Our Environment - MCQs

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.