Revision summary
Biodiversity is variety of life at genetic, species, and ecosystem levels plus linking processes. CBD treats it as a common concern and a sovereign resource. Tropics combine high stable energy, long ice-free time, and complex forests and reefs. Warm climates and barriers raise speciation and endemism. Wet forests and reefs are peaks; converted dry plains may be poor, and clearing now threatens the richest countries.
Model answer
Introduction
Biodiversity is the variety of life at gene, species, and ecosystem levels—and the ecological processes that link them. Tropical countries, lying roughly between the Tropics of Cancer and Capricorn, hold a disproportionate share of that variety, which is why India, Brazil, Indonesia, and the Congo basin dominate global species lists.
Body
Definition
- Genetic diversity is variation within a species (landraces of rice, cattle breeds).
- Species diversity is the number and relative abundance of species in a place.
- Ecosystem diversity is the range of habitats—coral reef, rainforest, wetland, alpine meadow—and the services they provide.
- The Convention on Biological Diversity treats this variety as a common concern of humankind and a sovereign resource of each state.
Why the tropics are rich
- High, relatively stable solar energy and a long growing season support more net primary productivity, which can feed more trophic levels and more specialised consumers.
- Absence of Pleistocene ice sheets over most tropical land left longer evolutionary time without a continental reset, so lineages accumulated.
- Structural complexity—multi-storey rainforest, coral architecture—creates many niches in a small area (vertical packing).
- Warm, moist climates speed metabolism and generation times for many taxa, raising speciation rates, though extinction is also active.
- Geographic mosaics: mountains, islands, and river barriers in the tropics fragment populations and promote endemism (Western Ghats, Andes, Malesia).
- Mutualisms (fig–wasp, coral–zooxanthellae) lock in extra species that colder seasonal systems support less often.
Caveat
- Tropical richness is not uniform: dry tropics and heavily converted plains can be poor; diversity peaks in wet forests and reefs. Human clearing now makes these countries both the richest and the most threatened.
Flow diagram
flowchart TD B[Biodiversity genes species ecosystems] --> T[Tropical belt] T --> E[Stable solar energy long season] T --> X[No ice-sheet reset] T --> N[Forest reef niches] T --> S[Speciation endemism] E --> R[High species richness] X --> R N --> R S --> R
Conclusion
Biodiversity is variety at gene, species, and ecosystem scales. Tropical countries are rich because of stable energy, long evolutionary time, habitat complexity, fast speciation, and geographic isolation—not because of a single ‘tropical gene’. That richness is a development and conservation trust, not an automatic surplus.
Quick related
Students also ask
-
What are 'digital rights'? Discuss their objectives.
Next question in the 2019 paper (Q10). View answer →
-
Are all tropical countries equally biodiverse?
No. Wet forests and reefs are richest. Arid tropics and intensively farmed plains hold far fewer species.
-
Is tropical richness only because of rainfall?
Rain and warmth matter, but evolutionary time, habitat structure, and isolation also explain the extra species.
PYQ trend
When UPSC asked this
Related PYQs from other years, newest first. Open a question to read it.
-
2025 · Q6 · UPGS3 · 8 marks
How can inclusive and sustainable industrialization (SDG 9) drive economic growth (SDG 8), while ensuring environmental sustainability (SDG 12, 13) in India? -
2020 · Q7 · UPGS3 · 8 marks
Critically examine the challenges of conservation of wild life.
More from this paper
Q1 · UPSC Mains 2019 · UPGS3 · 8 marks
Explain with examples the role of science and technology in enhancing national power.
Science and technology in daily life
National power is military, economic, and legitimacy capacity; S&T now sits in all three. Nuclear and space programmes illustrate strategic autonomy after 1998 and ISRO/NavIC. Agronomy and pharma cut food and health vulnerability. Digital rails and IT enlarge fiscal reach and export skill. Power follows organised use of knowledge, not laboratory prestige alone.
Q2 · UPSC Mains 2019 · UPGS3 · 8 marks
Analyse corruption as a threat to internal security.
Internal security
Internal security needs order, borders, and public consent; corruption attacks all three. Bribes move arms, narcotics, and wanted persons through police and customs posts. Graft in recruitment and procurement creates insiders and hollow equipment. Lost trust in FIR and welfare is recruited by crime and extremist networks. Lokpal, CVC, DBT, e-procurement, and fast uniformed trials are security tools, not only ethics.
Q3 · UPSC Mains 2019 · UPGS3 · 8 marks
'Armed Forces Special Powers Act' of the Parliament of India has come under criticism by the States as being draconian and sometimes as unconstitutional. Examine analytically.
Economic planning and NITI Aayog
AFSPA 1958 notifies a disturbed area and gives armed forces fire, search, and arrest powers. Section 6 prior sanction is criticised as de facto immunity. States say law and order is theirs, yet the Army overlays policing for years. NPMHR 1997 upheld the Act with review and dos-and-don’ts; EEVFAM 2016 denied encounter immunity. Jeevan Reddy 2005 found the Act too sweeping; validity on paper is not the same as justice on the ground.
Toppers' copies
Toppers' copies for this question will be uploaded soon.