Ecosystem and Biodiversity
Ecosystem and Biodiversity
An ecosystem is a community of living things working with its non-living surroundings: producers make food, consumers eat it, and decomposers return nutrients to the soil. Biodiversity is the variety of life at three levels: genes, species and ecosystems. NTPC asks the role of each part of a food chain, the 10% law, ecological pyramids, biodiversity hotspots and endemic species.
1. Ecosystem Basics
| Term | Meaning |
|---|---|
| Producers | Green plants and algae; make food by photosynthesis |
| Primary consumers | Herbivores, such as deer and grasshoppers |
| Secondary and tertiary consumers | Carnivores that eat herbivores, and top predators |
| Decomposers | Bacteria and fungi; break down dead matter and return nutrients to the soil |
| Food chain | Single path of energy, such as grass to deer to tiger |
| Food web | Many interconnected food chains |
| Trophic level | Position of an organism in a food chain |
10% law (Lindeman): only about 10% of the energy at one trophic level passes to the next
Energy flow is one-way; nutrients cycle
| Ecological pyramid | Shape |
|---|---|
| Pyramid of energy | Always upright |
| Pyramid of numbers in a tree ecosystem | Inverted (one tree supports many insects) |
| Pyramid of biomass in the sea | Inverted (phytoplankton biomass is small at any time) |
2. Biodiversity
| Term | Meaning or example |
|---|---|
| Biodiversity hotspot | Region with very high endemism under threat; 36 in the world |
| Hotspots in India | Himalaya, Indo-Burma, Western Ghats and Sri Lanka, Sundaland (Nicobar Islands) |
| Endemic species | Found naturally in only one region, such as the Nilgiri tahr (Western Ghats) and Sangai deer (Manipur) |
| In-situ conservation | In the natural home: national parks, sanctuaries, biosphere reserves |
| Ex-situ conservation | Outside the natural home: zoos, botanical gardens, seed and gene banks |
| Keystone species | Species whose loss changes the whole ecosystem, such as the fig tree in tropical forests |
| Biological Diversity Act | 2002; National Biodiversity Authority at Chennai |
✗ Decomposers are producers because they make soil rich | ✓ Decomposers break down dead matter and recycle nutrients; producers make food by photosynthesis
✗ The Eastern Ghats are a biodiversity hotspot | ✓ India's hotspots are the Himalaya, Indo-Burma, Western Ghats and Sri Lanka, and Sundaland
हिंदी नोट: अपघटक (बैक्टीरिया और कवक) मृत पदार्थों को तोड़कर पोषक तत्व मिट्टी में लौटाते हैं। 10% नियम के अनुसार एक पोषी स्तर से अगले स्तर तक केवल लगभग 10% ऊर्जा जाती है। भारत में चार जैव विविधता हॉटस्पॉट हैं: हिमालय, इंडो-बर्मा, पश्चिमी घाट-श्रीलंका और सुंडालैंड।
Exam Pointer: Verified NTPC patterns: biodiversity hotspots (March 2021 CBT-1), the role of decomposers (March 2026 Graduate CBT-1) and the meaning of endemic species (August 2025 UG CBT-1). The 10% law and pyramids are tagged syllabus-based.
Pariksha Pattern: Every Way NTPC Asks This Topic
Pattern 1: Biodiversity hotspots in India
[PYQ: NTPC CBT-1 19-Mar-2021 Shift-2]
EXAM LEVEL
Q. How many biodiversity hotspots fully or partly cover India?
Four: the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland (through the Nicobar Islands).
Answer: Four
EXAMATLAS LEVEL
Q. Which of these is NOT a biodiversity hotspot found in India: Indo-Burma, Western Ghats, Thar Desert, Himalaya?
The Thar Desert has low endemism and is not a hotspot. The other three are hotspots.
Answer: Thar Desert
Pattern 2: Producers, consumers and decomposers
[PYQ: NTPC Graduate CBT-1 27-Mar-2026 Shift-2]
EXAM LEVEL
Q. Which organisms act as decomposers in an ecosystem?
Bacteria and fungi.
Answer: Bacteria and fungi
EXAMATLAS LEVEL
Q. In the chain grass, grasshopper, frog, snake, eagle, which is the secondary consumer, and what would happen to nutrients if decomposers disappeared?
The frog eats the herbivorous grasshopper, so it is the secondary consumer. Without decomposers, dead matter would pile up and nutrients would not return to the soil, so producers would starve.
Answer: Frog; nutrients would stop recycling
Pattern 3: Endemic species and conservation
[PYQ: NTPC UG CBT-1 13-Aug-2025 Shift-2]
EXAM LEVEL
Q. A species found naturally only in one area and nowhere else is called what?
An endemic species.
Answer: Endemic species
EXAMATLAS LEVEL
Q. Classify as in-situ or ex-situ conservation: a seed bank, a national park, a botanical garden, a biosphere reserve.
A national park and a biosphere reserve protect species in their natural homes, so they are in-situ. A seed bank and a botanical garden are ex-situ.
Answer: In-situ: national park, biosphere reserve; ex-situ: seed bank, botanical garden
Pattern 4: Energy flow and ecological pyramids
[Pattern: syllabus-based, PYQ-style]
EXAM LEVEL
Q. If producers trap 10,000 J of energy, how much reaches the secondary consumers under the 10% law?
Primary consumers get 1,000 J and secondary consumers get 100 J.
Answer: 100 J
EXAMATLAS LEVEL
Q. Which ecological pyramid is always upright, and why is the pyramid of numbers in a tree ecosystem inverted?
The pyramid of energy is always upright because energy is lost at every level. In a tree ecosystem a single tree supports a large number of insects, so the base is narrower than the next level.
Answer: Pyramid of energy; one tree supports many insects
60-Second Revision
- Producers make food; decomposers (bacteria, fungi) recycle nutrients.
- 10% law: 10,000 J, 1,000 J, 100 J, 10 J up the chain.
- Pyramid of energy always upright; numbers inverted in a tree; biomass inverted in the sea.
- India's 4 hotspots: Himalaya, Indo-Burma, Western Ghats-Sri Lanka, Sundaland.