Limits to Growth n Limiting Factor Any factor

Density-Dependent Factors n Factors that only become limiting when the population goes above a

Density-Dependent Factors – Predation (Predator-Prey Cycling) § Number of prey animals increases. § Predators

Density-Dependent Factors – Parasitism and Disease § As organisms live closely together, it is

Density Independent Factors n Factors that affect populations the same way regardless of density.

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Limits to Growth n Limiting Factor: Any factor that can cause the population’s size to decrease – Examples § Competition § Predation § Parasitism/Disease § Drought § Human Disturbance

Density-Dependent Factors n Factors that only become limiting when the population goes above a certain density. – Examples: § Competition: When there are lots of the same organism, they need to fight for food, nesting places etc.

Density-Dependent Factors – Predation (Predator-Prey Cycling) § Number of prey animals increases. § Predators have an easier time catching them. § Number of predators increases. § Predators eat more and more prey. § Number of prey animals decrease. § Number of predators decrease from starvation. § Number of prey animals increase again.

Density-Dependent Factors – Parasitism and Disease § As organisms live closely together, it is easier for diseases and parasites to infect more organisms. § Why do people get more colds during the winter? – People are indoors more of the time, so the population density increases. – It is easier for cold viruses to be passed from person to person.

Density Independent Factors n Factors that affect populations the same way regardless of density. – Bad storms – Tornadoes – Droughts – Damming Rivers – Clear-cutting forests