CBSE Notes Class 10 Science Chapter 13 - Our Environment

Our environment includes all living organisms, natural resources, and physical surroundings that interact to support life on Earth. Understanding how plants, animals, microorganisms, and humans depend on one another helps explain the balance of nature and the impact of human activities on ecosystems.

CBSE Notes Class 10 Science Chapter 13 – Our Environment provide clear and exam-oriented explanations of key concepts such as food chains, food webs, trophic levels, biodegradable and non-biodegradable substances, and ecosystem stability. These our environment class 10 notes are designed as quick-revision material, helping CBSE students grasp core ideas easily, strengthen conceptual clarity, and score better in board exams with structured, syllabus-aligned content.

1.0Download CBSE Notes for Class 10 Science Chapter 13: Our Environment - Free PDF!!

Download Free CBSE Class 10 Science Chapter 12: Magnetic Effects of Electric Current Notes PDF covering magnetic fields, right-hand thumb rule, Fleming’s left and right-hand rules, electromagnetic induction, and numericals—perfect for quick revision and CBSE board exam success.

2.0Ecosystems and Their Components

• Ecosystem is the basic unit of ecology and the biotic and abiotic components present in it influence each other. 
• Both the components are essential for the sustenance of life. 
• Ecosystem term was given by Arthur Tansley Ecosystem is a self-sustained unit of living things (plants, animals and decomposers) and their nonliving environment (soil, air and water). 
• Biotic components : The biotic components include all kinds of living organisms with which the organism interacts (all animals, plants, microorganisms). 
• Abiotic components : The abiotic components are the physical factors such as climatic factors (e.g., Air, Water, Temperature, Humidity, Light, Wind, Precipitation etc.).

Biotic (living) components

• The biotic community of an ecosystem includes 3 types of organisms 
• Producers : Those organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight in the presence of chlorophyll. e.g., Green plants and certain blue green algae. 
• Consumers : Those organisms which consume food or eat food prepared by producers are called consumers. The consumers depend on producers for food, directly or indirectly. All the animals are consumers.
• Consumers can be further divided into three groups 
• Herbivores - Those animals which eat only plants are called herbivores. e.g., Buffalo, goat, sheep, horse, deer, camel, grasshopper, etc. Since herbivores obtain their food directly from plants or producers therefore herbivores are primary consumers. 
• Carnivores - Those animals which eat only other animals as food are called carnivores or those animals which eat the meat or flesh of other animals are called carnivores. e.g., Lion, tiger, frog, vulture, kingfisher, etc. 
• Omnivores - Those animals which eat both plants and animals, are called omnivores or those animals which eat plant food as well as the meat or flesh of other animals. e.g., Man, dog, crow, sparrow, bear and ant, etc.
• Decomposers -  The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like feces, urine into simpler substances are called decomposers. e.g., Bacteria and fungi.

3.0Food Chains and Food Webs

• Food Chains and Food Webs describe how energy and nutrients flow through living organisms in an ecosystem. A food chain is a series of organisms, each feeding on the one below it, showing a direct and linear transfer of energy. These chains are structured into distinct levels known as trophic levels.
• At the base of every food chain are autotrophs or producers, such as green plants and algae. They convert solar energy into chemical energy through photosynthesis, forming the primary source of energy that supports all life on Earth.
• The second trophic level consists of herbivores, which feed directly on producers. Small carnivores occupy the third trophic level, feeding on herbivores, while larger carnivores form the fourth trophic level, preying on smaller carnivores.
• As energy flows through these trophic levels, a significant portion is lost at each step in the form of heat, respiration, digestion, and reproduction. On average, only about 10% of the energy from one trophic level is transferred to the next. This limited energy transfer explains why food chains rarely extend beyond three or four trophic levels.
• In real ecosystems, organisms do not depend on a single food source. Instead, multiple food chains interconnect to form a food web, which represents a more complex and realistic pattern of energy flow. Food webs increase ecosystem stability, as the availability of alternative food sources helps organisms survive environmental changes or population fluctuations.

4.0Energy Flow and its Unidirectional Nature

• The energy flow through an ecosystem is unidirectional, meaning it moves from producers to consumers and decomposers, never returning to the previous level. 
• Once autotrophs capture energy from sunlight, it is progressively passed on but diminishes at each trophic level. 
• As a result, energy becomes less available as it moves up the food chain.
• In addition to energy loss, harmful chemicals can also travel up the food chain in a process known as biological magnification. 
• Chemicals used in agriculture, such as pesticides, can be absorbed by plants and eventually consumed by animals and humans. 
• Since these chemicals are non-biodegradable, they accumulate in increasing concentrations at each trophic level, posing serious health risks to those at the top, including humans.

Ten Percent law 

• It was put forth by Lindeman (1942). It is also termed as the second law of thermodynamics or law of entropy. 
• According to this law, transfer of energy from one trophic level to another trophic level is never 100 percent. 
• It is so because most of the energy gets lost as heat in the environment during each transfer. On an average, about 10% of energy is actually available to the next trophic level.

5.0Human Impact on the Environment

• Humans are an integral part of the environment, and our activities significantly impact it. 
• Environmental degradation due to pollution, deforestation, and industrial waste has been well-documented. 

Ozone Layer Depletion

• This is a protective shield in the upper atmosphere, and is critical in blocking the Sun's harmful ultraviolet (UV) radiation. 
• UV radiation can cause severe health issues, including skin cancer. 
• The ozone layer is formed when UV radiation reacts with oxygen molecules (O2), breaking them apart into individual oxygen atoms. These atoms combine with other oxygen molecules to form ozone (O3).
• However, human-made chemicals, especially chlorofluorocarbons (CFCs), have caused significant depletion of the ozone layer. 
• CFCs, used in refrigeration and fire extinguishers, release chlorine atoms when they reach the upper atmosphere. They react with ozone and break it down. 
• Recognising the threat posed by CFCs, the international community agreed to limit their production under the Montreal Protocol in 1987. Since then, efforts have been made to phase out CFCs and manufacture CFC-free products to protect the ozone layer.

Waste Disposal and Its Challenges

• Waste disposal is another major environmental challenge. We produce vast amounts of waste daily, including non-biodegradable materials like plastics. 
• While bacteria and fungi break down biodegradable materials into simpler substances that nature can reuse, non-biodegradable materials persist in the environment for a long time, often harming ecosystems.
• For instance, plastic waste accumulates in landfills and water bodies, posing risks to wildlife. 
• Animals may ingest plastics, mistaking them for food, which can lead to injury or death. 
• Moreover, non-biodegradable materials can release toxic substances over time, polluting soil and water sources.

6.0Benefits of CBSE Notes for Class 10 Science Chapter 13 - Our Environment

• Building a Strong Foundation: Understanding the concepts in "Our Environment" is crucial for future science studies, and these notes can help build a strong foundation.
• Clarity on Definitions and Terms: Notes often provide clear and concise definitions of important scientific terms used in the chapter.
• Understanding Relationships: They can help you understand the interrelationships between different components of the environment and human impact.
• Focus on Important Diagrams and Processes: CBSE Notes may emphasise key diagrams and the steps involved in various environmental processes.
• Supplement to Textbook: They act as a valuable supplement to your textbook, offering an alternative way to learn and reinforce the material.
• Increased Confidence: Having well-prepared notes can boost your confidence for tests and exams.

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