Our Environment Class 10 Science Notes

13.1 Eco-System — What are its Components?

An ecosystem is a community of interacting living organisms (biotic components) and their physical surroundings (abiotic components). These components are interdependent and maintain a balance in nature.

Biotic Components: All living organisms, including plants, animals, microorganisms, and human beings. They obtain their sustenance and interact with each other.
Abiotic Components: The non-living physical factors of the environment, such as temperature, rainfall, wind, soil, and minerals. These factors influence the growth, reproduction, and activities of living organisms.

Examples of Ecosystems:

Natural Ecosystems: Forests, ponds, lakes, grasslands, oceans.
Artificial (Human-made) Ecosystems: Gardens, crop fields, aquariums. These are created and maintained by humans.

Remember
Every natural environment is an ecosystem, whether it's a vast forest or a small pond.

Exam-smart
Questions may describe a scenario (e.g., a garden, an aquarium) and ask to identify biotic and abiotic components, or classify it as natural/artificial.

Organisms in an Ecosystem

Organisms within an ecosystem can be classified based on how they obtain their food:

Producers: Organisms that produce their own food using sunlight, water, and carbon dioxide. They form the base of most food chains.
Example: All green plants and certain bacteria that perform photosynthesis.
Consumers: Organisms that obtain energy by feeding on other organisms.
Herbivores (Primary Consumers): Organisms that eat only producers (plants).
Example: Deer, rabbits, insects.
Carnivores (Secondary/Tertiary Consumers): Organisms that eat other animals.
Secondary Consumers: Eat herbivores. Example: Frogs (eat insects), lions (eat deer).
Tertiary Consumers: Eat secondary consumers. Example: Snakes (eat frogs), tigers (eat lions).
Omnivores: Organisms that eat both plants and animals.
Example: Humans, bears, crows.
Parasites: Organisms that live on or inside another organism (host) and obtain nutrients from it, often harming the host.
Example: Lice, tapeworms, mosquitoes.
Decomposers: Microorganisms like bacteria and fungi that break down dead organic matter (dead plants and animals) and waste products into simpler inorganic substances. These substances then return to the soil, replenishing it for the producers.
Example: Bacteria, fungi.

Remember
Decomposers are nature's recycling agents. Without them, dead matter would accumulate, and soil fertility would decline.

Exam-smart
Given a list of organisms, students might be asked to classify them as producers, consumers (specifying type), or decomposers, and explain their roles.

Food Chains and Food Webs

Food Chain: A series of organisms in an ecosystem where one organism eats another to obtain energy. Each step or level in a food chain is called a trophic level.
Example: Grass $\to$ Deer $\to$ Lion
Trophic Level 1 (Producers): Grass
Trophic Level 2 (Primary Consumer/Herbivore): Deer
Trophic Level 3 (Secondary Consumer/Carnivore): Lion
Trophic Levels:

Producers (Autotrophs): Capture solar energy.
Primary Consumers (Herbivores): Feed on producers.
Secondary Consumers (Carnivores/Omnivores): Feed on primary consumers.
Tertiary Consumers (Carnivores): Feed on secondary consumers.

Energy Flow:
Energy flows from one trophic level to the next.
Unidirectional Flow: Energy captured by producers does not revert to the sun. Energy moves forward through the food chain.
Energy Loss: At each trophic level, a significant amount of energy is lost as heat, used for metabolic processes, or remains undigested.
10% Law: Only about 10% of the energy from one trophic level is transferred to the next. The remaining 90% is lost.
Limited Trophic Levels: Due to the significant energy loss at each step, food chains usually have only 3 to 4 trophic levels. Very little usable energy remains after that.
Pyramid of Numbers: There are generally more individuals at lower trophic levels (producers) than at higher levels.
Food Web: A complex network of interconnected food chains in an ecosystem. An organism is usually eaten by more than one type of predator and often eats more than one type of prey. This creates a branching structure.

Remember
The 10% energy transfer limits the length of food chains. More producers are needed to support fewer herbivores, and even fewer carnivores.

Exam-smart
Students may be asked to construct a food chain from a given set of organisms, identify trophic levels, explain the 10% law, or illustrate the concept of a food web.

Biological Magnification

Definition: The progressive accumulation of non-biodegradable harmful chemicals (like pesticides) in the bodies of organisms at each successive trophic level in a food chain.
How it Happens: Chemicals enter the food chain through producers (absorbed from soil/water). When consumers eat these organisms, the chemicals get transferred and accumulate in their bodies. Since the chemicals are not broken down, they concentrate at higher trophic levels.
Impact: Organisms at the top of the food chain (like humans) accumulate the highest concentration of these harmful chemicals, leading to severe health problems.
Example: Pesticides used on crops can enter food chains, reaching high concentrations in humans who consume fruits, vegetables, or animals from these contaminated environments.

