Self-study
P1
Scientists have long known that the soft surface of the bill of the platypus is perforated with openings that contain sensitive nerve endings. ████ █████████ ████████ ████ ██████████ █████████ ██ ███ █████ ██ ███ ████████ ████ ███ ██████ ████ ███ ████ ██ ██████ ███ ████ █████ ███████████ █ ██████████ █████████ ██ ███ ████ ████ ███ ████████ █████ █████ ███ ████████ ███ ██████ ████ ██ ██ ██████████ ███
Biologists' conclusion ·
Platypus uses its bill to locate prey underwater
We've known for a long time that the bill has nerve endings. Now biologists think those nerves on the bill are used for finding prey underwater.
New evidence supporting conclusion ·
Neurophysiological studies
Studies reveal two sensory receptors in pores on platypus bills: mechanoreceptors (respond to physical pressure), and electroreceptors (respond to electrical fields).
Bohringer's conclusion ·
Bill is the primary sensory organ for the platypus
This was supported by studies showing the bill is sensitive to touch.
Puzzle ·
How does platypus locate prey at a distance?
If a platypus isn't touching its prey with its bill, how can it find the prey? (Probably has to do with the electroreceptos, since we discussed the mechanoreceptors earlier.)
P2
█████████ ██████████████████ ███████ ██████████ ██ ███████ ████ ████████ ███ ███████ ████ ██████ ████ ████ █ ████████ ██████ ██ █████ ██████ ████████ ███████ ███ ████ ████ ████ ██ ████ █████ ████ ██ ████████████ ██ █████████ ████████ ██ █████████ █████████ █████████████ ██ ███████ █████████ ██ ███ ████ ████ █ █████ ████ ██ ███ ██████ ██ █ ████ ██ ██████ █████ ██ ████████ ██ ██████ ██ ██ ███ ██████ ███ ███████ ███ ███
Set-up for Scheich's hypothesis ·
Platypus hunts by steadily wagging bill, then moving bill erratically after prey it finds prey
The erratic movements are called "searching behavior."
Scheich's hypothesis ·
Platypus distinguishes prey from non-prey by detecting electric fields
Scheich's experiment ·
Confirms platypus can detect electric fields
Platypus switches to searching behavior when it encounters electric field from battery. Then platypus attacked the battery like it was food.
Scheich's speculation ·
All invertebrates that platypus eats produce electric fields
We already know that shrimp prey of platypus produces an electric field.
Passage Style
Phenomenon-hypothesis (RC)
Single position
16.
The primary purpose of the ███████ ██ ██
a
explain how the ████████ ███████ ████ ██ █ ████████
How the platypus locates prey at a distance is the subject of P2. But P2 is part of the support for the biologists’ conclusion at the beginning.
b
present some recent ██████████ ████████ ██ ███ ████████ ██ ███ ██████████ ████
This best captures the primary purpose. The author presents recent research on the purpose of the platypus’s bill. This research is described in P1 and P2 and supports the claim that the platypus uses its bill to locate prey underwater.
c
assess the results ██ ███████████ ████████████ ████ █████ ███ ████████
Bohringer’s work is just some of the research presented in this passage, and it’s not any more important than Scheich’s research discussed later. So it wouldn’t make sense for (C) to be the primary purpose. Also, the author doesn’t “assess” the results of Bohringer’s work; rather, she merely reports on the results.
d
present Scheich's contributions ██ ██████████ ████ █████ ███ ████████
Scheich’s work is just some of the research presented in this passage, and it’s not more important than Bohringer’s work discussed earlier. So it wouldn’t make sense for (D) to be the primary purpose.
e
describe two different █████ ██ █████ ██ ███ ██████████ ████
This is too narrow. Although the author does describe two different kinds of receptors within pores, the author focuses on the function of those receptors and how they relate to how the platypus uses its bill.