Biology · Biodiversity and Conservation · NEET
No. Habitat loss destroys the place a species lives in (like cutting the Amazon for soya bean farms). Over-exploitation kills the species directly by removing too many individuals (hunting, over-fishing). Both are in the Evil Quartet, but habitat loss is cause (i) and the most important cause, while over-exploitation is cause (ii). NEET often asks you to match the example to the correct cause, so keep them separate.
NCERT says: humans have always depended on nature for food and shelter (that is 'need'), but when 'need' turns to 'greed', it leads to over-exploitation of natural resources. This one line is the exact definition of over-exploitation. Learn it word for word, because NEET statement-type questions copy NCERT sentences directly.
Three exact NCERT examples: (1) Steller's sea cow and (2) the passenger pigeon, both driven extinct in the last 500 years by over-exploitation by humans, and (3) many marine fish populations that are over-harvested today, endangering commercially important species. If an example is about a species being hunted or fished too much, it is over-exploitation.
Yes. NCERT clearly states that presently many marine fish populations around the world are over-harvested, endangering the continued existence of some commercially important species. 'Over-harvested' is just another word for over-exploited. This is the modern, still-happening example, unlike the extinct sea cow and pigeon which are historical.
Over-exploitation is humans removing a native species too fast (hunting, fishing). Alien species invasion is a foreign species (like Nile perch or African catfish Clarias) being introduced and then wiping out native species. In over-exploitation the human is the direct cause; in alien invasion an introduced organism is the cause. NEET mixes these up in match-the-following questions, so watch the wording.
Which of the following statements are correct? A. The Amazon rainforest being cut and cleared for cultivation of soyabeans is an example of habitat loss. B. Steller's sea cow and passenger pigeon became extinct due to over-exploitation by humans. C. The Nile perch introduced into Lake Victoria in East Africa helped in population growth of cichlid fish in the lake. D. Water hyacinth is an invasive species. E. When a species becomes extinct, the plant and animal species associated with it are not affected.
Habitat loss and fragmentation, over exploitation, alien species invasion and co-extinction are causes for:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Over-exploitation is the removal of a species from nature faster than it can reproduce, driven by human 'greed', leading to population decline or extinction. It is cause (ii) of the Evil Quartet.
Steller's sea cow and the passenger pigeon. Both became extinct in the last 500 years due to over-exploitation by humans.
Yes. NCERT states many marine fish populations are over-harvested, endangering commercially important species. Over-harvesting is over-exploitation.
It is the second cause, after habitat loss and fragmentation (which is the most important cause), and before alien species invasions and co-extinctions.
By humans. NCERT clearly attributes it to human activity, using the 'need turns to greed' idea to describe how it happens.
