Complete Exam Guide Subject-wise practice platform
0 XP
Biodiversity and Conservation

Threats to Biodiversity Practice Questions

20 free Threats to Biodiversity practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

Practice in Quiz Mode

Question 1 of 20 Medium

Which set of four factors is often described as the 'Evil Quartet' driving the decline of biodiversity?

  1. A Pollution, overpopulation, global warming, and forest fires
  2. B Habitat loss, over-exploitation, alien species invasion, and co-extinctions
  3. C Fragmentation, predation, competition, and parasitism
  4. D Genetic drift, inbreeding depression, mutation load, and natural selection pressure

Correct answer: Habitat loss, over-exploitation, alien species invasion, and co-extinctions

The 'Evil Quartet' is a term used to describe the four major causes of biodiversity loss. According to NCERT, these are habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions.

Question 2 of 20 Medium

Which human activity is considered the most important cause driving animals and plants to extinction?

  1. A Introduction of alien species into native ecosystems
  2. B Co-extinction of interdependent organisms
  3. C Habitat loss and fragmentation
  4. D Over-exploitation of economically valuable species

Correct answer: Habitat loss and fragmentation

Habitat loss and fragmentation is the primary driver of biodiversity loss. When large habitats are broken into small fragments due to human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected.

Question 3 of 20 Medium

The tropical rain forests, which once covered 14 percent of Earth's land surface, now cover no more than:

  1. A 10 percent
  2. B 8 percent
  3. C 6 percent
  4. D 4 percent

Correct answer: 6 percent

Tropical rain forests are being destroyed rapidly. NCERT notes that their coverage has shrunk from 14% to a mere 6% of the Earth's land surface due to human encroachment.

Question 4 of 20 Medium

The Amazon rain forest is being cut and cleared for which primary purpose?

  1. A Urban expansion and smart city infrastructure projects
  2. B Soya bean cultivation and cattle ranching on cleared land
  3. C Large-scale commercial extraction of tropical timber for export
  4. D Establishment of industrial chemical processing zones in the basin

Correct answer: Soya bean cultivation and cattle ranching on cleared land

The Amazon rain forest, often called the 'Lungs of the planet', is being cleared primarily for cultivating soya beans or for conversion to grasslands for raising beef cattle.

Question 5 of 20 Medium

When a large habitat is broken into small fragments due to various human activities, which types of organisms are worst affected?

  1. A Small insects with high reproductive rates and short life cycles
  2. B Mammals and birds requiring large territories
  3. C Microorganisms and soil-dwelling decomposer organisms
  4. D Planktonic algae and microscopic zooplankton in nearby ponds

Correct answer: Mammals and birds requiring large territories

Habitat fragmentation is particularly detrimental to large mammals and birds that need extensive home ranges. It disrupts their foraging and breeding patterns, leading to population declines.

Question 6 of 20 Medium

Which of the following fish species became extinct in Lake Victoria after the introduction of the Nile Perch?

  1. A Native catfish
  2. B Cichlid fish
  3. C Nile dogfish
  4. D Tilapia species

Correct answer: Cichlid fish

The introduction of the Nile Perch (an alien species) into Lake Victoria in East Africa led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish.

Question 7 of 20 Medium

Which invasive weed species, introduced to India, has caused environmental damage and threats to native species?

  1. A Parthenium (carrot grass)
  2. B Lantana
  3. C Eichhornia (water hyacinth)
  4. D All of the above

Correct answer: All of the above

Parthenium, Lantana, and Eichhornia are all examples of invasive alien species in India. They grow uncontrollably, outcompete native flora, and disrupt local ecosystems.

Question 8 of 20 Medium

The illegal introduction of which African catfish for aquaculture is posing a threat to indigenous catfishes in Indian rivers?

  1. A Clarias gariepinus
  2. B Labeo rohita
  3. C Catla catla
  4. D Mystus vittatus

Correct answer: Clarias gariepinus

Clarias gariepinus, the African catfish, was introduced illegally for aquaculture. It is highly predatory and competes with or preys upon the indigenous catfish species in India.

Question 9 of 20 Medium

What is 'co-extinction' in the context of biodiversity?

  1. A Clarias gariepinus
  2. B Labeo rohita (Rohu)
  3. C Catla catla (Catla)
  4. D Mystus vittatus (Striped dwarf catfish)

Correct answer: Clarias gariepinus

Clarias gariepinus, the African catfish, was introduced illegally for aquaculture. It is highly predatory and competes with or preys upon the indigenous catfish species in India.

Question 10 of 20 Medium

A plant-pollinator mutualism where the extinction of one leads to the extinction of the other is an example of:

  1. A Simultaneous extinction of two genetically unrelated species in the same region
  2. B Extinction of a species when its obligate host or mutualistic partner goes extinct
  3. C A mass extinction event triggered by a large-scale volcanic eruption
  4. D Competitive exclusion leading to the extinction of a weaker native species

Correct answer: Extinction of a species when its obligate host or mutualistic partner goes extinct

Co-extinction occurs when a species is obligatorily associated with another. For example, if a host fish becomes extinct, its unique assemblage of parasites also meets the same fate.

