National Year 13 Environmental Science
Chapters: 4
1. 3.4 Pollution
3.4.1 Properties of pollutants · 3.4.2 Environmental features and pollution severity · 3.4.3 Pollution control strategies
- Pollution: Air, Water, Land and Noise – Pollution is the release of harmful substances or energy into air, water or land faster than nature can remove them. Main air pollutants are particulates, carbon monoxide, sulfur dioxide, nitrogen oxides and ozone; they cause acid rain and smog. Water pollution by nutrients, sewage and toxins causes eutrophication and biomagnification. We reduce pollution by cutting emissions at the source, cleaning waste before release, and the 3Rs.
- Geographical Perspective on Selected Issues and Problems (Class 12) – Pollution means harmful things added to air, water, land or sound. Air pollution comes from burning fuel, factories and vehicles; water pollution from sewage, industry and farm chemicals; land pollution from garbage and chemicals; noise pollution from traffic and loudspeakers. Cities make huge amounts of solid waste that should be sorted, recycled and safely disposed. People move from villages to cities because of push factors (poverty, no work) and pull factors (jobs, services); many end up in slums with poor housing and services. Land degradation from erosion, waterlogging, salinity, mining and overgrazing can be healed, as shown by watershed work in Jhabua.
2. 3.5 Biological resources
3.5.1 Agriculture · 3.5.2 Aquatic food production systems · 3.5.3 Forest resources
- Agriculture and the Environment: Agroecosystems, Green Revolution and Sustainability – A farm is an agroecosystem: a simplified ecosystem where people grow few species and add energy and materials (fertiliser, water, fuel, pesticides) to raise yields. Better crop and livestock genetics and the Green Revolution package (HYV seeds, irrigation, fertilisers, pesticides, machines) multiplied food output. But intensive farming can cause eutrophication, salinisation, soil erosion and degradation, pesticide resistance, biodiversity loss and greenhouse gases. Social and economic forces shape farming choices. Sustainable methods (rotation, IPM, conservation tillage, efficient irrigation, agroforestry) aim to keep yields high while protecting land and water.
- Aquatic Food Production: Productivity, Fishing and Aquaculture – Seas are productive where light and nutrients meet: shallow continental shelves, upwelling zones, estuaries and coral reefs. The open ocean is poor in nutrients. About 90% of energy is lost at each feeding level, so food from low trophic levels (seaweed, shellfish, small fish) is more efficient. Fishing methods differ in how selective they are and how much bycatch and seabed damage they cause. If catch is larger than the stock's growth, the stock collapses (overfishing). The maximum sustainable yield (MSY) is the largest catch that can be taken year after year, usually at about half the unfished stock. Aquaculture (fish farming) now supplies over half of the fish we eat; it can reduce pressure on wild stocks but can cause pollution, disease, escapes and habitat loss.
- Forest Resources – Forests cover about 31% of Earth's land. They give timber, fuelwood, paper pulp, food, medicines and fibres, and they also clean air, store carbon, hold soil, control floods and shelter most land species. Forestry, the managing and harvesting of forests, is part of the primary sector. When trees are cut faster than they regrow, deforestation causes soil erosion, floods, loss of wildlife and more carbon dioxide in the air. Sustainable forestry cuts no more than the forest grows each year and replants, while protected areas, community forests and agroforestry help conserve forests.
3. 3.6 Sustainability
3.6.1 Dynamic equilibria · 3.6.2 Energy in natural systems · 3.6.3 Material cycles · 3.6.4 The circular economy
- Dynamic Equilibria: Feedback, Tipping Points and Resilience – A system is in dynamic equilibrium when it keeps changing but its average state stays steady, because inputs balance outputs. Negative feedback pushes the system back towards its set state after a change (for example predator–prey numbers or carbon dioxide uptake by plants). Positive feedback makes a change bigger (for example melting ice exposing darker surfaces that absorb more heat). If a disturbance pushes a system past a tipping point, positive feedback takes over and the system flips into a new, different equilibrium that is hard to reverse. Diverse systems with many species and links are usually more resilient: they can absorb disturbances and recover.
- Sustainability – Sustainability means meeting our needs today without taking away the ability of future people to meet theirs. It rests on three pillars — environment, society and economy. A resource is used sustainably when we use it no faster than it renews. Today humanity uses about 1.7 Earths' worth of resources a year, and this use is very unequal. Stewardship, careful planning and spatial tools like GIS help us move towards sustainability.
- Material Cycles: Linear Human Systems and Nature's Loops – Most human systems are linear: we take raw materials, make products, use them and throw them away. This uses up resources and creates waste that piles up. Natural systems work in cycles: materials such as carbon, nitrogen, water and phosphorus are passed from producers to consumers to decomposers and back to the soil, air or water, so nothing is wasted. Natural wastes (carbon dioxide, oxygen, dung, dead leaves) are non-toxic at natural levels and are a resource for other organisms. Many human wastes are toxic or persistent (plastics, heavy metals, pesticides, CFCs) because no organism can break them down. Sustainable systems copy nature by closing the loop through reduce, reuse, repair, recycle and compost, and by designing products from safe, biodegradable or fully recyclable materials.
4. 3.7 Research methods
3.7.1 Scientific methodologies · 3.7.2 Sampling techniques
- The Scientific Method – The scientific method is the careful way scientists find out how the world works. Observe something, ask a testable question, make a hypothesis (a clear, testable guess), test it with a fair experiment (change one variable, measure one, keep the rest the same), repeat and record data, analyse it, draw a conclusion and share it so others can check. Results that fail the test are useful too: they send you back to a new hypothesis.
- Sampling: Learning About a Population from a Sample – A population is the whole group we want to know about; a sample is a smaller part we actually check. A good sample is chosen at random so that it represents the population. Simple random sampling gives everyone an equal chance; stratified sampling takes the right share from each group; systematic sampling takes every k-th item. Different samples give slightly different answers (sampling variation), but bigger samples wobble less (law of large numbers). A biased sample gives a wrong answer however big it is.