Biology 12

472 MHR • Unit 5 Population Dynamics

SECTION REVIEW

1. What is the biological definition of the term
   “population”?


2. Why is it important to be able to develop
   accurate estimates of natural populations of plants,
   animals, and other species of living organisms?


3. Why is it often necessary to estimate population
   size, rather than counting each member of a
   population individually?


4. Describe what is meant by the density of a
   population.


5. When is it useful to use transects to sample
   populations?


6. Develop a procedure in which transects are used
   to sample the species within a region. Select a local
   ecosystem for study.
   7. Suppose that in a study of a particular species
   of rodent, a sample of 200 was trapped, marked,
   and released. Later, a second sample of 200 was
   obtained and it was discovered that 20 percent of
   these animals were recaptured (that is, they were
   already marked). Based on these data, estimate
   the size of the total population.
   8. How might the abundance and distribution of
   food in a habitat influence how a species is dispersed
   in its environment?
   9. Research the types of sampling techniques
   typically used to estimate populations of migrating
   species, such as the caribou (Rangifer tarandus) in
   northern Canada. How do researchers attempt to
   improve the accuracy of their observations?

I

K/U

I

I

K/U

K/U

K/U

MC

K/U

Figure 14.8Many species of bats tend to forage (find food)

alone at night, but roost in colonies during the day.

Figure 14.9Each homeowner in this development has his

or her own territory.

the members of a population, and that offspring

disperse more or less equally over all distances.

Since these conditions are rarely met in nature,

random dispersion patterns are unusual.

It is important to recognize that the dispersion

pattern displayed by a population may vary between

seasons, or even with the time of day (as with the

bats shown in Figure 14.8). The scale at which a

population is examined is also important. For

example, the human population of Canada has a

clumped dispersion. Looking at the country overall,

most of its human population is concentrated in

cities and towns. But if you focus on a smaller

scale and look at the population of one city, you

will often find a more uniform distribution (as

illustrated in Figure 14.9).

Whether members are clumped, randomly

scattered, or uniformly dispersed, many populations

change in size. In the next section, you will learn

how and why this happens and what factors affect

the rate at which such change occurs.