Self-study
Some killer whales eat fish exclusively, but others also eat seals. █████████ ██████ ██ ██████ ██████ █████████ ██ ████████ █████████ ███ ███ ████████ ██ ███████████ ██████ ██████ ███ ████████████ █████████ ████ █████ ██ ██████ ██████ ████ ██ ███ ███ ██████ ██████ █████ ███ █████ ███████ ██ ███████████ ███████ █████████ ████████████ ████████ ██ █████ ███████████ ██████ ███████ ██████ ██████████ ███████████ ████ █████ ██████ █████ █████ ████ ██ ████████ ██ ███ ██████ ██████ ███ ████ █████ ██ ██████ █████ ████ ██ ███ ███ ██████
Summarize Argument: Phenomenon-Hypothesis
The marine biologists hypothesize that young harbor seals start by avoiding all killer whales, but eventually learn which killer whales eat only fish. Why? Because seal-eating and fish-eating killer whales make chattering noises that sound different from each other, and harbor seals use that difference to tell which killer whales are dangerous.
Notable Assumptions
The marine biologists assume harbor seals avoid seal-eating killer whales because they learn to identify the fish-eating killer whales, and not for any other reason. This means assuming the reverse dynamic—that young seals start with no aversion to killer whales, but acquire an aversion to seal-eating whales—doesn’t happen. It also means assuming the ability to identify seal-eating whales is learned, not purely genetic.
18.
Which one of the following, ██ █████ ████████ ███ █████████ ███████ ███ ███ ███████████ ███████████
a
Killer whales that ███ █████ ████ ███ █████ ██████ ███████ ████ ███ ███████ ██ ████ ██ ██████
This doesn’t affect the argument. It’s equally compatible with the leading alternative hypothesis: that young seals start with no aversion to killer whales, but acquire an aversion to seal-eating whales by observing them eat mammals similar to their own size.
b
Unlike harbor seals, █████ ███ ████ ████████████ ███████ ████ ██ █████ ██████████ ████ ████ ██████ ████ ████ ████████ ████ █████ ██ █████
This is irrelevant. There’s no indication harbor seals use the behavior of fish to distinguish between seal-eating and fish-eating killer whales.
c
When mature harbor █████ █████ ██████ ██ ███ ████████ ███████ ██ ██████ ██████ ████ ███ ████ ████ ███ █████ ███████ ██ ███████████ ███ █████ ███████ ████ ████ ████ ███ ██████
This strengthens the marine biologists’ hypothesis that young seals start with an aversion to all killer whales. It casts doubt on the leading alternative hypothesis: that young seals start with no aversion to killer whales, but learn to be afraid of the seal-eating ones.
Plausibility
Plausibility
Presenting evidence that corroborates (in Strengthen) or conflicts (in Weaken) with the author's hypothesized explanation or the predictions that follow from that explanation.
d
Young harbor seals ████ ██ ███████ ████████ ██ ███ ████ █████████ █████ ████ ██████ ███████
If anything, this makes the leading alternative hypothesis more likely. Since it means young seals start with no aversion to other predator species, it suggests the marine biologists’ hypothesis—that young seals start with an aversion to killer whales—would be an anomaly.
e
If a fish-eating ██████ █████ ██████████ ███████ █ ██████ █████ ████ █████ ██ ██ █████████ ████ ████████████ █████ ███ ██████ ██████ ████ ███████ ██ ███ ██████████ ████████ ███ █████ ██████ █████ ████ ████
If anything, this makes the leading alternative hypothesis more likely. It implies harbor seals at least sometimes learn to pick out the chattering of dangerous killer whales and acquire an aversion to those whales.