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Chapter 4

Chapter 4.docx


Department
Environmental Studies
Course Code
ENV 1101
Professor
Sonia Wesche
Chapter
4

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Chapter 4: Species Interactions and Community Ecology
Compare and Contrast the Major Types of Species interactions:
- Competition results when individuals or species vie for limited resources. It can occur within or
among species and it can result in coexistence or exclusion. T can also lead to realized niches,
resource partitioning and character displacement.
- In prediation, one species kills and consumes another. It I the basis of food webs and can influence
population dynamics and community composition
- In Parasitism, one species derives benefit by harming another (but not killing)
- Herbivory is an exploitative interaction whereby an animal feeds on a plant
- In mutualism, species benefit from one another. Some mutualists are symbiotic, whereas other
mutualists are free-living
Feeding Relationships and Energy Flow:
- Energy is transferred in food chains among trophic levels
- Lower trophic levels generally contain more energy, biomass and numbers of individuals than
higher trophic levels
- Food webs illustrate feeding relationships and energy flow among species in a community
Keystone Species:
- Keystone species have impacts on communities that are out of proportion to their abundance
- Top predators are frequently considered keystone species, but other organisms may be thought of
as keystones for other reasons
The Process of Succession and the Debate over the Nature of Communities
- Succession is a stereotypical pattern in change within a community through time
- Primary succession begins with an area devoid of life. Secondary succession begins with an area
that has been severely disturbed
Impacts of Invasive Species on Communities
- Invasive species such as the zebra muscle have altered the composition, structure, and function
of communities
- Humans are the cause of most modern species invasions, but we also can respond to invasion with
prevention and control measures
Goals and Methods of Ecological Restoration:
- Ecological restoration aims to restore communities to a more natural state, variously defined as
before human or industrial interference
- Restoration efforts in the field are informed by the growing science of restoration ecology
Terrestrial Biomes of the World:
- Biomes represent major classes of communities spanning large geographic areas
- The distribution of biomes is determined by temperature, precipitation and other factors
- The biome concept by tradition refers to terrestrial systems. Aquatic systems can be classified in
similar ways, determined by different factors
TERMS
Amensalism: a relationship between members of different species in which one organism is harmed and
the other is unaffected
Commensalism: a relationship between members of different species in which one organism benefits and
the other is unaffected
Primary Succession: A stereotypical series of changes as an ecological community develops over time,
beginning with a lifeless substrate. In terrestrial systems, primary succession begins when a bare expanse of
rock, sand, or sediment becomes newly exposed to the atmosphere and pioneer species arrive
Secondary Succession: A stereotypical series of changes as an ecological community develops over time,
beginning when some event disrupts or dramatically alters an existing community.
Biome: a major regional complex of similar plant communities; a large ecological unit defined by its
dominant plant type and vegetation structure
Ecoregion: a large area of land or water that contains a geographically distinct assemblage of natural
communities that share a large majority of their species and ecological dynamics; share similar
environmental conditions; and interact ecologically in ways that are critical for their long-term persistence
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