Environment and Ecosystem

Overview

Environment and Ecosystem is a foundational topic in the Science section of Bihar TET Paper II, bridging biology with environmental awareness. This topic tests your understanding of how living organisms interact with each other and their physical surroundings—a concept central to both scientific literacy and environmental citizenship.

For Bihar TET, expect questions on ecosystem components, energy flow through food chains and food webs, ecological pyramids, and types of pollution with their causes and effects. The topic often appears with 2-4 questions and frequently connects to Bihar's local environmental issues like Ganga pollution, deforestation in the Chota Nagpur region, and air quality concerns in urban centres.

Mastery requires understanding the structural and functional aspects of ecosystems, tracing energy transfer through trophic levels, and knowing the major pollutants affecting air, water, and soil. Questions typically test conceptual clarity rather than rote memorisation.

Key Concepts

• **Environment** comprises all biotic (living) and abiotic (non-living) factors surrounding an organism, including air, water, soil, temperature, light, plants, animals, and microorganisms.

• **Ecosystem** is a self-sustaining functional unit where living organisms interact with each other and their physical environment through energy flow and nutrient cycling. Examples: pond ecosystem, forest ecosystem, grassland ecosystem.

• **Biotic components** include producers (autotrophs like green plants), consumers (herbivores, carnivores, omnivores), and decomposers (bacteria, fungi). Abiotic components include sunlight, temperature, water, soil, and minerals.

• **Food chain** represents a linear sequence of organisms where energy transfers from one trophic level to the next. Energy transfer efficiency is only about 10% at each level (10% Law by Lindeman).

• **Food web** is an interconnected network of multiple food chains, representing the complex feeding relationships in an ecosystem. It provides stability—if one species disappears, alternatives exist.

• **Ecological pyramids** graphically represent trophic structure. Pyramid of numbers shows organism count, pyramid of biomass shows dry weight, and pyramid of energy shows energy content at each level. Energy pyramids are always upright.

• **Biogeochemical cycles** describe the movement of nutrients (carbon, nitrogen, water) through biotic and abiotic components, ensuring continuous availability of essential elements.

• **Pollution** is the introduction of harmful substances (pollutants) into the environment, degrading air, water, or soil quality and affecting living organisms.