Ecology Notes 4-Ecology Notes 4-22

Community InteractionsCommunity Interactions

Biotic vs. AbioticBiotic vs. Abiotic Biotic factorsBiotic factors – living factors in an – living factors in an

environment. Ex. Trees, birds, environment. Ex. Trees, birds, bacteria, etc.bacteria, etc.

Abiotic factorsAbiotic factors – non living factors – non living factors in an environment. Ex. Temp., in an environment. Ex. Temp., rainfall, humidity, soil.rainfall, humidity, soil.

NicheNiche Niche Niche – full range of conditions in – full range of conditions in

which an organism lives (biotic and which an organism lives (biotic and abiotic). It is like your “occupation”. abiotic). It is like your “occupation”.

CompetitionCompetition CompetitionCompetition – occurs when – occurs when

organisms attempt to use a organisms attempt to use a resource (water, nutrients, resource (water, nutrients, light, food or space) at the light, food or space) at the same time. same time.

We call this a +/- We call this a +/- relationship. relationship.

Competitive Exclusion Competitive Exclusion PrinciplePrinciple – no two – no two organisms can occupy organisms can occupy exactly the same niche in exactly the same niche in the same habitat at the the same habitat at the same time.same time.

PredationPredation

One organism One organism captures and captures and feeds on another feeds on another organism.organism.

This is a +/- This is a +/-

relationship.relationship.

SymbiosisSymbiosis – any relationship – any relationship where two organisms live where two organisms live closely together.closely together.

3 types of Symbiosis3 types of Symbiosis

1. 1. MutualismMutualism +/+ +/+ both both organisms benefit. Ex. organisms benefit. Ex. Flowers/insects.Flowers/insects.

2. 2. Commensalism Commensalism +/0 one +/0 one organism benefits and the other is organism benefits and the other is neither helped nor harmed. Ex. neither helped nor harmed. Ex. Whales/barnaclesWhales/barnacles

3. 3. ParasitismParasitism +/- One organism +/- One organism lives on or in another organism. Ex. lives on or in another organism. Ex. Dog/fleaDog/flea