A?

2. The number of walruses in a certain bay is increasing exponentially. On April 1, 1979, the population was 323. On April 16, 1978, the population was 298.
(a) How many months ago (before April 1, 1979) was the population 200? (Assume that 1 month = 30.0 days.)
(b) What would the population have been on Aug. 16, 1974?

3. This question tests your understanding of the wording of questions.
(a) N = N0ekt (or ln(N/N0) = kt)
If the population increases by a factor of 1.6, then which of the following is true?

(a) N = 2.6 N0
(b) N = 1.16 N0
(c) N = N0/2.6
(d) N = 1.6 N0
(e) N = N0/1.6

(b) The statement in (a) is equivalent to saying that the population increases by x% where x is equal to:
Note carefully the bold portions of 3a and 3b.

(c) At some time in the future, there are 7 times as many cells in A as there are in B. Which of the following is true?

(d) N = N0e-kt (or ln(N/N0) = -kt)
If the population decreases by a factor of 3 every 2 days, which of the following is true?
(a) 3 = e-2k
(b) ln(1/3) = -2k
(c) 2/3 = e-2k
(d) ln(2/3) = -3k
(e) ln (1/3) = -3k

(e) N = N0e-kt (or ln(N/N0) = -kt)
If the population decreases by a factor of 33 1/3% every 2 days, which of the following is true?
(a) 3 = e-2k
(b) ln(1/3) = -2k
(c) 2/3 = e-2k
(d) ln(2/3) = -3k
(e) ln (1/3) = -3k

Note carefully the difference in wording between 3d and 3e.

4. A wolf population increases with a growth constant of 0.278 yr-1. After 5.00 yr,

(a) by what factor has the population increased?
(b) by what percentage has it increased?

5. A deer population is declining with a decay constant of magnitude 0.327 yr-1. After 6.00 yr,

(a) by what factor has the population declined?
(b) by what percentage has it declined?