Maarg Manthan · Topic 7.3

Extinction of Species and Mass Extinction

Environment & Ecology › Threats to Biodiversity and Conservation Strategies · Topic 7.3

Extinction is the permanent disappearance of a species when its last individual dies. Related terms: extirpation (local extinction), extinct in the wild (survives only in captivity) and functional extinction (too few to play their ecological role). Extinction is natural, with a background rate of roughly one to five species a year, but five mass extinctions have occurred in Earth's history, each wiping out a large share of species within a geologically short period: the Ordovician-Silurian (about 445 million years ago), Late Devonian (about 372), Permian-Triassic (about 252, the largest, killing about 90 percent of marine species), Triassic-Jurassic (about 201) and Cretaceous-Paleogene (about 66, which ended the non-avian dinosaurs). Scientists argue that a sixth mass extinction, caused by humans, is now under way, with current rates estimated at 100 to 1,000 times the background rate.

5 min read · UPSC Prelims · Environment & Ecology · Threats to Biodiversity and Conservation Strategies

At a Glance

Mass extinctions Five so far
Largest Permian-Triassic
Dinosaur end About 66 million years ago
Background rate 1 to 5 species a year
Current wave Sixth, human-driven
Exam link UPSC Prelims, Environment & Ecology: Threats to Biodiversity and Conservation Strategies

Where Does It Fit?

This topic follows the effects of biodiversity loss. It places the present crisis in geological context and leads to the IUCN Red List used to measure extinction risk. Previous topic: Effects of Loss of Biodiversity. Next topic: IUCN Red List and Its Classification Scheme.

What Are the Five Mass Extinctions?

Event	Approximate date and cause
End Ordovician	About 445 million years ago. Global cooling and glaciation, falling sea level; about 85 percent of species lost, mostly marine
Late Devonian	About 372 million years ago. Ocean oxygen loss, climate change and volcanism; reef builders and many marine groups lost
End Permian (Great Dying)	About 252 million years ago. Siberian Traps volcanism releasing carbon dioxide and methane, warming, acidification and anoxia; about 90 to 96 percent of marine and about 70 percent of land vertebrate species lost
End Triassic	About 201 million years ago. Volcanism of the Central Atlantic Magmatic Province, climate change; opened the way for dinosaurs
End Cretaceous (K-Pg)	About 66 million years ago. Asteroid impact at Chicxulub, Mexico, with Deccan Traps volcanism in India; about 75 percent of species lost, including non-avian dinosaurs and ammonites
Evidence	Iridium layer at the K-Pg boundary found by Luis and Walter Alvarez in 1980
Recovery	Biodiversity usually takes millions of years to recover

What Is the Sixth Extinction and How Are Extinctions Classified?

Holocene or Anthropocene extinction: human-driven losses over the last few centuries, with estimates of rate far above background
Evidence: since 1500 over 800 documented species extinctions among animals and plants; IUCN estimates; check latest
Local extinction: extirpation: cheetah gone from India by 1952, though reintroduced from 2022
Extinct in the wild: species surviving only in captivity or cultivation, such as the Hawaiian crow
Functional extinction: population too small to affect its ecosystem
Co-extinction: loss of a dependent species
Pseudo-extinction: a species evolves into another form
Man-made drivers: habitat loss, hunting, invasives, pollution and climate change

What Else Should You Remember?

Big Five: a common name for the five mass extinctions
Great Dying: the Permian event
Chicxulub: the crater under the Yucatan peninsula, about 180 km wide
Deccan Traps: large igneous province of western India, linked to end-Cretaceous climate stress
Siberian Traps: a huge volcanic province linked to the Permian event
Trilobites: died out at the end of the Permian
Ammonites: died out at the end of the Cretaceous
Dinosaur survivors: birds are living dinosaurs
Mammal rise: mammals diversified after the K-Pg event
Elizabeth Kolbert: author of The Sixth Extinction
Recent extinctions: Baiji or Yangtze river dolphin (functionally extinct by 2006), Western black rhinoceros (2011), Spix’s macaw (extinct in the wild)
Pinta Island tortoise: last individual, Lonesome George, died in 2012
Himalayan quail: not seen since 1876
Pink-headed duck: last confirmed in the 1930s in India
Asiatic cheetah: extinct in India; remnant in Iran
Indian species lost: Indian aurochs and Indian cheetah, plus the Javan rhino from the Sundarbans region
Amphibian crisis: about 40 percent of amphibian species are threatened, per IUCN
Coral threat: a third of reef-building corals threatened
Species at risk: over 44,000 species are on the Red List as threatened; check latest
Background rate debate: estimates vary by method and group
Anthropocene: proposed epoch of human impact; the geologists’ body decided in 2024 not to formalise it
Link to previous: see Effects of Loss of Biodiversity
Link to next: see IUCN Red List and Its Classification Scheme
Link to Deccan: see Geography macros for the Deccan Traps
Caution: dates and percentages differ slightly by source; learn the order and causes
Exam hint: remember Permian as the largest and K-Pg as the dinosaur event
Sixth mass extinction: a proposed ongoing event that differs from the earlier five in having a single biological cause, humans, and in being slowed or stopped by policy choices

