Causes of Biodiversity Losses Questions in English

(A) Excessive exploitation of a species,whether a plant or animal,reduces the size of its population,making it vulnerable to extinction.
$Steller's$ sea cow and the passenger pigeon are classic examples of species that were driven to extinction primarily due to over-exploitation by humans.
Many marine fish populations,such as whales,are also declining globally due to over-harvesting.
Therefore,the correct cause for the extinction of these specific species is over-exploitation.

(D) Anthropogenic extinctions are the extinctions abetted by human activities like settlements,hunting,overexploitation,and habitat destruction.

(D) Rhododendrons are found in abundance at high altitudes,specifically between $12000$ to $16000$ feet in the Himalayas. Birds often play a crucial role in the pollination and seed dispersal of these high-altitude plants. Therefore,if bird populations decline or go extinct at these altitudes,the survival and propagation of Rhododendrons are directly threatened.

(D) The primary causes of biodiversity loss are often referred to as the '$Evil Quartet$'.
These include:
$1$. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$2$. Over-exploitation: Humans have over-exploited many species (e.g.,Steller's sea cow,passenger pigeon).
$3$. Alien species invasions: When alien species are introduced unintentionally or deliberately,some of them turn invasive and cause the decline or extinction of indigenous species.
$4$. Coextinctions: When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct.
Since all the options listed ($A$,$B$,and $C$) are major causes of biodiversity loss,the correct answer is $D$.

(C) The primary cause of the decline in wildlife populations is the destruction of habitats. While factors like hunting and predation contribute to the decline,the loss of natural habitats (often due to deforestation,urbanization,and industrialization) is the most significant and overarching reason that forces wildlife into smaller,fragmented areas,making them more vulnerable to other threats.

(C) The world is facing accelerated rates of species extinctions,largely due to human interference. There are four major causes of biodiversity loss,collectively referred to as 'The Evil Quartet'. These are:
$1$. Habitat loss and fragmentation.
$2$. Over-exploitation.
$3$. Alien species invasions.
$4$. Co-extinction.

(A) species becomes prone to extinction due to two primary categories of attributes: drastic environmental changes and specific population characteristics.
Population traits that increase the risk of extinction include small population size,large body size,and a higher trophic level status.

(C) The species-area relationship,represented by the equation $S = CA^z$,is a fundamental concept in ecology. Ecologists use this relationship to estimate the number of species extinctions that occur as a result of habitat destruction. As the area of a habitat decreases,the number of species that can be supported also decreases,allowing scientists to predict biodiversity loss.

(D) The correct matches for the extinct animals and their respective regions are as follows:
$1$. Thylacine: Found in Australia.
$2$. Dodo: Found in Mauritius.
$3$. Quagga: Found in Africa.
$4$. Steller's sea cow: Found in Russia.
Therefore, the correct matching sequence is $a(iii), b(ii), c(iv), d(i)$.

(C) The term 'Evil Quartet' is used to describe the four major causes of biodiversity loss. These four causes are:
$1$. Habitat loss and fragmentation
$2$. Over-exploitation
$3$. Alien species invasions
$4$. Co-extinctions

(C) Habitat fragmentation is a major cause of biodiversity loss. When large habitats are broken into small fragments,animals that require large territories or have migratory habits are the most severely affected because they cannot complete their life cycles or find sufficient resources within the restricted,isolated patches.

(B) The introduction of the Nile perch,an alien predator fish,into Lake Victoria in East Africa caused the extinction of an ecologically unique assemblage of more than $200$ species of cichlid fish in the lake. This is a classic example of biodiversity loss due to the introduction of alien species.

(A) Co-extinction refers to the phenomenon where the extinction of one species leads to the extinction of another species that is obligately associated with it. In this case,when a host fish species becomes extinct,the parasites that are specifically dependent on that host for their survival and reproduction also face extinction because they lose their habitat and source of nutrition.

(D) The Amazon rainforest is often referred to as the 'lungs of the planet'.
It is estimated that the Amazon rainforest produces approximately $20\%$ of the total oxygen in Earth's atmosphere through photosynthesis.
Therefore,$A$ is Amazon and $B$ is $20$.
The correct option is $D$.

(D) The major causes of biodiversity loss are often referred to as the 'Evil Quartet'. These include:
$1$. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$2$. Over-exploitation: Humans have over-exploited many species (e.g.,Steller's sea cow,passenger pigeon) for food or commercial needs.
$3$. Intensive agriculture: The conversion of natural ecosystems into agricultural land leads to a significant loss of biodiversity.
Therefore,all the given options are major threats to biodiversity.

