Which of the following is not a characteristic of all...

Which of the following is not a characteristic of all chordates?
a. notochord and postanal tail
b. segmental body wall and tail muscles
c. segmented nervous system
d. dorsal hollow nerve cord
e. perforated pharynx

Key Concepts

Pharyngeal Slits

Pharyngeal slits, which are perforations in the pharynx, are one of the major chordate characteristics. In aquatic chordates, these structures can develop into gill slits for respiration, while in others they serve different functions or undergo modification.

Dorsal Hollow Nerve Cord

A hallmark of chordates, the dorsal hollow nerve cord forms the central nervous system. Unlike in many segmented animals where the nervous system is divided, chordates possess a single, continuous nerve cord that becomes the brain and spinal cord.

Body Segmentation

Segmentation in chordates is typically observed in the repeated muscle blocks along the body, which facilitate coordinated movement. However, the nervous system in chordates is not organized into segments, distinguishing it from the segmented musculature.

Chordate Body Plan

The chordate body plan encompasses a set of fundamental features present in all members of the phylum, including the notochord, dorsal hollow nerve cord, pharyngeal slits, and a postanal tail. These features establish the blueprint for chordate development and evolution, though not every structure is segmented.

Notochord

The notochord is a defining, flexible rod-like structure that provides skeletal support during development. It is a key feature of chordates, offering structural stability and playing an inductive role in the development of surrounding tissues.

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