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Practice biodiversity with 20 free MCQ questions covering environment-and-ecology. Detailed explanations in English and Hindi, perfect for UPSC, SSC, and competitive exam preparation.
Attempt the quiz above first, then review every question with its correct answer and a short explanation below.
Q1.Which of the following is considered the most important cause driving animal and plant species to extinction?
Explanation: NCERT Class 12 Biology Chapter 15 states: 'Habitat loss and fragmentation is the most important cause driving animals and plants to extinction.' The classic example is the destruction of tropical rainforests, which once covered 14% of the Earth's land but now cover less than 6%.
Q2.The 'Amazon Rainforest', often called the 'lungs of the planet', is being cut and cleared primarily for which purpose?
Explanation: NCERT notes that the Amazon rainforest is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle, leading to massive habitat loss for millions of species.
Q3.The introduction of which predatory fish into Lake Victoria in East Africa led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish?
Explanation: NCERT explicitly documents: 'The Nile perch introduced into Lake Victoria in East Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.' This is a classic example of alien species invasion.
Q4.Which of the following is NOT an invasive alien weed species threatening native biodiversity in India?
Explanation: NCERT Class 12 Biology mentions Parthenium (carrot grass), Lantana, and Eichhornia (water hyacinth) as invasive alien weeds that have caused environmental damage and threat to native species in India. Sandalwood is a native, valuable parasitic timber tree of India, not an invasive weed.
Q5.The illegal introduction of which African fish for aquaculture purposes in India poses a threat to indigenous catfishes in our rivers?
Explanation: NCERT Chapter 15 states: 'The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.'
Q6.When a host fish species becomes extinct, its unique set of parasites also faces extinction. This phenomenon is called:
Explanation: NCERT states: 'When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate. Another example is co-evolved plant-pollinator mutualism.'
Q7.Which of the following causes of species extinction is represented by the passenger pigeon and Steller's sea cow?
Explanation: NCERT Class 12 Biology explains: 'Humans have always depended on nature for food and shelter, but when "need" turns to "greed", it leads to over-exploitation of natural resources. Many species extinctions in the last 500 years (Steller's sea cow, passenger pigeon) were due to over-exploitation by humans.'
Q8.According to the IUCN Red List (2004), how many species have documented extinctions in the last 500 years?
Explanation: NCERT Chapter 15 states: 'The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.'
Q9.Which recent historical animal, endemic to Mauritius, went extinct due to overhunting and habitat changes introduced by humans?
Explanation: NCERT Chapter 15 lists several examples of recent extinctions: the Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller's Sea Cow (Russia), and three subspecies of tiger (Bali, Javan, Caspian).
Q10.The current rate of species extinction is estimated to be 100 to 1,000 times faster than pre-human times. This ongoing mass extinction is termed as the:
Explanation: NCERT states that Earth has experienced five episodes of mass extinction in its history. The current species loss represents the Sixth Extinction episode. The key difference is that the current rate is 100 to 1000 times faster, and human activities are responsible.
Q11.Which of the following major taxonomic groups appears to be the most vulnerable to extinction globally, with 32 percent of its species threatened?
Explanation: NCERT Class 12 Biology explicitly notes: 'Globally, 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31 per cent of all gymnosperm species in the world face the threat of extinction.' Thus, amphibians are the most vulnerable.
Q12.What is the collective term used for the four major human-caused drivers of biodiversity loss (Habitat loss, Over-exploitation, Alien invasion, Co-extinctions)?
Explanation: In NCERT Chapter 15, the four major causes of biodiversity loss are dramatically referred to as 'The Evil Quartet': (1) Habitat loss and fragmentation, (2) Over-exploitation, (3) Alien species invasions, and (4) Co-extinctions.
Q13.Which organization maintains the 'Red List' of threatened and endangered species globally, serving as the authority on biodiversity conservation status?
Explanation: The International Union for Conservation of Nature (IUCN) compiles and publishes the IUCN Red List of Threatened Species, which is the world's most comprehensive inventory of the global conservation status of biological species.
Q14.The Jhum cultivation (slash and burn agriculture) practiced in North-Eastern states of India has primarily contributed to which threat to biodiversity?
Explanation: Jhum cultivation involves clearing forest tracts by cutting and burning trees for farming. In recent decades, due to increased population, the fallow cycle has shortened, preventing forest recovery and leading to widespread deforestation and habitat fragmentation (NCERT Class 12 Biology, Chapter 16).
Q15.Which category under the IUCN Red List describes a species that has been completely cleared from its natural habitat but survives in botanical gardens, zoos, or breeding facilities?
Explanation: A species is categorized as 'Extinct in the Wild' (EW) when it is known only to survive in captivity, cultivation, or as a naturalized population well outside its past historic range, meaning it no longer exists in its wild native habitats.
Q16.Why does habitat fragmentation (dividing large habitats into small patches) affect mammals and birds more severely than many other animals?
Explanation: NCERT Class 12 Biology notes: 'When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines.'
Q17.The introduction of the Nile Perch in Lake Victoria represents a threat to biodiversity because the alien species:
Explanation: As an apex predator introduced into a system with no natural controls, the Nile Perch fed heavily on cichlid fish. Lacking defenses, more than 200 species of native cichlid fish were driven to extinction.
Q18.Which of the following is a classic example of co-extinctions involving obligate plant-pollinator mutualism?
Explanation: In obligate mutualisms (like fig-wasp or yucca-pronuba moth), neither partner can survive or reproduce without the other. If the specific wasp pollinator is lost, the fig plant cannot reproduce and will eventually face extinction, and vice-versa (NCERT Chapter 13 & 15).
Q19.The passenger pigeon (Ectopistes migratorius), which once numbered in billions in North America, went extinct in 1914 due to:
Explanation: The passenger pigeon was hunted for food and sport on a massive commercial scale in the 19th century. This extreme over-exploitation, combined with deforestation clearing their nesting grounds, caused their rapid decline and ultimate extinction in 1914.
Q20.When did the first IUCN Red Data Book get published, establishing a systematic tracking of global biodiversity threats?
Explanation: The IUCN Red Data Book was first published in 1964. It is compiled by the IUCN and provides comprehensive data on the conservation status of plants and animals globally.
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