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Ecology Biological Communities NO species exists independently of other species.

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Presentation on theme: "Ecology Biological Communities NO species exists independently of other species."— Presentation transcript:

1 Ecology Biological Communities NO species exists independently of other species

2 The Community A group of populations of different species living close enough to interact A group of populations of different species living close enough to interact Interspecific interactions between populations of different species within a community

3 Community structure Community ~ an assemblage of populations living close enough together for potential interaction Community ~ an assemblage of populations living close enough together for potential interaction Richness abundance and distribution of numbers of different species Richness abundance and distribution of numbers of different species Species diversity number of different species Species diversity number of different species Hypotheses: Hypotheses: –Individualistic chance assemblage with similar abiotic requirement –Interactive ~ 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. 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 When two species use the same resource, they participate in a biological interaction called competition How Competition Shapes Communities

6 Intraspecific – between individuals of the SAME species Interspecific – between individuals of DIFFERENT species

7 Interspecific Competition Competition occurs when resources are in short supplyCompetition occurs when resources are in short supply Competition is -/- interaction between the species involvedCompetition is -/- interaction between the species involved

8 Competition evidence Resource partitioning ~ sympatric species consume slightly different foods or use other resources in slightly different ways Resource partitioning ~ sympatric species consume slightly different foods or use other resources in slightly different ways Character displacement ~ sympatric species tend to diverge in those characteristics that overlap Character displacement ~ sympatric species tend to diverge in those characteristics that overlap Ex: Anolis lizard sp. perching sites in the Dominican Republic Ex: Darwin’s finch beak size on the Galapagos Islands

9 Central to Competition and Community The Ecological Niche The Ecological Niche Law of Competitive Exclusion Law of Competitive Exclusion No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. No 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. 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. Given resource can only be partitioned a finite number of times.

10 Interaction By Predation The act of one organism killing another for foodThe act of one organism killing another for food +/- interaction +/- interaction Often involves keystone speciesOften involves keystone species

11 Types of predators Carnivores – kill the prey during attack Carnivores – kill the prey during attack Herbivores – remove parts of many prey, rarely lethal. Herbivores – remove parts of many prey, rarely lethal. Parasites – consume parts of one or few prey, rarely lethal. Parasites – consume parts of one or few prey, rarely lethal. Parasitoids – kill one prey during prolonged attack. Parasitoids – kill one prey during prolonged attack.

12 Striking adaptations often characterize predators and their prey Cryptic Coloration Predators may evolve cryptic morphology (camouflage)

13 Cryptic Coloration Prey may evolve to blend in too!Camouflage

14 Aposematism Prey may evolve warning morphology Aposematic colors = warning

15 Mimicry Organisms may evolve to look like other organisms Batesian mimicry harmless mimic evolves to look like harmful model harmless mimic evolves to look like harmful model looks like something that is dangerous or tastes bad looks like something that is dangerous or tastes bad Viceroy Monarch Milk Snake Coral Snake

16 Mimicry Mullarian mimicry Bracoria Millipedess Nudibranchs Two bad tasting organisms resemble each other, ostensibly so that predators will learn to avoid them equally.

17 Predation defense review Cryptic (camouflage) coloration Cryptic (camouflage) coloration Aposematic (warning) coloration Aposematic (warning) coloration Mimicry ~ 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 Mimicry ~ 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.Where two organisms live together in close association. Can be mutually beneficial or benefit one organism and leave the other unharmedCan be mutually beneficial or benefit one organism and leave the other unharmed

19 Herbivory +/- interaction in which an herbivore eats part of a plant. +/- 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. 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. A plant’s main protective devices are chemical toxins, spines, and thorns.

20 Commensalism One member benefits while other is neither benefited nor harmed mites hitching a ride on a beetle

21 A symbiotic relationship in which both species benefit +/+ Mutualism

22 Tick TapewormParasitism Parasites derive nourishment from their hosts +/- interaction Parasites derive nourishment from their hosts +/- interaction endoparasites endoparasites ectoparasites ectoparasites

23 Often described in terms of how the organism affects energy flow within the ecosystem, it is a pattern of living To understand how competition influences the makeup of communities, you must look at the functional role of the species: Ecological Niche Niche Niche Habitat & microhabitat (Space utilization) Habitat & microhabitat (Space utilization) Food “spectrum,” essential nutrients Food “spectrum,” essential nutrients Reproductive requirements Reproductive requirements –Nutrition, nest/den sites Seasonality: When are resources required, used. Seasonality: When are resources required, used. NOT TO BE CONFUSED WITH: Habitat - location where a particular organism lives Habitat - location where a particular organism lives

24 What is the niche? set of conditions within which an organism within which an organism can maintain a viable can maintain a viable population populationmulti-dimensional with as many with as many dimensions as their dimensions as their are limiting conditions are limiting conditions temperature light intensity okay salinity ecological niche

25 Size of the Niche Fundamental niche Fundamental niche – The entire range of opportunity – The organism’s potential (the role it could play) in the absence of biotic enemies – depends on physical (abiotic) conditions. Realized niche Realized niche – The actual range of the organism (the role it does play in the community) – in the presence of biotic enemies – depends on biotic as well as abiotic conditions

26 Competition and Limitation of Resources Barnacles compete for space on rocky intertidal shores What is the realized niche of each barnacle? What is the fundamental niche of each?

