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Community Ecology Chapter 47. Community Ecology 2Outline The Concept of the Community  Diversity and Composition Models The Structure of Communities.

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Presentation on theme: "Community Ecology Chapter 47. Community Ecology 2Outline The Concept of the Community  Diversity and Composition Models The Structure of Communities."— Presentation transcript:

1 Community Ecology Chapter 47

2 Community Ecology 2Outline The Concept of the Community  Diversity and Composition Models The Structure of Communities  Island Biogeography  Habitat and Ecological Niche  Competition Between Populations  Predator-Prey Interactions  Symbiotic Relationships Community Development Community Biodiversity

3 Community Ecology 3 Community Concept An assemblage of populations interacting with one another within the same environment  Composition is a listing of various species in the community  Diversity includes both species richness and species diversity

4 4 Community Structure

5 Community Ecology 5 Diversity and Composition Models Gleason - Individualistic Model  Each population is there because its abiotic requirements are met Clements - Interactive Model  Community is the highest level of organization  Dependent on biotic interactions

6 6 Species Richness of Communities

7 Community Ecology 7 Island Biogeography MacArthur and Wilson  Developed a general model of island biogeography  Explains and predicts how the community diversity of an island is affected by ­Distance from the mainland, and ­Size of the island

8 8 Model of Island Biogeography

9 Community Ecology 9 Community Structure Competition  When two species compete, the abundance of both species is negatively impacted  Predation (or parasitism) ­Expected to increase the abundance of the predator (or parasite) ­And reduce the abundance of the prey (or host)

10 Community Ecology 10 Habitat and Ecological Niche Habitat  The area an organism lives and reproduces in Ecological niche  The role a species plays in its community ­Includes its habitat, and ­Its interactions with other organisms  Fundamental niche - All conditions under which the organism can survive  Realized niche - Set of conditions under which it exists in nature

11 11 Feeding niches for Wading Birds

12 Community Ecology 12 Competition Between Populations Interspecific competition  Members of different species require the same resource  The supply of the resource is limited Competitive Exclusion Principle  No two species can occupy the same niche at the same time  Resource Partitioning decreases competition  Can lead to character displacement

13 13 Competition Between Two Laboratory Populations of Paramecium

14 14 Character Displacement in Finches on the Galápagos Islands

15 15 Niche Specialization Among Five Species of Coexisting Warblers

16 16 Competition Between Two Species of Barnacles

17 Community Ecology 17 Predator-Prey Interactions Predation  One living organism, the predator, feeds on another, the prey ­Predator is larger ­Predator has lower reproductive rate ­Prey usually entirely consumed  Presence of predators can decrease prey densities, and vice-versa

18 18 Predator-prey Interaction Between Paramecium caudatum and Didinium nasutum

19 19 Predator-prey Interaction Between a Lynx and a Snowshoe Hare

20 Community Ecology 20 Prey Defenses Prey defenses  Mechanisms that thwart the possibility of being eaten by a predator ­Spines ­Tough Epidermis ­Poisonous Chemicals ­Camouflage ­Bright Coloration ­Flocking Behavior

21 21 Camouflage in the Anglerfish

22 22 Anti-predator Defenses

23 Community Ecology 23MimicryMimicry  One species resembles another species  Mimicked species possesses an overt antipredator defense Batesian Mimicry - Mimic lacks defense of the organism it resembles Müllerian Mimicry - Mimic shares same protective defense

24 24 Mimicry Among Insects with Yellow and Black Stripes

25 Community Ecology 25 Symbiotic Relationships Symbiosis  Interactions in which there is a close relationship between members of two species  Parasitism ­Parasite derives nourishment from a host, and may use host as habitat and mode of transmission  Endoparasites  Ectoparasites

26 26 The Life Cycle of a Deer Tick

27 Community Ecology 27Commensalism Symbiosis, cont.  Commensalism ­A symbiotic relationship in which one species benefits and the other is indifferent  Remoras and Sharks ­Many supposed examples may turn out to be mutualism or parasitism ­Inferred amount of harm or benefit two species do to one another is subject to investigator bias

28 28 Clownfish Among Sea Anemone’s Tentacles

29 Community Ecology 29Mutualism Symbiosis, cont.  Mutualism ­A symbiotic relationship in which both members of the association benefit ­Need not be equally beneficial to both species  Cleaning Symbiosis ­Often help each other obtain food or avoid predation  Bacteria in human intestinal tract

30 30 Mutualism Between the Bullhorn Acacia Tree and Ants

31 31 Cleaning Symbiosis

32 Community Ecology 32 Community Development Ecological Succession  A predictable pattern of change in species replacements following a disturbance ­Primary Succession occurs in areas where there is no soil formation ­Secondary Succession begins in areas where soil is present  Pioneer Species

33 33 Secondary Succession

34 34 Secondary Succession in a Forest

35 Community Ecology 35 Succession Models Facilitation Model  Each stage facilitates invasion and replacement by organisms of the next stage  Succession in a particular area will always lead to the same type of community  Climax Community

36 Community Ecology 36 Succession Models Inhibition Model  Colonists remain and inhibit growth of other plants until the colonists are damaged or die Tolerance Model  Different types of plants can colonize an area at the same time  Chance determine which seeds arrive first

37 Community Ecology 37 Community Diversity Community stability can be recognized in three ways  Persistence through time  Resistance to change  Recovery once a disturbance has occurred

38 Community Ecology 38 Intermediate Disturbance Hypothesis If widespread disturbances occur frequently, diversity will be limited If diversity is high, only moderate disturbances have been occurring with moderate frequency

39 39 The Intermediate Disturbance Hypothesis

40 Community Ecology 40 Predation, Competition, and Biodiversity Predation by a particular species may reduce competition and increases diversity  Such predators are referred to as keystone predators Exotic species  May lead to unbridled competition  Resultant reduction in biodiversity

41 41 Effect of a Keystone Species

42 Community Ecology 42Review The Concept of the Community  Diversity and Composition Models The Structure of Communities  Island Biogeography  Habitat and Ecological Niche  Competition Between Populations  Predator-Prey Interactions  Symbiotic Relationships Community Development Community Biodiversity

43 Community Ecology Ending Slide Chapter 47


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