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Multiple Choice
Which of the following correctly labels the anterior and posterior ends of a polychaete worm (phylum Annelida)?
A
Both ends of a polychaete worm are identical and cannot be distinguished.
B
The anterior end is always the thicker end, regardless of sensory structures.
C
The anterior end is the head region with sensory structures; the posterior end is the tail region.
D
The anterior end is the tail region; the posterior end is the head region with sensory structures.
Verified step by step guidance
1
Understand the anatomy of a polychaete worm: Polychaetes are segmented worms belonging to the phylum Annelida. They have a distinct body plan with a head (anterior end) and a tail (posterior end).
Identify the anterior end: The anterior end of a polychaete worm is the head region, which typically contains sensory structures such as eyes, antennae, or palps. These structures help the worm sense its environment.
Identify the posterior end: The posterior end is the tail region, which does not have sensory structures and is primarily involved in excretion and other functions.
Eliminate incorrect options: Review the provided options and eliminate those that contradict the anatomical features of polychaete worms. For example, the statement that both ends are identical is incorrect because the anterior end has sensory structures, while the posterior end does not.
Select the correct answer: Based on the anatomical features, the correct labeling is that the anterior end is the head region with sensory structures, and the posterior end is the tail region.