Introductory Ecology

Food Web

Network of feeding relationships showing energy transfer among species in a community

Trophic Level

Position an organism occupies in a food web based on feeding role; usually producer to top consumer

Connectance

Proportion of observed feeding links relative to all possible links in a food web; measures food web complexity

Trophic Cascade

Ripple effect through a food web caused by changes at higher trophic levels

Keystone Species

Species with a disproportionately large effect on community structure relative to its abundance

Robert Paine Hypothesis

Predators can increase species diversity by preventing competitive exclusion among prey species

Dominant Species

Species with high biomass that strongly influences community structure

Keystone Species Types

Predators

Ecosystem Engineer

Organism that physically modifies the environment and creates or alters habitats for other species

Landscape Architect

Species that substantially alters landscape structure and ecosystem processes; e.g.

Beaver Effects

Build dams

Ecological Niche

Environmental requirements and ecological role needed for a species to survive and reproduce

Hutchinsonian Niche

An abstract concept defined by environmental conditions required for survival and reproduction

Fundamental Niche

Potential range of conditions a species can occupy without interactions from other species

Realized Niche

Actual niche occupied after competition

Generalist Species

Species able to tolerate a broad range of environmental conditions and resources

Specialist Species

Species adapted to a narrow range of environmental conditions or resources

Community Ecology

Study of interactions among species and how they shape community structure

Ecosystem Ecology

Study of living organisms and abiotic components

Landscape Ecology

Study of spatial patterns and interactions among ecosystems across a heterogeneous landscape

Landscape

Heterogeneous area composed of distinct habitat patches

Patch

Relatively homogeneous area that differs from its surroundings

Matrix

Dominant and most continuous landscape element surrounding patches

Habitat Fragmentation

Breaking of continuous habitat into smaller isolated patches

Corridor

Strip of habitat connecting isolated patches and facilitating organism movement

Edge Effect

Ecological changes occurring at habitat boundaries due to fragmentation

Ecotone

Sharp transition zone between two habitat types or communities

Ecocline

Gradual transition zone between communities along an environmental gradient

Island Biogeography Theory

Species richness on islands reflects a balance between immigration and extinction rates

Species Turnover

Continuous replacement of species over time while total richness may remain stable

Macroecology

Study of relationships between organisms and environment at continental scales

Global Ecology

Study of ecological processes and interactions at a planetary scale

Alpha Diversity

Diversity within a single habitat or patch

Beta Diversity

Difference in species composition between habitats or patches

Gamma Diversity

Total diversity across a larger region; combines alpha and beta diversity

Species Richness

Number of different species in a community

Species Evenness

Relative abundance distribution of species within a community

Shannon-Wiener Index

Diversity metric that combines species richness and evenness into a single value

Rank-Abundance Curve

Graph of species relative abundance versus rank used to assess diversity and dominance

Disturbance

Event that disrupts community or ecosystem structure and alters resources or physical conditions

Abiotic Disturbance

Non-living disturbance such as drought

Biotic Disturbance

Disturbance caused by living organisms such as invasive species

Intermediate Disturbance Hypothesis

Species diversity is predicted to be highest at intermediate disturbance levels because competition and colonization are balanced

Environmental Heterogeneity

Diversity and variation in habitat conditions; generally increases species diversity

Primary Production

Conversion of radiant energy into chemical energy by autotrophs; foundation of food webs

Autotroph

Organism that produces its own food using light

Gross Primary Production (GPP)

Total carbon fixed by photosynthesis in an ecosystem

Net Primary Production (NPP)

GPP minus carbon lost through producer respiration; energy available to consumers

Eutrophication

Excess nutrient input (especially phosphorus and nitrogen) causing algal blooms and oxygen depletion in water bodies

Hypoxic Dead Zone

Area with dissolved oxygen below 2 mg/L

Community Stability

Persistence of a community or ecosystem despite disturbance

Resistance

Ability of a community to maintain structure and function during disturbance

Resilience

Ability of a community to recover after disturbance

Insurance Hypothesis

Greater biodiversity increases community and ecosystem stability because multiple species can perform similar functions

Succession

Gradual change in community composition over time following disturbance

Primary Succession

Community development on newly exposed substrates lacking soil

Secondary Succession

Community recovery after disturbance where soil remains intact

Pioneer Community

Earliest colonizing species during succession

Climax Community

Relatively stable late-successional community that persists until disturbed

Disclimax Community

Community maintained by continual external disturbance

Facilitation Model

Early species modify the environment in ways that help later species establish

Tolerance Model

Species coexist and later species eventually outcompete earlier ones without environmental modification

Inhibition Model

Early colonizers hinder establishment of later species and slow succession

Life History

Major adaptations and traits affecting growth

Life History Strategy

Suite of traits shaped by natural selection that optimizes survival and reproductive success

Fecundity

Reproductive output

Recruitment

Addition of surviving offspring into a population or reproductive population

Survivorship Curve

Graph showing survival patterns of a population across age classes

Type I Survivorship

High survival until old age

Type II Survivorship

Constant mortality rate across all ages

Type III Survivorship

High juvenile mortality with few survivors living long lives

Parental Care

Protection and provisioning of offspring that increases recruitment success

Semelparity

Reproductive strategy involving a single major reproductive event before death

Iteroparity

Reproductive strategy involving multiple reproductive events over a lifetime

r-selected Species

Species adapted to unpredictable environments with high fecundity

K-selected Species

Species adapted to stable environments with low fecundity

Reproductive Value (RV)

Current reproduction plus future reproductive potential (residual reproductive value)

Grime's CSR Model

Plant life-history classification based on combinations of Competition

Competitor Strategy (C)

Plants adapted for resource-rich environments with strong competitive ability

Stress-Tolerator Strategy (S)

Plants adapted to stressful environments by conserving resources and growing slowly

Ruderal Strategy (R)

Plants adapted to disturbed environments through rapid colonization and high reproduction