Population Dynamics notes
Populations
- Recall that a population refers to all members of a particular species living in the same
area
- Population ecology refers to the study of factors affecting the size and distribution of
individuals within a population
- 2 important characteristics of a population are:
- Density
- Dispersion
Population density
- Is a measure of the number of individuals living in a given area or volume
- D=N/A where
- D = density
- N = the population
- A = the area (or volume) measured
- Ex. 4 deer/km^2 or 200 trees/ha or 5000000 diatoms/m^3
Density
- Low density
- Individuals are well spaced apart (highly territorial, solidary, mammal species)
- High density
- Individuals are crowded together. There are many individuals close together (ant colony)
Measuring density
- It is often time consuming and expensive to count every individual in an entire are
- For that reason estimates are usually made
- A number of smaller areas, quadrats are set up in the larger area. The number of
individuals in each quadrat are counted and the results are extrapolated to the
larger area
, Measuring density: quadrat
Population dispersion
- Dispersion refers to the patterns of spacing between individual in a species
- Dispersion can be uniform, clumped, or random
Uniform dispersion
- This distribution may result from competition for resources
- The individuals are evenly spaced out so that they each have control over the resources
in their immediate area
- Ex. Creosote bushes in the desert have extensive root systems that compete for
water. They cannot be too close to other individuals or else they lose water to
another bush
Clumped dispersion
- Caused by patches of resources in specific areas or by behavior interactions between
members of a species
- Ex. herds of caribou or humans who tend to live close to areas in high food or
resources
Random distribution
- An unpredictable, patternless dispersion
- Caused by the lack of a strong attraction or repulsion between members of a species
- Ex. adult mosquitoes - each adult flies around randomly looking for food.
Population growth
Populations
- Recall that a population refers to all members of a particular species living in the same
area
- Population ecology refers to the study of factors affecting the size and distribution of
individuals within a population
- 2 important characteristics of a population are:
- Density
- Dispersion
Population density
- Is a measure of the number of individuals living in a given area or volume
- D=N/A where
- D = density
- N = the population
- A = the area (or volume) measured
- Ex. 4 deer/km^2 or 200 trees/ha or 5000000 diatoms/m^3
Density
- Low density
- Individuals are well spaced apart (highly territorial, solidary, mammal species)
- High density
- Individuals are crowded together. There are many individuals close together (ant colony)
Measuring density
- It is often time consuming and expensive to count every individual in an entire are
- For that reason estimates are usually made
- A number of smaller areas, quadrats are set up in the larger area. The number of
individuals in each quadrat are counted and the results are extrapolated to the
larger area
, Measuring density: quadrat
Population dispersion
- Dispersion refers to the patterns of spacing between individual in a species
- Dispersion can be uniform, clumped, or random
Uniform dispersion
- This distribution may result from competition for resources
- The individuals are evenly spaced out so that they each have control over the resources
in their immediate area
- Ex. Creosote bushes in the desert have extensive root systems that compete for
water. They cannot be too close to other individuals or else they lose water to
another bush
Clumped dispersion
- Caused by patches of resources in specific areas or by behavior interactions between
members of a species
- Ex. herds of caribou or humans who tend to live close to areas in high food or
resources
Random distribution
- An unpredictable, patternless dispersion
- Caused by the lack of a strong attraction or repulsion between members of a species
- Ex. adult mosquitoes - each adult flies around randomly looking for food.
Population growth
