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

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

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

Community Structure

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

Species Richness of Communities

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

Model of Island Biogeography

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)

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

Feeding niches for Wading Birds

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

Competition Between Two Laboratory Populations of Paramecium

Character Displacement in Finches on the Galápagos Islands

Niche Specialization Among Five Species of Coexisting Warblers

Competition Between Two Species of Barnacles

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

Predator-prey Interaction Between Paramecium caudatum and Didinium nasutum

Predator-prey Interaction Between a Lynx and a Snowshoe Hare

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

Camouflage in the Anglerfish

Anti-predator Defenses

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

Mimicry Among Insects with Yellow and Black Stripes

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

The Life Cycle of a Deer Tick

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

Clownfish Among Sea Anemone’s Tentacles

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

Mutualism Between the Bullhorn Acacia Tree and Ants

Cleaning Symbiosis

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

Secondary Succession

Secondary Succession in a Forest

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

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

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

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

The Intermediate Disturbance Hypothesis

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

Effect of a Keystone Species

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

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