NCERT Ecosystem Chapter Explained Line by Line for NEET 2026 by Vipin Sir

Have you ever wondered how a tiny pond or a massive forest functions so perfectly without anyone "managing" them? In this NCERT Ecosystem chapter, students can learn about the "Functional Unit of Ecology." As Dr. Vipin Sir explains in the NCERT Line by Line series, an ecosystem is where the biotic (living) and abiotic (non-living) worlds meet and interact to sustain life. 

What is an Ecosystem?

An ecosystem is a community of living organisms (plants, animals, and microbes) interacting with each other and their non-living environment (like water, air, and soil) in a specific area. These interactions form a balanced system where each component depends on the other for survival. 

The term "Ecosystem" was first coined by A.G. Tansley in 1935, and it remains the cornerstone of environmental biology. 

Types of Ecosystems: Man-made vs. Natural

Not all ecosystems are created by Mother Nature. It can be broadly categorised into:

1. Natural Ecosystems: These exist without human interference. Examples include forests, grasslands, deserts (terrestrial), and ponds, lakes, or oceans (aquatic). 

2. Man-made (Anthropogenic) Ecosystems: These are managed by us. Think of a crop field where you decide what to grow, or a home aquarium where you choose the fish and plants. 

The Four Pillars of an Ecosystem

To function correctly, every ecosystem, be it a small puddle or a giant rainforest, must have four specific processes:

1. Productivity (Making Food)

Everything starts with the sun. Plants (producers) use solar energy to create organic matter. This is called Primary Production. 

• Gross Primary Productivity (GPP): The total energy a plant produces. 

• Net Primary Productivity (NPP): The energy left after the plant uses some for its own "breathing" (respiration). This is what's available for animals to eat! 

2. Energy Flow (Who Eats Whom?)

Energy moves in a unidirectional way. It flows from the sun to producers, then to herbivores, and finally to carnivores. You won't see a cabbage eating a human! This flow ensures that life continues at every level. 

3. Decomposition (The Cleanup Crew)

When plants or animals die, they don't just stay there. Decomposers like bacteria and fungi break down complex organic matter into simple inorganic nutrients. This "trash to treasure" process is essential for keeping the soil fertile. 

4. Nutrient Cycling

The nutrients released during decomposition go back into the soil. New plants then absorb these minerals through their roots, starting the cycle all over again. 

The Pond Ecosystem

A pond ecosystem is a small freshwater ecosystem that supports a variety of life. It has both biotic (living) and abiotic (non-living) components that interact with each other. 

• Abiotic factors: Water, dissolved oxygen, sunlight, and soil at the bottom.

• Biotic factors: Phytoplankton (producers), Zooplankton and fish (consumers), and bacteria/fungi (decomposers). 

Even in this small space, all four pillars, i.e., productivity, energy flow, decomposition, and cycling, work in perfect harmony. 

What is Stratification?

In a forest, there are different layers of vegetation. This vertical distribution of species is called Stratification.

• Top Layer: Tall trees.

• Middle Layer: Shrubs.

• Bottom Layer: Herbs and grasses.