This set of Class 12 Biology Chapter 15 Multiple Choice Questions & Answers (MCQs) focuses on “Causes of Biodiversity Losses”.
1. What does ‘The Evil Quartet’ describes?
a) An increase in the number of species
b) The decrease in the number of species
c) Mass extinction
d) Formation of the universe
View Answer
Explanation: ‘The Evil Quartet’ is the sobriquet used to describe the reasons for the decline in the number of species. The four reasons include Loss of habitat and fragmentation, Over-exploitation of species, Invasion of alien (new) species and Co-extinctions.
2. Which one of the following is said to be the most important cause or reason for the extinction of animals and plants?
a) Loss of habitat and fragmentation
b) Over-exploitation of species
c) Invasion of alien species
d) Co-extinctions
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Explanation: The most important reason for the extinction of animals and plants is the loss of habitat and fragmentation. Habitat loss due to destruction, fragmentation, or degradation of habitat makes natural habitat incapable of supporting its native species.
3. Previously how much of the Earth’s land surface was covered by the tropical rain forests?
a) 50 %
b) 14 %
c) 24 %
d) 35 %
View Answer
Explanation: The forests occurring in tropical areas of heavy rainfall are known as tropical rain forests. It has abundant species of wildlife and vegetation. Previously 14 percent of the Earth’s land surface was covered by the tropical rain forests.
4. Currently, how much area of the Earth’s land surface is covered by the tropical rain forests?
a) 90 %
b) 50 %
c) 1 %
d) 6 %
View Answer
Explanation: The forests occurring in tropical areas of heavy rainfall are known as tropical rain forests. It has abundant species of wildlife and vegetation. Currently, 6 percent area of the Earth’s land surface is covered by the tropical rain forests.
5. Which of the following rain forest is known as ‘lungs of the planet’?
a) The African rain forest
b) The Australian rain forest
c) The Amazon rain forest
d) The Southeast Asian rain forest
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Explanation: The Amazon rainforest is the world’s largest tropical rainforest and is also known as the Amazon Jungle or Amazonia. It is known as the ‘lungs of the planet’ because it harbors probably millions of species.
6. Which animals are badly affected when a large habitat is broken up into small fragments due to various human activities?
a) Extinct species
b) Migratory species
c) Non-migratory species
d) Humans
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Explanation: When a large habitat is broken up into small fragments due to various human activities, the migratory species are badly affected. These areas are fragmented by humans for agriculture and urban development.
7. What are the excess and the unsustainable use of resources called?
a) Loss of habitat and fragmentation
b) Co-extinctions
c) Invasion of alien species
d) Over-exploitation
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Explanation: The excess and unsustainable use of resources is known as over-exploitation. It is also known as overharvesting. Overexploitation of any kind of resource leads to rapid decline and destruction of that resource that may cause serious damage to the ecosystem.
8. What was the reason for the exploitation of the Steller’s sea cow and the passenger pigeon?
a) Competition
b) Loss of habitat
c) Human activities
d) Mutualistic relationships
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Explanation: The excess and unsustainable use of resources is known as over-exploitation. Many species such as the Steller’s sea cow and the passenger pigeon are lost in last 500 years due to human activities such as poaching.
9. What happens when alien species are introduced unintentionally or deliberately?
a) Decrease of alien species
b) Increase in habitat
c) They turn invasive and cause increase species
d) They turn invasive and cause decline or extinction of indigenous species
View Answer
Explanation: The unintentional or deliberate introduction of alien (new) species into a habitat cause the aliens to turn invasive and thus causing the decline or extinction of indigenous species. They can affect all types of organisms (animals, plants, fungi, and microorganisms) and ecosystems.
10. What happened when the Nile perch introduced into Lake Victoria in east Africa?
a) Extinction of trees
b) Increase in the number of trees
c) Extinction of cichlid fish
d) Increase in the number of cichlid fish
View Answer
Explanation: The cichlid fish, native of Lake Victoria in east Africa were extinct due to the introduction of alien species that is the Nile perch. It destroyed nearly 200 species of cichlid fish through predation and competition for food.
11. Which of the following contains chemicals like parthenin, is toxic to cattle and cause pollen allergy in humans?
a) Nile perch
b) The carrot grass
c) Rose
d) Wheat
View Answer
Explanation: The carrot grass also known as Parthenium is an erect and annual herb. It is responsible for environmental, medical, and agricultural hazards. It contains chemicals like parthenin, is toxic to cattle and causes pollen allergy in humans.
12. What is Eicchornia called?
a) The carrot grass
b) Nile perch
c) Water hyacinth
d) Water lily
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Explanation: Eichhornia crassipes also known as water hyacinth. It was first introduced from South America into China that later on became a serious environmental problem. It reduces the sunlight penetration and lowers the oxygen content in the water that hampers the water ecosystem.
13. Why was the African catfish Clarias gariepinus introduced?
a) Horticulture
b) Aquaculture
c) Sericulture
d) Poultry
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Explanation: The African catfish Clarias gariepinus was introduced for aquaculture purposes. The introduction was illegal and posed a threat to the indigenous catfishes in our rivers due to disease introduction, competition, and environmental modification.
14. Which phenomenon explains that ‘When a species becomes extinct, the plant and animal species also become extinct that are obligatorily associated with the host species’?
a) Aquaculture
b) Fragmentation
c) Invasion
d) Co-extinction
View Answer
Explanation: Co-extinction is the phenomenon that tells, when a species becomes extinct, the plant and animal species also become extinct that are obligatorily associated with the host species. If a host is extinct the parasite associated with it is also extinct.
15. Which phenomenon does the coevolved plant-pollinator mutualism explain?
a) Co-extinction
b) Fragmentation
c) Invasion
d) Loss of habitat
View Answer
Explanation: The coevolved plant-pollinator mutualism explains the phenomenon of co-extinction. Co-extinction is the phenomenon that tells, when a species becomes extinct, the plant and animal species also become extinct that are obligatorily associated with the host species.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
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