14.1 Characteristics of
Populations
Ewen Lee and Adriena Wong
Special Key Terms
 habitat – the place where an organism or species
normally lives
 species – organisms that resemble one another in
appearance, behaviour, chemistry, and genetic
makeup, and that interbreed, or have the ability to
interbreed, with each other under natural conditions
to produce fertile offspring
Population Size and
Density
 To study populations, scientists measure certain
characteristics:
 Population size
 Population density (D)
 Population dispersion
Population Density (D)
 The number of individuals of the same species that
occur per unit area or volume
D = N/S
 N = total number counted
 S = amount of space
Example
 What is the population density of 480 elephants
living in a 600 hectare (ha) region?
D = N/S
D= 480 elephants/600 ha
D=0.8 elephants/ha
Population Density
 Population density can be deceiving because of the
unusable space within a habitat
 Ecologists need to distinguish between:
1. Crude Density
2. Ecological Density
Population Dispersion
1. Clumped dispersion
2. Uniform dispersion
3. Random dispersion
Measuring Population
Characteristics
 Biologists use different techniques to measure
population because it is usually unreasonable to
count the exact number of organism
 This may include:
 Using a quadrat
 The mark-recapture method
Mark-Recapture Method
 Used for fish species and large animals
 Animals are first captured and tranquillized (if
necessary)
 They are then marked with tags or bands or dye and
released
 After enough time as passed for the marked animals
to mix with the non-marked ones, a second sample
is captured
Mark-Recapture Method
M/N = m/n
 M = total # marked
 N = total population
 m = # of recaptures
 n = size of second sample
Example
 Using the mark-recapture method, scientists mark
80 seals were marked and then released. Two weeks
later, 110 seals were captured. 12 of them were
marked. What is the total size seal population of the
area?
N = Mn/m
N = (80)(110)/12
N= 733.33
Technological Tracking
 Instead of marking the animals with dye or bands,
biologists may also attach radio collars, satellitelinked devices or other equipment to the animals
 This helps researchers track animals over a large
geographic range.
 Patterns can be mapped in geographic information
systems (GIS)
Ethics of Studying Wild
Populations
 People are concerned with the the effects of these
techniques:
1. What are the effects on animals being pursued,
captured and marked?
2. What are the long-term effects of repeated
tranquillizing of large animals?
3. Are marking techniques humane?
4. Can the collars and tags harm the animals?
CCAC
 CCAC – the Canadian Council of Animal Care
 Is developing ethical guidelines for wildlife
research:
1. Researchers must reduce their use of animals
2. Researchers must refine techniques to minimize
stress and pain
3. Researchers must replace the trapping of animals
with other techniques when possible
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