Self-study
Last summer, after a number of people got sick from eating locally caught anchovies, the coastal city of San Martin advised against eating such anchovies. ███ █████████ ████ ██████████ ███████ ████ ██████ █████ █ ███████ ███████████ ████████ █ ████████ ████ ██ ███ ██████████ ██ ██ █████████ ████████ ██ ███████ ████ ██████ ███ █████ ███████ ██████ █████████ ████ ██ ██ ████ █████ ████ ██ ███ ███████ ██████ ██████████
"Surprising" Phenomenon
Why does the decrease in plankton numbers make the anchovies safe to eat?
Objective
The correct answer will establish a relationship between the number of P. australis and the safety of the anchovies. It will imply that fewer plankton means less domoic acid in the anchovies or that a decrease in plankton makes the domoic acid in anchovies safer to consume.
22.
Which one of the following, ██ █████ █████ ████ ████ ██ ███████ ███ ██ ██ ███ ████ ██ ████ ███ █████████
a
P. australis is ███ ██ ███████ █████████ ██ ████████ ██████ ██ ███ ██████ █████ ████ ████████ ██ ██████████ █████ ███ ██████ ██ ███████ █████ ███████ ██ ██████ █████
This states that anchovies will secrete, not contain, domoic acid after ingesting P. australis. It is not implied that anchovies secreting domoic acid must contain that acid, nor that domoic acid in the water builds up in anchovies’ bodies.
b
P. australis naturally ████████ ██████ █████ ██████ █████████ ███████ ██████ ██ ██████ █████ ████ ████ ███ ██████████ ██ ██ █████████ ██ ███████████████ ██████
This explains why a decrease in P. australis numbers makes the anchovies safe. Once the plankton are less prevalent, the domoic acid in anchovies lowers to safe levels.
c
Scientists have used ██ █████████ ████████ ██ ██████ ██████ ████ ██ ███ ███████████
This does not imply that high P. australis numbers cause anchovies to contain domoic acid. It is possible that P. australis does not naturally produce or contain domoic acid, in which case its relationship to the anchovies remains unexplained.
d
A sharp decline ██ ███ ██████████ ██ ██ █████████ ██ █████████ ████████ ██ █ █████████████ ████ ██ ███ █████ ███████ ███████████
This does not explain why locally caught anchovies are safe to eat. It does not imply that the surviving anchovies are in any way safer to consume.
e
P. australis cannot ███████ ██ █████ ███████ ██ ████████ ████ ████ ███ ███████ ███████████ ██████████ ██ ██████ ████ █████ ████ ████████ █████ ██████████
This establishes a condition necessary for the survival of P. australis, but does not imply that a decrease in plankton must accompany a decrease in domoic acid. It is possible the plankton died for a different reason and domoic acid is still prevalent in the water.