Biodiversity and Conservation (Advanced Level / Expected MCQs)

Correct Answer: (b)
A drastic reduction in population size leads to a 'genetic bottleneck.' In small populations, genetic drift has a much larger effect, leading to a loss of alleles and decreased heterozygosity. This reduced genetic variation makes the population less able to adapt to environmental changes, increasing extinction risk.

Correct Answer: (d)
Invasive predators can decimate native prey populations that have no evolved defenses (top-down cascade). They also compete with native predators for the same food resources and often bring novel pathogens or parasites that native species lack the immunity to survive.

Correct Answer: (a)
A conservation hotspot is a biogeographic region that is both a significant reservoir of biodiversity and is threatened with destruction. To qualify as a hotspot, a region must contain at least 1,500 species of vascular plants as endemics and it has to have lost at least 70% of its primary vegetation.

Correct Answer: (c)
Captive breeding is often a 'last resort' conservation strategy. While it can prevent immediate extinction, it is only effective in the long term if the released individuals have a suitable, protected habitat to return to and if the original threats (like poaching or pollution) are regulated.

Correct Answer: (d)
Fragmentation breaks large, contiguous habitats into smaller, isolated patches. This physically prevents movement (reducing gene flow), exposes more of the habitat to 'edge effects' (like different microclimates or increased predation), and often leaves patches too small to maintain the minimum viable population size for certain species.

Correct Answer: (d)
Island species are uniquely vulnerable. Their evolution in isolation often means they lack defenses against mainland predators. Furthermore, islands have finite resources and space, leading to smaller population sizes that are more susceptible to being wiped out by introduced diseases or competition from invasive species.

Correct Answer: (c)
Indirect ecosystem services, such as water purification, flood control, and carbon sequestration, often provide massive economic benefits. Studies have shown that the long-term value of maintaining a healthy ecosystem often far outweighs the short-term economic gain from converting that land for agriculture or development.

Correct Answer: (d)
While it is true that 99% of all species are extinct, this reflects billions of years of 'background extinction' and five mass extinction events. The current rate of extinction caused by human activity is estimated to be 100 to 1,000 times higher than the natural background rate, meaning the fact that extinction is 'natural' does not mean current rates are normal.

Correct Answer: (d)
The global decline of amphibians is a complex issue driven by multiple interacting factors, including habitat loss, climate change, pollution, UV radiation, and specifically the spread of the chytrid fungus. Because the decline involves more than just local destruction or just climate change, 'None of the choices' is the best summary for these specific options.

Correct Answer: (a)
While the Endangered Species Act focuses on individual species, biological conservation must occur at the ecosystem level. Protecting a species without protecting the habitat it relies on is futile. Successful conservation requires maintaining the functional processes of the entire ecosystem to sustain all its inhabitants.