Loss of Biodiversity Questions in English

(B) According to the $IUCN$ Red List $(2004)$ documents,the total number of species that have become extinct is $784$.
This includes $338$ vertebrates,$359$ invertebrates,and $87$ plants.

(C) The $Dodo$ (Mauritius), $Quagga$ (Africa), and $Thylacine$ (Australia) are examples of species that have gone extinct in relatively recent times due to human activities.
In contrast, $Dinosaurs$ went extinct approximately $65$ million years ago during the $Cretaceous-Paleogene$ extinction event, which is considered a mass extinction event in geological history, not a recent one.

(A) According to the $IUCN$ Red List $(2004)$,the total number of species that have gone extinct in the last $500$ years is $784$.
This total includes $338$ vertebrates,$359$ invertebrates,and $87$ plants.
Therefore,the number of vertebrate species that went extinct is $338$.

(D) According to the $IUCN$ Red List $(2004)$ data provided in the $NCERT$ textbook,the threat of extinction is distributed across various taxa. Specifically,$31\%$ of gymnosperm species are currently facing the threat of extinction. Therefore,the correct option is $D$.

(B) Biodiversity is the result of millions of years of evolution.
However,due to various anthropogenic activities,this biodiversity is being lost at an alarming rate.
If the current rate of species loss continues,we may lose a significant portion of our biodiversity in less than $200$ years.
Since the loss of biodiversity affects the global ecosystem,climate,and food security,its conservation is considered a critical international environmental issue.

(N/A) Since the origin and diversification of life on Earth $3$ billion years ago,there have been five episodes of mass extinction of species.
The current rate of species extinction is estimated to be $100$ to $1000$ times faster than the natural rate. If this rate of extinction continues,it is estimated that nearly half of all species on Earth might be wiped out within the next $100$ years.
The loss of biodiversity leads to:
$(a)$ $A$ decline in plant production.
$(b)$ Lowered resistance to environmental perturbations such as drought.
$(c)$ Increased variability in certain ecosystem processes such as plant productivity,water use,and pest and disease cycles.

(B) The 'Red' in the $IUCN$ Red List $(2004)$ indicates species that are threatened with extinction. It serves as a critical indicator for conservation efforts to identify and protect organisms that are at risk of disappearing from the wild.

(N/A) The biological wealth of the Earth is declining rapidly,and human activities are the major reasons for it. For example,the colonization of tropical Pacific Islands by humans has led to the extinction of more than $2,000$ native bird species.
The International Union for Conservation of Nature and Natural Resources $[IUCN]$ was founded in $1948$ and is headquartered in Switzerland. It works in the field of nature conservation and the sustainable use of natural resources.
The $IUCN$ Red List of Threatened Species is an inventory of the global conservation status of biological species,compiled in the Red Data Book,which was initiated in $1964$.
Some examples of recent extinctions include:
$(i)$ Dodo (Mauritius),Quagga (Africa),Thylacine (Australia),Steller's Sea Cow (Russia),and three subspecies of tiger (Bali,Javan,and Caspian).
$(ii)$ About $27$ species have disappeared in the last $20$ years globally. More than $15,500$ species are currently endangered. Presently,$12\%$ of all bird species,$23\%$ of all mammal species,$32\%$ of all amphibian species,and $31\%$ of all gymnosperms face an extinction threat,with amphibians appearing most vulnerable.
$(iii)$ The $2012$ Red List contains $132$ plant and animal species from India. Some endangered species include the Asiatic lion,Bengal tiger,Lion-tailed macaque,Nilgiri langur,and Ganges river dolphin.
Fossil records reveal that large-scale loss of species occurred even before humans appeared. There have been five episodes of mass extinction over the last $3$ billion years due to natural calamities (e.g.,extinction of dinosaurs). Currently,the Earth is heading towards the sixth extinction,which differs from previous episodes in its rate. Current extinction rates are estimated to be $100$ to $1,000$ times faster than pre-human times,driven by human activities. If this continues,$50\%$ of species might be wiped out within the next $100$ years.
Effects of loss of biodiversity include:
$(i)$ Decline in plant production.
$(ii)$ Lower resistance to environmental perturbations such as drought.
$(iii)$ Increased variability in ecosystem processes such as plant productivity,water use,and pest and disease cycles.

(C) According to the $IUCN$ Red List $(2004)$ documents,the extinction of $784$ species (including $338$ vertebrates,$359$ invertebrates,and $87$ plants) has been recorded in the last $500$ years. Therefore,the correct option is $C$.

(D) The loss of biodiversity in a region may lead to the extinction of species. According to the $NCERT$ textbook,the recent extinctions include:
$i)$ Dodo (Mauritius)
$ii)$ Thylacine (Australia)
$iii)$ Steller's sea cow (Russia)
$iv)$ Quagga (Africa)
$v)$ Javan (Indonesia)
All these species have become extinct in the recent past due to human activities. Therefore,the correct option is $D$.

