Ecosystems and CommunitiesEcosystems and Communities
Chapter 4Chapter 4
Section 2Section 2
What Shapes an Ecosystem?What Shapes an Ecosystem?
Abiotic FactorsAbiotic Factors
Non-living parts ofthe environmentsuch as rocks, thesun, andtemperatureNon-living parts ofthe environmentsuch as rocks, thesun, andtemperature
What shapes an ecosystem?What shapes an ecosystem?
Biotic FactorsBiotic Factors
The living parts of theenvironment such asplants, bacteria, andanimalsThe living parts of theenvironment such asplants, bacteria, andanimals
What is a Community?What is a Community?
A community is formed when populations ofdifferent species live together in a certain area.A community is formed when populations ofdifferent species live together in a certain area.
Sharing close living quarters forces them tointeract.Sharing close living quarters forces them tointeract.
Community InteractionsCommunity Interactions
CompetitionCompetition
PredationPredation
SymbiosisSymbiosis
MutualismMutualism
CommensalismCommensalism
ParasitismParasitism
Competition Between SpeciesCompetition Between Species
Competition occurs whentwo or more species rely onthe same resource, such asfood, water, or space.Competition occurs whentwo or more species rely onthe same resource, such asfood, water, or space.
Competitive Exclusionoccurs when competitionleads to a clear winner andclear loser.Competitive Exclusionoccurs when competitionleads to a clear winner andclear loser.
Within a community, eachspecies has a unique niche(or living arrangement)Within a community, eachspecies has a unique niche(or living arrangement)
No two species can have theexact same niche!No two species can have theexact same niche!
Kenai Fjords National ParkKenai Fjords National Park
PredationPredation
The interaction in whichone organism eats anotherThe interaction in whichone organism eats another
Both predators and preyevolve adaptations tosurvive (camouflage,stingers, poisonouschemicals, etc.)Both predators and preyevolve adaptations tosurvive (camouflage,stingers, poisonouschemicals, etc.)
Symbiotic RelationshipsSymbiotic Relationships
A close interaction between species that live in or oneach other:A close interaction between species that live in or oneach other:
Parasitism- One organism (parasite) obtains itsnourishment at the expense of the other (host)Parasitism- One organism (parasite) obtains itsnourishment at the expense of the other (host)
Ex: tapeworm in intestineEx: tapeworm in intestine
Mutualism- Both species benefitMutualism- Both species benefit
Ex: bees and flowersEx: bees and flowers
Commensalism- One organism benefits and the otheris neither helped nor harmedCommensalism- One organism benefits and the otheris neither helped nor harmed
Ex: Barnacle on a whaleEx: Barnacle on a whale
Disturbance in a CommunityDisturbance in a Community
Communities tend to be in a continual state ofchangeCommunities tend to be in a continual state ofchange
Natural disturbances such as fires, volcaniceruptions, floods, and tornadoes can destroyorganisms and their resourcesNatural disturbances such as fires, volcaniceruptions, floods, and tornadoes can destroyorganisms and their resources
Fortunately, some organisms thrive in thewake of destruction. The process of rebuildingthe community is called ecological successionFortunately, some organisms thrive in thewake of destruction. The process of rebuildingthe community is called ecological succession
Types of SuccessionTypes of Succession
PRIMARYPRIMARY
When a communityarises out of a lifelessarea that has no soilWhen a communityarises out of a lifelessarea that has no soil
SECONDARYSECONDARY
When a disturbancedamages an existingcommunity but leavesthe soil intactWhen a disturbancedamages an existingcommunity but leavesthe soil intact
Lichens and moss are pioneer species
Climax CommunityClimax Community
A stable group of plants and animals that isthe end result of the succession process
Does not always mean big trees:
Grasses in prairies
Cacti in deserts
Human Disturbances ThreatenCommunities and BiodiversityHuman Disturbances ThreatenCommunities and Biodiversity
Humans clear-cut forests for lumber and landHumans clear-cut forests for lumber and land
We also intentionally or accidentally introduceexotic species to communities when we travel fromone geographic region to another. The invasivespecies may out compete or prey upon nativespecies.We also intentionally or accidentally introduceexotic species to communities when we travel fromone geographic region to another. The invasivespecies may out compete or prey upon nativespecies.
Overexploitation reduces population size and canthreaten species to the point of extinctionOverexploitation reduces population size and canthreaten species to the point of extinction
