Presentation on theme: "Ecology Biological Communities"— Presentation transcript:
1 Ecology Biological Communities NO species exists independently of other species
2 The CommunityA group of populations of different species living close enough to interactInterspecificinteractions between populations of different species within a community
3 Community structureCommunity~ an assemblage of populations living close enough together for potential interactionRichness abundance and distribution of numbers of different speciesSpecies diversity number of different speciesHypotheses:Individualistic chance assemblage with similar abiotic requirementInteractive~ assemblage locked into association by mandatory biotic interactions
4 Interaction in Communities Community interactions are classified by whether they help, harm, or have no effect on the species involved.Co-evolution is a result of this history of interaction
5 How Competition Shapes Communities When two species use the same resource, they participate in a biological interaction called competition
6 How Competition Shapes Communities Intraspecific – between individuals of the SAME speciesInterspecific – between individuals of DIFFERENT species
7 Interspecific Competition Competition occurs when resources are in short supplyCompetition is -/- interaction between the species involved
8 Competition evidenceResource partitioning~ sympatric species consume slightly different foods or use other resources in slightly different waysCharacter displacement~ sympatric species tend to diverge in those characteristics that overlapEx: Anolis lizard sp. perching sites in the Dominican RepublicEx: Darwin’s finch beak size on the Galapagos Islands
9 Central to Competition and Community Law of Competitive ExclusionNo two species will occupy the same niche and compete for exactly the same resources for an extended period of time.One will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource.Given resource can only be partitioned a finite number of times.The Ecological Niche
10 Interaction By Predation The act of one organism killing another for food+/- interactionOften involves keystone species
11 Types of predators Carnivores – kill the prey during attack Herbivores – remove parts of many prey, rarely lethal.Parasites – consume parts of one or few prey, rarely lethal.Parasitoids – kill one prey during prolonged attack.
12 Cryptic ColorationStriking adaptations often characterize predators and their preyPredators may evolve cryptic morphology (camouflage)
13 Cryptic ColorationPrey may evolve to blend in too! Camouflage
14 Prey may evolve warning morphology AposematismPrey may evolve warning morphologyAposematic colors = warning
15 Mimicry Batesian mimicry Organisms may evolve to look like other organismsBatesian mimicryharmless mimic evolves to look like harmful modellooks like something that is dangerous or tastes badViceroyMonarchMilk SnakeCoral Snake
16 Mimicry Mullarian mimicry Two bad tasting organisms resemble each other, ostensibly so that predators will learn to avoid them equally.Mullarian mimicryBracoria MillipedessNudibranchs
17 Predation defense review Cryptic (camouflage) colorationAposematic (warning) colorationMimicry~ superficial resemblance to another species √ Batesian~ palatable/ harmless species mimics an unpalatable/ harmful model √ Mullerian~ 2 or more unpalatable, aposematically colored species resemble each other
18 Interaction By Symbiosis Where two organisms live together in close association.Can be mutually beneficial or benefit one organism and leave the other unharmed
19 Herbivory +/- interaction in which an herbivore eats part of a plant. It is advantageous for an animal to be able to distinguish toxic from nontoxic plants.A plant’s main protective devices are chemical toxins, spines, and thorns.
20 CommensalismOne member benefits while other is neither benefited nor harmedmites hitching a ride on a beetle
21 A symbiotic relationship in which both species benefit +/+ MutualismA symbiotic relationship in which both species benefit +/+
22 ParasitismParasites derive nourishment from their hosts +/- interactionendoparasitesectoparasitesTapewormTick
23 Ecological Niche Niche Often described in terms of how the organism affects energy flow within the ecosystem, it is a pattern of livingTo understand how competition influences the makeup of communities, you must look at the functional role of the species:NicheHabitat & microhabitat (Space utilization)Food “spectrum,” essential nutrientsReproductive requirementsNutrition, nest/den sitesSeasonality: When are resources required, used.NOT TO BE CONFUSED WITH:Habitat - location where a particular organism lives
24 What is the niche? set of conditions multi-dimensional with as many within which an organismcan maintain a viablepopulationmulti-dimensionalwith as manydimensions as theirare limiting conditionsecologicalnichelight intensityokaytemperaturesalinity
25 Size of the Niche Fundamental niche Realized niche The entire range of opportunityThe organism’s potential (the role it could play) in the absence of biotic enemiesdepends on physical (abiotic) conditions.Realized nicheThe actual range of the organism (the role it does play in the community) – in the presence of biotic enemiesdepends on biotic as well as abiotic conditions
26 Competition and Limitation of Resources Barnacles compete for space on rocky intertidal shoresWhat is the realized niche of each barnacle?What is the fundamental niche of each?