Remember
Biological magnification is a serious consequence of using persistent, non-biodegradable chemicals in the environment.

Exam-smart
Questions might describe a scenario involving pesticide use and ask to explain biological magnification, or predict its impact on different organisms in a food chain.

13.2 How Do Our Activities Affect the Environment?

Human activities significantly impact the environment, leading to various problems.

Ozone Layer and its Depletion

Ozone ( $O_{3}$ ): A molecule made of three oxygen atoms. While oxygen ( $O_{2}$ ) is essential for life, ozone in the stratosphere (higher atmosphere) is crucial for shielding Earth.
Ozone Layer's Role: It acts as a protective shield, absorbing most of the harmful ultraviolet (UV) radiation from the Sun. UV radiation can cause skin cancer and damage DNA in living organisms.
Formation of Ozone: UV radiation splits molecular oxygen ( $O_{2}$ ) into free oxygen atoms ( $O$ ). These atoms then combine with other $O_{2}$ molecules to form ozone ( $O_{3}$ ).

O_{2} \overset{U V}{\to} O + O

O + O_{2} \to O_{3}

Ozone Depletion: The ozone layer began to deplete significantly in the 1980s.
Cause: Primarily due to synthetic chemicals called chlorofluorocarbons (CFCs).
Uses of CFCs: Refrigerants (in refrigerators and air conditioners), fire extinguishers, aerosol propellants.
Mechanism: CFCs rise into the stratosphere and release chlorine atoms. These chlorine atoms catalytically destroy ozone molecules, leading to a decrease in ozone concentration.
Global Action: The United Nations Environment Programme (UNEP) played a key role in forging an international agreement (like the Montreal Protocol) to freeze CFC production and promote CFC-free alternatives.

Remember
The ozone layer is vital for life on Earth. Its depletion by CFCs was a major environmental crisis, but international cooperation has helped to address it.

Exam-smart
Questions may ask about the function of the ozone layer, the chemicals responsible for its depletion, and the impact of UV radiation.

Managing the Garbage We Produce

Human activities generate vast amounts of waste, which can be classified as:

Biodegradable Waste: Substances that can be broken down into simpler, harmless substances by the action of microorganisms (bacteria and fungi).
Examples: Food waste (vegetable peels, spoiled food), paper, cotton, wood, dung.
Process: Natural decomposition by decomposers.
Non-biodegradable Waste: Substances that cannot be broken down by the action of microorganisms and persist in the environment for very long periods.
Examples: Plastics, glass, metals, synthetic fibres, pesticides, electronic waste.
Impact: Accumulate in landfills, pollute soil and water, harm wildlife, and can enter food chains (biological magnification).

Waste Management Strategies:

Reduce: Minimize the generation of waste in the first place.

Use reusable items instead of disposable ones.
Buy products with minimal packaging.

Reuse: Use items multiple times for their original purpose or a new one.

Refillable water bottles, reusable shopping bags.

Recycle: Process waste materials to create new products.

Recycling paper, plastic, glass, and metals saves resources and energy.
Challenges: Not all materials are easily recyclable, and recycling processes themselves can have environmental impacts.

Composting: A method of decomposing biodegradable waste (kitchen scraps, yard waste) to create nutrient-rich soil. This is a natural way to manage organic waste.
Landfills: Sites where non-biodegradable waste is buried. These require careful management to prevent soil and groundwater contamination.
Incineration: Burning waste at high temperatures. This reduces waste volume but can release harmful pollutants into the air if not properly controlled.

Specific Waste Issues:

Disposable Items: Increased use of disposable cups (plastic, paper, kulhads), cutlery, etc., contributes significantly to waste. While disposable cups offered hygiene, their disposal is a major problem. Making kulhads on a large scale can deplete fertile topsoil.
Electronic Waste (E-waste): Contains hazardous materials that require specialized disposal methods to prevent environmental contamination.
Sewage and Industrial Waste: Untreated sewage and industrial effluents can pollute water bodies and soil, harming aquatic life and human health. Proper treatment before discharge is crucial.

Remember
The "Three Rs" (Reduce, Reuse, Recycle) are fundamental to effective waste management. Prioritizing biodegradable waste for composting is also key.

Exam-smart
Questions might ask to differentiate between biodegradable and non-biodegradable waste, list methods of waste management, explain the impact of specific wastes (like plastics or e-waste), or suggest solutions for local waste problems.

Our Environment — Notes

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