Our Environment
Frequently Asked Questions
Environment is the sum total of all external conditions and influences, both living (biotic) and non-living (abiotic), that affect the life and activities of organisms in a given area. It includes air, water, soil, temperature, plants, animals and human beings.
An ecosystem is a structural and functional unit of nature in which living organisms interact with each other and with the physical environment, leading to a self-sustaining system of energy flow and nutrient cycling. A pond, forest and desert are common examples.
An ecosystem has two main components: biotic components (living organisms such as plants, animals and microorganisms) and abiotic components (non-living factors like sunlight, temperature, air, water and soil). Together they regulate life processes and energy transfer.
Biotic components are the living parts of an ecosystem, including producers (green plants, algae), consumers (herbivores, carnivores, omnivores) and decomposers (bacteria, fungi). They form food chains and food webs and are responsible for energy flow.
Abiotic components are the non-living physical and chemical factors that influence organisms, such as light, temperature, rainfall, humidity, wind, soil type, pH, minerals and gases like oxygen and carbon dioxide. They set the limits for survival of species.
Producers are green plants and some microorganisms that can make their own food from simple inorganic substances like carbon dioxide and water using sunlight energy through photosynthesis. They form the first trophic level and supply energy to all consumers.
Consumers are organisms that cannot prepare their own food and depend directly or indirectly on producers. Herbivores eat plants, carnivores eat other animals, omnivores eat both plants and animals, and parasites derive food from a host organism.
Decomposers are microorganisms such as bacteria and fungi that break down the dead remains and waste products of organisms into simpler substances. They recycle nutrients back to the soil and complete the cycle of matter in ecosystems.
A food chain is a linear sequence of organisms where one organism is eaten by the next, showing the direct pathway of energy flow. A typical example is: grass ? grasshopper ? frog ? snake ? eagle, each representing a different trophic level.
A food web is a network of interconnected food chains operating in an ecosystem. It shows that most organisms have multiple food sources and are eaten by more than one type of consumer, making natural ecosystems more stable than a single chain.
A trophic level is the specific step or position that an organism occupies in a food chain or food web according to the source of its food or energy. Producers form the first level, primary consumers the second, secondary consumers the third, and so on.
The 10% law states that when energy is transferred from one trophic level to the next, only about 10% of the energy is stored in the biomass of the next level, while the rest is lost as heat during metabolic activities such as respiration and movement.
With only about 10% of energy passing to each higher trophic level, the available energy becomes very small beyond four or five steps, making it difficult for additional higher-level populations to survive. Therefore, very long food chains are energetically unstable.
Biodegradable waste consists of materials that can be broken down into simpler substances by natural decomposers such as bacteria and fungi. Examples include vegetable peels, leftover food, paper, cotton, and dead plant or animal matter.
Non-biodegradable waste is material that cannot be easily decomposed by natural organisms. It persists in the environment for a long time. Common examples are plastics, glass, metals, synthetic fibres, many chemicals and electronic waste.
Biodegradable waste: decomposes quickly, returns nutrients to soil, and usually does not accumulate in the environment. Non-biodegradable waste: does not break down easily, can accumulate and cause pollution, and may enter food chains causing harm.
Biological magnification is the process in which the concentration of certain persistent, non-biodegradable chemicals (such as DDT, mercury or PCBs) increases progressively at each higher trophic level of a food chain, reaching the maximum in top consumers.
If a lake is contaminated with a small amount of pesticide, tiny plankton absorb it. Small fish eating many plankton collect higher amounts, larger fish get still more by eating many small fish, and fish-eating birds or humans at the top receive the highest concentration, which can damage health.
Top predators and humans are usually at the last trophic level and eat organisms from lower levels over long periods. Persistent toxins build up in their tissues without being broken down or excreted efficiently, leading to high internal concentrations and serious health impacts.
Biomagnification can lead to damage of the nervous system, reproductive failure, thinning of eggshells in birds, cancers and other chronic diseases in humans. It also reduces biodiversity by making sensitive species decline or disappear from ecosystems.
Ozone is a form of oxygen in which three oxygen atoms join to form each molecule. A protective layer of ozone is present high in the stratosphere, where it absorbs a large portion of the sun’s harmful ultraviolet (UV) radiation before it reaches the Earth’s surface.
Ozone layer depletion is the thinning or reduction of the ozone layer in the upper atmosphere due to the release of certain man-made chemicals, especially chlorofluorocarbons (CFCs) from old refrigerators, air-conditioners and aerosol sprays.
Ozone depletion allows more UV radiation to reach the Earth, increasing the risk of skin cancer, eye cataracts and sunburn in humans; it also inhibits photosynthesis, reduces crop yield and harms plankton in oceans, disturbing food webs.
