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Biotic & Abiotic Influences on Ecosystems

October 19, 2012

SNC1D1

Limiting Factor

Any factor that restricts the size of a population

Can be biotic (competition) or abiotic (access to water, temperature)

Human influences often act as limiting factors

Influence of Abiotic Factors

Temperature, light, soil

Tolerance range: the range in which a species is able to survive

Tolerance Range

Some species have wide ranges, while others have narrow ranges. Wide range: widely distributed and easily

invade other ecosystems Narrow range: only found in certain areas

Eg. Buckthorn – wide tolerance range Lady’s slipper orchid – narrow tolerance range

Influence of Abiotic Factors in Terrestrial Ecosystems

Distribution of terrestrial plant species limited by temperature, precipitation and light

Eg. Black spruce in North America Limited to regions with long, cold winters and moderate precipitation

Influence of Abiotic Factors in Aquatic Ecosystems

Key abiotic factors:

salt concentration – can be negative availability of sunlight – decreases with

depth Availability of oxygen – decreases with

depth availability of nutrients - varies

Influence of Biotic Factors

Abiotic factors determine where a species can live, but biotic factors determine the success of a species

Eg. Deer can survive in dense forests, but prefer open woodlands

Influence of Biotic Factors- 5 main types

Individuals are often in competition with members of their own species and with other species Compete for limited resources like food,

light, space and mates

Eg. Red Squirrels Compete for pine cones and mates

Influence of Biotic Factors- 5 main types

Another interaction is predation. Occurs when an individual kills and eats

another individual Eg. Wolves and caribou

Influence of Biotic Factors- 5 main types

Mutualism occurs when two organisms interact, and both benefit Eg. Nectar-producing plants and

pollinators

Parasitism occurs when one organism lives on or in a host and feeds on it Eg. Leeches

Influence of Biotic Factors- 5 main types

The last type of interaction is commensalism Occurs when one individual benefits and

the other neither benefits or is harmed

Eg. Barnacles on a whale

Carrying Capacity

The upper sustainable limit that an ecosystem can support Maximum number of individuals of a

particular species in an ecosystem

Can be altered by human activities Eg. Removal of wolves = increase in carrying

capacity for moose

Activity

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