Problem 3 - Campbell Biology Concepts & Connections

Question

A lamprey, a shark, a lizard, and a rabbit share all the following characteristics except a. pharyngeal slits in the embryo or adult. b. vertebrae, c. hinged jaws. d. a dorsal, hollow nerve cord.

Step-by-Step Solution

Answer

Hinged jaws are not shared by all the animals listed.

Step 1: Identify Common Characteristics

List the characteristics mentioned in the options: pharyngeal slits, vertebrae, hinged jaws, and a dorsal, hollow nerve cord. Determine which of these characteristics are shared by all of the animals mentioned: lamprey, shark, lizard, and rabbit.

Step 2: Review Pharyngeal Slits

Pharyngeal slits are present in all these animals at some developmental stage, even if they are not retained into adulthood. This feature is a common characteristic among all the animals listed.

Step 3: Check for Vertebrae

Verify that all these animals possess vertebrae. A lamprey, shark, lizard, and rabbit all have vertebrae, so this trait is also common among them.

Step 4: Examine Hinged Jaws

Review whether all these animals have hinged jaws. Lampreys do not possess hinged jaws, whereas sharks, lizards, and rabbits do. Thus, hinged jaws are not a universal characteristic among all these animals.

Step 5: Consider the Dorsal, Hollow Nerve Cord

Determine if all animals have a dorsal, hollow nerve cord. Each of the listed animals possesses this feature, making it a shared characteristic.

Step 6: Select the Correct Answer

Since hinged jaws are not present in all the animals listed (specifically, not in lampreys), the correct answer choice is the characteristic that is not shared by all.

Key Concepts

pharyngeal slits

Pharyngeal slits are openings found in the pharyngeal region of an embryo. These slits are a common feature in the early developmental stages of chordates, a group that includes all the animals in the exercise. Even if pharyngeal slits are not present in adult forms of some animals, they exist in the embryo.

Pharyngeal slits serve different purposes across species. In aquatic animals like sharks and lampreys, they often develop into gills, playing a crucial role in respiration. In terrestrial animals like lizards and rabbits, these slits are involved in the development of the ear and throat.

The presence of pharyngeal slits highlights shared evolutionary ancestry. Despite their different uses in adult animals, this feature is a universal characteristic seen during development.

vertebrae

Vertebrae are the bones that form the vertebral column, commonly known as the backbone. All the animals mentioned in the problem—lamprey, shark, lizard, and rabbit—have vertebrae.

Vertebrae play a crucial role in providing structural support and protecting the spinal cord.

• Lampreys have a simple cartilaginous rod-like structure.
• Sharks possess cartilaginous vertebrae for flexibility and strength.
• Lizards and rabbits have more complex, calcified vertebrae for additional support.

The presence of vertebrae is essential for movement and the protection of nerves. Despite the variety in structure, vertebrae are a trait shared among these animals, demonstrating their classification as vertebrates.

hinged jaws

Hinged jaws are a feature allowing the opening and closing of the mouth, crucial for feeding. Sharks, lizards, and rabbits all have hinged jaws, but lampreys lack them. Lampreys are jawless vertebrates.

Hinged jaws are typical in most vertebrates but absent in primitive ones like lampreys. They significantly impact an animal's ability to capture and process food, making them a pivotal evolutionary advancement.

• Sharks use hinged jaws to grasp prey forcefully.
• Lizards and rabbits use them to chew their food thoroughly.

Though not present in all vertebrates, hinged jaws represent an important evolutionary step for many.

dorsal hollow nerve cord

The dorsal hollow nerve cord is a defining feature of chordates and runs along the back of the organism. In vertebrates like lampreys, sharks, lizards, and rabbits, this nerve cord develops into the central nervous system, including the brain and spinal cord.

This feature is crucial for transmitting nerve signals throughout the body and is a common developmental characteristic. Unlike other nerve cords found in different animal groups, the dorsal hollow nerve cord is hollow and situated dorsally (on the back).

This nerve cord's presence underscores the animals' shared ancestry and critical functions in controlling movement and processing sensory information.