Question
The IUCN Red List classifies species into different threat categories. Arrange the following in increasing order of threat: Vulnerable, Least Concern, Critically Endangered, Endangered.
Also name two Indian species from the Critically Endangered category.
(NEET 2024 pattern — appears almost every year in some form)
Solution — Step by Step
The IUCN Red List has 9 categories. For NEET, you need the threatened trio — remember them as a gradient from bad to worse.
The full order from least to most threatened:
| Category | Code | What it means |
|---|---|---|
| Least Concern | LC | Population stable, no immediate threat |
| Near Threatened | NT | Close to qualifying as threatened |
| Vulnerable | VU | High risk of extinction in the wild |
| Endangered | EN | Very high risk |
| Critically Endangered | CR | Extremely high risk — on the edge |
| Extinct in the Wild | EW | Only in captivity |
| Extinct | EX | Gone completely |
Increasing order of threat means going from less threatened to more threatened:
So the answer is: Least Concern → Vulnerable → Endangered → Critically Endangered
The NEET question almost always asks for Indian CR species. Keep these ready:
- Great Indian Bustard (Ardeotis nigriceps) — fewer than 150 individuals left
- Hangul / Kashmir Stag (Cervus elaphus hanglu) — restricted to Dachigam National Park
- Namdapha Flying Squirrel (Biswamoyopterus biswasi) — known from a single specimen
- Gharial (Gavialis gangeticus) — CR since 2007
For the two-species answer: Great Indian Bustard and Hangul are the safest picks.
IUCN uses specific numbers to assign categories. These numbers appear as MCQ options to trip you up.
- CR: Population reduction >80% over 10 years OR fewer than 250 mature individuals
- EN: Population reduction >50% over 10 years OR fewer than 2,500 mature individuals
- VU: Population reduction >30% over 10 years OR fewer than 10,000 mature individuals
The pattern: each step roughly halves the threshold numbers going from VU → EN → CR.
Why This Works
The IUCN system is a standardised global framework — every country uses the same criteria, so a “Critically Endangered” label means the same thing whether the species is in India or Brazil. This is why it carries weight in policy and conservation funding decisions.
The thresholds aren’t arbitrary. They’re derived from population viability models — below certain numbers, inbreeding depression and stochastic events (floods, disease) can wipe out a population even if the immediate pressure is removed. The Great Indian Bustard, for instance, has a generation time of ~10 years, which makes recovery painfully slow.
For your exam, the key insight is that threat categories reflect risk of extinction, not current population size alone. A species with 10,000 individuals declining at 30%/decade is Vulnerable; a stable species with 500 individuals might only be Near Threatened.
Alternative Method — The “EX to LC” Mnemonic
If you blank on the order during the exam, use this phrase:
“Every Extinct Wild Cat Eats Noisy Lunch”
| Word | Category |
|---|---|
| Every | Extinct (EX) |
| Extinct | Extinct in the Wild (EW) |
| Wild | Critically Endangered (CR) |
| Cat | Endangered (EN) |
| Eats | Vulnerable (VU) |
| Noisy | Near Threatened (NT) |
| Lunch | Least Concern (LC) |
Read it backwards for increasing threat order (LC to EX). Works reliably under pressure.
Common Mistake
Students confuse “Extinct in the Wild” with “Extinct” — and often skip EW entirely.
Extinct in the Wild means the species survives only in captivity or cultivation — like the Saharan Oryx before its reintroduction. It is NOT extinct. If a NEET question asks “which category comes just before Extinct?”, the answer is Extinct in the Wild, not Critically Endangered. Many students write CR here and lose a mark.
NEET loves asking about Red Data Book vs Red List. The Red Data Book is the physical publication that lists threatened species; the Red List is the online database. In exams, treat them as the same system — the distinction that matters is IUCN vs other bodies (like Wildlife Protection Act for India-specific protection status).