CBSE Class 12 Biology – Biodiversity and Conservation
NCERT-aligned chapter resource | Biology Code 044
1. Meaning of Biodiversity
Biodiversity occurs at genetic, species and ecosystem levels. Variation within a species, diversity among species and diversity among ecosystems together contribute to biological richness.
2. Patterns of Biodiversity
Species richness generally changes with latitude, and tropical regions tend to contain greater species diversity. Species–area relationships describe how the number of species changes with the area sampled.
S = C AZ
3. Importance of Biodiversity
Biodiversity provides ecosystem services, food, medicines, genetic resources, cultural value and ecological stability. Species also have intrinsic value independent of direct human use.
4. Biodiversity Loss
Major causes include habitat loss and fragmentation, over-exploitation, invasive alien species and co-extinctions. Human activities can accelerate extinction far beyond natural background rates.
5. Conservation Strategies
| Approach | Meaning | Examples |
|---|---|---|
| In situ | Conservation in natural habitat | National parks, wildlife sanctuaries, biosphere reserves |
| Ex situ | Conservation outside natural habitat | Zoos, botanical gardens, seed banks |
6. Hotspots and Sacred Groves
Biodiversity hotspots are regions with exceptional species richness and high levels of endemism facing substantial threat. Sacred groves are community-protected patches that can preserve local biodiversity.
7. Species–Area Relationship
The relationship S = CAZ shows that species richness increases with area. On a logarithmic scale, log S = log C + Z log A, allowing the relationship to be represented as a straight line.
Worked Interpretation
If two habitats have the same sampling method but one covers a substantially larger area, the larger habitat is generally expected to contain more species, assuming comparable ecological conditions.
Chapter-Specific MCQs
- Genetic diversity refers to variation: (A) within a species (B) only between ecosystems (C) only between kingdoms (D) only in climate. Answer: A.
- National parks represent mainly: (A) in situ conservation (B) ex situ conservation (C) artificial selection (D) genetic engineering. Answer: A.
- A major cause of biodiversity loss is: (A) habitat loss (B) photosynthesis (C) pollination only (D) decomposition. Answer: A.
Competency Questions
- Compare in situ and ex situ conservation for a threatened species and justify when each is useful.
- Explain why habitat fragmentation can increase extinction risk.
- Interpret a species–area relationship and explain the meaning of its slope on a log scale.