Productivity in ecosystem: Definition, Types, Diagram
Productivity in an ecosystem refers to the rate at which energy is captured by producers and transferred across trophic levels. It includes primary productivity by plants and secondary productivity by consumers. Understanding ecosystem productivity becomes very important, as it has a direct impingement on ecosystem stability, diversity, and sustainability. Ecosystem productivity is an important topic for Class 12 Biology and NEET ecology.
This Story also Contains
- What is Productivity in an Ecosystem?
- Types of Productivity
- Factors Affecting Ecosystem Productivity
- Ecological Pyramids and Productivity
- Human Impact on Ecosystem Productivity
- Productivity in Ecosystem NEET MCQs (With Answers & Explanations)
What is Productivity in an Ecosystem?
Productivity in an ecosystem refers to the rate at which energy is produced and converted into organic material by producers (mainly plants and algae). This process is vital for the survival of all organisms in an ecosystem, as it forms the foundation of the food chain. This energy feeds an entire ecosystem and promotes the growth of organisms, and their subsequent reproduction through different trophic levels.
Types of Productivity
Productivity in the ecosystem is categorised into two types: primary and secondary productivity. Primary Productivity is further divided into two categories i.e. gross primary productivity and net primary productivity.
Primary Productivity
Primary production is the rate at which the solar energy is stored or captured by autotrophs. In other words, the amount of biomass or organic food produced by autotrophs per unit during photosynthesis. It is thus the base of the food web, sustaining herbivores and other consumers.
Gross Primary Productivity (GPP)
Gross primary productivity (GPP) represents the total organic matter synthesized by the producers through photosynthesis in a given area and time. It includes the organic matter or basically energy used up during the metabolic processes.
Net Primary Productivity (NPP)
Net primary productivity (NPP) is simply the amount of energy remaining after the amount used by plants for respiration. It is the amount of energy available for growth and the reproduction of plants, and ultimately for consumption by herbivores and higher trophic levels.
Secondary Productivity
Secondary productivity represents energy storage at the consumer level. The energy resulting from the primary production furnishes the energy provided to the rest of the higher trophic levels. Some of the energy in the form of food is consumed by herbivores or carnivores. It is dependent upon the efficiency of energy transfer between trophic levels.
Factors Affecting Ecosystem Productivity
Ecosystem productivity is a product of abiotic and biotic factors undergoing complex interactions to determine both the efficiency and overall rate of energy transfer from one trophic level to another. Controlling factors are very important to understand since they help in the prediction of changes occurring in ecosystem dynamics and the management of natural resources sustainably.
Abiotic Factors (Light, Temperature, Water, Nutrients)
Light intensity and quality are important as they have a direct impact on photosynthesis, with higher light availability normally raising primary productivity.
Temperature—through its variation—affects metabolic processes and growth rates of organisms, hence overall productivity.
The availability of water is critical for photosynthesis and the survival of plants, while that of nutrients, especially nitrogen and phosphorus, is important for plant growth and biochemical processes.
Biotic Factors (Diversity, Herbivory, Predation)
The diversity of species contributes toward this purpose by allowing niche complementarity, wherein different species efficiently use resources.
It is expected that the productivity result will be impacted through trophic interactions such as predation and herbivory, because of their regulating effect on energy flow and nutrient cycling.
Predation and herbivory control the balance between population dynamics and energy transfer efficiency to have balanced ecosystems.
Ecological Pyramids and Productivity
Ecological pyramids are graphical representations of energy, biomass, or the number of organisms at each stage of the trophic levels in an ecosystem. Thereby providing information on the efficiency and structure of energy flow and matter cycling.
Pyramid of Energy
The energy pyramid represents the passage of energy from one level of a trophic system to the next in an ecosystem.
Every higher level of the trophic structure receives less energy than that preceding it, due to loss in metabolic processes mainly as heat.
As energy moves up from primary producers to apex predators, the quantity of energy goes on decreasing. In reality, only about 10% of the energy at one trophic level is revamped into the next, while all the rest is dissipated as heat.
Pyramid of Biomass Pyramid of Numbers
The pyramid of biomass is the graphical representation of biomass per unit area of different trophic levels, with producers at the base and top carnivores at the tip.
Biomass is calculated by the mass of each individual multiplied by the number of individuals at each trophic level.
In an aquatic ecosystem, it is inverted where the biomass of trophic level depends upon the reproductive potential and longevity of the member.
Pyramid of Numbers
The pyramid of numbers is the graphical representation of the number of individuals per unit area of various trophic levels.
Large numbers of producers tend to form the base whereas lower numbers of top carnivores occult the top.