Why Does It Matter for the Exam?

Events: five
Largest: Permian
Dinosaurs: K-Pg
Current affairs link: Red List updates and Spix’s macaw
Common errors: giving the asteroid as cause of all events or mixing the order

As an analytical point, past mass extinctions followed rapid environmental change, and current drivers are changing faster than most species can adapt. Unlike past events, the present one is caused by a single species that can choose to act.

Why Is This Topic Important?

Past Five events
Now Human-driven
Hope Action possible

What Came Next?

The next topic covers the IUCN Red List and its classification scheme. Next topic: IUCN Red List and Its Classification Scheme.

Key People and Terms

Extirpation Local extinction
Extinct in the wild Survives only in captivity
Background rate Natural extinction rate
Great Dying Permian extinction
K-Pg Cretaceous-Paleogene boundary
Anthropocene Proposed human epoch

Exam Corner

Points to Remember

Five mass extinctions: O, D, P, T, K.
Largest: Permian (252 mya).
Dinosaurs: 66 mya.
Sixth is human-driven.
Impact site: Chicxulub.

Do Not Confuse With

Extinct and extinct in the wild Gone everywhere versus captive survivors
Extinction and extirpation Global versus local
Mass extinction and background extinction Sudden many versus steady few

Memory Hook

Ordovician, Devonian, Permian, Triassic, Cretaceous: O-D-P-T-K, the Big Five.

Mains Angle

Questions ask for order, causes and the sixth wave. These points help.

Events Five
Causes Volcano, impact
Now Sixth

A Question You May Face

An original practice question, not a past paper question.

“What are mass extinctions? Describe the five major events in Earth’s history and discuss whether a sixth is under way.”

How to Answer

Define Mass extinction.
Events Five.
Now Sixth.
Action Conserve.

GS Relevance

Prelims: types of extinction, five mass extinctions, sixth extinction. GS Paper 3: biodiversity and conservation.

Frequently Asked Questions

What is a mass extinction?

A mass extinction is a short period in geological time during which a large share of Earth's species, typically more than three quarters, disappear across many groups. Five such events are known from the fossil record, each linked to rapid environmental change such as volcanism, climate shifts, ocean anoxia or an asteroid impact.

Which was the largest mass extinction?

The Permian-Triassic extinction, about 252 million years ago, known as the Great Dying, was the largest. It eliminated about 90 percent of marine species and about 70 percent of land vertebrates, probably because of massive Siberian volcanic eruptions that caused global warming, ocean acidification and loss of oxygen.

What caused the extinction of the dinosaurs?

Non-avian dinosaurs died out in the Cretaceous-Paleogene mass extinction about 66 million years ago, mainly due to the impact of a huge asteroid at Chicxulub in Mexico, which caused global darkness and cooling. Volcanic eruptions of the Deccan Traps in India also contributed to climate stress at that time.

What is the sixth mass extinction?

The sixth mass extinction is the term for the current high rate of species loss caused by human activities such as habitat destruction, overexploitation, invasive species, pollution and climate change. Estimates suggest extinction rates 100 to 1,000 times higher than the natural background rate, and about a million species face risk.

What is the difference between extinct in the wild and extirpated?

A species is extinct in the wild when it survives only in captivity, cultivation or outside its natural range, as with the Hawaiian crow. Extirpation means a species has disappeared from a particular region or country but still survives elsewhere, as the cheetah did when it was declared extinct in India in 1952.

PYQ Practice — Statement Analysis

1 The Permian-Triassic extinction was the largest mass extinction.

True

About 252 million years ago.

2 Dinosaurs went extinct at the end of the Triassic.

False

At the end of the Cretaceous.

3 The Chicxulub crater is linked to the K-Pg extinction.