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← Theoretical 2

Q100 — Cold-Exposure Duration, Acclimation and Mollusc Survival

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Comparative Thermoregulation

One of the modern environmental problems is the spread of invasive alien species, the success of which is due to the adaptive properties of these species. Temperature is one of the most important environmental factors for species. The experiment examined the cold resistance of the Melanoides granifera mollusc, a representative of the tropical fauna, to low temperatures. The molluscs were initially kept at low temperatures for 8 hours or 168 hours, then transferred to 18°C or 20°C conditions for acclimation (Figure 1). The lowest temperature threshold for survival was investigated.

Line graph of survival percentage vs. temperature, with three curves. Curve 1 (8 hours cold exposure, 18°C acclimation) rises from 0% survival at 6°C to 100% by about 9°C. Curve 2 (8 hours cold exposure, 20°C acclimation) is shifted right, reaching 100% survival only around 10°C. Curve 3 (168 hours cold exposure, 20°C acclimation) is shifted much further right, reaching 100% survival only around 16°C. Figure 1. The survival of molluscs Melanoides granifera after acclimation, as a function of the temperature of cold exposure. Curve 1: survival after 8 hours cold exposure and acclimation at 18°C. Curve 2: survival after 8 hours cold exposure and acclimation at 20°C. Curve 3: survival after 168 hours cold exposure and acclimation at 20°C.

Using the information and the figure, indicate whether the following statements are true or false.

A. The survival of Melanoides granifera depends on the acclimation temperature and the duration of initial exposure to low temperatures.
B. Reducing the acclimation temperature by 2°C leads to an increase in the cold resistance of the mollusc.
C. Prolonged exposure to initial low temperatures increases the cold resistance of the mollusc.
D. If the mollusc has a good ability for spreading, it can spread from tropical areas to a temperate zone with temperatures below 10 C and become a successful invasive species.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)