Our Environment — RBSE Class 10 (Science)
Everything alive is connected — the grass, the deer that eats it, the tiger that eats the deer, and the microbes that recycle them all. This chapter zooms out to the ecosystem: how energy flows through it, why it flows only one way, and how our waste and chemicals ripple through the whole living web.
1. Ecosystem and its components
An ecosystem is a self-contained unit of living organisms interacting with their non-living surroundings.
- Biotic (living) components: producers, consumers, decomposers.
- Abiotic (non-living) components: temperature, light, water, air, soil, minerals.
By role:
- Producers (green plants, some bacteria) — make food by photosynthesis.
- Consumers — herbivores (primary), carnivores (secondary/tertiary), omnivores.
- Decomposers (bacteria, fungi) — break down dead matter, returning nutrients to the soil. Without them, nutrient cycling would stop.
2. Food chains, food webs and trophic levels
A food chain is a sequence of who-eats-whom, each step a trophic level: Real ecosystems are food webs — many interlinked food chains — which give stability (if one prey vanishes, predators have alternatives).
3. Flow of energy — the 10% law
Energy enters as sunlight, is fixed by producers, and passes up the chain. But at each transfer, most energy is lost as heat, movement and life processes. Only about 10% of the energy at one trophic level reaches the next (Lindeman's 10% law).
Consequences:
- Energy flow is unidirectional (sun → producers → consumers; it does not cycle back).
- Food chains are usually short (3–4 levels) — too little energy remains for more.
- Producers hold the most energy; top carnivores the least.
4. Biological magnification
Harmful, non-biodegradable chemicals (like pesticides — DDT) enter the food chain and, because organisms cannot excrete them, they accumulate and increase in concentration at each higher trophic level. This is biological magnification — top-level consumers (including humans) end up with the highest, most dangerous concentrations.
5. Biodegradable vs non-biodegradable, and waste
- Biodegradable substances (food scraps, paper, cotton, cattle dung) are broken down by decomposers.
- Non-biodegradable substances (plastics, DDT, glass, metals) are not broken down naturally — they persist and pollute, and enable biomagnification.
Waste management: reduce, reuse, recycle; segregate and treat waste; compost biodegradable waste; safely dispose of non-biodegradable waste.
6. The ozone layer
High in the atmosphere, ozone (O₃) absorbs the Sun's harmful ultraviolet (UV) radiation, shielding life (UV causes skin cancer, cataracts and harms crops).
Man-made CFCs (chlorofluorocarbons, from refrigerants and sprays) destroy ozone, thinning the layer (the "ozone hole"). The Montreal Protocol (1987) globally froze/reduced CFC production — a rare, successful international environmental action.
7. Closing thought
An ecosystem runs on one-way energy flow (the 10% law keeps food chains short) and cycling of matter by decomposers. Our impact shows in biomagnification of non-biodegradable chemicals and ozone depletion by CFCs — both fixable by responsible choices. Learn the trophic structure, the 10% law and the biodegradable/CFC facts. In the RBSE board this chapter reliably gives 4–5 easy, concept-based marks.
