Class 10 Our Environment Mind Map for Revision

Our Environment: With the Class 10 Science board exam scheduled for 25 February 2026, maximizing your revision efficiency is key. The chapter Our Environment is high-scoring and focuses on ecological balance, energy dynamics, and the impact of human activities. It frequently appears in exams through flowcharts, food web analysis, and reasoning questions on waste management.

To streamline your last-minute prep, this structured breakdown captures the essence of the chapter's core concepts. It is designed to help you quickly master the interactions between biotic and abiotic components, the 10% law of energy flow, and critical environmental issues like ozone depletion. Use this guide to connect these topics logically and ensure a confident performance on exam day.

Class 10 Our Environment Mind Map Series: Master Unidirectional Flow of Energy and Ecosystems

The chapter Our Environment holds significant importance in the Class 10 Science syllabus and is known for carrying good weight in board examinations. While the concepts seem simple, students often find it challenging because of technical energy calculations, the unidirectional flow of energy, and complex interlinked concepts like biomagnification. To simplify understanding and make revision more effective, especially for competency-based questions before exams, a well-structured approach is crucial.

Watch this video to for easy explanation of Class 10 Our Environment Mind Map Series

This video-based mind map presents the entire chapter in a clear and connected format, making ecological concepts easy to grasp and helping students revise quickly and confidently for the board exam.

Introduction to Environment and Ecosystem

The term Environment refers to our surroundings. These surroundings differ based on geographical location. For example, the environment in a city like Delhi, with its specific temperature, water, soil, and plant life, is distinct from that of a desert in Rajasthan.

Within the larger environment, there are distinct, self-sustaining units called Ecosystems. An Ecosystem is a specific geographical area where biotic (living) and abiotic (non-living) components interact and are interdependent. Every ecosystem has a unique combination of these components. Examples include ponds, lakes, mountains, deserts, grasslands, and forests.

Components of an Ecosystem

An ecosystem has two fundamental types of components:

For instance, in a Pond Ecosystem, biotic components include plants, fish, frogs, snails, and bacteria. Abiotic components include sunlight, the water in the pond, the soil at the bottom, and the surrounding air and temperature.

Biotic Components: Classification

Living organisms (biotic components) in an ecosystem are classified into three main functional categories based on how they obtain nutrition:

Producers (Autotrophs)

• Function: Organisms that produce their own food, primarily through photosynthesis. They form the base of the food chain.

• Examples: All plants, and certain photosynthetic bacteria like Cyanobacteria (blue-green algae).

Consumers (Heterotrophs)

Function: Organisms that obtain energy by feeding on other organisms. They cannot produce their own food.

Classification by Trophic Level:

• Primary Consumers: Feed directly on producers (e.g., a grasshopper eating grass).

• Secondary Consumers: Feed on primary consumers (e.g., a snake eating a grasshopper).

• Tertiary Consumers: Feed on secondary consumers (e.g., a hawk eating a snake).

• Quaternary Consumers: Feed on tertiary consumers.

Classification by Diet:

• Herbivores: Plant-eaters.

• Carnivores: Meat-eaters.

• Omnivores: Eat both plants and animals.

Decomposers (Saprotrophs)

Function: Organisms that feed on dead and decaying organic matter. They break down complex organic substances into simpler inorganic nutrients, returning them to the soil.

Examples: Bacteria and Fungi.

The Functioning and Interdependence of an Ecosystem

An ecosystem functions through the continuous interaction and interdependence of its biotic and abiotic components, creating a self-sustaining cycle.

Energy Capture by Producers: Producers, such as plants, use abiotic components—solar energy (sunlight), carbon dioxide from the air, and minerals/water from the soil—to synthesize food through photosynthesis. This shows the dependence of living organisms on non-living factors.

Energy Transfer Through Consumers: Energy captured by producers transfers through the ecosystem when consumers feed on them. A primary consumer (e.g., a goat) eats a producer (plant), transferring energy. A secondary consumer (e.g., a lion) eats the primary consumer (goat), further transferring energy. This sequence of eating and being eaten is called a food chain.

