Ecology Community Concepts Quiz

Community Boundaries

• Communities can have distinct or gradual boundaries.
• Ecotones are transition zones between communities.
• Edge species are found in ecotones.

Serpentine Soils

• Serpentine soils are low in nutrients and high in heavy metals, which can create distinct ecotones.

Community Philosophy

• Frederic Clements proposed the superorganism concept, where communities are highly organized and interdependent.
• Henry Gleason proposed the independent distribution concept, where communities are composed of species with individual distributions.

Species Interdependence

• Extreme environmental conditions often show evidence of interdependence among species.
• Tundra and alpine tundra are examples of stressful environments where interdependence is observed.
• Neighbor removal experiments can show the effects of species interactions on community structure.

Community Concepts

• Species richness is the number of species in a community.
• Species evenness is the relative abundance of each species in a community.

Species Abundance

• Log-normal distributions are often used to describe species abundance in communities.
• The shape of the distribution is dependent on sample size.

Species Diversity Indices

• Simpson's index and Shannon's index are used to quantify species diversity.
• Simpson's index measures the probability of selecting two individuals of the same species.
• Shannon's index measures the uncertainty in predicting the species of the next individual selected.

Factors Affecting Species Diversity

• Resources (nutrients, light)
• Habitat diversity
• Keystone species
• Disturbance

Fertility Effects on Species Richness

• The Park Grass Experiment showed that adding nutrients can reduce species richness by favoring dominant species.

Reversing the Effects of Added Nutrients

• Reducing nutrient levels can increase species richness by allowing less dominant species to thrive.
• Shade intolerant species can benefit from reduced nutrient levels and increased light availability.

High Diversity Ecosystems

• High-diversity ecosystems often have low nutrient levels, which can promote species richness.
• Tropical rainforests, sclerophyllous woodlands, and shrublands are examples of high-diversity ecosystems.

Habitat Diversity and Species Diversity

• Increased habitat diversity leads to increased species diversity.

Keystone Species

• Keystone species have a disproportionate impact on community structure, even if they are not the most abundant.
• Sea stars, ecosystem engineers, and keystone resources are examples of keystone species.

Intermediate Disturbance Hypothesis

• Intermediate levels of disturbance can promote highest species diversity.
• Disturbances can create habitat heterogeneity and prevent dominant species from outcompeting others.

Community Stability

• Community stability is the ability of a community to resist and recover from disturbances.
• Species richness can contribute to community stability by providing redundancy and alternative pathways for ecosystem processes.

Test your knowledge on the concepts of ecological communities, including boundary types, soil characteristics, and species interdependence. Explore the theories proposed by Frederic Clements and Henry Gleason, and learn how extreme environments influence community structure.