Chapter 8: Community Ecology

EDGE EFFECTS

• The differences in the physical structures
• of 2 different ecological zones meeting.
• -The boundary of a forest and a desert.

Species Equilibrium Model

• The number of species found on an island is determined by 
• a balance between the immigration rate and the extinction rate
• -the rates will even out to form a balance/ equlibrium
• Also called the Theory of Island Biogeography

Native vs Non-Natice Species

• Native species are normally in an ecosystem
• Non-native species aren't normally in an ecosystem
• -They are often introduced through outside means
• -Introduction of a new species can potentially be harmful

Indicator Species

• A species that serves as a sort of warning system
• That notes if the ecosystem is in trouble
• -Most often it is the population that is noted

Keystone Species

• A species that has multiple important roles
• that are important to the ecosystem
• -More so than most other species

Interspecific Competition

• Competition between 2 or more species
• over the limited resources in an ecosystem

Interference Competition

• A Situation in which one species limits 
• access of a resource to another species
• -Doesn't matter is resource is abundant or not

Exploitation Competition

• Situation where 2 species competing
• have equal access to a specific resourse
• -Differ in how quickly or efficiently 
• they can exploit it

Resource Partitioning

• Dividing up scarce resources so
• species with specific needs use them
• at different times, ways or places

Predation

• When one species feeds directly
• on all or part of a living organism
• -Predators (eg "meat-eaters")

Predator- Prey Relationship

• One organism feeds on parts or all
• of another organism
• -When one animal eats another

Symbiosis

• Species live together in an
• intimate association

Parasitism

• One species literally lives off of
• another species (the host)

Mutualism

• An interaction where both species
• actually benefit from each other

Commensalism

• Somewhat like mutualism
• BUT the other is not helped as much

Ecological Succesion

• The gradual change in species composition
• of a given area due to
• changing environmental conditions

Primary Sucession

• Gradual establishment of life
• on a nearly lifeless ground

Secondary Sucession

• Re-establishment of life in an area
•  where life was already present

Pioneer Species

• First, hardy species that begin
• the growth of life in an area
• -Often small plants and microbes

Early Successional Plant Species

• Plant species found in the early stages of succession
• Grow close to ground
• Can establish large population in harsh conditions

Mid Sucessional Plant Species

• Grasses and low shrubs
• Less hardy than 1st species

Late Successional Plant Species

• Mostly trees and such
• Can form a stable complex community

Distubance

• Something that disrupts
• an ecosystem or community

Inertia (Persistence)

• Ability of a living system
• to resist being changed

Constancy

• Ability of a living system
• to maintain a healthy population
• with its limits (available resources)

Resilience

• Ability of a living system
• to "bounce back" after a
• change that was not too drastic

Precautionary Principle

• When there is uncertainty about
• potentially serious harm from stuff,
• one should act to prevent harm
• to humans and the envoirnment