Download Biotic Factors

Biotic & Abiotic
Influences on
Ecosystems
October 19, 2012
SNC1D1
S
Limiting Factor
S Any factor that restricts the size of a
population
S Can be biotic (competition) or abiotic (access
to water, temperature)
S Human influences often act as limiting factors
Influence of Abiotic Factors
S Temperature, light, soil
S Tolerance range: the range in which a species
is able to survive
Tolerance Range
S Some species have wide ranges, while others
have narrow ranges.
S Wide range: widely distributed and easily invade
other ecosystems
S Narrow range: only found in certain areas
S Eg. Buckthorn – wide tolerance range
Lady’s slipper orchid – narrow tolerance range
Influence of Abiotic Factors in
Terrestrial Ecosystems
S Distribution of terrestrial plant species limited by
temperature, precipitation and light
S Eg. Black spruce in North America
S Limited to regions with long, cold
winters and moderate precipitation
Influence of Abiotic Factors in
Aquatic Ecosystems
S Key abiotic factors:
S salt concentration – can be negative
S availability of sunlight – decreases with depth
S Availability of oxygen – decreases with depth
S availability of nutrients - varies
Influence of Biotic Factors
S Abiotic factors determine where a species can
live, but biotic factors determine the success of
a species
S Eg. Deer can survive in dense forests, but prefer
open woodlands
Influence of Biotic Factors
- 5 main types
S Individuals are often in competition with
members of their own species and with other
species
S Compete for limited resources like food, light, space
and mates
S Eg. Red Squirrels
S Compete for pine cones and mates
Influence of Biotic Factors
- 5 main types
S Another interaction is predation.
S Occurs when an individual kills and eats another
individual
S Eg. Wolves and caribou
Influence of Biotic Factors
- 5 main types
S Mutualism occurs when two organisms interact,
and both benefit
S Eg. Nectar-producing plants and
pollinators
S Parasitism occurs when one organism lives
on or in a host and feeds on it
S Eg. Leeches
Influence of Biotic Factors
- 5 main types
S The last type of interaction is commensalism
S Occurs when one individual benefits and the other
neither benefits or is harmed
S Eg. Barnacles on a whale
Carrying Capacity
S The upper sustainable limit that an ecosystem
can support
S Maximum number of individuals of a particular
species in an ecosystem
S Can be altered by human activities
S Eg. Removal of wolves = increase in carrying capacity
for moose
Activity
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