27 Competition and Limitation of Resources How can we determine the fundamental niche of each barnacle?Removal experiments –remove each species and see where the other growsBalanus aloneBalanusfundamentalnichegrowthrateChthamalus aloneChthamalus fundamental nichelowmiddlehighLocation in intertidal zone
28 Chthamalus realized niche Competition and Limitation of ResourcesHow can we determine the realized niche of each barnacle?Where do they grow when allowed to compete?BalanusChthamalusgrowthrateBalanusrealizednicheChthamalus realized nichelowmiddlehighLocation in intertidal zone
29 Competitive Exclusion Principle Two species cannot coexist if they occupy the same niche(the barnacles did not coexist where their fundamental niches overlapped)Competition between two species with identical niches results either in competitive exclusion or the evolution of resource partitioningStable coexistence requires niche differentiation,members of each species compete more strongly among themselves than with members of the other species(intraspecific > interspecific)
30 Avoiding CompetitionResource partitioning sympatric species consume slightly different foods or use other resources in slightly different waysCharacter displacement sympatric species tend to diverge in those characteristics that overlapEx: Anolis lizard sp. perching sites in the Dominican RepublicEx: Darwin’s finch beak size on the Galapagos Islands
32 Competition: a closer look Interference~ actual fighting over resourcesExploitative~ consumption or use of similar resourcesCompetitive Exclusion Principle(Lotka / Volterra)~ 2 species with similar needs for the same limiting resources cannot coexist in the same place
33 interspecific competition Gause Experimenttwo species of Parameciumpredict the outcome ofinterspecific competitionP. aureliaP. caudataCompetitive exclusionWhen forced to compete, one species eliminates other
34 Species DiversityMeasures the number of different species in the community (species richness) and the relative abundance of each species.Community with even species abundance is more diverse than one in which one or two species are abundant and the remainder are rare.
35 Keystone Species Exerts strong control on the community structure The affect on its community or ecosystem is much larger and more influential than would be expected from mere abundance.Often large predatorsCritical food organisms (bamboo and pandas)Often, many species are intricately interconnected so that it is difficult to tell which is the essential component.Picky predators can promote coexistence among competing prey species.Competitive exclusion is prevented when the dominant competitor is the preferred prey.
36 How Keystone Species Affect Community Structure StarfishPisasterpreditorHow do starfish promote coexistence?competitorsBarnacles MusselsBalanus MytilusStarfish are picky – they prefer to eat mussels (dominant competitor), allowing barnacles (weaker competitor) to coexist.
37 Removal experiment - mussels are the dominant competitor - competitive exclusion of barnaclesstarfishremovedmussels%ofinter-tidalzonebarnaclestime
38 GENERALIST VS SPECIALIST Animals are generally selective and efficient in their food choicesSome animals, such as gulls, are feeding “generalists”Other animals, such as koalas, are feeding “specialists”
39 GENERALIST VS SPECIALIST narrowdietspecialist consumes only one prey typebroad dietgeneralist consumes many prey types
40 GENERALIST VS SPECIALIST Generalists - Broad nicheWhen generalists and specialists collide, generalists usually winSpecialists - Narrow niche
41 Invasive Species Invasive species competitively exclude native species Imported fire antKudzuPurple loosestrifeZebra musselSquirrels
42 Ecosystem Change: Succession Succession - orderly, natural changes that take place in communities of an ecosystem over time.Pioneer species: first organisms to live in a new habitat.Tend to be small, fast growing plants, lichens, fungus. Increase soil and make the ground more hospitable for other species.
43 Ecosystem Change Constant state of change Disturbance influences species diversity and compositionStorm, fire, flood, human activity changes a community by removing organisms or changing resource availabilityNot necessarily bad
44 Ecosystem Change Intermediate disturbance hypothesis Moderate levels of disturbance create conditions that foster greater species diversity than low or high levels of disturbance
45 Primary SuccessionPrimary succession is colonization by communities of organisms where life has not existed before.
47 Secondary SuccessionSecondary succession is the sequence of community changes that occur when a community is disrupted by natural disasters or human actions.
48 Climax CommunityThe final stable plant community is called a climax community. This community may reach a point of stability that can last for hundreds or thousands of years.
49 Ecosystem StabilityThe interrelationships and interdependencies of organisms affect the development of stable ecosystems – in other words the homeostasis of ecosystems.
50 ToleranceTolerance is the ability to withstand fluctuations in biotic and abiotic environmental factors.Biodiversity gives an ecosystem more tolerance.The greater the biodiversity, the healthier the ecosystem.
51 Island BiogeographyBecause of their isolation and limited size, islands are natural laboratories for studying bio-geographical factorsAlso applies to islands of land such as national parks or preserves.
52 Island Biogeography Two factors Rates of immigration and extinction are influenced primarily by the size of the island and the distance of the island from the mainland.The greater the size of the island, the higher the immigration rates and lower the rates of extinction.As the distance from the mainland increases, the rate of immigration falls, whereas extinction rates increase