(A) $Eichhornia \text{ } crassipes$ (Water Hyacinth) is an exotic species that was introduced into India by Europeans for its beautiful flowers and leaf shape. It is known as the 'Terror of Bengal' because it grows excessively in standing water and drains oxygen from the water, leading to the death of fishes.

(D) The process of extinction is generally a slow,natural,and continuous process,although human activities have significantly accelerated it. Therefore,the Assertion is incorrect.
The Reason states that any species not adapted to environmental conditions cannot survive,which is a fundamental principle of natural selection and is correct.
Thus,Assertion is incorrect,but Reason is correct.

(A) Habitat destruction and fragmentation are the primary causes of biodiversity loss.
When large habitats are fragmented into smaller patches,the total perimeter (edge) of the habitat increases relative to its area.
This phenomenon is known as the 'edge effect'.
Increased edge area leads to greater exposure to external environmental factors,which reduces the stable 'core area' required by many species for survival.
Therefore,both the Assertion and the Reason are correct,and the Reason provides a valid explanation for why habitat destruction leads to biodiversity loss.

(B) The four major causes of biodiversity loss are collectively known as the '$Evil \text{ } Quartet$'.
$1$. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$2$. Over-exploitation: Humans have over-exploited many species (e.g., Steller's sea cow, passenger pigeon) for food or commercial needs.
$3$. Alien species invasion: When alien species are introduced unintentionally or deliberately, some of them turn invasive and cause the decline or extinction of indigenous species.
$4$. Co-extinction: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.
Therefore, these factors are the primary causes of biodiversity loss.

(C) Water hyacinth $(Eichhornia) \text{ } crassipes$ is one of the most invasive weeds found growing wherever there is standing water.
It drains oxygen from the water, which leads to the death of fishes.
Therefore, it decreases the $O_2$ level in water, not increases it.
It is known as the 'Terror of Bengal' because it grows at a phenomenal rate and spreads all over the water body in a short period.
It was introduced in India primarily due to its beautiful flowers and unique shape of leaves.

(D) Parthenium,commonly known as carrot grass,was introduced into India as a contaminant with imported wheat.
It is now ubiquitous in occurrence,meaning it is found everywhere.
It is well-known for causing severe pollen allergies in humans.
Therefore,all the given statements are correct.

(C) According to the $NCERT$ textbook,the colonization of tropical Pacific islands by humans has led to the extinction of more than $2000$ species of native birds. This is a significant example of biodiversity loss caused by human activities.

(D) The $3$ recently extinct subspecies of the tiger $(Panthera \text{ } tigris)$ are:
$1$. Bali tiger $(Panthera \text{ } tigris \text{ } balica)$
$2$. Javan tiger $(Panthera \text{ } tigris \text{ } sondaica)$
$3$. Caspian tiger $(Panthera \text{ } tigris \text{ } virgata)$
These subspecies have gone extinct due to human activities such as hunting and habitat destruction. Therefore, the correct option is $D$.

(D) The correct matches for the extinct species and their regions are as follows:
$(P)$ Dodo: Extinct from Mauritius $(II)$.
$(Q)$ Quagga: Extinct from Africa $(III)$.
$(R)$ Thylacine: Extinct from Australia $(IV)$.
$(S)$ Steller's sea cow: Extinct from Russia $(I)$.
Therefore, the correct sequence is $(P-II), (Q-III), (R-IV), (S-I)$.

(D) David Tilman's experiments showed that ecosystems with higher biodiversity are more productive and exhibit greater stability against environmental perturbations.
Loss of biodiversity leads to:
$1$. $A$ decline in plant production.
$2$. Lower resistance to environmental perturbations such as drought.
$3$. Increased variability in certain ecosystem processes such as water use,pest,and disease cycles.
Therefore,the correct option is $D$.

(A) The 'Evil Quartet' is a term used to describe the four major causes of biodiversity loss. These are:
$1$. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$2$. Over-exploitation: Humans have over-exploited many species (e.g.,Steller's sea cow,passenger pigeon).
$3$. Alien species invasions: When alien species are introduced unintentionally or deliberately,they often become invasive and cause the decline or extinction of indigenous species.
$4$. Co-extinctions: When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct.

(D) When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct. This phenomenon is known as $Co-extinction$. In the case of a host fish species,if it goes extinct,the parasites that are specifically dependent on that host for their survival will also face extinction. This is a classic example of $Co-extinction$ as a cause of biodiversity loss.

