Chapter 20: Problem 7

How does primary productivity function as a constraint on secondary productivity in ecosystems?

Short Answer

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Answer: Primary productivity functions as a constraint on secondary productivity because the total amount of energy available for secondary productivity depends on the energy produced by primary productivity. As energy transfers between trophic levels, only about 10% of the energy is passed on to the next level, leading to energy losses. If primary productivity is low, the energy available for secondary productivity will also be limited, thereby constraining the growth and activities of consumers and decreasing the overall productivity of the ecosystem.

Step by step solution

Define Primary Productivity

Primary productivity is the rate at which plants and other photosynthetic organisms produce organic compounds (such as glucose) through the process of photosynthesis. In this process, they convert light energy from the sun, carbon dioxide from the atmosphere, and water from the soil into chemical energy stored in organic compounds.

Define Secondary Productivity

Secondary productivity refers to the rate at which consumers (herbivores, carnivores, and decomposers) in an ecosystem convert the organic compounds produced by primary producers (plants and other photosynthetic organisms) into new biomass through the process of cellular respiration. Consumers obtain energy and nutrients from the organic compounds to support their growth, reproduction, and other activities.

Energy Transfer and Trophic Levels

In an ecosystem, energy flows through a food chain or a food web from primary producers to various levels of consumers, which are classified into different trophic levels. Primary producers are the first trophic level, herbivores (primary consumers) are the second trophic level, and carnivores are the third trophic level or higher. As energy transfers from one trophic level to another, some of it is lost due to heat loss, cellular respiration, and waste production. On average, only about 10% of the energy from one trophic level is passed on to the next.

Primary Productivity as a Constraint on Secondary Productivity

Because of the energy losses between trophic levels and the fact that the amount of available energy decreases with each trophic level, primary productivity can act as a constraint on secondary productivity. The total amount of energy that can flow through an ecosystem is dependent on the energy produced by primary productivity. A higher primary productivity means that more energy is available to sustain higher amounts of secondary productivity. On the other hand, if primary productivity is low, the energy available for secondary productivity will also be limited, thereby constraining the growth and activities of consumers and decreasing the overall productivity of the ecosystem.

Importance of Primary Productivity

Primary productivity serves as the foundation for energy flow and nutrient cycling within an ecosystem. By understanding how primary productivity functions as a constraint on secondary productivity, it becomes clear that the health and stability of any ecosystem largely depend on the ability of primary producers to generate sufficient amounts of energy. Therefore, maintaining and optimizing primary productivity can be essential for supporting the overall health and functioning of the ecosystem, which in turn influences secondary productivity and the abundance and diversity of organisms within the ecosystem.

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How does primary productivity function as a constraint on secondary productivity in ecosystems?

Short Answer

Step by step solution

Define Primary Productivity

Define Secondary Productivity

Energy Transfer and Trophic Levels

Primary Productivity as a Constraint on Secondary Productivity

Importance of Primary Productivity

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