What is the key difference between a dominant species and a keystone species in an ecosystem?

• A. A dominant species can only exist in aquatic ecosystems, while a keystone species is found only in terrestrial ecosystems.
• B. A dominant species is the most abundant or has the highest biomass, while a keystone species has a disproportionately large effect on ecosystem structure relative to its abundance.
• C. A dominant species is always a top predator, while a keystone species is always a primary producer.
• D. A dominant species is defined by its genetic diversity, while a keystone species is defined by its reproductive rate.

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of a dominant species. A dominant species is one that is the most abundant in an ecosystem or has the highest biomass. This means it has a significant presence in terms of numbers or physical mass, which can influence the ecosystem's structure and function.
2. Step 2: Next, explore the concept of a keystone species. A keystone species is not necessarily abundant but has a disproportionately large impact on the ecosystem relative to its population size. Its role is critical in maintaining the structure and balance of the ecosystem.
3. Step 3: Compare the two concepts. The key difference lies in their influence and abundance. A dominant species exerts influence due to its abundance or biomass, while a keystone species exerts influence due to its ecological role, regardless of its abundance.
4. Step 4: Address the incorrect statements in the problem. For example, the idea that dominant species are always top predators or that keystone species are always primary producers is incorrect. Both types of species can occupy various roles in the food web.
5. Step 5: Conclude by emphasizing the correct answer: A dominant species is the most abundant or has the highest biomass, while a keystone species has a disproportionately large effect on ecosystem structure relative to its abundance.