Many countries agreed under international treaties such as the Montreal Protocol to gradually stop the production and use of CFCs and to adopt safer alternatives in refrigeration and aerosols. This collective action has helped in slow recovery of the ozone layer.
Waste management is the planned handling, segregation, treatment, recycling and safe disposal of solid and liquid waste so that it causes minimum damage to health and the environment. It includes household, municipal, industrial and biomedical waste.
The 3Rs are Reduce, Reuse and Recycle. “Reduce” means generating less waste, “Reuse” means using items again instead of discarding them, and “Recycle” means processing waste materials to obtain raw material for new products, thereby saving resources.
Reduce: Carrying a cloth bag to avoid new plastic bags. Reuse: Refilling glass bottles or using old containers for storage. Recycle: Sending waste paper, metal cans and certain plastics to recycling units to make fresh paper or new objects.
Segregation at source means separating waste into different categories (such as biodegradable and non-biodegradable, or dry and wet waste) in households, schools and workplaces at the point where it is produced. This makes later treatment and recycling easier and safer.
Composting is the natural process of converting biodegradable waste such as kitchen scraps, leaves and garden waste into nutrient-rich manure with the help of microorganisms. It reduces the amount of waste going to landfills and improves soil fertility.
Vermicomposting is a method of making compost by using earthworms along with microorganisms. Earthworms break down organic matter faster, produce fine, nutrient-rich castings and improve soil texture. It is suitable for school or household level waste management.
A sanitary landfill is a scientifically designed site where solid waste is compacted and buried in layers, with measures such as lining, leachate collection and soil cover to minimise pollution of air, soil and groundwater. It is safer than open dumping but requires land and maintenance.
Open burning releases toxic smoke and gases, contributing to air pollution and respiratory problems. Open dumping encourages flies, rats and stray animals, produces foul smell, contaminates soil and water, and spoils the aesthetic appearance of surroundings.
Plastics are non-biodegradable; they remain in the environment for decades, clog drains, block soil pores, and can choke animals that accidentally eat them. When burnt, many plastics release poisonous fumes, adding to air pollution and health hazards.
Eco-friendly packaging uses materials that are biodegradable, recyclable or reusable, such as paper, jute, cloth and certain plant-based plastics. Such packaging reduces solid waste, saves resources and is safer for soil and water bodies.
Human activities such as deforestation, overuse of resources, industrialisation, urbanisation, use of fossil fuels and careless waste disposal alter natural habitats, pollute air, water and soil, accelerate climate change and reduce biodiversity.
Forests regulate climate, influence rainfall, prevent soil erosion, conserve biodiversity, act as carbon sinks by absorbing carbon dioxide, and provide resources like timber, medicine and food. Destroying forests disturbs ecological balance.
Students can reduce the use of plastics by carrying reusable bottles and bags, practise waste segregation and composting at home or school, save electricity and water, plant and care for trees, and participate in awareness campaigns.
An ecosystem is called self-sustaining because producers capture solar energy, consumers utilise this stored energy through food chains, decomposers recycle nutrients, and natural cycles of water, carbon and nitrogen operate continuously without external help under normal conditions.
Ecological balance is a state of dynamic equilibrium in which the numbers and relationships among organisms and their physical environment remain relatively stable over time. Balanced ecosystems support diverse species and resist sudden changes.
In exams, students are often asked to draw or complete food chains, identify trophic levels, predict the effect of removing one organism, or explain biomagnification and energy flow. Clear understanding of food chains and webs helps answer such application-based questions correctly.
First identify the producer (usually a green plant). The organism eating the plant is the primary consumer (second trophic level). The organism eating the primary consumer is the secondary consumer, and so on. Decomposers are written separately as acting on all levels.
Common diagrams include simple food chains, food webs, a pyramid of energy or numbers, the structure of a pond ecosystem, a flow chart of waste management, or a schematic of ozone layer depletion. Students should practise neat, labelled diagrams with correct arrows.
The pyramid of energy is always upright because energy decreases at each successive trophic level due to the 10% law. It visually represents that lower levels contain more energy and support fewer organisms at higher levels.
Decomposers do not belong to a single trophic level; they act on the dead remains and wastes of organisms from all levels. They are usually drawn at the base or side of diagrams with arrows from all living groups towards them to show nutrient recycling.
Use key terms such as ecosystem, trophic level, biodegradable, non-biodegradable, biological magnification, ozone depletion and 3Rs. Draw small labelled diagrams where relevant, underline important terms, and give at least one example to support definitions for full marks.
