Problem 3 - Campbell Biology

Question

Based on the intermediate disturbance hypothesis, a community's species diversity is increased by (A) frequent massive disturbance. (B) stable conditions with no disturbance. (C) moderate levels of disturbance. (D) human intervention to eliminate disturbance.

Step-by-Step Solution

Answer

(C) moderate levels of disturbance.

Step 1: Understand the Intermediate Disturbance Hypothesis

The intermediate disturbance hypothesis suggests that species diversity is maximized when ecological disturbances occur at a moderate level. This means that neither too frequent nor too infrequent disturbances result in the highest diversity of species.

Step 2: Evaluate Each Option

Now evaluate each option in the context of the intermediate disturbance hypothesis: (A) Frequent massive disturbances tend to wipe out existing species, reducing diversity. (B) Stable conditions with no disturbance may lead to competitive exclusion, where dominant species outcompete others, reducing diversity. (C) Moderate levels of disturbance prevent competitive exclusion and allow for coexistence of a greater number of species. (D) Human intervention to eliminate disturbance usually does not allow for the natural processes that contribute to species diversity according to this hypothesis.

Step 3: Select the Correct Answer

Based on the evaluations above, the option that aligns with the intermediate disturbance hypothesis is moderate levels of disturbance (Option C).

Key Concepts

Species Diversity

Species diversity is a key concept in ecology. It refers to the variety and abundance of different species within a community or ecosystem. Higher species diversity is generally beneficial because it contributes to ecosystem stability and productivity.
The two primary components of species diversity are:

• **Species richness:** The number of different species present in an ecosystem.
• **Species evenness:** The relative abundance of each species. A community where all species have similar abundance has higher evenness.

Species diversity can be influenced by various factors, including environmental conditions, availability of resources, and ecological disturbances. For students, understanding the drivers of species diversity is critical for grasping broader ecological principles.

Ecological Disturbances

Ecological disturbances are events that disrupt ecosystem structure and function. These disturbances can range from natural events like hurricanes, fires, and floods to human activities such as deforestation and pollution.
Disturbances play a crucial role in maintaining ecological balance by:

• Creating opportunities for new species to colonize and grow.
• Preventing single species from becoming too dominant (competitive exclusion).
• Changing resource availability and habitat structures.

The Intermediate Disturbance Hypothesis highlights the impact of disturbance frequency on species diversity. Moderate levels of disturbance foster an environment where neither competitive exclusion nor severe disruption can occur, allowing for greater species coexistence and higher diversity.

Competitive Exclusion

Competitive exclusion is an important ecological concept that occurs when one species outcompetes another for the same limited resources. This can lead to the local extinction of the less competitive species. Competitive exclusion is more likely in stable environments with little to no disturbances.
Key points to remember about competitive exclusion:

• It reduces overall species diversity in an ecosystem.
• Dominant species monopolize resources, making it difficult for other species to survive.
• Disturbances can mitigate competitive exclusion by creating opportunities for multiple species to thrive.

In the context of the Intermediate Disturbance Hypothesis, moderate disturbances break the cycle of competitive exclusion by continually resetting competitive dynamics, thereby promoting a more diverse and balanced ecosystem.