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Outline

Outline. 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.

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Outline

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  1. Outline • 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

  2. 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

  3. Community Structure

  4. 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

  5. Species Richness of Communities

  6. 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

  7. Model of Island Biogeography

  8. 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

  9. Feeding niches for Wading Birds

  10. 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)

  11. Competition Between Populations • Interspecific competition • Members of different species require the same resource • The supply of the resource is limited

  12. Competition BetweenTwo Laboratory Populations of Paramecium

  13. Competition Between Populations • Competitive Exclusion Principle • No two species can occupy the same niche at the same time • Resource Partitioning decreases competition • Can lead to character displacement

  14. Character Displacement in Fincheson the Galápagos Islands When on the same island, the beak sizes are appropriate for eating small, medium, and large-sized seeds. When on separate islands, beaks have the same intermediate size, allowing them to eat seeds that vary in size.

  15. Niche Specialization AmongFive Species of Coexisting Warblers

  16. Competition BetweenTwo Species of Barnacles

  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. Predator-prey Interaction BetweenParamecium caudatum and Didiniumnasutum Didinium ate all the Paramecium and then dies out

  19. Predator-prey InteractionBetween a Lynx and a Snowshoe Hare

  20. Prey Defenses • Prey defenses • Mechanisms that thwart the possibility of being eaten by a predator • Spines • Tough Epidermis • Poisonous Chemicals • Camouflage (cryptic coloration) • Bright Coloration (warning coloration) • Flocking Behavior http://www.youtube.com/watch?v=B2JdRPKYyTc

  21. Camouflage in the Anglerfish http://www.youtube.com/watch?v=fUDY9Y_3TNc

  22. Mimicry • One species resembles another species • Mimicked species possesses an overt antipredatordefense (warning coloration) • Batesian Mimicry - Mimic lacks defense of the organism it resembles • MüllerianMimicry - Mimic shares same protective defense

  23. Anti-predator Defenses Poison arrow frog used to make arrows lethal weapons. Eastern tiger swallowtail butterfly caterpillar has false eyespots to confuse predator. South American lantern fly has a large false head that resembles and alligator.

  24. Mimicry Among Insects withYellow and Black Stripes

  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 -Inside host body • Ectoparasites – Outside host body Beetle infected with wasp larvae Fleas on your dog/cat/you

  26. Commensalism • 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

  27. Clownfish AmongSea Anemone’s Tentacles

  28. Mutualism • 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

  29. Mutualism Betweenthe Bullhorn Acacia Tree and Ants a. Tree provides nourishment for ants. Ants live inside hollow thorns. b. Nectaries at base of leaves from which ants feed. c. Ants harvest larval food at tips of leaves

  30. Cleaning Symbiosis

  31. 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

  32. Secondary Succession

  33. Secondary Successionin a Forest

  34. 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

  35. 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

  36. Community Diversity • Community stability can be recognized in three ways • Persistence through time • Resistance to change • Recovery once a disturbance has occurred

  37. 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

  38. The Intermediate Disturbance Hypothesis

  39. 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

  40. Effect of a Keystone Species

  41. Review • 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

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