Limiting factors are those things in an ecosystem that restrict the size, growth, and/or distribution of a population. Biotic or biological limiting factors are things like food, availability of mates, disease, and predators. Abiotic or physical limiting factors are non-living things such as temperature, wind, climate, sunlight, rainfall, soil composition, natural disasters, and pollution.
Carrying Capacity
The population size of a species that can be supported by an ecosystem is called its carrying capacity. When populations increase in size, there is a greater demand for resources which increases competition. Natural selection comes into play and the individuals who are the most capable of competing and adapting will survive while the others die out. This is one of many natural feedback loops that help control the size of populations.
Limiting factors are further subdivided into two categories related to the density of the population—density dependent factors and density independent factors.
Density Dependent Factors
Some abiotic limiting factors affect members of a population because of the population density. These things include disease, food supply, and increased predation. Diseases and parasites are more easily transmitted in larger populations. More individuals mean increased competition for the food that is available. In addition, larger populations attract more predators who seek out individuals that are weak, injured, or diseased.
Density Independent Factors
Other limiting factors affect populations regardless of its density such as drought, floods, earthquakes, human activity, fires, and pesticides. Density independent factors are often abrupt and can kill all members of smaller populations.
Some Abiotic Factors are Unique to Ecosystems
All organisms need food to survive, so this biotic limiting factor is common to all ecosystems. Other environments like freshwater biomes, the desert, tropical rainforests, and the arctic tundra have biotic limiting factors that are unique to that area. For example, arctic foxes and polar bears are unique predators on the arctic tundra. Also, scorpions and cacti are biotic limiting factors in the desert that are not present on the arctic tundra.
References
- Limiting factor. (2018, May 12). In Wikipedia. Retrieved from https://en.wikipedia.org/w/index.php?title=Limiting_factor&oldid=840885313