DP Biology (last assessment 2024)

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Question 18M.3.HL.TZ2.a

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Date May 2018 Marks available [Maximum mark: 1] Reference code 18M.3.HL.TZ2.a
Level HL Paper 3 Time zone TZ2
Command term State Question number a Adapted from N/A
a.
[Maximum mark: 1]
18M.3.HL.TZ2.a

An organism’s diminished response to a repeated stimulus is referred to as habituation. The diagrams show the experiments performed on habituation to a stimulus in a sea slug (Aplysia californica). The sea slug is a mollusc that has an external gill for gas exchange. If the siphon of the sea slug is stimulated mechanically, it withdraws the gill in a simple reflex action.

State the effector in this reflex arc. 

[1]

Markscheme

muscle «that retracts gill»

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