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100 questions in this collection · Page 4 of 10
Question 31 of 100
📘 CLASS XII
Biodiversity And Conservation
Consider the following statements regarding the history of species extinctions on Earth:
I. During the long period of more than 3 billion years since the origin and diversification of life on Earth, there were five episodes of mass extinction of species. II. Mass extinctions of species are a completely modern phenomenon that never occurred before humans appeared on the scene. III. The sixth mass extinction currently in progress is completely identical in speed and causation to the previous five episodes.
Which of the statements given above is/are correct?
Earth's fossil history reveals that five episodes of mass extinction occurred long before humans appeared. The current sixth extinction is different because it is estimated to be 100 to 1,000 times faster and is primarily driven by human activities. Hence, statements II and III are incorrect.
Question 32 of 100
📘 CLASS XII
Biodiversity And Conservation
Study the following statements regarding the Sixth Extinction currently in progress:
I. The current species extinction rates are estimated to be 100 to 1,000 times faster than in pre-human times. II. Human activities and resource exploitation are directly responsible for these faster rates of extinction. III. Ecologists warn that if the present trends continue, nearly half of all the species on Earth might be wiped out within the next 100 years.
Which of the statements given above are correct?
All three statements are correct. The present extinction rate is estimated to be 100 to 1,000 times higher than the natural background rate due to human activities, and nearly half of all species could disappear within the next 100 years if current trends continue.
Question 33 of 100
📘 CLASS XII
Biodiversity And Conservation
With reference to the consequences of biodiversity loss in a geographic region, evaluate the following statements:
I. Loss of biodiversity in a region leads to an increase in plant production due to reduced competition. II. It leads to lowered resistance of ecosystems to environmental perturbations such as drought. III. It leads to increased variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles.
Which of the statements given above are correct?
Statement I is incorrect because biodiversity loss results in a decline in plant production. Statements II and III are correct as biodiversity loss lowers ecosystem resistance to disturbances and increases variability in ecosystem processes.
Question 34 of 100
📘 CLASS XII
Biodiversity And Conservation
Consider the following statements about the major drivers of extinction, collectively known as the Evil Quartet:
I. The Evil Quartet is the sobriquet used to describe the four major causes of accelerated global species extinctions. II. The four causes are habitat loss and fragmentation, over-exploitation, alien species invasions, and co-extinctions. III. Among these four, over-exploitation is considered the single most important cause driving animals and plants to extinction.
Which of the statements given above are correct?
Statements I and II are correct. Statement III is incorrect because habitat loss and fragmentation is the most important cause of extinction, not over-exploitation.
Question 35 of 100
📘 CLASS XII
Biodiversity And Conservation
Study the following statements regarding habitat loss in tropical rain forests:
I. The most dramatic examples of habitat loss come from tropical rain forests. II. These rain forests once covered more than 14 per cent of the Earth's land surface, but now cover no more than 6 per cent. III. The destruction of these rain forests has completely stopped in the 21st century due to international conservation policies.
Which of the statements given above are correct?
Statement III is incorrect because tropical rain forests continue to be destroyed rapidly. Statements I and II are correct.
Question 36 of 100
📘 CLASS XII
Biodiversity And Conservation
Read the following statements about the rate of forest degradation and its drivers:
I. By the time you finish reading this chapter, 1,000 more hectares of rain forest would have been lost. II. The rate of rainforest loss is exceptionally slow, meaning only a few hectares are lost annually. III. Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species.
Which of the statements given above are correct?
Statement II is incorrect because rainforest destruction is occurring very rapidly. Statements I and III are correct.
Question 37 of 100
📘 CLASS XII
Biodiversity And Conservation
With reference to the Amazon rain forest, identify the correct statements from the following:
I. The Amazon rain forest is so huge that it is called the lungs of the planet. II. Large tracts of the Amazon rain forest are being cut and cleared to cultivate soya beans. III. Another major reason for clearing the Amazon forest is its conversion to grasslands for raising beef cattle.
Which of the options represents the correct statements?
All three statements are correct. The Amazon rain forest is called the lungs of the planet and is being cleared for soya cultivation and conversion into grasslands for beef cattle.
Question 38 of 100
📘 CLASS XII
Biodiversity And Conservation
Consider the following statements about the effects of habitat fragmentation on animal populations:
I. Fragmentation occurs when large habitats are broken up into small fragments due to various human activities. II. Mammals and birds requiring large territories are badly affected by fragmentation, leading to population declines. III. Animals with migratory habits are unaffected by fragmentation as long as the total forest area remains constant.
Which of the statements given above are correct?
Statement III is incorrect because migratory animals are severely affected by habitat fragmentation. Statements I and II are correct.
Question 39 of 100
📘 CLASS XII
Biodiversity And Conservation
Read the following statements regarding human over-exploitation of natural resources:
I. When human 'need' turns to 'greed', it leads to the over-exploitation of natural resources. II. Many species extinctions in the last 500 years, such as the Steller's Sea Cow and Passenger Pigeon, were due to over-exploitation by humans. III. Presently, many marine fish populations around the world are overharvested, endangering commercially important species.
Which of the statements given above are correct?
All three statements are correct. Over-exploitation occurs when resources are harvested beyond sustainable limits. It has historically caused the extinction of species such as the Passenger Pigeon and Steller's Sea Cow and continues to threaten marine ecosystems through excessive fishing.
Question 40 of 100
📘 CLASS XII
Biodiversity And Conservation
Consider the following statements regarding alien species invasions:
I. Introduction of alien species always leads to positive ecological adaptations and never causes extinctions of native species. II. The Nile Perch was introduced into Lake Victoria in East Africa. III. This introduction eventually led to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
Which of the statements given above are correct?
Statement I is incorrect because invasive alien species can cause severe ecological damage and extinction of native species. Statements II and III are correct and represent the classic Lake Victoria example.