Skip to content
← Theoretical B

Q38 - Salinity and Genetic Structure Among Baltic Fish

Theoretical B Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Genetic Drift, Gene Flow & Mutation

The marine transition area between the Bothnian Bay (the northernmost part of the Baltic Sea between Sweden and Finland) and the Eastern Atlantic ocean is characterized by a steep cline in salinity (Fig. B) and it is inhabited by a number of fish species. Studies show genetic differences, measured as FST (Fig.) between two populations, one being the Bothian Bay population, which is considered the reference population. FST = 0 means complete random mating across populations, FST = 1 means no mating between populations.

Figure. A, Bothnian Bay (I), Southern Baltic Sea (II), and North Sea (III); B, changes in genetic variation among populations (FST) of five fish species (blue filled circles = flounder (inset); red filled inverted triangles = herring (inset); open squares, triangles, and circles= three other fish species); C, change in salinity [NaCl] from the Bothnian Bay (I) towards the North Sea (III) (from Limborg et al. 2009).

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Salinity might be important in shaping the genetic structure of marine fish
B. Baltic Sea fish are adapted to local environmental conditions
C. The random mating of Herring is less affected by salinity than is that of the other four species
D. Flounder is less sensitive to changes in salinity than the other four species
← Previous: Q37 Next: Q39 →

Question reproduced from IBO 2015, Theoretical Exam B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)