(D) David Tilman's long-term ecosystem experiments using outdoor plots showed that increased diversity contributed to higher productivity. Loss of biodiversity in a region leads to:
$1$. $A$ decline in plant production.
$2$. Increased variability in certain ecosystem processes such as plant productivity,water use,and pest and disease cycles.
$3$. Increased susceptibility to environmental disturbances like drought.
Biodiversity loss does not lead to increased resistance to pests; rather,it makes the ecosystem more vulnerable to pest outbreaks. Therefore,option $D$ is the correct answer.

(B) According to the $IUCN$ Red List $(2004)$, a total of $784$ species have gone extinct in the last $500 \; \text{years}$.
This total includes $338$ vertebrates, $359$ invertebrates, and $87$ plants.

(C) Gene pool is the total aggregate of genes in a population at any one time. If any species (e.g.,Bengal tiger) becomes extinct,its gene pool will be lost forever.

(D) Loss of biodiversity has significant negative impacts on ecosystem stability.
$I$. Lowered resistance to environmental perturbations is a direct consequence of reduced species richness.
$II$. $A$ decrease in plant production is observed as biodiversity loss disrupts ecosystem functions.
$III$. Increased variability in ecosystem processes (such as water use,pest/disease cycles,and plant productivity) occurs because the ecosystem becomes less stable and resilient.
$IV$. An increase in plant production is incorrect,as biodiversity loss generally leads to a decline in ecosystem productivity.
Therefore,statements $I$,$II$,and $III$ are correct consequences of biodiversity loss.

(A) According to the $NCERT$ textbook,the colonisation of tropical Pacific islands by humans has led to the extinction of more than $2000$ species of native birds.

(B) According to the $IUCN$ Red List $(2004)$,the total number of species documented as extinct in the last $500$ years is $784$.
Therefore,$A = 784$ and $B = 500$.
This corresponds to option $B$.

(D) According to David Tilman's long-term ecosystem experiments,increased biodiversity contributes to higher productivity and stability in an ecosystem.
Conversely,the loss of biodiversity leads to:
$1$. $A$ decline in plant production.
$2$. Lowered resistance to environmental perturbations such as drought.
$3$. Increased variability in certain ecosystem processes like plant productivity,water use,and pest/disease cycles.
Endemism refers to species being unique to a defined geographic location. Loss of biodiversity involves the extinction or reduction of species,which decreases the number of unique species,thus it does not lead to increased endemism.

(C) According to the $IUCN$ Red List $(2004)$,the current statistics regarding the threat of extinction for various groups are as follows:
$23\%$ of all mammal species are threatened with extinction.
$31\%$ of all gymnosperm species are threatened with extinction.
Therefore,$A = 23$ and $B = 31$.

(C) According to the $IUCN$ Red List criteria,a taxon is considered 'Critically Endangered' when it is facing an extremely high risk of extinction in the immediate future.

(B) According to the $IUCN$ Red List $(2004)$,the last $20$ years have witnessed the disappearance of $27$ species. This data highlights the alarming rate of biodiversity loss due to human activities and environmental changes.

(C) Throughout the history of life on Earth,there have been $5$ major mass extinction events. These events are characterized by a significant and rapid decrease in the biodiversity on Earth. The $5$ major extinctions are the Ordovician-Silurian,Late Devonian,Permian-Triassic,Triassic-Jurassic,and Cretaceous-Paleogene extinction events. Currently,scientists suggest we are entering a $6$th mass extinction,often referred to as the Anthropocene extinction,driven primarily by human activities.

(B) According to the $NCERT$ textbook,the current rate of species extinction is estimated to be $100$ to $1000$ times faster than the pre-human extinction rate. This rapid loss is primarily attributed to human activities such as habitat destruction,over-exploitation,and pollution.

(D) According to the $IUCN$ Red List and ecological studies on biodiversity loss,it is estimated that if the current rate of species extinction continues,approximately $50 \%$ of all species on Earth could become extinct within the next $100$ years. This is primarily due to human activities such as habitat destruction,pollution,and climate change.

(C) The current loss of biodiversity is often referred to as the $6^{th}$ extinction (the question text mentioned $7^{th}$,which is a common misconception; it is scientifically recognized as the $6^{th}$ mass extinction).
Unlike the previous five mass extinctions which were caused by natural phenomena,the current extinction is primarily driven by human activities.
$A$ key difference is the speed at which this process is occurring.
While natural extinctions occur over geological time scales,the current rate of species extinction is estimated to be $100$ to $1000$ times faster than the natural background rate.

(D) The correct answer is $D$. The Thylacine (Tasmanian wolf) was an extinct carnivorous marsupial native to Australia,Tasmania,and New Guinea,not Thailand. The other pairs are correct: Dodo was from Mauritius,Steller's Sea Cow from Russia,and Quagga from Africa.