Nutrient Recycling by Decomposers: When producers and consumers die, their bodies are broken down by decomposers (bacteria and fungi). This process, decomposition, releases essential nutrients (e.g., calcium, phosphorus) from the dead organisms back into the soil. These soil nutrients are then absorbed by producers (plants) to grow, completing the cycle.

This cycle illustrates universal interdependence: consumers depend on producers for food; producers depend on decomposers for soil nutrients; and decomposers depend on the death of producers and consumers for their sustenance.

Types of Ecosystems

Ecosystems are broadly classified into two main types:

The Case of the Aquarium: An Artificial Ecosystem

An aquarium is a prime example of a man-made ecosystem. Its water must be changed frequently because, unlike natural ecosystems, aquariums lack decomposers (bacteria). Without decomposers, fish waste accumulates, making the water toxic and poisonous. Regular cleaning and water changes are vital to prevent fish from dying due to high toxicity, highlighting the lack of self-sustainability in artificial ecosystems.

Food Chain and Trophic Levels

A Food Chain is a linear sequence showing how energy transfers from one organism to another, illustrating who eats whom. A Trophic Level refers to the specific position an organism occupies in a food chain.

• Trophic Level 1 (T1): Always occupied by Producers (e.g., Plants).

• Trophic Level 2 (T2): Occupied by Primary Consumers (Herbivores).

• Trophic Level 3 (T3): Occupied by Secondary Consumers (Carnivores/Omnivores).

• Trophic Level 4 (T4): Occupied by Tertiary Consumers.

• Trophic Level 5 (T5): Occupied by Quaternary Consumers.

Examples of Food Chains and Trophic Levels:

1. Terrestrial Food Chain:

Plant (Producer, T1) → Grasshopper (Primary Consumer, T2) → Mouse (Secondary Consumer, T3) → Snake (Tertiary Consumer, T4) → Hawk (Quaternary Consumer, T5)

2. Aquatic Food Chain:

Phytoplankton (Producer, T1) → Zooplankton (Primary Consumer, T2) → Small Fish (Secondary Consumer, T3) → Large Fish (Tertiary Consumer, T4) → Killer Whale (Quaternary Consumer, T5)

Key Terms in Aquatic Food Chains:

• Phytoplankton: Microscopic, photosynthetic organisms (like algae) that float on water and act as primary producers.

• Zooplankton: Microscopic animals (e.g., amoeba) that feed on phytoplankton, acting as primary consumers. (Memory Tip: The prefix "Zoo" reminds us of animals. Animals are consumers; they do not make their own food. Therefore, Zooplankton are consumers.)

The 10% Law of Energy Transfer

The 10% Law is a fundamental principle governing energy flow in an ecosystem and is one of the most important concepts in the chapter.

• The Law States: Only 10% of the energy from one trophic level is transferred and stored in the next trophic level.

• Energy Loss: The remaining 90% of the energy is lost to the environment as heat, or used by the organism for its own life processes (respiration, growth, movement).

Example Calculation:

Consider a food chain: Plant → Grasshopper → Mouse → Snake

1. Assume the Plant (T1) has 6000 Joules of energy.

2. When the Grasshopper (T2) eats the plant, it receives 10% of that energy: 10% of 6000 J = 600 Joules.

3. When the Mouse (T3) eats the grasshopper, it receives 10% of the grasshopper's energy: 10% of 600 J = 60 Joules.

4. When the Snake (T4) eats the mouse, it receives 10% of the mouse's energy: 10% of 60 J = 6 Joules.

Conclusion: Energy significantly decreases at each successive trophic level. Top-level consumers receive the least amount of energy.

Sample Problem:

• Question: In a food chain, if the primary consumer has 45 Joules of energy, how much energy will be available at the third trophic level (secondary consumer)?

• Solution:

• Energy at Primary Consumer (T2) = 45 J

• Energy transferred to Secondary Consumer (T3) = 10% of 45 J

• Answer: 4.5 Joules

Food Web

In a natural ecosystem, feeding relationships are not simple, isolated food chains. An organism can be food for multiple predators. A Food Web is a complex network of many interconnected food chains, providing a more realistic representation of the feeding relationships in an ecosystem. For instance, a grasshopper might be eaten by a frog or a rat, not just one specific predator.