(B) The decline in marine fish populations due to over-harvesting is a classic example of $Over-exploitation$.
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 (e.g.,Steller's sea cow,passenger pigeon) were due to over-exploitation by humans.
Currently,many marine fish populations around the world are being over-harvested,endangering the continued existence of some commercially important species.

(B) The introduction of the Nile perch,an alien predator fish,into Lake Victoria in East Africa caused the extinction of an ecologically unique assemblage of more than $200$ species of cichlid fish in the lake. This is a classic example of biodiversity loss due to alien species invasion.

(D) Alien species invasion is one of the major causes of biodiversity loss. When alien species are introduced unintentionally or deliberately for whatever purpose,some of them turn invasive and cause decline or extinction of indigenous species. In India,$Parthenium$ $hysterophorus$ (carrot grass),$Lantana$ $camara$,and $Eichhornia$ $crassipes$ (water hyacinth) are classic examples of alien species that have become invasive and caused significant environmental damage. Therefore,all the given options are correct.

(B) Clarias gariepinus is the scientific name for the African catfish. It is an invasive alien species that has been illegally introduced into Indian rivers for aquaculture purposes. This introduction poses a significant threat to the indigenous catfish species in these rivers,leading to a loss of biodiversity.

(B) Water hyacinth $(Eichhornia\,crassipes)$ is an invasive alien species,not an indigenous plant of India.
It was introduced in India because of its beautiful flowers and shape of leaves.
Since it can propagate vegetatively at a phenomenal rate and spread all over the water body in a short period,it is very difficult to get rid of them.
It is known as the 'Terror of Bengal' because it drains oxygen from the water,which leads to the death of fishes and other aquatic organisms.
Therefore,option $B$ is the incorrect statement.

(B) The 'Evil Quartet' refers to the four major causes of biodiversity loss: habitat loss and fragmentation,over-exploitation,alien species invasions,and co-extinctions.
Among these,habitat loss and fragmentation is considered the most important cause driving animals and plants to extinction,as it directly destroys the living environment required for survival.

(C) The major causes of biodiversity loss,often referred to as the 'Evil Quartet',are:
$(1)$ Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$(2)$ Over-exploitation: Humans have over-exploited many species (e.g.,Steller's sea cow,passenger pigeon).
$(3)$ Alien species invasions: When alien species are introduced unintentionally or deliberately,some of them turn invasive and cause the decline or extinction of indigenous species.
$(4)$ Co-extinctions: When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct.
Comparing these with the given options,$A$ (Over-exploitation),$B$ (Co-extinction),and $D$ (Habitat loss and fragmentation) are recognized as major causes. Therefore,the correct option is $A, B$ and $D$ only.

(C) The passenger pigeon $(Ectopistes migratorius)$ was once the most abundant bird in North America. Its extinction was primarily caused by human activities, specifically over-exploitation through excessive hunting and commercial slaughter for food. While habitat loss also played a role, the primary driver for its rapid decline and eventual extinction was over-exploitation by humans.

(D) The causes of biodiversity loss are collectively known as the '$Evil Quartet$'.
These four major causes are:
$1$. Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.
$2$. Over-exploitation: Humans have over-exploited many species (e.g.,Steller's sea cow,passenger pigeon) for food or commercial needs.
$3$. Alien species invasion: When alien species are introduced unintentionally or deliberately,some of them turn invasive and cause the decline or extinction of indigenous species.
$4$. Co-extinction: When a species becomes extinct,the plant and animal species associated with it in an obligatory way also become extinct.
Since all four listed factors $(a, b, c, d)$ are recognized causes of biodiversity loss,the correct answer is $4$.

(C) The 'evil quartet' is a term used to describe the four major causes of biodiversity loss as identified by ecologists. These are:
$1$. Habitat loss and fragmentation.
$2$. Over-exploitation.
$3$. Alien species invasions.
$4$. Co-extinctions.
Since all four options provided in the original list (Habitat loss and fragmentation,Over-exploitation,Alien species invasion,and Pollution) are often discussed in the context of biodiversity loss,it is important to note that 'Pollution' is a significant factor,but the specific term 'evil quartet' refers to the four listed above. However,in many standard textbooks,the four causes are Habitat loss,Over-exploitation,Alien species invasions,and Co-extinctions. Therefore,if the question asks which is $NOT$ part of the quartet,and 'Pollution' is listed as an option,it is the correct choice as it is not one of the four components of the 'evil quartet'.

(B) The illegal introduction of the African catfish,$Clarias$ $gariepinus$,into Indian rivers for aquaculture has become a significant threat to the indigenous catfishes. This is a classic example of the 'Alien Species Invasion',which is one of the major causes of biodiversity loss. When alien species are introduced unintentionally or deliberately for whatever purpose,some of them turn invasive and cause decline or extinction of indigenous species.

