Question 19N.3.SL.TZ0.14a
| Date | November 2019 | Marks available | [Maximum mark: 3] | Reference code | 19N.3.SL.TZ0.14a |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | a | Adapted from | N/A |
Blue fin tuna (Thunnus orientalis) are top carnivores in the marine ecosystem. Some radioisotopes of elements are produced by nuclear reactors. Following a nuclear accident at Fukushima in Japan in March 2011, the levels of certain radioisotopes were measured in the bodies of blue fin tuna caught off California in August 2011, the other side of the Pacific Ocean from Japan. The becquerel (Bq) is a measure of radioactivity.
[Source: reproduced from Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California
Daniel J. Madigan, Zofi a Baumann, and Nicholas S. Fisher PNAS June 12, 2012 109 (24) 9483–9486]
Explain how the levels of the Caesium (Cs) radioisotopes could have accumulated in the tissues of these fish.
[3]
a. radioisotopes entered the sea/found in the water «in Japan» ✔
b. taken up by producers/phytoplankton/enter gills of fish ✔
c. producers eaten by consumers/fish ✔
d. «radioisotopes» are passed on up the food chain
OR
contaminated fish are eaten by tuna /other fish ✔
e. radioisotopes are not easily excreted ✔
f. at each level there is bioaccumulation/biomagnification ✔