The shape of the pyramid varies from ecosystem to ecosystem. In aquatic ecosystems and grassland communities, autotrophs are present in large numbers per unit area. A lesser number of herbivores, which in turn support fewer carnivores.
Human Impact on Ecosystem Productivity
Human activities have a major impact on the productivity of the ecosystem.
Deforestation and Habitat Loss
Deforestation and habitat loss reduce primary productivity by destroying habitats and reducing photosynthetic surface area and ultimately reducing the productivity of ecosystem.
Pollution and Nutrient Loading
Pollution and nutrient loading alters nutrient cycles and consecutively leads to eutrophication and reduced productivity of the aquatic ecosystems.
Climate Change
Climate change and global warming alter the temperature and precipitation regimes, thus having an overall effect on the growth and distribution of plants.
Overexploitation
Overexploitation of species reduces their biodiversity and, as such, the resiliency of ecosystems.
Productivity in Ecosystem NEET MCQs (With Answers & Explanations)
This topic carries a significant weightage in the NEET exam. Here is a list of important topics that should be covered during the preparation of the exam.
Primary Productivity and Secondary Productivity
Gross Primary Productivity and Net Primary Productivity
Ecological Pyramids
10% Law of Energy Transfer
Practice Questions for NEET
Q1. Which of the following factors can limit the productivity of an ecosystem?
Sunlight
Nutrient availability
Water availability
All of the above
Correct answer: 4) All of the above
Explanation:
All of the factors listed can limit the productivity of an ecosystem. Sunlight is the primary source of energy for photosynthesis, which is the basis for primary production in most ecosystems. Nutrient availability can limit the growth of plants and other producers, which in turn limits the productivity of the ecosystem. Water availability can limit plant growth and photosynthesis in some ecosystems, especially those that experience droughts or have limited water resources.
Hence, the correct answer is option 4) All of the above.
Q2. Component of ecosystem is /are:
Productivity
Energy flow
Nutrient cyclicing
All of these
Correct answer: 4) All of these
Explanation:
Component of the ecosystem -
Productivity is the speed at which organic matter is created, typically by plants' photosynthesis.
Decomposition is the process by which dead biological matter is broken down into more basic inorganic substances. In this process, decomposers such as fungi and bacteria are essential.
Flow of energy is the movement of energy from producers to consumers and decomposers along a food chain. Ecosystems rely on the sun as their primary energy source.
Nutrient cycling is the transfer of nutrients between non-living elements (rock, soil, and air) and living systems (biotic organisms).
Hence, the correct answer is option 4) All of these.
Q3. Assertion: Decomposers play a crucial role in energy flow in an ecosystem.
Reasoning: Decomposers break down dead organic matter and return nutrients to the soil, which can then be taken up by producers and recycled through the ecosystem.
Both assertion and reasoning are true and reasoning is the correct explanation for the assertion.
Both assertion and reasoning are true, but reasoning is not the correct explanation for the assertion.
Assertion is true, but reasoning is false.
The assertion is false, but the reasoning is true.
Correct answer: 1) Both assertion and reasoning are true and reasoning is the correct explanation for the assertion.
Explanation:
Decomposers play a crucial role in energy flow in an ecosystem by breaking down dead organic matter and returning nutrients to the soil. This process of decomposition releases nutrients such as nitrogen and phosphorus back into the ecosystem, which can then be taken up by producers and used to produce new organic matter. Without decomposers, nutrients would become trapped in dead organic matter and unavailable to other organisms, leading to a buildup of dead matter and a decrease in productivity.
Hence, the correct answer is option 1) Both assertion and reasoning are true and reasoning is the correct explanation for the assertion.
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Frequently Asked Questions (FAQs)
Ecosystem productivity is the quantity of energy that producers in an ecosystem gain through photosynthesis or chemosynthesis and store as organic matter within their parts. It includes both primary and secondary productivity, thus showing the energy associated with sustaining life.
Primary productivity is usually measured by gross and net primary productivity. GPP measures the total energy captured by producers. By contrast, NPP accounts for energy used during plant respiration and that is available for growth and subsequent consumption by herbivores.
Light intensity, temperature, availability of water and nutrients and biotic factors like species diversity, trophic interactions and predation.
Productivity determines how much energy is stored that remains available for all trophic levels. It sustains growth and reproduction, thus determining overall ecosystem health. High productivity brings about high biodiversity and promises ecological stability.
Climate change influences temperature and precipitation patterns, in turn altering plant growth and nutrient cycles of ecosystems. The changes induced by such factors may lead to a change in species distribution and ecosystem structure, hence reducing productivity.