Populations and Resources

Population

Is a group of organisms of one species that lives in the same place, at the same time, and can successfully reproduce.

Example: Elephants.

Exponential Growth

Accelerating growth that produces a J-like curve when the population is graphed.Only occurs for short periods in natureUsually when the organism has a lot of resources.

Limiting Factors

Exponential growth cannot be sustained in nature because no ecosystem has an unlimited supply of resources.These restrictions are called limiting factors.Abiotic limiting factors: temperature, pH, oxygen, light, hiding placesBiotic limiting factors: food, etc.

Carrying Capacity

Is the size of a population that can be supported indefinitely by the resources and services of an ecosystem.

When a population is maintained at its carrying capacity, it is at an equilibrium or balance.

There is an equal amount of organisms being born or moving into the ecosystem as there are dying or leaving.

Graphing Carrying Capacity

Humans and Carrying Capacity

Humans alter natural ecosystems often, causing a change to carrying capacities.Urban sprawl is the growth of relatively low-density development on the edges of urban areas.Human population in the Golden Horseshoe is expected to increase by 3.7 million between 2005 and 2031. How do we make room for all these people without affecting other ecosystems?

Ecological Niche

As species go about their daily activities, they interact with other species.

An ecological niche is the way an organism occupies a position in an ecosystem, including abiotic and biotic factors.

Example: brown batBiotic niche: insects that it eats, its competitors like the nighthawk, and its predators.Abiotic niche: place for roosting and hibernation, the time of night it hunts, airspace it flies in, the temperature range it can live at.

Population RegulationPredators: organism that kills and consumes other organismsPrey: is eaten as food by a predatorBottom-Up Population regulation: a shortage of plant resource at the base of the food chain causes declines in the animals in the higher trophic levels.Top-Down Population regulation: more rabbits in a population, lead to more coyotes to eat them, then more coyotes lead to fewer rabbits.

Competition

Competition occurs when 2 or more organisms compete for the same resource.

Can limit size of population

Can influence the ecological niche of an organism

Symbiosis

Mutualism: 2 species benefit from the relationship

Example: algae lives in coral. The algae gives the coral energy and the coral gives the algae protection and carbon dioxide.

Parasitism: when an organism benefits at the expense of a different organism.