1. The Study of Populations
Climate Change
The Study of Populations

2. Population In ecology, a population includes all living species
group of individuals of a single species inhabiting a specific area
share the same environment, they benefit from the same resources, like water, food and sunlight
probabilities that they interact together are very high (ex. at time of the reproduction)

3. Size of Population the number of individuals in the group
Over time, size of a population can increase, remain stable, or decrease.
Four factors explain variations in the size of a population: birth rate, death rate, immigration, and emigration.

4. Factors affecting size of population
Birth rate
Death rate
Immigration
Emigration
Description
Birth of individuals within a population
Death of individuals within a population
Arrival of individuals from other regions
Departure of individuals to other regions

5. Methods of Measuring the Size of Populations
Counting Individuals
Use of quadrants
Capture-recapture

6. Counting Individuals
When possible, the number of individuals within a region are counted
May use aerial photographs to count large mammals in open areas

7. Quadrats
Rectangular piece of land separated by rope or tape which divides the piece of land
Count all individuals in the quadrant

8. Average Number of individuals per quadrat = Size of Population
Area of quadrat Total Area
Size of Population= Average number of individuals per quadrat * Total Area
Area of quadrat

9. Capture-Recapture
Used to estimate size of upwardly mobile animals such as birds, fish, seals, whales
Install cages or nets in the region that the population occupies
Counting captured animals and mark with tags, bands, or paint
Release animals to mix with other unmarked animals
Replace cages or nets
Count captured animals and recaptured animals

10. Estimated Population Size
Number of animals marked and recaptured = number of animals marked
Number of animals captured second time size of population
Size of population = number of animals marked * number of animals captured second time
number of animals marked and recaptured

11. Example 100 geese are captured, marked, and released
200 geese are captured the second time and 50 are already marked
Size of population= 100 * 200 50
= 400 individuals

12. Density of a Population
Number of individuals per unit of area or unit of volume
Density of a population=
# individuals / space(area or volume) occupied
For the same species, the density of the population may vary depending upon the habitat

13. Density of a Population
Density of population= number of individuals space occupied (area or volume)
Example: A 100 L aquarium has 5 goldfish in it.
Density of population= 5 individuals
100 L of water
= 0.05 individuals per liter of water

14. Distribution of a Population
Way in which the individuals are spread out within the space that the population occupies
Clumped distribution, regular distribution, random distribution

15. Clumped Distribution
Most frequent type of distribution in which individuals form groups
Attraction between individuals or attraction to a common resource
Ex. fish living in schools

16. Uniform Distribution
Individuals are uniformly spaced throughout the environment
Antagonistic interactions between individuals or local depletion of resources

17. Random Distribution
An individual has an equal probability of occurring anywhere in an area
Neutral interactions between individuals, and between individuals and local environment

18. Ecological Factor
An element in an environment which can have an effect on the other living species which live there
Abiotic- (nonliving) physical or chemical elements ex. pH
Biotic- (living) linked to actions of living organisms ex. predation

19. Abiotic and Biotic Factors
Abiotic Factors
Biotic Factors
Quantity of light
Birth
pH of soil or water
Sickness
Terrain
Amount of food
Thickness of snow
Predation
Temperature
competition
Humidity of the air
Human activities

20. Limiting Factors
Ecological factor which reduces the density of a population
An ecological factor can be limiting if it is absent in an environment, if there is an insufficient amount, or if it is in excess
Ex. light, water, prey

21. Biological Cycles
Includes periods during which the population increases in size and decreases in size. These periods are of fixed duration and repeat continuously.

22. Notes
See word document