PACKET #81CHAPTERS #54 & #50

Community Ecology

Review & Introduction

Community Assemblage of

populations, of different species, that live and interact in the same place at the same time

Community Ecology Description and

analysis of patterns and processes within the community

Introduction II

Communities are difficult to study Large number of organisms and many different

species that interact with one another and are interdependent in a variety of ways Species compete for food, water, living space and other

resources Communities vary in size Lack precise boundaries Rarely completely isolated Within a community, no species exists independently

of other species.

COMMUNITY STRUCTURE & FUNCTIONING

Community Ecology

Niche

The role of a species within a community

Describes all aspects of an organism’s existence Not only habitat, but

much moreFundamental Niche

Niche that an organism would occupy in the absence of competition

Realized Niche Niche that an organism

occupies in the presence of competition

Niche II

Limiting resources restrict the ecological niche of a species Soil composition Climatic extremes Any environmental resource that is scarce or

unfavorable

Biotic and abiotic factors may influence an organism’s niche

Competition

Intraspecific Competition between

members of same species Interspecific

Competition between members of different species

Competition between two species with overlapping niches may lead to competition exclusion Results in the exclusion of

one species due to interspecific competition

Coexistence occurs when overlap between niches is reduced

Natural Selection

DEFENSE MECHANISMS

Community Ecology

Defense MechanismsHiding

Use of warning colors Aposmatic Colors

A warning coloration such as a 'striking' color pattern designed to attract attention and to warn predators away.

Defense MechanismsHiding

Batesian mimicry Resemblance of a

harmless organism to a harmful or unpalatable organism

Defense MechanismsHiding

Mullerian mimicry Similar morphology of

a group of harmful or unpalatable organism Monarch & Viceroy

butterflies

Symbiosis

Any intimate relationship or association between members of two or more species Greek sym = together Greek bios = life

Types of Symbiosis I

Mutualism Benefits are shared

Nitrogen fixing bacteria & legumes

Zooxanthellae and reef-building coral

Mycorrhizae facilitate mutalistic relationships between fungi and the roots of a wide variety of plants

Types of Symbiosis II

Commensalism Taking without harm

Epiphytes living on tropical tress benefit from the habitat of the host, but the host is not harmed or benefited

Types of Symbiosis III

Parasitism Taking at another’s

expense Parasite benefits while

host is harmed Well adapted parasite

does not kill the host Parasite that causes

the death of the host is a pathogen

Keystone Species

Affect the character of the communityHave a great effect on other species in the

community Commonly are the top predators

Dominant species influence the community as a result of their greater size or abundance Trees are the dominant species in forests because

they change the local environment Coral, an animal, in coral reefs

COMMUNITY DEVELOPMENT

Community Ecology

Succession

Process of community development over time, with one species being replaced by another

Succession II

Primary Succession Occurs when a

community develops in a “lifeless” environment Occurs on bare rock

when rock is eventually transformed into soil

Occurs on newly formed volcanic larva and recently glaciated rock

Succession III

Secondary Succession Occurs when a

community develops where a previous community existed

Occurs where soil already exists Areas denuded or

modified by fire or agriculture

Abandoned farmlandKeep in mind that

disturbances impact succession

Studying Succession

Ecologists continue to study community structure

Clements Developed organismic model

Emphasizes the interdependence of species within the community

Gleason Developed individualistic model

Emphasizes species individually Most research is conducted here

Review

Review

Students are encouraged to place their own questions and charts on the following slides.