Community Ecology Chapter 47 Mader: Biology 8th Ed.

Diversity and Composition Models Island Biogeography Outline Diversity and Composition Models Island Biogeography Habitat and Ecological Niche Competition Between Populations Predator-Prey Interactions Symbiotic Relationships Community Development Community Diversity Mader: Biology 8th Ed.

Composition is a listing of various species in the community. Community Concept A community is 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. Mader: Biology 8th Ed.

Diversity and Composition Models Gleason - Individualistic Model Each population in community is there because its own particular abiotic requirements are met by a particular habitat. Clements - Interactive Model Community is the highest level of organization. Dependent on biotic interactions. Mader: Biology 8th Ed.

Island Biogeography MacArthur and Wilson developed a general model of island biogeography to explain and predict the effects of distance from the mainland and size of an island on community diversity. Island size and distance from population source affects species diversity. Mader: Biology 8th Ed.

Model of Island Biogeography Mader: Biology 8th Ed.

Community Structure Competition for limited resources between two species has a negative effect on the abundance of both species. Predation and parasitism are expected to increase the abundance of the predator and parasite at the expense of the abundance of the prey and its host. Mader: Biology 8th Ed.

Habitat and Ecological Niche Habitat is the area an organism lives and reproduces in. Ecological niche is the role an organism plays in its community, including 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. Mader: Biology 8th Ed.

Feeding Niches for Wading Birds Mader: Biology 8th Ed.

Competition Between Populations Interspecific competition occurs when members of different species try to utilize a resource in limited supply. Competitive Exclusion Principle - No two species can occupy the same niche at the same time. Resource Partitioning decreases competition. Can lead to character displacement. Mader: Biology 8th Ed.

Competition Between Barnacle Species Mader: Biology 8th Ed.

Character Displacement in Galápagos Finches Mader: Biology 8th Ed.

Predator-Prey Interactions Predation occurs when one living organism, the predator, feeds on another, the prey. Presence of predators can decrease prey densities, and vice-versa. Mader: Biology 8th Ed.

Lynx-Snowshoe Hare Interactions Mader: Biology 8th Ed.

Prey Defenses Prey defenses are mechanisms that thwart the possibility of being eaten by a predator. Spines Tough Epidermis Poisonous Chemicals Camouflage Bright Coloration Flocking Behavior Mader: Biology 8th Ed.

Camouflage in the Anglerfish Mader: Biology 8th Ed.

Batesian - Mimic lacks defense of the organism it resembles. Mimicry Mimicry occurs when one species resembles another that possesses an overt antipredator defense. Batesian - Mimic lacks defense of the organism it resembles. Müllerian - Mimic shares same protective defense. Mader: Biology 8th Ed.

Symbiotic Relationships Symbiosis refers to interactions in which there is a close relationship between members of two populations. Parasitism Parasite derives nourishment from a host, and may use host as habitat and mode of transmission. Endoparasites Ectoparasites Mader: Biology 8th Ed.

Many examples may turn out to be mutualism or parasitism. Commensalism Commensalism is a symbiotic relationship in which one species is benefited and the other is neither benefited nor harmed. Remoras and Sharks Many examples may turn out to be mutualism or parasitism. Amount of harm or benefit two species do to one another is partially determined by the investigator. Mader: Biology 8th Ed.

Often help organisms obtain food or avoid predation. Mutualism Mutualism is a symbiotic relationship in which both members of the association benefit. Often help organisms obtain food or avoid predation. Bacteria in human intestinal tact. Need not be equally beneficial to both species. Cleaning Symbiosis Mader: Biology 8th Ed.

Mutualism Between Bullhorn Acacia and Ants Mader: Biology 8th Ed.

Cleaning Symbiosis Mader: Biology 8th Ed.

Community Development Ecological Succession A change involving a series of species replacements in a community 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 Mader: Biology 8th Ed.

Secondary Succession in a Forest Mader: Biology 8th Ed.

Succession Models Facilitation Model Succession in a particular area will always lead to the same type of community. Climax Community Each stage facilitates invasion and replacement by organisms of the next stage. Mader: Biology 8th Ed.

Different types of plants can colonize an area at the same time. Succession Models Inhibition Model Colonists hold onto their space 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. Mader: Biology 8th Ed.

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. Mader: Biology 8th Ed.

Intermediate Disturbance Hypothesis Moderate amounts of disturbances at moderate frequency are required for a high degree of community diversity. If widespread disturbances occur frequently, diversity will be limited. Mader: Biology 8th Ed.

Intermediate Disturbance Hypothesis Mader: Biology 8th Ed.

Predation, Competition, and Biodiversity In certain communities, predation by a particular species reduces competition and increases diversity. Predators that regulate competition and maintain community diversity are referred to as keystone predators. Introduction of exotic species into a new area may lead to unbridled competition and resultant reduction in biodiversity. Mader: Biology 8th Ed.

Diversity and Composition Models Island Biogeography Review Diversity and Composition Models Island Biogeography Habitat and Ecological Niche Competition Between Populations Predator-Prey Interactions Symbiotic Relationships Community Development Community Diversity Mader: Biology 8th Ed.

Mader: Biology 8th Ed.