27 Competition and Limitation of Resources growthrate Location in intertidal zone lowhighmiddle Chthamalus alone Balanus alone How can we determine the fundamental niche of each barnacle? Removal experiments – remove each species and see where the other grows Balanusfundamentalniche Chthamalus fundamental niche

28 growthrate Location in intertidal zone lowhighmiddle How can we determine the realized niche of each barnacle? Where do they grow when allowed to compete? Balanusrealizedniche Chthamalus realized niche Balanus Chthamalu s Competition and Limitation of Resources

29 Two species cannot coexist if they occupy the same niche ( the barnacles did not coexist where their fundamental niches overlapped) Competitive Exclusion Principle Competition between two species with identical niches results either in competitive exclusion or the evolution of resource partitioning Competition between two species with identical niches results either in competitive exclusion or the evolution of resource partitioning Stable coexistence requires niche differentiation, Stable coexistence requires niche differentiation, – members of each species compete more strongly among themselves than with members of the other species – (intraspecific > interspecific)

30 Avoiding Competition Resource partitioning sympatric species consume slightly different foods or use other resources in slightly different ways Resource partitioning sympatric species consume slightly different foods or use other resources in slightly different ways Character displacement sympatric species tend to diverge in those characteristics that overlap Character displacement sympatric species tend to diverge in those characteristics that overlap Ex: Anolis lizard sp. perching sites in the Dominican Republic Ex: Darwin’s finch beak size on the Galapagos Islands

31 Resource Partitioning

32 Competition: a closer look Interference~ actual fighting over resources Interference~ actual fighting over resources Exploitative~ consumption or use of similar resources Exploitative~ consumption or use of similar resources Competitive Exclusion Principle Competitive Exclusion Principle –(Lotka / Volterra)~ 2 species with similar needs for the same limiting resources cannot coexist in the same place

33 predict the outcome of interspecific competition Gause Experiment two species of Paramecium P. caudata P. aurelia Competitive exclusion Competitive exclusion –When forced to compete, one species eliminates other

34 Species Diversity Measures the number of different species in the community (species richness) and the relative abundance of each species. Measures 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. 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 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. The affect on its community or ecosystem is much larger and more influential than would be expected from mere abundance. –Often large predators –Critical 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 Barnacles Mussels Balanus Mytilus StarfishPisaster Starfish are picky – they prefer to eat mussels (dominant competitor), allowing barnacles (weaker competitor) to coexist. How do starfish promote coexistence? How Keystone Species Affect Community Structure preditor competitors

37 Removal experiment time starfishremoved %ofinter-tidalzone mussels - mussels are the dominant competitor - competitive exclusion of barnacles barnacles

38 GENERALIST VS SPECIALIST Animals are generally selective and efficient in their food choices Animals are generally selective and efficient in their food choices –Some animals, such as gulls, are feeding “generalists” –Other animals, such as koalas, are feeding “specialists”

39 GENERALIST VS SPECIALIST specialist consumes only one prey type generalist consumes many prey types broad diet narrow diet

40 GENERALIST VS SPECIALIST Generalists - Broad niche Specialists - Narrow niche When generalists and specialists collide, generalists usually win

41 Invasive Species Invasive species competitively exclude native species Invasive species competitively exclude native species –Imported fire ant –Kudzu –Purple loosestrife –Zebra mussel –Squirrels

42 Succession - orderly, natural changes that take place in communities of an ecosystem over time. Succession - orderly, natural changes that take place in communities of an ecosystem over time. Ecosystem Change: Succession 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 Constant state of change – Disturbance influences species diversity and composition – Storm, fire, flood, human activity changes a community by removing organisms or changing resource availability – Not necessarily bad

44 Ecosystem Change Intermediate disturbance hypothesis Intermediate disturbance hypothesis – Moderate levels of disturbance create conditions that foster greater species diversity than low or high levels of disturbance

45 Primary Succession Primary succession is colonization by communities of organisms where life has not existed before. Primary succession is colonization by communities of organisms where life has not existed before.

46 Terrestrial Primary Succession

47 Secondary Succession Secondary succession is the sequence of community changes that occur when a community is disrupted by natural disasters or human actions. Secondary succession is the sequence of community changes that occur when a community is disrupted by natural disasters or human actions.

48 Climax Community The 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. The 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 Stability The interrelationships and interdependencies of organisms affect the development of stable ecosystems – in other words the homeostasis of ecosystems. The interrelationships and interdependencies of organisms affect the development of stable ecosystems – in other words the homeostasis of ecosystems.

50 Tolerance Tolerance is the ability to withstand fluctuations in biotic and abiotic environmental factors.Tolerance is the ability to withstand fluctuations in biotic and abiotic environmental factors. Biodiversity gives an ecosystem more tolerance.Biodiversity gives an ecosystem more tolerance. The greater the biodiversity, the healthier the ecosystem.The greater the biodiversity, the healthier the ecosystem.

51 Island Biogeography Because of their isolation and limited size, islands are natural laboratories for studying bio-geographical factors Because of their isolation and limited size, islands are natural laboratories for studying bio-geographical factors Also applies to islands of land such as national parks or preserves. Also applies to islands of land such as national parks or preserves.

52 Island Biogeography Two factors 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. 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 As the distance from the mainland increases, the rate of immigration falls, whereas extinction rates increase

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