Problem 1 - Campbell Biology

Question

Vertebrates and tunicates share (A) jaws adapted for feeding. (B) a high degree of cephalization. (C) an endoskeleton that includes a skull. (D) a notochord and a dorsal, hollow nerve cord.

Step-by-Step Solution

Answer

(D) a notochord and a dorsal, hollow nerve cord

Step 1: Identify the key features

Start by identifying the primary characteristics that vertebrates and tunicates have in common.

Step 2: Analyze vertebrate characteristics

Notice that vertebrates are known for having jaws, a high degree of cephalization, and an endoskeleton including a skull. Verify if these features are also present in tunicates.

Step 3: Analyze tunicate characteristics

Tunicates, also known as urochordates, primarily have a notochord and a dorsal, hollow nerve cord in their larval stage.

Step 4: Compare both groups

Compare the characteristics of vertebrates and tunicates to find the common features. Tunicates do not have jaws adapted for feeding, a high degree of cephalization, or an endoskeleton that includes a skull. However, both share a notochord and a dorsal, hollow nerve cord.

Key Concepts

notochord

The notochord is a key feature shared between vertebrates and tunicates, but it serves different roles in each group. The notochord is a flexible, rod-shaped structure that provides support. It runs along the back of the organism, offering a place for muscles to attach. In vertebrates, the notochord is present during the embryonic stage and later develops into part of the vertebral column (spine). On the other hand, in tunicates, the notochord is only found in the larval stage and does not develop further. This backbone structure is primary to both groups but has different functions depending on the species.

dorsal hollow nerve cord

Another crucial structure found in both vertebrates and tunicates is the dorsal hollow nerve cord. This nerve cord runs along the 'back' or dorsal side of the organism and is hollow inside. In vertebrates, the dorsal hollow nerve cord develops into the central nervous system, which consists of the brain and spinal cord. This system controls the body's functions and responses to the environment. In tunicates, the dorsal hollow nerve cord is also found during the larval stage but is largely lost or transformed as they grow into adults. This nerve cord acts as a significant common thread that highlights the evolutionary link between vertebrates and tunicates.

cephalization

Cephalization refers to the concentration of sensory organs and nerve tissues at the front end (head) of an organism, leading to the formation of a head. In vertebrates, a high degree of cephalization is evident. They have well-developed brains and sensory organs such as eyes, ears, and noses located in the head. This structure helps them interact actively and efficiently with their environment. Tunicates, however, do not exhibit a high degree of cephalization. As adults, they tend to be sessile (non-moving) and lack a distinct head structure. They filter feed by drawing water through their bodies, making a complex head with sensory organs unnecessary.