Transcript Biotic and Abiotic Influences on Ecosystems

Biotic and Abiotic Influences on
Ecosystems
Section 2.7
Limiting Factor
 The factor that restricts the
size of a population
 Can be biotic – availability of
food
 Can be abiotic – access to
water
 Humans are often the limiting
factor in ecosystems
Key Limiting Abiotic Factors – Page 53
Abiotic Factor
Light Availability
Water availability
Temperature
Nutrient availability
Water acidity
Water salinity
Human Action & Result
clear-cut forests and expose organisms to too much
light, erosion reduces the light in water ecosystems
built dams, irrigation – reduces water for organisms
Global warming is decreasing suitable habitats,
industries release heated water into lakes causing an
increase in the water temp.
Farming increases or decreases soil/water nutrients
which can affect plant growth
Acid rain has increased the acidity of bodies of water –
killing marine life
Run off from roads that have been treated with salt
increases the salt content of water – killing marine life
Key Limiting Biotic Factors
 Can be between individuals of the same species or between
species
 Competition – two individuals fight for the same resource
 Predation – one feeds off another
 Mutualism – two individuals benefit from each other (nitrogen
bacteria that grow on plant roots)
 Parasitism – one individual lives in or on another (tapeworms)
 Commensalism – one benefits and the other one neither
benefits nor is harmed (moss on trees)
Tolerance Range
 The abiotic conditions within
which a species can survive
 Some have a wide range
others do not
 Optimal range is where the
organism grows best.
Carrying Capacity
 The maximum population size of a particular species that a
given ecosystem can sustain.
 Can be altered through natural or human activity
Today’s Task
 Pg. 55# 2, 3, 4