Biomagnification

Biomagnification (or biological magnification) is the process where the concentration of harmful, non-biodegradable chemicals (like pesticides) increases at each successive trophic level in a food chain. This is a very important topic.

• Mechanism:

1. Harmful chemicals enter the ecosystem, often in water or soil.

2. Producers (plants) absorb these chemicals from the environment.

3. When consumers eat these producers, the chemicals transfer to their bodies.

4. Because these chemicals are non-biodegradable, they are not broken down or excreted. Instead, they accumulate in the organism's tissues.

5. At each higher trophic level, the organism consumes many individuals from the level below, accumulating all their stored chemicals.

• Result: The chemical concentration magnifies at each step up the food chain. The highest concentration is found in the top-level consumers.

Humans, often at the top of various food chains, are highly susceptible to diseases caused by the accumulation of environmental toxins due to biomagnification.

Environmental Problem I: Ozone Layer Depletion

The Ozone Layer is a protective shield of ozone (O₃) gas located in the Stratosphere, a layer of Earth's atmosphere.

Formation of Ozone (O₃)

1. High-energy ultraviolet (UV) radiation from the sun strikes an oxygen molecule (O₂) in the stratosphere.

2. The UV radiation splits the oxygen molecule into two free oxygen atoms (O + O).

3. A free oxygen atom (O) then combines with another oxygen molecule (O₂) to form an ozone molecule (O₃).

• O₂ + UV light → O + O

• O + O₂ → O₃ (Ozone)

Function and Importance of the Ozone Layer

The ozone layer is crucial for life on Earth because it absorbs most of the harmful UV radiation from the sun, preventing it from reaching the Earth's surface.

Harmful Effects of UV Radiation

If the ozone layer depletes, increased UV exposure can cause:

• Skin cancer

• Cataracts (clouding of the eye lens)

• DNA damage

• Weakened immune system

• Reduced crop productivity

• Damage to marine life

Causes of Ozone Depletion

The primary cause of ozone depletion is the release of certain man-made chemicals, most notably Chlorofluorocarbons (CFCs). Other damaging chemicals include hydrochlorofluorocarbons (HCFCs), methyl bromide, and methyl chloroform.

• Source of CFCs: Previously used in refrigerators, air conditioners (ACs), and fire extinguishers.

• Mechanism of Depletion:

1. CFCs are stable and rise into the stratosphere.

2. In the stratosphere, UV radiation breaks down CFC molecules, releasing a highly reactive chlorine atom.

3. This chlorine atom reacts with an ozone molecule (O₃), breaking it down into an oxygen molecule (O₂) and a chlorine monoxide molecule.

4. This process destroys the ozone, creating "holes" or thinning in the ozone layer.

Global Action:

The United Nations Environment Programme (UNEP) facilitated international agreements (like the Montreal Protocol) to phase out the production and use of CFCs. As a result, the use of CFCs has drastically reduced, and the ozone layer is slowly beginning to recover.

Environmental Problem II: Waste Management

Waste can be classified based on its ability to be broken down by microorganisms.

Methods of Waste Disposal and Management

Composting: Biodegradable waste is placed in a pit and allowed to decompose naturally. The resulting nutrient-rich material, called compost or manure, can improve soil fertility.

Landfill: Large, low-lying areas are dug, and waste is dumped and compacted. The area is then covered with soil. This is a common method but can lead to soil and groundwater pollution if not managed properly.

Incineration: A process of burning waste at very high temperatures. It reduces waste volume but can release harmful gases and toxins into the atmosphere.

Sewage Treatment: Wastewater (sewage) from homes and industries is treated in Sewage Treatment Plants (STPs) to remove pollutants before discharge into rivers. Solid sludge byproduct can produce biogas or compost.

The 3 R's: A strategy to minimize waste generation:

• Reduce: Decrease the amount of waste produced.

• Reuse: Use items multiple times before discarding them.

• Recycle: Process waste materials to create new products (e.g., recycling paper, plastic, or glass). Using recycled products is also encouraged.