Upload
bruno-parker
View
218
Download
3
Embed Size (px)
Citation preview
• Chapter 53 – Community Ecology
What is a community?What is a community?
• A community is a group of populations of various species living close enough for potential interaction
Community InteractionsCommunity Interactions
• Interspecific – interactions between different species within a community
• Competition
• Predation
• Herbivory
• Symbiosis
• Disease
CompetitionCompetition
• Interspecific competition occurs when species compete for a resource that is in limited supply
• Competitive exclusion principle: one species will use the limiting resources more efficiently thereby eliminating the local competitor.
• Example: barnacle species in Scotland
Competitive Exclusion Principle Competitive Exclusion Principle and the Concept of Nicheand the Concept of Niche
• Relates to concept of Niche: the sum total of the biotic and abiotic resources used by a species’
• Fundamental niche = potential• Realized niche = actual
NicheNiche
• Two species cannot occupy the same niche = leads to competition
• Resource partitioning: altering ones niche to avoid competition; lizard example
• Character displacement: characteristics become more divergent; finch beak example
Resource Partitioning
Character Displacement
PredationPredation
• Predator kills and eats prey; a +/- interaction• Predator mechanisms: acute senses, claws,
teeth, fangs, stingers, poison, speed, agility, coloration, and camouflage
• Defense mechanisms: alarm calls, maternal/paternal protection, mechanical defenses (spikes, spines, and hard shells), chemical defenses (toxins, poisons, and bad taste), coloration (aposematic coloration) and mimicry (Batesian and Mullerian).
Coloration and MimicryColoration and Mimicry
Cryptic Coloration Aposematic Coloration
Batesian Mimicry
Mullerian Mimicry
HerbivoryHerbivory
• Herbivory: a +/- interaction in which an herbivore eats parts of a plant or alga
• Predator mechanisms include specialized teeth or digestive systems, enhanced senses, and selective eating (leaving part of plant behind)
• Similar defense mechanisms as with predation, but chemical defenses and coloration are most common
SymbiosisSymbiosis• Mutualism: an interaction that
benefits both species; a +/+ interaction, example = acacia trees and ants
• Commensalism: an interaction between species where one benefits while the other is neither harmed nor helped; a +/0 interaction, example = egrets and water buffalo
• Parasitism: a +/- interaction in which one organism (parasite) derives nourishment from another (host); pathogen = lethal
• Can you think of any additional examples (at least 1 of each)?
Mutualism
Commensalism
MutualismMutualism
Which forest is more diverse?Which forest is more diverse?
• Species diversity has 2 components:
• Species richness: total number of different species
• Relative abundance: proportion each species represents
• Answer = Ecologists would say community 1 has greater species diversity
Species Diversity
Trophic StructureTrophic Structure
• Feeding relationships• Transfer of energy up
trophic levels– Primary producers– Primary consumers– Secondary consumers– Tertiary consumers– Quaternary consumers
• Food Chains, food webs
Trophic Levels
Dominant and Keystone Dominant and Keystone SpeciesSpecies
• Dominant species: most abundant and have the most biomass, impact on a community can vary
• Keystone species: not abundant, but play critical role because of the niche they occupy within the community; examples include sea stars and sea otters
Examples of Keystone SpeciesExamples of Keystone Species
Sea Star
Sea Otters
DisturbanceDisturbance• An event that changes a community by
removing organisms and altering resources• Examples include a storm, fire, flood,
drought, overgrazing, or human activity• Can have long-term, positive effects
Prairie Disturbance Recovery
SuccessionSuccession
• Transition in the species composition of a community overtime
• Primary succession: begins in a lifeless area with no soil, example – a new volcanic island
• Secondary succession: when an existing community has been cleared by some disturbance, leaves soil intact
Ecological Succession