Chapter 16 Ecology

Species Abundance

Distribution of species abundance in communities.

Species Diversity

Combination of species richness and evenness.

Community

Association of interacting species in a defined area.

Community Structure

Attributes like species number and diversity.

Guild

Group of organisms sharing similar living methods.

Life-form

Combination of plant structure and growth dynamics.

Lognormal Distribution

Bell-shaped curve of species abundance frequency.

Preston's Concept

Distribution of commonness and rarity in species.

Sample Size Effect

Larger samples capture rare species better.

Species Richness

Number of different species in a community.

Species Evenness

Relative abundance of species in a community.

Shannon Wiener Index

Quantitative measure of species diversity.

H' Value

Result of Shannon Wiener diversity index calculation.

Pi

Proportion of the ith species in a community.

Logepi

Natural logarithm of the proportion of species.

Rank-Abundance Curve

Graph showing species abundance against rank.

Slope of Curve

Indicates species evenness in a community.

Intermediate Disturbance Hypothesis

Moderate disturbances enhance species diversity.

Complex Environments

Support higher species diversity than simple ones.

Tide Pool A

Example with 4 species, higher richness.

Tide Pool B

Example with 2 species, lower richness.

Caddisfly Rank-Abundance Curves

Specific example of rank-abundance analysis.

Environmental Complexity

Variation in habitat structure affecting species diversity.

Species Diversity

Variety of different species in an ecosystem.

Foliage Height

Measure of vegetation stature influencing bird diversity.

MacArthur's Findings

Warbler diversity increases with higher foliage height.

Paradox of the Plankton

Coexistence of species in nutrient-limited environments.

Nutrient Requirements

Specific nutrients needed for algal niche survival.

Silicate to Phosphate Ratio

Determines diatom coexistence in freshwater environments.

Diatom Dominance

Varies with nutrient availability in lakes.

Spatial Variation

Differences in nutrient concentrations across environments.

Nitrogen and Moisture Variation

Influences plant community structure in fields.

Soil Heterogeneity

Variation in soil types affecting plant diversity.

Tropical Forest Diversity

High species richness within Amazon forest communities.

Plant Community Composition

Distinct species arrangement in different ecological areas.

Nutrient Enrichment

Increase in nutrients leading to reduced species diversity.

Limiting Nutrients

Nutrients that restrict growth when in short supply.

Light Limitation

Single resource limiting species growth in enriched environments.

Dominant Species

Species that outcompete others for light resources.

Ectomycorrhizal Fungal Diversity

Variety of fungi associated with plant roots.

Atmospheric Nitrogen Deposition

Increase in nitrogen from the atmosphere affecting ecosystems.

Fungal Taxa Decline

Reduction in fungal species linked to nitrogen levels.

Soil pH Decline

Decrease in soil acidity correlating with nitrogen increase.

Patchiness in Ecosystems

Irregular distribution of resources affecting community structure.

Environmental Complexity

Influences plant species diversity levels.

Intermediate Disturbance Hypothesis

Suggests moderate disturbance increases community diversity.

State of Equilibrium

Stable environmental conditions maintained by opposing forces.

Disturbance

Varies with organisms; includes abiotic and biotic factors.

Abiotic Disturbance Sources

Includes fire, hurricanes, and floods.

Biotic Disturbance Sources

Includes disease and predation.

Human-Caused Disturbance

Includes deforestation and pollution effects.

Connell's Findings

High diversity results from changing environmental conditions.

Effects of Disturbance

Influences community diversity significantly.

Intermediate Disturbance Levels

Allow species colonization without competitive exclusion.

Sousa's Study

Examined disturbance effects on intertidal algae and invertebrates.

Boulder Size Impact

Larger boulders require more force to disturb.

Prairie Dog Disturbance

Creates burrows, affecting vegetation and plant colonization.

Pest Control Impact

Reduced prairie dog populations decreased plant community dynamics.

Urban Biota Diversity

Urbanization can reduce bird species richness.

Bird Species Richness

Peaks with intermediate land use intensity.

Diversity Decline Causes

High disturbance levels threaten numerous species.

Species Threats

Thousands of species face extinction risks.

Intertidal Zone Diversity

Greatest diversity found at intermediate disturbance levels.

Temperate Grasslands Disturbance

Prairie dogs significantly influence North American prairies.

Human Disturbance Effects

Widespread impacts on ecosystems and species diversity.

Urbanization Effects

Can lead to both diversity loss and retention.