500 MHR • Unit 5 Population Dynamics
17.In order to estimate the size of a population
of oak trees, a forester runs several 100 m
transects through a 100 ha woodlot and counts
the number of oaks within 5 m of the line. Five
of the transects produced the following results:
15, 17, 25, 16, and 20.
(a)What is the forester’s estimate of the
density of oaks in the woodlot?
(b)Estimate the size of the oak population in
this woodlot.
(c)Design a sampling procedure that would
allow the forester to obtain a more accurate
estimate.
18.A researcher caught and tagged a sample of
50 deer mice in an isolated field. She waited
two weeks and then captured a second sample,
consisting of 63 mice. Of these 63 mice, 10
were tagged — they had been in the original
sample and were captured a second time. How
big was the population of mice in the field?
What might cause this estimate to be biased?How might the researcher reduce such bias in
future studies?
19.Brewer’s yeast is a type of fungus that produces
ethyl alcohol as a waste product of metabolism.
Reproduction most often occurs asexually by
a process called budding, in which one cell
produces another identical to itself. Consider
this to be an example of reproduction in which
two offspring are produced and the “parent”
dies. Under good conditions, yeast reproduces
every 15 minutes.
(a)If a small amount of yeast (say 500 cells)
were used to start a culture, how many
cells would be present after 24 h?
(b)What do you think naturally limits the
growth of yeast populations?
(c)Design an experiment that would allow
you to determine what naturally limits
the growth of yeast populations.
20.Moose are not native to Newfoundland. The
first moose — two males and two females —7.How might predation or parasitism explain
why a population’s size does not increase
indefinitely?
8.In what way is the relationship between a
population of herbivores and the plants they
eat similar to the relationship between predator
and prey populations?
9.Compare competition and mutualism with
respect to their effect on the growth of two
interacting populations.- (a)Explain why two species with very similar
niches have a high probability of competing
with each other. How can they co-exist?
(b)What process or processes might occur to
reduce the competition?
11.Is a virus a predator or a parasite?
12.Female grizzly bears typically have only one
offspring each year. Black bears, however, often
produce twins or even triplets if conditions are
favourable. Female grizzlies do not begin
breeding until they are three to four years old,
whereas black bear females reach sexual
maturity at two years of age. Grizzly bears have
a more restricted diet and are more particular
about what type of sites they will use for dens.
Grizzly bears are also larger than black bears.
Which of these species do you think is more
K-selected? Justify your answer.
13.Give three examples of species that typically
have Type III survivorship curves and three
that usually have Type I survivorship curves.
14.Clumped dispersion patterns are often the
result of what might be called positive
interactions among members of a species; if
one individual is present at a given spot, the
chances are higher that more will be at the
same spot. Uniform dispersions are the result
of negative interactions. In this case, the
presence of an individual (or pair) tends to
lower or decrease the probability (chance)
that another individual will be found nearby.
With this in mind, how might you describe a
random distribution in terms of the probability
of finding individuals near each other?
15.For a population with overlapping generations
to increase in size, the growth rate (r) must be
greater than zero. In a population with non-
overlapping generations, what must the
replacement rate be for the population to
increase in size?
16.A population of deer contains 10 000
individuals. During a year, 5000 individuals
are born and 4500 die. What will be the size
of this population 10 years from now?INQUIRY