Which option lists all four shared chordate traits?

Which option lists all four shared chordate traits?

• A. Dorsal hollow nerve cord; notochord; pharyngeal gill slits; muscular post-anal tail
• B. Dorsal hollow nerve end; notochord; pharyngeal gill slits; muscular post-anal tail
• C. Dorsal nerve cord; spinal cord; pharyngeal arches; tail
• D. Dorsal hollow nerve cord; notochord; gill slits; muscular tail

Answer: (A)

Chordates are defined by four traits that appear at some stage in their development: a dorsal hollow nerve cord, a notochord, pharyngeal gill slits, and a muscular post-anal tail. The dorsal hollow nerve cord runs along the back and develops into the central nervous system. The notochord is a flexible rod that provides support along the body axis, often replaced by the vertebral column in many vertebrates. Pharyngeal gill slits are openings in the pharynx used for filter feeding or gas exchange in aquatic relatives, and can take on other roles in different lineages. The muscular post-anal tail extends past the anus and aids in propulsion. The option that lists these four features exactly matches this canonical set, making it the best choice. The other options use an incorrect term for the nerve cord, replace it with a non-hollow or later-formed structure, substitute pharyngeal arches in place of gill slits, or omit the precise pharyngeal descriptor, which means they don’t accurately reflect the four shared chordate traits.

Chordates are defined by four traits that appear at some stage in their development: a dorsal hollow nerve cord, a notochord, pharyngeal gill slits, and a muscular post-anal tail. The dorsal hollow nerve cord runs along the back and develops into the central nervous system. The notochord is a flexible rod that provides support along the body axis, often replaced by the vertebral column in many vertebrates. Pharyngeal gill slits are openings in the pharynx used for filter feeding or gas exchange in aquatic relatives, and can take on other roles in different lineages. The muscular post-anal tail extends past the anus and aids in propulsion.

The option that lists these four features exactly matches this canonical set, making it the best choice. The other options use an incorrect term for the nerve cord, replace it with a non-hollow or later-formed structure, substitute pharyngeal arches in place of gill slits, or omit the precise pharyngeal descriptor, which means they don’t accurately reflect the four shared chordate traits.