Ecology Community Concepts Quiz

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Questions and Answers

What do sharp boundaries at ecotones signify in community structure?

They indicate the presence of invasive species.

They occur only in aquatic environments.

They represent distinct changes between communities. (correct)

They are always associated with high diversity.

Which statement about interdependent and independent community philosophies is accurate?

Independent distribution of trees is supported by Frederic Clements.

Henry Gleason believed in the super-organism concept.

Frederic Clements emphasized the flexibility of species interactions.

The interdependent community philosophy is associated with the 1920s. (correct)

What factor influences log-normal distributions of species abundance?

Geographic location.

Climate change factors.

Sample size. (correct)

Predation pressure.

In terms of species diversity, what does greater diversity indicate?

More species and more equal abundances. Signup and view all the answers

How do nurse plants facilitate species in stressful environments?

By enhancing soil fertility and moisture. Signup and view all the answers

What is meant by 'species evenness' in a community?

The distribution of individuals among species. Signup and view all the answers

What is the primary focus of facilitation experiments in ecology?

To understand species interactions and dependencies. Signup and view all the answers

What indicates the importance of gradual zones in terrestrial communities?

They can hint at changes in environmental conditions. Signup and view all the answers

What does Simpson's index primarily measure?

Species richness Signup and view all the answers

Which of the following factors does NOT affect species diversity?

Species migration patterns Signup and view all the answers

What is one characteristic of ecosystems that have high species diversity?

Presence of keystone species Signup and view all the answers

According to the Intermediate Disturbance Hypothesis, what is a characteristic of K strategists?

Exhibit high parental care Signup and view all the answers

Which of the following species would most likely be affected by an increase in added nutrients?

Shade intolerant species Signup and view all the answers

What is the primary purpose of the Park Grass Experiment initiated in 1856?

To improve hay production with fertilizers Signup and view all the answers

Which biome is associated with high species diversity but low nutrient levels?

Tropical rainforests Signup and view all the answers

What defines a keystone species?

A species that has a disproportionate impact on its ecosystem Signup and view all the answers

Study Notes

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.

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Description

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.