Question

In both aquatic and terrestrial communities, secondary productivity by herbivores is approximately one-tenth of the primary productivity upon which it is based. This has led some to suggest the operation of a \(10 \%\) law. Do you subscribe to this view?

Short answer

Yes, the approximate 10% secondary productivity supports the 10% Law view.

Step-by-step solution

Define Primary Productivity

Primary productivity is the rate at which producers in an ecosystem create organic material through photosynthesis, forming the base of the energy pyramid.

Understand Secondary Productivity

Secondary productivity refers to the generation of biomass by consumers, like herbivores, which consume the primary producers.

Explain the 10% Law

The 10% Law suggests that when energy is transferred from one trophic level to the next, only about 10% of the energy is transferred; the rest is lost mostly as heat.

Relate the 10% Law to Herbivores

In the context of the question, herbivores (secondary producers) are benefiting from only 10% of the energy stored by the primary producers they consume.

Conclusion on the 10% Law

Because secondary productivity by herbivores is approximately 10% of primary productivity, this situation supports the operation of the 10% Law in both aquatic and terrestrial ecosystems.

Key concepts

Primary Productivity

Primary productivity is the cornerstone of energy transfer in ecosystems. It represents the rate at which organisms, typically plants and algae, capture and convert solar energy into organic compounds via photosynthesis. These primary producers fuel the energy pyramid's base by converting carbon dioxide and water into glucose, providing the initial energy source for all other organisms in the ecosystem.

Without primary productivity, ecosystems would lack the fundamental energy needed to sustain life. It directly affects the biomass availability for herbivores, which play a critical role in energy distribution across different levels of an ecosystem.

In summary, primary productivity is crucial for sustaining life, providing energy to be passed through the food chain, and supporting diversity in both terrestrial and aquatic environments.

Secondary Productivity

Secondary productivity refers to the creation of organic material by consumers, specifically among herbivores. Herbivores obtain their energy by consuming primary producers, like plants and algae. This process involves the digestion and conversion of plant material into animal biomass.

Unlike primary productivity, which is powered through photosynthesis, secondary productivity relies on the consumption of pre-existing organic material. It represents how efficiently herbivores can transform the energy-originating from plants-into their own biomass.

The success of secondary productivity is affected by several factors, such as the quality of plant matter, environmental conditions, and the herbivore's specific metabolic processes. These factors, in turn, influence energy transfer efficiency within the ecosystem.

Trophic Levels

In an ecosystem, trophic levels signify the different strata within a food chain. Each level represents organisms that share a similar role in the nutrient and energy flow. Organisms at each trophic level acquire energy by consuming those below them.

The base of the trophic pyramid consists of primary producers, followed by primary consumers or herbivores, secondary consumers, and so on. This organization acts as a structured map indicating how energy is transferred throughout the ecosystem.

As energy moves up the trophic levels—starting from plants and moving up to top predators—the energy available diminishes, affecting organism populations and ecosystem dynamics. Thus, understanding trophic levels is vital for assessing ecological balance and for conservation efforts.

10% Law

The 10% Law is a fundamental principle in ecology, expressing how energy is transferred through trophic levels in an ecosystem. It states that only about 10% of the energy from one trophic level is passed on to the next. The remainder, approximately 90%, is lost as heat, metabolism, and waste.

This concept helps elucidate why energy pyramids are broader at the base and narrow at the top. As primary producers pass on their energy to herbivores, only a fraction of that energy helps build herbivore biomass. Similarly, when carnivores consume herbivores, only 10% of that energy transfers to their level.

The 10% Law underscores the inefficiency of energy transfer in ecosystems and highlights the importance of conserving energy at the base of the food chain to sustain larger and more complex organisms higher up.