IB Biology HL C4.1.13 Endemic Vs Invasive Species Questions

Analyse distribution maps, population data and named case studies to explain invasive-species establishment, impacts on endemic species and control trade-offs in IB Biology HL C4.1.13.

Exam points

Define endemic and invasive alien species, distinguishing a species native to a restricted area from one introduced beyond its natural range.
Analyse how invasive species establish and alter endemic or native populations through competition, predation, food-web disruption, rapid growth or missing limiting factors.
Evaluate invasive-species control or management using named ecological evidence, including biological-control benefits, unintended effects and evidence from population or distribution data.

[Maximum number: 2]

The prickly pear cactus (Opuntia stricta) was first recorded in Kruger National Park, South Africa, in 1950 . It spread rapidly, mainly through seeds being dispersed by baboons and elephants.

In 1997, the cactus moth (Cactoblastis cactorum) from South America was introduced into the area as a biological control. The larvae of the moth feed on the cactus. The graph shows the number of cladodes (flattened stem sections) of cactus found per $\mathrm{m}^{2}$ in the years before and after the introduction of the cactus moth.

Figure for Question IB Biology HL C4.1.13 Endemic Vs Invasive Species Questions question 1 — IB Biology HL

Outline how the prickly pear cactus may become an ecological problem in Kruger National Park.

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a	they can become an invasive species because they lack predators OR uncontrolled population growth due to lack of predators;
b	compete with local/endemic species for nutrients/habitat;
c	may cause (endemic) species to become extinct/reduction in numbers;

IB Biology HL C4.1.13 Endemic Vs Invasive Species Questions question 1