Chapter 39

List the characteristics that would be found in a typical vertebrate.

A typical vertebrate would have, at some time in their life, a notochord, a dorsal hollow nerve cord, pharyngeal pouches, and a post-anal tail. They also have a vertebral column, cranium, and an endoskeleton.

Word Roots and Origins The word Actinopterygii comes from the Greek actinos, meaning "ray," and pteryx, meaning "wing" or "fin." Using this information, explain why Actinopterygii is a good name for these fish.

Actinopterygii is a good name because these fish have narrow, ray-shaped fins.

Why is it important to use unique characteristics to classify animals?

Answers may vary. Animals may have similar characteristics due to the same adaptations to similar environments or due to shared ancestry. Thus, it is important to look at unique characters for classification.

Bottom-dwelling fish often lack a swim bladder. Explain why lack of a swim bladder is an adaptive advantage.

Answers may vary. The lack of a swim bladder allows bottom dwellers to remain on the bottom with little effort.

Explain how the heart and gills function in fish.

Blood is pumped by the heart through the gill filaments, enabling efficient gas exchange to occur.

List three key features that characterize bony fishes.

Bony fishes have a skeleton of bone, scales on the body, and a swim bladder or lungs.

Describe the external anatomy of a bony fish.-

Bony fishes have scales, distinct head, trunk, and tail regions. Each side of the head has an operculum.

Explain the relationship between olfactory bulbs and lateral line system.

Both are used in receiving sensory stimuli from the environment.

Contrast the feeding behavior of hagfish to the feeding behavior of lampreys.

Both fish are jawless. Hagfishes have movable plates that it uses to pinch off chunks of flesh. Lamprey attach to hosts with its disk-shaped mouth. Lamprey grind a hole in the host with its rough tongue, feeding on the bodily fluids of the host.

Describe the key characteristics that distinguish cartilaginous fishes.

Cartilaginous fishes have an internal skeleton made of cartilage and their skin is covered with placoid scales.

List three characteristics that distinguish cartilaginous fishes from living jawless fishes.

Cartilaginous fishes have moveable jaws, skeletons, and paired fins.

State the characteristics of early jawless fishes.

Early fishes did not have jaws or paired fins, and most were shorter than 15 cm in length.

Use the following key terms in the same sentence: cerebrum, optic tectum, cerebellum, and medulla oblongata.

From front to rear, a fish's brain includes the cerebrum, optic tectum, cerebellum, and medulla oblongata.

List the nine classes of vertebrates, using both their scientific and common names.

Hagfishes (Myxini); Lampreys (Cephalaspidomorphi); Sharks, Rays, Skates, and Ratfishes (Chondrichthyes); Ray-finned Fishes (Actinopterygii); Lobe-finned Fishes (Sarcopterygii); Amphibians (Amphibia); Reptiles (Reptilia); Birds (Aves); Mammals (Mammalia)

Identify the advantages of internal fertilization versus external fertilization.

Internal fertilization helps ensure that sperm are deposited near the egg. In some fishes, the eggs develop and are protected within the female.

Identify the advantages for fish of having jaws and paired fins over not having these structures.

Jaws afford fish a much greater ability to capture prey, and paired fins allow for greater stability in water and more maneuverability for escaping predators or capturing prey.

Contrast the reproductive strategy of lampreys with the reproductive strategy of sharks.

Lamprey utilize external fertilization while sharks utilize internal fertilization.

Name one characteristic of early chordates that distinguishes hagfishes from lampreys.

Like early chordates, hagfishes are unique in that they lack vertebrae.

Contrast ray-finned and lobe-finned fishes.

Lobe-finned fishes have fleshy fins supported by a series of bones. Ray-finned fishes have thin fins supported by long, segmented, flexible bony elements.

Explain the differences between the two main groups of bony fishes.

Lobe-finned fishes have fleshy fins with a central bony axis. Ray-finned fishes have non-fleshy fins supported by long, flexible bones called rays.

Identify the structures that are involved in sensory systems in fishes.

Nostrils; olfactory sacs; and taste buds located on lips, fins, skin, and barbels are involved in chemoreception. Eyes function in vision. The lateral line senses vibration in the water. Ears detect sound. The Ampullae of Lorenzini detect electric fields.

Organisms that use external fertilization usually produce more eggs at one time than organisms that use internal fertilization. What might explain this difference?

Since sperm is placed inside the female in internal fertilization, the chance of reproductive success is much higher and therefore fewer eggs are necessary.

Forming a Hypothesis A student takes fish A from a saltwater tank and fish B from a freshwater tank. The student returns each fish to the wrong aquarium, and the next day both fish are dead. Form a hypothesis that explains why.

Students should hypothesize that the drastic change in the salt/water concentration would have caused the fish to lose water (in the case of B) or gain water (in the case of A), causing death.

Identify the characteristics that distinguish bony fishes from cartilaginous fishes.

The bony skeleton of bony fishes is harder and heavier than cartilage. Bony fishes have either lungs or a swim bladder and hard, thin scales.

State how the caudal, dorsal, pectoral, and pelvic fins function in helping fish swim.

The caudal fin moves from side to side to propel a fish. Dorsal fins keep fish upright and moving in a straight line. Pectoral and pelvic fins are used to help the fish maneuver.

Describe two unique sensory systems that can be found in fishes.

The lateral line enables fish to detect vibrations in the water, and the ampullae of Lorenzini can detect weak electric fields.

Evaluate the relationship between fishes' body form and function in an aquatic environment.

The streamlined body, along with backward-facing scales and a mucous-covered layer, enable fishes to move through water with little resistance.

Identify each characteristic of fishes that makes them well suited to aquatic life.

The streamlined shape of fishes and their muscular tail helps them move through water with little resistance. Paired fins help fish to maneuver efficiently, and a secretion of mucus reduces friction as they move through the water.

Name two functions of the swim bladder.

The swim bladder is used to adjust buoyancy and, in some fishes, is used to amplify sound and transfer it to the inner ear.

List three distinguishing characteristics of vertebrates.

They have vertebrae, a cranium, and an endoskeleton of bone or cartilage.

1. For each pair of terms, explain how the meanings of the terms differ. a. atrium and ventricle b. caudal fin and anal fin c. internal fertilization and external fertilization d. operculum and gill

a. The atrium receives blood from the body while the ventricle pumps it from the heart through the circulatory system. b. The caudal fin extends posteriorly from the tail, and the anal fin is a ventral fin near the anal opening. c. In internal fertilization, sperm are placed in the female; in external fertilization sperm are released near where eggs have been released. d. The operculum is the hard plate that covers a gill.