Causes of Biodiversity Losses Questions in English

(B) $Parthenium$ or carrot grass was introduced into India as a contaminant with imported wheat. It has since spread throughout the country and is now ubiquitous. Its pollen grains are a well-known cause of respiratory allergies in humans.

(D) is the incorrect match.
Steller's Sea Cow ($Hydrodamalis$ $gigas$) became extinct from the Commander Islands in Russia (Bering Sea) due to overexploitation by humans within $27$ years of its discovery in $1741$.
It was not native to North America.

(D) The correct answer is $D$.
Habitat destruction,defined as the elimination or alteration of the conditions necessary for animals and plants to survive,is the primary cause of species extinction and endangerment.
It not only impacts individual species but also the overall health of the global ecosystem.
Habitats are destroyed or fragmented by various human activities such as industrial development,deforestation,and pollution.
While over-hunting and poaching also have harmful effects,habitat loss remains the most significant threat to biodiversity.

(A) The correct answer is $A$.
The introduction of high-yielding varieties (HYVs) is considered the greatest threat to genetic diversity in agricultural crops.
This is because the widespread adoption of a few genetically uniform high-yielding varieties often leads to the replacement and loss of traditional,locally adapted,and diverse crop varieties (landraces).
This process,known as genetic erosion,significantly reduces the overall genetic diversity within the agricultural ecosystem.
While the extensive use of fertilizers,insecticides,and pesticides can negatively impact soil health and local ecosystems,the replacement of diverse germplasm with uniform HYVs has a more direct and irreversible impact on genetic diversity.

(D) habitat destruction.
Habitat destruction is the primary threat to most endangered species,as it leads to the loss of living spaces and essential resources.
While over-hunting,acid rain,and competition with introduced species are significant threats,habitat destruction is recognized as the most widespread and critical issue causing the decline of biodiversity globally.

(A) The correct matches are as follows:
$(i)$ Dodo is from Mauritius $(i-q)$.
$(ii)$ Quagga is from Africa $(ii-p)$.
$(iii)$ Thylacine is from Australia $(iii-s)$.
$(iv)$ Steller's sea cow is from Russia $(iv-r)$.
Therefore,the correct sequence is $(i-q), (ii-p), (iii-s), (iv-r)$.

(B) The sixth mass extinction is primarily driven by human activities.
Its rate is estimated to be $100$ to $1000$ times faster than the natural background rate observed in pre-human times.
Therefore,option $(2)$ is the correct answer.

(C) The term "The Evil Quartet" is used to describe the four major causes of biodiversity loss:
$1$. 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.
Therefore,option $(3)$ correctly lists all four components.