Question

What is the single greatest threat to biodiversity?

(A) overharvesting of commercially important species

(B) habitat alteration, fragmentation, and destruction

(C) introduced species that compete with native species

(D) novel pathogens

Short answer

1. The option “overharvesting of commercially important species” is false.
2. The option “habitat alteration, fragmentation, and destruction” is true.
3. The option “introduced species that compete with native species” is false.
4. The option “novel pathogens” is false.

Step-by-step solution

Biodiversity

Biodiversity refers to the variety of life forms on the planet.It refers to the different organisms distinguished through variations in morphology, genes, character, species, and ecosystems.

Explanation of option ‘(A)’

Overharvesting causes depletion of species and can even lead to its extinction. As a result, it is capable of lowering biodiversity.

Thus, overharvesting can affect biodiversity but is not the greatest threat to biodiversity.

Therefore, the given statement is false.

Explanation of option ‘(B)’

All the three processes such as habitat alteration, fragmentation, and destruction lead to the loss of habitat for various life forms on Earth. Organisms cannot bear habitat loss.

Such a loss affects several species in an area and can lead to mass extinction.

Thus, habitat alteration, fragmentation, and destruction affect various species and pose the greatest biodiversity threat.

Therefore, the given statement is true.

Explanation of option ‘(C)’

Alien species introduced in a habitat that usually competes with the native habitants are known as exotic species. Such species occupy and conquer the new habitat, deplete the nutrition, and set new ecological conditions.

These conditions threaten the native species and can lower biodiversity.

Thus, exotic species can lower biodiversity but are not the most significant threat.

Therefore, the given statement is false.

Explanation of option ‘(D)’

Novel pathogens can cause disease in organisms. Most of them can withstand pathogenic conditions, resist and survive, while some cannot. Such pathogens can affect biodiversity to some extent.

Thus, novel pathogens can affect biodiversity but are not the most significant threat.

Therefore, the given statement is false.