Measuring and Modeling Population Change SBI4U

Demography The statistical study of the processes that change the size and density of a population through time. Why is Demography important? Used to predict the growth of a population or develop plans to protect endangered species. What are some factors that would change the size and density of a population through time? Natality (birth rate), mortality(death rate), immigration, and emigration are factors that generate changes in a population  population dynamics How do ecologists record/follow these changes? Routine sampling What are some types of sampling an ecologist would use?

Life Tables What are some techniques demographers use? Life table – summarizes the demographic characteristics of a population How are Life Tables created? Cohort

Population Dynamics Fecundity is the potential to produce offspring in one lifetime Varies from species to species What conditions could effect a population’s fecundity? Environmental Other regulating factors: Generation time Sex ratio Parental care

Survivorship curves Used to depict data collected on a life table Displays the survival of individuals in a population over the lifespan of the species. There are 3 general survivorship curve types: I = many survive childhood and die of old age Large animals with few young and high parental care Long gestation periods II = consistent birth and death rate Short gestation period, usually prey for larger animals, feed on Type III III = high childhood mortality Large number of offspring produced

Carrying Capacity The carrying capacity is the maximum number of organisms that can be sustained by available resources for a specific amount of time. K is the carrying capacity Determined by factors in the environment

Calculating Changes Open populations Uses the equation above Closed populations No immigration or emigration Biotic potential The maximum rate of population growth under ideal conditions

Population Growth Models Geometric growth Geometric growth is growth where organisms reproduce at fixed intervals at a constant rate Growth is intermittent See example on page 663 Exponential growth Exponential growth is growth where organisms reproduce at continuously at a constant rate Growth is continuous See example on page 665

Modeling Logistic Growth Lag phase Log phase Stationary phase

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