Limiting Factors Lecture

What are Limiting factors? Any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.

Abiotic Factors Temperature Climate Biome/Ecosystem Wind pH

Biotic Factors Food Availability Parasites Predators Symbiosis Competition Habitat Destruction

Situation/Example Think Grassland where grass, seeds, and mice live. If there was a drought, what would happen to the mice? Answer: Think about the grass.. Grass dies, produces less seeds. Mice get fewer seeds to eat. Mice population decreases. What about the hawks that eat the mice?

Tolerance Sometimes, organisms may survive but may not reproduce because of limiting factors. I.E. Corn needs lots of sun for 2 months to make seeds and reproduce. If grown in shade for most of that time… it will survive, but not make new plants. Tolerance is the ability to withstand fluctuations in abiotic and biotic factors.

Range of Tolerance Tolerance varies among species

Density dependent vs. density independent Factors Density Dependent means… It depends on the density (or how cramped) the population is. Density Independent means… It does not matter how dense the population is.

Density Independent variables Some Include: Temperature Storms Floods Drought Habitat Disruption (Cutting trees)

Density Dependent variables Some Include: Water Source (competition) Disease (outbreak) Food Source (starvation) Shelter Parasites

Predation as a factor