Summary and Quick Revision

Ecosystem

  • Ecosystem = all interacting organisms + non-living surroundings. Components: biotic (living) + abiotic (temperature, water, soil, minerals, light).
  • Natural: forest, pond, lake. Artificial: garden, crop-field, aquarium.
  • Producers (autotrophs - green plants) make food by photosynthesis; consumers (heterotrophs - herbivores/carnivores/omnivores/parasites) eat others; decomposers (bacteria, fungi) recycle dead matter to the soil.

Food chains, trophic levels, energy

  • Food chain = straight feeding sequence; food web = interconnected chains (more stable).
  • Trophic levels: producer (1) → primary consumer (2) → secondary (3) → tertiary (4). Arrows show energy/food flow.
  • Energy flow is unidirectional and decreases up the chain. Plants capture ~1% of sunlight; ten per cent law → only ~10% passes to each next level → food chains have only 3-4 steps.

Biological magnification

  • Non-degradable chemicals (pesticides) enter food chains via soil/water and accumulate, increasing at each higher trophic level.
  • Maximum concentration reaches humans at the top of the food chain; residues cannot always be washed off.

Ozone layer

  • Ozone (O₃) = 3 oxygen atoms; high in the atmosphere it absorbs harmful UV radiation (UV causes skin cancer). Formed by: O2→UVO+OO_2 \xrightarrow{UV} O + O; O+O2→O3O + O_2 \rightarrow O_3.
  • Depleted by CFCs (refrigerants, aerosols). 1987 UNEP agreement froze CFC production; CFC-free products are now mandatory. At ground level, ozone is a pollutant.

Waste management

  • Biodegradable = broken down by microbes (peels, paper, cloth, food, wood). Non-biodegradable = not broken down (plastic, glass, metal, DDT).
  • Enzymes are specific, so microbes cannot break down man-made materials like plastic.
  • Problems: biodegradable waste → smell, disease, water pollution if unmanaged; non-biodegradable → persists, pollutes, harms animals, biomagnifies.
  • Solutions - the 3 R's: Reduce, Reuse, Recycle. Segregate waste, compost biodegradables, carry cloth bags, save energy.

One-line recall

  • Ecosystem = biotic + abiotic. Producer(1) → consumer(2,3,4). Energy: one-way, ~10% per level, 3-4 levels.
  • Biomagnification ↑ up the chain (max in humans). Ozone shields UV; CFCs deplete it. Waste: biodegradable vs non-biodegradable; 3 R's.