Learning Targets Identify characteristics of populations and significant population growth patterns. Summarize the current state and effects of human population growth.

Population Ecology

 Population Size Factors that affect population size: Birth Rate: number of individuals being born into the population. Mortality/Fatality: number of individuals that are dying in the population. Immigration (IN): number of individuals coming into the population. Emigration (Exit): number of individuals leaving the population.

Population Growth Curves Explain what is happening to the populations below:

Biotic Potential = Reproductive Potential  Biotic Potential = Reproductive Potential Rate at which a population could grow if it had unlimited resources If a population reached its biotic potential it would have exponential growth 

No Limiting Factors!

The “J” Curve (Exponential Growth)

The “S” Curve: Logistic Growth  The “S” Curve: Logistic Growth This graph shows a typical population growth curve. Under ideal conditions a population would have a growth with a slow start. Then a very fast rate of increase finally the growth slows down and stops (reaches carrying capacity). 

Carrying Capacity Maximum number of individuals of a particular species that the environment can normally and consistently support.

Population Crash Dramatic decline in the size of a population over a short period of time.

Population Density Measurement of the number of individuals living in a defined space.

Population Dispersion Way in which individuals in a population are spread throughout an area. Clumped Dispersion: organisms live close together in groups. Uniform Dispersion: individuals living at specific distances from one another due to territory disputes and competition. Random Dispersion: individuals spread out randomly.

Environmental Limits on populations  Environmental Limits on populations Density-dependent: Affected by the number of individuals in an area. Include many different species interactions. Disease Food Parasitism Predation Competition Density-independent: Environmental factors that affect a population regardless of the population density. Temperature Storms Floods Drought Habitat Disruption

Competitive Exclusion Density Dependent This graph shows the effect of interspecific competition on the population size of two species of paramecia, Paramecium aurelia and Paramecium caudatum. Competitive Exclusion

Density Independent This graph shows the decline in the population of one of Darwin's finches on Daphne Major, a tiny (100-acre) member of the Galapagos Islands. The decline (from 1400 to 200 individuals) occurred because of a severe drought that reduced the quantity of seeds on which this species feeds. The drought ended in 1978, but even with ample food once again available the finch population recovered only slowly.

Organism Interactions Limit Population Size  Organism Interactions Limit Population Size Predation Competition Within a species (Intraspecies Competition) Between 2 Species (Interspecies Competition) Parasitism Crowding/stress

The Human Population Why has there been exponential growth since 1850?