(C) The most dramatic example of habitat loss is the destruction of tropical rain forests. Originally,these forests covered as much as $14\%$ of the Earth's land surface,but now they cover no more than $6\%$. They are being destroyed fast,particularly for agricultural purposes like converting them into grasslands for raising beef cattle or for cultivation of crops like soybean. This rapid deforestation leads to a massive loss of biodiversity.

(A) The extinction of species due to over-exploitation by humans is a major cause of biodiversity loss.
$1$. The $Dodo$ bird, $Steller's$ sea cow, and $Passenger$ pigeon are classic examples of species that went extinct primarily due to over-exploitation by humans.
$2$. $Dinosaurs$ went extinct approximately $65$ million years ago due to natural causes (likely a massive asteroid impact and subsequent climate change), long before the evolution of modern humans.
Therefore, $Dinosaurs$ are not an example of extinction caused by human over-exploitation.

(C) The 'Evil Quartet' is a term used to describe the four major causes of biodiversity loss as identified by ecologists. These four causes are:
$1$. Habitat loss and fragmentation
$2$. Over-exploitation
$3$. Alien species invasions
$4$. Co-extinctions
Endemism refers to species being unique to a defined geographic location and is not a cause of biodiversity loss; therefore,it is not part of the 'Evil Quartet'.

(C) Biodiversity loss can be caused by both natural and anthropogenic (human-made) factors.
$A$,$B$,and $D$ (Volcanic eruption,Forest fires,and Earthquakes) are natural phenomena that can lead to the destruction of habitats and loss of biodiversity.
$C$ (Reclamation) refers to the process of creating new land from oceans,riverbeds,or lake beds,which is an anthropogenic activity.
Therefore,reclamation is the exception as it is a man-made cause.

(D) Biodiversity loss can be caused by both natural and anthropogenic (human-induced) factors.
Natural causes include events like $A$ (Volcanic eruptions),$B$ (Forest fires),and $C$ (Earthquakes),which occur independently of human activity.
$D$ (Human settlement) is an anthropogenic factor,as it involves habitat destruction,fragmentation,and resource exploitation driven by human expansion. Therefore,it is not a natural reason for the loss of biodiversity.

(C) The correct answer is $C$. Steller's sea cow $(Hydrodamalis \, gigas)$ became extinct in the $18^{th}$ century, primarily due to overexploitation by humans for its meat and oil. While the Dodo $(Raphus \, cucullatus)$ and Thylacine $(Thylacinus \, cynocephalus)$ also went extinct due to human activities, the Steller's sea cow is the classic textbook example cited for extinction specifically driven by overexploitation.

(D) The Amazon rain forest,often referred to as the 'lungs of the planet',is being extensively cut and cleared for agricultural purposes.
Specifically,large areas are being converted into fields for the cultivation of $Soybean$ and for creating grasslands for cattle ranching.
This deforestation poses a significant threat to global biodiversity.

(D) Steller's Sea Cow (Hydrodamalis gigas) was a large marine mammal that was hunted to extinction in the $18^{th}$ century. It was found in the Bering Sea near Russia.
$A$. Dodo was from Mauritius.
$B$. Quagga was from Africa.
$C$. Thylacine was from Australia.
Therefore,the correct option is $D$.

(D) $Clarias \text{ } gariepinus$ (African catfish) is an invasive species introduced illegally for aquaculture purposes in India. It is harmful to indigenous catfish species because it competes with them for food and habitat, and it is also predatory in nature, leading to a decline in the population of native catfish.

(A) The Amazon rain forest,often referred to as the '$Lungs$ of the planet',is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle. This large-scale deforestation is the primary cause of biodiversity loss in this region,which is categorized as habitat loss and fragmentation.

(C) The Steller's sea cow $(Hydrodamalis \text{ gigas})$ was a large marine mammal that became extinct in the $18^{th}$ century. The primary reason for its extinction was over-exploitation by humans for its meat, fat, and skin. Within less than $30$ years of its discovery by Europeans, the species was hunted to extinction. Therefore, the correct option is $C$.

(C) Statement $(A)$ is correct because the Caspian tiger $(Panthera \text{ tigris virgata})$ is indeed one of the recently extinct subspecies of tigers.
Reason $(R)$ is incorrect because the colonization of tropical Pacific islands by humans is associated with the extinction of the Dodo (from Mauritius) and other island species, not the Caspian tiger, which inhabited regions around the Caspian Sea.