Loss of Biodiversity: Meaning and Mass Extinctions
Biology · Biodiversity and Conservation · NEET
Loss of biodiversity means the number of species on Earth is dropping fast, because species are dying (extinction) but almost no new species are being added. NCERT says the IUCN Red List (2004) recorded 784 extinctions in the last 500 years, and human activity is the main cause. Memory hook: "784 gone in 500 years" and remember that Earth has already had FIVE mass extinctions, and we are now in the SIXTH.
Biodiversity loss happens because extinction (out) far outpaces slow speciation (in). Earth had five past mass extinctions; the current Sixth Extinction differs mainly by its 100 to 1,000 times faster, human-driven rate.
Your doubts, answered
What exactly does 'loss of biodiversity' mean?
It means the total number of species on Earth is falling. NCERT explains that hardly any new species are being added by speciation, while species keep going extinct. So the net result is a steady, fast decline in the biological wealth of the planet. The 'accusing finger' points to human activities as the main reason.
How many species have gone extinct, according to NCERT?
The IUCN Red List (2004) documents the extinction of 784 species in the last 500 years. This 784 breaks down into 338 vertebrates, 359 invertebrates and 87 plants. Also, more than 15,500 species worldwide are currently facing the threat of extinction. Learn 784 as an exact NEET number.
Which groups of animals are most vulnerable to extinction?
NCERT says extinctions across taxa are NOT random. Some groups, especially amphibians, are more vulnerable. The percentages facing threat: 12% of birds, 23% of mammals, 32% of amphibians and 31% of gymnosperms. Amphibians (32%) top the animal list, so 'amphibians are most vulnerable' is a common NEET point.
What is the Sixth Extinction and how is it different from earlier ones?
Earth has already had FIVE episodes of mass extinction over 3 billion years, all before humans existed. The Sixth Extinction is happening now. The key difference is the RATE: current extinction rates are 100 to 1,000 times faster than pre-human times, and human activities are responsible. This rate difference is the exact point NEET asks.
Are new species not being added at all?
NCERT phrases it carefully: it is 'doubtful if any new species are being added through speciation', while there is 'no doubt' about continuing losses. So speciation is far too slow to balance the fast losses. This imbalance (few in, many out) is the core meaning of biodiversity loss.
⚠️ The NEET trap ✗ The Sixth Extinction is different because far MORE species are dying than in the five earlier mass extinctions. ✓ The Sixth Extinction differs mainly in the RATE, not the total count. NCERT states current extinction rates are 100 to 1,000 times faster than pre-human rates, and human activity drives this speed. 🧠 When NEET asks how the Sixth Extinction differs, the answer is RATE (100 to 1,000 times faster), not number.
Real NEET questions
NEET 2024
List of endangered species was released by
A · WWF
B · FOAM
C · IUCN ✓
D · GEAC
Solution: The list documenting extinct and threatened species is the IUCN Red List. NCERT states the IUCN Red List (2004) documented the extinction of 784 species in the last 500 years. WWF and FOAM do not release this list, and GEAC (Genetic Engineering Appraisal Committee) deals with GMOs, so they are wrong.
Solved Biodiversity and Conservation NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
