Environment: concepts, ecosystems and biodiversity
What this domain tests
This section of the Maharashtra HSC paper checks whether you can use ecological vocabulary precisely - organism, population, community, ecosystem, biome - and explain how energy and matter move through a system. Expect a definition paired with an application: identify a trophic level, say what makes the Western Ghats globally important, or classify a species as endemic or invasive.
Core concepts
- Levels of organisation: organism → population → community → ecosystem → biome → biosphere. A population is one species; a community is all species living together.
- Energy flow is unidirectional, following the 10% law: roughly a tenth of the energy at one trophic level is stored in the biomass of the next.
- Matter cycles, energy does not. Carbon, nitrogen and phosphorus move through biogeochemical cycles; energy is lost as heat.
- Pyramids: energy pyramids are always upright; pyramids of number can invert (one banyan tree supports thousands of insects).
- Three levels of biodiversity: genetic, species, ecosystem. India is megadiverse with four hotspots, and the Western Ghats–Sri Lanka hotspot runs along Maharashtra's Sahyadri crest - habitat of the state animal, the Indian giant squirrel (Shekru), and the state bird, the yellow-footed green pigeon (Hariyal).
- Species roles: keystone (fig trees), indicator (lichens for sulphur dioxide), endemic (lateritic plateau herbs of the Konkan), invasive (water hyacinth, Lantana).
Worked example
A grassland's producers fix 10,000 kcal. Under the 10% law herbivores receive 1,000 kcal, primary carnivores 100 kcal, top carnivores 10 kcal. The reasoning: at each transfer, energy is spent on respiration and lost as heat and undigested matter. That is why long food chains support very few top predators, and why a tiger needs a large inviolate territory such as Melghat or Tadoba.
Traps that cost marks
Reducing biodiversity to "number of species" and forgetting genetic and ecosystem diversity. Writing that energy is recycled. Calling the energy pyramid invertible. Labelling the Western Ghats a biosphere reserve when the question asks for a biodiversity hotspot - the Nilgiri Biosphere Reserve is a separate designation.