Question

Which hypothesis best describes the idea that a small decline in species richness results in a large drop in ecosystem function? a. Diversity-stability hypothesis b. Redundancy hypothesis c. Keystone hypothesis d. Idiosyncratic hypothesis e. Community hypothesis

Short answer

The correct answer is c. Keystone hypothesis.

Step-by-step solution

Understanding the hypotheses

First, it is important to understand the definition of each mentioned hypothesis:\n 1. Diversity-stability hypothesis: States that ecosystems with many different species (high biodiversity) are more stable and less likely to experience dramatic shifts in population levels.\n 2. Redundancy hypothesis: Suggests that more species-rich communities are more stable due to overlapping roles. Therefore, if one species is lost, others can compensate for its role.\n 3. Keystone hypothesis: Proposes that some species (keystone species) have a disproportionately large effect on community structure or ecosystem function.\n 4. Idiosyncratic hypothesis: Suggests that every species impacts ecosystem function differently, thus the loss of any particular species may vary in its effect.\n 5. Community hypothesis: A broad idea which emphasizes the role of community structure, including species interactions, in shaping ecosystem function.

Analyzing the question

The question involves a situation whereby a small decline in species richness results in a large drop in ecosystem function. This particular situation suggests a phenomenon where the loss of some particular species leads to significant changes in ecosystem function.

Choosing the correct option

Given our understanding of the hypotheses, it is clear that the Keystone hypothesis (Option c) is the most fitting. Keystone species have a large impact on ecosystem functions, and thus a decline in such species would result in a significant drop in ecosystem function.

Key concepts

Species Richness

When discussing the health of an ecosystem, a core concept to understand is 'species richness'. This refers to the count of different species present in a certain habitat, which contributes significantly to the overall biodiversity. A varied cast of organisms ensures that numerous niches are filled and ecological processes can proceed efficiently.

Species richness is akin to having a diversified investment portfolio: the more diverse it is, the less impact the loss of a single investment (or species) will have on the portfolio (or ecosystem). Some ecosystem functions may rely on a few critical species, and when these are lost, it can result in dramatic consequences, much like the hypothesis stated in the exercise.

Enhancing species richness can therefore be a safeguard against ecological instability. Diverse ecosystems can be more resilient to disturbances whether they're natural or human-induced, providing a buffer that helps to maintain balance and support continued ecosystem function.

Ecosystem Function

Ecosystem function encompasses the myriad processes that happen within an ecological community. These functions include nutrient cycling, primary production (photosynthesis), decomposition, and pollination among others—essentially, the natural services that support life on Earth.

An interesting aspect of ecosystem function is the way in which different species contribute to these processes. While some species might play a significant role in a particular function, others might be less critical. This leads to the keystone hypothesis from the original exercise, which suggests that the loss of a keystone species—a species that has a disproportionate effect on its environment—can lead to a dramatic drop in ecosystem function.

Understanding the interdependencies within an ecosystem is crucial for conservation efforts. By identifying and protecting keystone species, we can strive to maintain or improve the functioning of ecosystems, which ultimately supports biodiversity and the resilience of these ecological communities.

Biodiversity

Biodiversity, a contraction of 'biological diversity', is the term used to describe the vast variety of life on Earth, covering all organisms from the smallest bacteria to the largest whales. It considers not only the number of species, or species richness, but also the genetic diversity within species, and the variety of ecosystems they create and inhabit.

Biodiversity is a reflection of the health of our planet, and it plays a crucial role in ecosystem function. It contributes to the stability, productivity, and resilience of ecological communities. A biodiverse ecosystem is more capable of withstanding environmental stress and adapting to changes.

One of the greatest values of biodiversity is its role in providing ecosystem services that humans rely on, such as clean water, fertile soil, and a stable climate. Understanding the underpinnings of biodiversity and how it influences ecosystem function is essential for effective conservation and sustainability measures, aligning closely with the keystone hypothesis presented in the exercise.