Home / IB DP Biology- A4.2 Conservation of biodiversity – IB Style Questions For SL Paper 1A

IB DP Biology- A4.2 Conservation of biodiversity - IB Style Questions For SL Paper 1A -FA 2025

IBDP Biology Paper 1 - All Chapters

Question

The North Island giant moa (Dinornis novaezelandiae) became extinct sometime between the arrival of humans in New Zealand and the early 19th century.

What is considered by scientists to be the most likely reason for this extinction?

A. Deforestation
B. New diseases
C. Competition with other megafauna
D. Overhunting

▶️ Answer/Explanation
Evidence suggests that the North Island giant moa was hunted extensively by early human settlers in New Zealand. The species’ large size and inability to fly made it an easy target. This intense human predation led to a rapid decline in population, ultimately resulting in overhunting-driven extinction.
✅ Answer: (D) Overhunting

Question

Tidal marshland A, which is adjacent to the San Francisco airport, has a Simpson’s Diversity Index of 0.65. Tidal marshland B, which is two miles from the airport, has a Simpson’s Diversity Index of 0.80. An oil spill occurs at a location at the halfway point between the two marshlands.

If both marshlands are equally contaminated by the oil spill, which marshland is more likely to recover from the oil spill?

(A) Tidal marshland A is more likely to recover, because its lower Simpson’s Diversity Index means that few species will be affected.
(B) Tidal marshland B is more likely to recover, because its higher Simpson’s Diversity Index means it has a wider variety of species and can better absorb the effects of a disturbance.
(C) Both ecosystems will be equally affected, because they are the same distance from the oil spill.
(D) Neither ecosystem will be able to recover, because oil is toxic to all organisms.

▶️ Answer/Explanation

Answer: (B) Tidal marshland B is more likely to recover, because its higher Simpson’s Diversity Index means it has a wider variety of species and can better absorb the effects of a disturbance.

Explanation:
Simpson’s Diversity Index measures biodiversity—the variety and abundance of species in an ecosystem. A higher value (closer to 1) indicates greater diversity. Ecosystems with higher biodiversity are generally more resilient and can recover faster from environmental disturbances such as oil spills, since a wider variety of species ensures that some can adapt or fill lost ecological roles.

Evaluation of Each Option:
(A) Incorrect — A lower diversity index means fewer species, which makes the ecosystem less resilient, not more.
(B) Correct — A higher diversity index means more species diversity, allowing the ecosystem to better resist and recover from damage.
(C) Incorrect — Equal distance from the spill does not determine recovery potential; biodiversity is the key factor.
(D) Incorrect — While oil is harmful, ecosystems with high diversity can recover over time.

Question

The Nile perch is a species of fish that was introduced into Lake Victoria in the 1950s. It has caused the extinction or near-extinction of several hundred native species in the lake. Which of the following is an accurate statement regarding the introduction of the perch to Lake Victoria?

(A) Eutrophication of a lake can decrease its carrying capacity.
(B) Humans can negatively impact the balance of an ecosystem.
(C) The Nile perch is a successful predator.
(D) The diversity in Lake Victoria is likely to increase because most extinction events are followed by a large increase in diversification.

▶️ Answer/Explanation

Answer: (B) Humans can negatively impact the balance of an ecosystem.

Explanation:
The introduction of a non-native species, such as the Nile perch, can disrupt ecosystems by preying on or outcompeting native species. This has led to the extinction of hundreds of species in Lake Victoria, showing how human intervention can severely affect biodiversity and ecological balance.

Option Analysis:
A. Incorrect — Eutrophication affects nutrient and oxygen levels but is unrelated to the introduction of Nile perch.
B. Correct — The Nile perch was introduced by humans, demonstrating that human activity can disturb ecosystem equilibrium and cause species extinction.
C. Incorrect — While true that Nile perch is a powerful predator, this option misses the focus on human-caused ecological imbalance.
D. Incorrect — Extinction events typically reduce biodiversity; diversification following extinction occurs over much longer evolutionary timescales.

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