COMMUNITY ECOLOGY Chapter 54. What is a community? Many species living closely together, so that...
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Transcript of COMMUNITY ECOLOGY Chapter 54. What is a community? Many species living closely together, so that...
COMMUNITY ECOLOGYCOMMUNITY ECOLOGYChapter 54
What is a community?What is a community?Many species living closely
together, so that they interact with each-other.
Population Interactions:Population Interactions:Intraspecific competition - within
a speciesInterspecific interactions -
Individuals of different species compete for a resource that limits their growth and survival
Interspecific competitionInterspecific competition-/- interaction Competition must occur:
◦interference competition - actual fighting occurs
◦exploitation competition - consumption or use of similar resource
Ex: weeds growing in a garden compete with garden plants, lynx and foxes compete for snowshoe hares
Competitive Exclusion Competitive Exclusion PrinciplePrincipleTwo species cannot coexist in a
community if their niches are identical
Ecologically similar species can coexist in a community if there are one or more differences in their niches
Competitive Exclusion PrincipleCompetitive Exclusion Principle
Ecological NicheEcological NicheSum total of a species’ use of the
biotic and abiotic resources in its environment
Habitat=addressNiche=habitat + occupation
Resource partitioning of lizardsResource partitioning of lizards
Fundamental / Realized NichesFundamental / Realized Niches
Character Character displace-displace-mentment
Upon What Do These Animals Prey?
Upon What Do These Animals Prey?
Animals
Upon What Do These Animals Prey?
Animals
Plants
Animal DefensesAnimal Defenses
RunningHidingPhysical or Chemical Defenses
Chemical Defense and Aposematic coloration are seen
here
Aposematic colorationAposematic coloration
Cryptic coloration
is seen here
Cryptic ColorationCryptic Coloration
MimicryMimicryBatesian mimicry - harmless
species resembles harmful or distasteful species
Mullerian mimicry - two or more unpalatable species resemble one another.
Batesian MimicryBatesian Mimicry
Batesian MimicryBatesian Mimicry
Mullerian MimicryMullerian Mimicry
Plant Defenses Against Plant Defenses Against Predators:Predators:
What defense is seen here?
Other defenses:
• Chemicals that cause plant to taste bad
• Poisonous chemicals
In this relationship, the ant hollows out the thorns of the plant for nests, feed on sweet secretions from the four nectaries at the base of each petiole, and protect these trees from invertebrate herbivores.
Heliconius butterflies (Heliconius sp.) lay their eggs on the leaves of the passionflower vine (Passiflora sp.). When the eggs hatch into hungry, leaf-eating Heliconius caterpillars, the passionflower vines protect themselves with an array of defenses.
Fake eggs . . . some passionflower vines grow parts that look like Heliconius caterpillar eggs. This keeps the female Heliconius butterfly from laying eggs on leaves that appear to be occupied by other cannibalistic caterpillars.
Dumpers . . . Some Heliconius butterflies like to lay their eggs on upward-curling tendrils of passionflower vines. Some vines produce fake tendrils that are weak and fall off under the weight of the developing butterfly eggs.
SymbiosisSymbiosisClose association between two
speciesParasitism +/-Commensalism +/0 interactionMutualism +/+ interaction
PredationPredation+/- interactionPredator eats prey
◦Ex. Lion eats an antelope, animal eats a plant
PredatorsPredators
Can reduce relative abundanceCan reduce diversity by
eliminating competitors - keystone predators◦sea star feeds on mussels and other
organisms, remove sea star and mussels take over the region and eliminate species diversity.
Parasites are also +/-Parasites are also +/-Endoparasites-live within the body of
their host◦Ex. tapeworms
Ectoparasites-parasites that feed on the external surface of a host◦Ex. Ticks, lice
Parasitoid insects-lay eggs on the body of the host, the larva then feed on the body of the host, eventually killing it
One parasite example:
MutualismMutualism+/+ interaction
◦Ex. Nitrogen fixation by bacteria in root nodules of legumes
◦Ex. Termites and microorganisms in their gut
Interspecific Interactions:Interspecific Interactions:What is co-evolution?Reciprocal evolutionary changes
between two or more species.Results in a close association
between certain species
CommensalismCommensalism+/0 interaction
◦Ex. Cowbirds and cattle egrets feed on insects flushed out of the grass
Which symbiosis is seen here?
Which symbiosis is seen here?
parasitic
Which symbiosis is seen here?Which symbiosis is seen here?
Which symbiosis is seen here?Which symbiosis is seen here?
Mutualism
Community StructureCommunity StructureFeeding relationshipsRichness - number of different
speciesRelative abundance - number in
individuals in each speciesDiversity - combination of abundance
and richnessCommunities with even distribution
of species are more diverse than communities with greater richness but skewed distributions
Trophic StructureTrophic StructureFeeding relationships-transfer of
food energyPlants to herbivores to carnivores
to decomposers = food chainFood web - interconnected food
chains
Control of community Control of community structurestructureDominant species-species in a community
that have highest abundance or biomass◦ Sugar maples
Keystone species-not abundant but exert strong control on community structure◦ Remove the species to determine if it is a
keystone species◦ Sea otters
Invasive species-no natural predators so their population is not held in check◦ Buckthorn, garlic mustard, purple loosestrife
NonequilibriumNonequilibriumMost communities are not stableDisturbances such as storms,
floods overgrazing etc. can effect stability
Humans bring disturbance
Succession Succession Example of disturbance leading
to changeprimary succession - soil never
formed beforesecondary succession - existing
community was disturbed and returned to original state.
Secondary SuccessionSecondary Succession
BiogeographyBiogeographyStudy of past and present
distribution of individual species and communities
Limitation of species to one region:◦species never dispersed◦pioneers did not survive◦species retracts from once larger
range to smaller boundaries
Island biogeographyIsland biogeography
Review the following slides Review the following slides and identify which community and identify which community interaction you are observinginteraction you are observing
Where is the Moth?
Can you see it now?Can you see it now?
What What coloration is coloration is seen in the seen in the next slides?next slides?What does What does this tell you this tell you about the about the way these way these animals live animals live in their in their communities?communities?
This animal is not a bee, why This animal is not a bee, why does it look like one?does it look like one?
Species Richness and Species Richness and Island SizeIsland Size
Species diversitySpecies diversity
Which forest is more diverse?