1. Biology, 9th ed, Sylvia Mader
Chapter 47
Chapter 47
Community Ecology
Community Ecology

2. The Concept of the Community The Structure of Communities
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

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. Community Structure

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. Species Richness of Communities

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. Model of Island Biogeography

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. Habitat and Ecological Niche
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. Feeding niches for Wading Birds

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. Competition Between Two Laboratory Populations of Paramecium

14. Character Displacement in Finches on the Galápagos Islands

15. Niche Specialization Among Five Species of Coexisting Warblers

16. Competition Between Two 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 Between Paramecium caudatum and Didinium nasutum

19. Predator-prey Interaction Between 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
Bright Coloration
Flocking Behavior

21. Camouflage in the Anglerfish

22. Anti-predator Defenses

23. Batesian Mimicry - Mimic lacks defense of the organism it resembles
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. Mimicry Among Insects with Yellow 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
Ectoparasites

26. The Life Cycle of a Deer Tick

27. 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

28. Clownfish Among Sea Anemone’s Tentacles

29. 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

30. Mutualism Between the Bullhorn Acacia Tree and Ants

31. Cleaning Symbiosis

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. Secondary Succession

34. Secondary Succession in a Forest

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. Succession Models Inhibition Model Tolerance 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 stability can be recognized in three ways
Community Diversity
Community stability can be recognized in three ways
Persistence through time
Resistance to change
Recovery once a disturbance has occurred

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. The Intermediate Disturbance Hypothesis

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. Effect of a Keystone Species

42. The Concept of the Community The Structure of Communities
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

43. Biology, 9th ed, Sylvia Mader
Chapter 47
Ending Slide Chapter 47
Community Ecology
Community Ecology