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Biodiversity and Conservation

Biology · Class 12NCERT pp. 216–2252 sets × 25 questions

Key facts and formulas for Biodiversity and Conservation, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.

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Key facts for this chapter

IdeaRule or fact
Three levels of biodiversityGenetic (within a species), species (number of species), ecological (variety of ecosystems)
Genetic examplesIndia: over 50,000 rice strains, about 1,000 mango varieties; reserpine potency varies in Rauwolfia
Species countsDescribed about 1.5 million; Robert May estimate about 7 million; animals over 70 per cent, insects over 70 per cent of animals
Latitudinal gradientTropics 23.5° N to 23.5° S are richest; birds: Colombia 1,400, India 1,200+, New York 105, Greenland 56
Species-area relationshipS = C A^Z; Z is the slope, C the intercept; Z 0.1 to 0.2 in regions, 0.6 to 1.2 for continents
Hotspots34 hotspots, under 2 per cent of land; India has 3 (Western Ghats and Sri Lanka, Indo-Burma, Himalaya); Myers: 1,500 endemic plants, 70 per cent habitat lost
Extinctions784 in 500 years: 338 vertebrates, 359 invertebrates, 87 plants; the Sixth Extinction is caused by humans
Causes (evil quartet)Habitat loss, over-exploitation, alien invasion, co-extinction
ConservationIn situ: parks, sanctuaries, biosphere reserves, sacred groves; ex situ: zoos, gardens, seed banks, cryopreservation (−196 °C)
India and summits448 sanctuaries, 90 national parks, 14 biosphere reserves; Rio 1992; Johannesburg 2002

Three sample questions

Q1. Identify the level of biodiversity in each example.
I. Reserpine potency differs in Rauwolfia vomitoria from different Himalayan ranges.
II. The Western Ghats have more amphibian species than the Eastern Ghats.
III. India has more ecosystem types than Norway.
  1. I genetic, II species, III ecological
  2. I species, II genetic, III ecological
  3. I ecological, II species, III genetic
  4. I genetic, II ecological, III species
Hint and solution

Hint: Ask what varies: differences inside one species, the number of species, or the variety of habitats.

  1. Within species = genetic — Example I compares one species, Rauwolfia vomitoria, across different ranges. Variation inside a species is genetic diversity.
  2. Number of species = species diversity — Example II counts amphibian species in two regions. Number and variety of species is species diversity.
  3. Variety of ecosystems = ecological — Example III compares types of ecosystems such as deserts, rain forests, mangroves and so on. That is ecological diversity.
  4. I genetic, II species, III ecological — Combining the three gives genetic, species, ecological. Option A.
Answer: A. Variation inside one species is genetic; number of species is species diversity; variety of ecosystems is ecological.
Q2. India has about how many genetically distinct rice strains and mango varieties respectively?
  1. About 1,000 and over 50,000
  2. Over 5,000 and about 100
  3. Over 50,000 and about 1,000
  4. Over 5,00,000 and about 10,000
Hint and solution

Hint: Recall the NCERT genetic diversity example: rice has many more strains than mango has varieties.

  1. Genetic diversity: rice > mango — NCERT uses rice and mango as examples of variation within one species.
  2. Rice: over 50,000 strains — India has more than 50,000 genetically different strains of rice.
  3. Mango: about 1,000 varieties — India has about 1,000 varieties of mango. This keeps the order rice first, mango second.
  4. 50,000+ and 1,000 — Only option C matches both numbers. Option C.
Answer: C. NCERT gives over 50,000 rice strains and about 1,000 mango varieties as genetic diversity examples.
Q3. About 45,000 plant species of India are known. If these form 22 per cent of the real plant total, the number of plant species still undescribed is closest to
  1. 50,000
  2. 2.0 lakh
  3. 1.6 lakh
  4. 45,000
Hint and solution

Hint: First find the real total using 45,000 as 22 per cent, then subtract the 45,000 already known.

  1. total = known ÷ 0.22 — If 45,000 is 22 per cent, the total is 45,000 divided by 0.22.
  2. 45,000 ÷ 0.22 ≈ 2,04,545 — The estimated total of plant species is about 2.05 lakh.
  3. undescribed = 2,04,545 − 45,000 — Subtract the known species from the total.
  4. ≈ 1,59,545 ≈ 1.6 lakh — So about 1.6 lakh plant species are still undescribed, matching NCERT's over 1,00,000. Option C.
Answer: C. Total = 45,000 ÷ 0.22 ≈ 2.05 lakh. Undescribed = 2.05 lakh − 45,000 ≈ 1.6 lakh, in line with NCERT's 'over 1,00,000'.

How to use this chapter

Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.

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