The Study of Populations Climate Change The Study of Populations

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)

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Notes See word document