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 Human Action & Result Light Availability clear-cut forests and expose organisms to too much light, erosion reduces the light in water ecosystems Water availability built dams, irrigation – reduces water for organisms Temperature Global warming is decreasing suitable habitats, industries release heated water into lakes causing an increase in the water temp. Nutrient availability Farming increases or decreases soil/water nutrients which can affect plant growth Water acidity Acid rain has increased the acidity of bodies of water – killing marine life Water salinity 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