Question 11 of 20 Medium

Stellar’s sea cow and the Passenger pigeon became extinct due to:

  1. A Alien species invasion disrupting local food webs
  2. B Over-exploitation by humans or commercial harvest
  3. C Co-extinction through obligate mutualism breakdown
  4. D Habitat fragmentation isolating small populations

Correct answer: Co-extinction through obligate mutualism breakdown

In an obligate mutualism, such as the one between a specific fig species and its wasp pollinator, the loss of one partner inevitably leads to the loss of the other, as neither can complete their life cycle alone.

Question 12 of 20 Medium

Which of the following is NOT a consequence of climate change on biodiversity?

  1. A Progressive habitat fragmentation and loss
  2. B Over-exploitation by humans
  3. C Displacement by invasive alien species
  4. D Climate-driven habitat degradation

Correct answer: Over-exploitation by humans

Both the Steller's sea cow and the Passenger pigeon are classic examples of species that were hunted to extinction. Their loss was caused by human greed and over-exploitation of natural resources.

Question 13 of 20 Medium

How does global warming specifically threaten coastal biodiversity?

  1. A By increasing the salinity of the open ocean
  2. B By causing sea-level rise which submerges coastal habitats
  3. C By reducing the amount of CO2 available for aquatic plants
  4. D By increasing the thickness of the ozone layer

Correct answer: By causing sea-level rise which submerges coastal habitats

Global warming leads to the melting of polar ice caps and thermal expansion of seawater. The resulting sea-level rise can submerge mangroves, salt marshes, and low-lying coastal breeding grounds.

Question 14 of 20 Medium

The 'Lungs of the Planet' is a title given to:

  1. A By increasing salinity and osmotic stress across the open ocean surface
  2. B By causing sea-level rise that submerges coastal habitats
  3. C By reducing the CO2 available for photosynthesis in aquatic plants
  4. D By promoting stratospheric ozone thickening over polar coastal zones

Correct answer: By causing sea-level rise that submerges coastal habitats

Global warming leads to the melting of polar ice caps and thermal expansion of seawater. The resulting sea-level rise can submerge mangroves, salt marshes, and low-lying coastal breeding grounds.

Question 15 of 20 Medium

Invasive alien species are successful in new environments primarily because:

  1. A They have higher mutation rates
  2. B They lack natural predators in the new habitat
  3. C They only consume inorganic nutrients
  4. D They are always larger in size than native species

Correct answer: They lack natural predators in the new habitat

In many cases, alien species become invasive because they are introduced into a new geographical area where their natural predators, parasites, or competitors are absent, allowing their populations to explode.

Question 16 of 20 Medium

Which of these is a direct effect of habitat fragmentation on animal populations?

  1. A Increased gene flow between populations
  2. B Reduction in edge effects
  3. C Isolation of small populations leading to inbreeding
  4. D Increase in the total carrying capacity of the ecosystem

Correct answer: Isolation of small populations leading to inbreeding

Fragmentation isolates populations into smaller groups. This lack of movement between fragments leads to inbreeding and reduced genetic variability, making the species more vulnerable to extinction.

Question 17 of 20 Medium

The recent extinction of the Dodo in Mauritius is attributed to:

  1. A Excessive use of agricultural pesticides in wetland areas
  2. B Introduction of alien species and hunting
  3. C Large-scale wildfires destroying forest and grassland cover
  4. D Progressive desertification reducing available freshwater

Correct answer: Introduction of alien species and hunting

The Dodo was a flightless bird that became extinct shortly after humans arrived in Mauritius. The introduction of animals like pigs and rats, combined with direct hunting, led to its rapid disappearance.

Question 18 of 20 Medium

Which of the following is a major threat to the biodiversity of the Great Barrier Reef?

  1. A Desertification
  2. B Ocean acidification and warming
  3. C Over-population of indigenous sharks
  4. D Excessive rainfall in the outback

Correct answer: Ocean acidification and warming

Increased atmospheric CO2 leads to ocean acidification and rising sea temperatures. These factors cause coral bleaching and interfere with the ability of corals to build their calcium carbonate skeletons.

Question 19 of 20 Medium

Loss of biodiversity in a region may lead to all of the following EXCEPT:

  1. A Decline in plant production
  2. B Lowered resistance to environmental perturbations
  3. C Increased variability in ecosystem processes like water use
  4. D Increased stability of the ecosystem

Correct answer: Increased stability of the ecosystem

A loss of biodiversity actually decreases the stability of an ecosystem. Diverse ecosystems tend to be more resilient and consistent in their productivity compared to species-poor systems.

Question 20 of 20 Medium

The impact of over-exploitation is most severely seen in species that have:

  1. A High reproductive rates and very short generation times
  2. B Short life spans and early sexual maturity
  3. C Low reproductive rates and long maturation times
  4. D Large population sizes with wide geographic distribution

Correct answer: Low reproductive rates and long maturation times

Species that reproduce slowly or take a long time to reach maturity (like whales or certain large sharks) cannot replenish their numbers as fast as they are being harvested, making them highly susceptible to over-exploitation.

0 / 20 answered