10% rule

Definition

The 10% rule refers to the principle in ecology that, on average, only about 10% of the energy from one trophic level is transferred to the next level in a food chain or food web. This energy transfer is significant because it highlights the inefficiencies of energy movement through an ecosystem and helps explain why there are fewer organisms at higher trophic levels compared to lower ones.

5 Must Know Facts For Your Next Test

1. The 10% rule indicates that only about 10% of the energy consumed by one trophic level is converted into biomass for the next level, with the rest lost as heat or used for metabolic processes.
2. Due to this energy loss, ecosystems typically have fewer organisms at higher trophic levels compared to those at lower levels, resulting in a pyramid shape when visualized.
3. In a typical food web, primary producers harness solar energy, and as energy moves up to herbivores and then carnivores, the amount available decreases dramatically.
4. The 10% rule is crucial for understanding population dynamics and ecosystem productivity, as it helps predict how many individuals can be supported at each trophic level.
5. Factors such as diet efficiency, predation rates, and environmental conditions can affect the actual percentage of energy transferred between trophic levels.

Review Questions

• How does the 10% rule explain the structure of ecosystems and the distribution of biomass among different trophic levels?
  • The 10% rule illustrates that only about 10% of energy from one trophic level is passed on to the next, leading to a significant decrease in available energy as one moves up the food chain. This loss of energy results in fewer organisms and less biomass at higher trophic levels compared to lower ones. Consequently, ecosystems tend to have a greater abundance of primary producers and primary consumers than secondary or tertiary consumers, which reflects this energy transfer inefficiency.
• Discuss how the concept of the 10% rule impacts biodiversity within an ecosystem.
  • The 10% rule has important implications for biodiversity since it influences population sizes across different trophic levels. With fewer resources available to higher trophic levels due to energy loss during transfer, ecosystems often exhibit a higher diversity of species at lower levels. This results in more primary producers and herbivores compared to carnivores, promoting a rich variety of interactions and dependencies that contribute to overall ecosystem health and resilience.
• Evaluate how human activities might disrupt the natural application of the 10% rule in ecosystems.
  • Human activities such as overfishing, habitat destruction, and pollution can significantly alter the natural dynamics of energy flow outlined by the 10% rule. For instance, overfishing removes key species from higher trophic levels, disrupting predator-prey relationships and leading to imbalances in population sizes. Additionally, habitat destruction can decrease primary productivity by reducing the number of primary producers. These disruptions can lead to cascading effects throughout the food web, impacting biodiversity and ecosystem stability.

Related terms

Trophic Levels: The hierarchical levels in an ecosystem that categorize organisms based on their primary source of energy, including producers, primary consumers, secondary consumers, and tertiary consumers.

Energy Pyramid: A graphical representation of the energy flow in an ecosystem, illustrating the amount of energy available at each trophic level and showing the decline in available energy as one moves up the pyramid.

Primary Producers: Organisms, such as plants and algae, that convert sunlight or inorganic compounds into organic matter through photosynthesis or chemosynthesis, forming the base of the food chain.