Which characteristic is associated with Phylum Chordata in the source material?

Which characteristic is associated with Phylum Chordata in the source material?

• A. Invertebrates lacking a notochord.
• B. Vertebrates without an endoskeleton.
• C. Notochord is absent in all chordates.
• D. Vertebrates with an endoskeleton and two body cavities.

Answer: (D)

In chordates, a common theme is the progression from body support structures like a notochord to an internal skeleton in the vertebrate lineage. Vertebrates develop an endoskeleton—an internal framework that supports the body and allows for greater size and complexity. The idea of having two main body cavities fits with the typical vertebrate body plan, where the body is organized into distinct internal spaces (such as the thoracic and abdominopelvic cavities) within a closed coelom. This makes the statement describing vertebrates with an endoskeleton and two body cavities the best match for the group being discussed. The other options conflict with what chordates and especially vertebrates possess: chordates have at least some life stage with a notochord, so saying there is no notochord is incorrect; vertebrates do have an endoskeleton, so claiming no endoskeleton for vertebrates is incorrect; and saying chordates are invertebrates lacking a notochord contradicts the defining chordate features.

In chordates, a common theme is the progression from body support structures like a notochord to an internal skeleton in the vertebrate lineage. Vertebrates develop an endoskeleton—an internal framework that supports the body and allows for greater size and complexity. The idea of having two main body cavities fits with the typical vertebrate body plan, where the body is organized into distinct internal spaces (such as the thoracic and abdominopelvic cavities) within a closed coelom.

This makes the statement describing vertebrates with an endoskeleton and two body cavities the best match for the group being discussed. The other options conflict with what chordates and especially vertebrates possess: chordates have at least some life stage with a notochord, so saying there is no notochord is incorrect; vertebrates do have an endoskeleton, so claiming no endoskeleton for vertebrates is incorrect; and saying chordates are invertebrates lacking a notochord contradicts the defining chordate features.