Ecosystem Class 12 Notes

According to the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 12.

An ecosystem is a biological community where the living and non-living components interact with each other and their physical environment. It is the functional unit of nature and varies greatly in size. Let us have a look at the structure, function and components of an ecosystem.

Structure of Ecosystem

The structure of the ecosystem comprises two different components:

• Biotic
• Abiotic

Biotic Components

Biotic Components are the living components involved in shaping the ecosystem. It includes biotic factors such as:

• Producers: All green plants in the ecosystem are termed producers, as they produce their own food by making use of solar energy. All living organisms are dependent on plants for both oxygen and food.
• Consumers: They include both primary consumers and secondary consumers. As animals depend on plants for their food, they are called consumers. Primary consumers feed directly on producers for their food, and secondary consumers feed on the primary consumers for their food. All herbivores animals are an example of primary consumers. Carnivores and apex predators make up the secondary and tertiary consumers.
• Decomposers: They are the saprophytes which include fungi and bacteria. Decomposers convert the dead matter into nitrogen and carbon dioxide, and the process is called decomposition.
• Energy Flow: Energy flow is the flow of energy along the food chain through different trophic levels. Energy is passed from the producers to the decomposers through various trophic levels.

Abiotic Components

Abiotic components include inorganic materials like air, water, and soil.

Also Read: What is Ecosystem

For more information on Ecosystem, watch the below videos

Ecosystem Types

There are three main types of ecosystems.

Terrestrial Ecosystem

These are the ecosystem found only on land. The terrestrial ecosystems include,

• Forest ecosystem
• Grassland ecosystem
• Desert ecosystem
• Mountain ecosystem

Aquatic Ecosystem

The aquatic ecosystem is the ecosystem in the water body. It includes,

Freshwater Ecosystem

The freshwater ecosystem can be divided into the following categories:

• Lentic: This includes slow-moving or still water such as lakes, ponds, pools, etc.
• Lotic: This includes fast-moving water bodies such as rivers and streams.
• Wetlands: These include the environment where the soil is saturated with water for a certain time period.

Oceanic Ecosystem

The ocean ecosystem is the largest ecosystem. It covers about 71% of the total earth’s surface. This is also known as the marine ecosystem and is divided into deep water, shallow water and deep ocean surface. A large variety of corals, echinoderms, brown algae, cephalopods and dinoflagellates are found here.

Ecological Pyramids

An ecological pyramid is a graphical representation of the relationship between different organisms. Each bar of the pyramid represents a different trophic level. The different types of ecological pyramids include:

Pyramid of Numbers

This represents the number of organisms in each trophic level, irrespective of their size.

Pyramid of Biomass

This represents the total mass of organisms at each trophic level.

Pyramid of Productivity

It is the total amount of energy present at each trophic level and the total energy lost between each trophic level.

Ecological Succession

Ecological succession refers to the change in the structure of species of an ecological community over time. There are two types.

Primary Succession

This is a type of succession in which plants and animals first colonize a barren piece of land.

Secondary Succession

This is the type of succession in which an ecosystem that is destroyed revives itself.

Function of Ecosystem

1. The level of organisms regulates the flow of energy.
2. The autotrophs are the producers that produce energy which is transferred through various trophic levels.
3. The minerals of the biosphere are cycled through the biosphere.
4. It supports life systems and provides stability.

Few Important Questions

• What is nutrient cycling?
• What is primary productivity?
• Explain the components of an ecosystem.
• Define ecological pyramids with examples.
• List out the differences between the food chain and the food web.

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Further Reading: