Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall
Biology Copyright Pearson Prentice Hall

30-2 Fishes Photo Credit: © Art Wolfe/Stone Copyright Pearson Prentice Hall

What Is a Fish? What are the basic characteristics of fishes? Copyright Pearson Prentice Hall

What Is a Fish? What Is a Fish? Fishes are aquatic vertebrates. Most fishes have paired fins, scales, and gills. Caudal fin Dorsal fin Lateral line Scales Eye Fishes come in many shapes and sizes. Like most fishes, this African cichlid has paired fins, scales, and gills. Photo Credit: ©Labat-Lanceau/AUSCAPE International Mouth Operculum (gill cover) Anal fin Pelvic fin Pectoral fin Copyright Pearson Prentice Hall

Form and Function in Fishes
Adaptations to aquatic life include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion. Copyright Pearson Prentice Hall

Feeding Every mode of feeding is seen in fishes. A single fish may exhibit several modes of feeding, depending on the type of food available. Copyright Pearson Prentice Hall

Food passes through the mouth and esophagus, into the stomach. In the stomach, the food is partially broken down. Esophagus Stomach The internal organs of a typical bony fish are shown here. Mouth Copyright Pearson Prentice Hall

In many fishes, the food is further processed in fingerlike pouches called pyloric ceca. The pyloric ceca secretes digestive enzymes and absorbs nutrients from the digested food. Pyloric cecum The internal organs of a typical bony fish are shown here. Copyright Pearson Prentice Hall

The liver and pancreas add enzymes and other digestive chemicals to the food as it moves through the digestive tract. Liver Pancreas Copyright Pearson Prentice Hall

The intestine completes the process of digestion and nutrient absorption. Intestine Only show “Intestine” label on this slide. Copyright Pearson Prentice Hall

Undigested material is eliminated through the anus. Anus Copyright Pearson Prentice Hall

Respiration Most fishes exchange gases using gills located on either side of the pharynx. Gills Copyright Pearson Prentice Hall

Fishes use their gills to exchange gases by pulling oxygen-rich water in through their mouths, pumping it over their gill filaments, and pushing oxygen-poor water out through openings in the sides of the pharynx. Gills Copyright Pearson Prentice Hall

Circulation Fishes have closed circulatory systems with a heart that pumps blood around the body in a single loop from the heart to the gills, from the gills to the rest of the body, and then back to the heart. Copyright Pearson Prentice Hall

In most fishes, the heart has four parts: the sinus venosus the atrium the ventricle the bulbus arteriosis Copyright Pearson Prentice Hall

Circulation in a Fish Gills Brain and head circulation Body muscle circulation Blood circulates through a fish’s body in a single loop—from the heart to the gills to the rest of the body, and then back to the heart again. Digestive system circulation Heart Copyright Pearson Prentice Hall

Oxygen-poor blood from the veins collects in the sinus venosus. Sinus Venosus Copyright Pearson Prentice Hall

The atrium is a large muscular chamber that serves as a one-way compartment for blood that is about to enter the ventricle. Blood enters the atrium and flows to the ventricle. Atrium Copyright Pearson Prentice Hall

The ventricle is a thick-walled, muscular chamber that is the actual pumping portion of the heart. The ventricle pumps blood into the bulbus arteriosus. Ventricle Copyright Pearson Prentice Hall

The bulbus arteriosus moves blood into the ventral aorta and toward the gills. Bulbus arteriosus Copyright Pearson Prentice Hall

Excretion Fishes eliminate nitrogenous wastes in the form of ammonia. Some wastes diffuse through the gills into the surrounding water. Copyright Pearson Prentice Hall

Others wastes are removed by kidneys. The kidneys of marine fishes concentrate wastes and return water to the body. Kidney The internal organs of a typical bony fish are shown here. Copyright Pearson Prentice Hall

The kidneys of freshwater fishes pump out dilute urine. Kidney Copyright Pearson Prentice Hall

Response Fishes have well-developed nervous systems organized around a brain. Brain The brain of a fish, like all vertebrate brains, is situated at the anterior end of the spinal cord and has several different parts. Copyright Pearson Prentice Hall

The olfactory bulbs are involved with the sense of smell, or olfaction. Olfactory bulb Copyright Pearson Prentice Hall

In most vertebrates, the cerebrum is responsible for all the voluntary activities of the body. In fishes, however, the cerebrum primarily processes the sense of smell. Cerebrum Copyright Pearson Prentice Hall

The optic lobes process information from the eyes. Optic lobe Copyright Pearson Prentice Hall

The cerebellum coordinates body movements. Cerebellum Copyright Pearson Prentice Hall

The medulla oblongata controls the functioning of many internal organs. Medulla oblongata Copyright Pearson Prentice Hall

Almost all fishes that are active in daylight have well-developed eyes and color vision. Many fishes have extraordinary senses of taste and smell. Most fishes have ears but may not hear sounds well. Copyright Pearson Prentice Hall

Fishes use the lateral line system to sense the motion of other fishes or prey swimming nearby. Some fishes can detect low levels of electric current. Copyright Pearson Prentice Hall

Many bony fishes have an internal, gas-filled organ called a swim bladder that adjusts their buoyancy. Swim bladder The internal organs of a typical bony fish are shown here. Copyright Pearson Prentice Hall

Movement Most fishes move by contracting paired sets of muscles on either side of the backbone. A series of S-shaped curves move down the fish’s body. The force and the action of the fins propels the fish forward. The fins of fishes are used to keep on course and adjust direction. Copyright Pearson Prentice Hall

Reproduction The eggs of fishes are fertilized either externally or internally, depending on the species. Fishes whose embryos in the eggs develop and hatch outside the mother's body are oviparous. The embryos of oviparous fishes obtain food from the yolk in the egg. Copyright Pearson Prentice Hall

In ovoviviparous species, the eggs stay in the mother's body after internal fertilization. Each embryo develops inside its egg, using the yolk for nourishment. The young are “born alive” like most mammals. Copyright Pearson Prentice Hall

In viviparous animals, the embryos stay in the mother's body after internal fertilization. These embryos obtain the substances they need from the mother's body (not from material in an egg). The young of viviparous species are “born alive.” Copyright Pearson Prentice Hall

Groups of Fishes What are the three main groups of fishes? Copyright Pearson Prentice Hall

Groups of Fishes Groups of Fishes All living fishes can be classified into three groups: jawless fishes, cartilaginous fishes, and bony fishes. Copyright Pearson Prentice Hall

Groups of Fishes Jawless Fishes Jawless fishes have no true teeth or jaws. Their skeletons are made of fibers and cartilage. They lack vertebrae, and keep their notochords as adults. Copyright Pearson Prentice Hall

Groups of Fishes Modern jawless fishes are divided into two classes: lampreys and hagfishes. Photo Credit: Animals Animals/©Zig Leszczynski Lamprey Copyright Pearson Prentice Hall

Groups of Fishes Lampreys are typically filter feeders as larvae and parasites as adults. Adult lampreys attach themselves to fishes, whales, and dolphins. They scrape away at the skin with small toothlike structures. The lamprey sucks up the tissues and body fluids of its host. Copyright Pearson Prentice Hall

Groups of Fishes Hagfishes have pinkish gray, wormlike bodies and four or six short tentacles around their mouths. They lack eyes, but have light-detecting sensors scattered around their bodies. They feed on dead and dying fish by using a toothed tongue to scrape a hole into the fish’s side. Copyright Pearson Prentice Hall

Groups of Fishes Sharks and Their Relatives The class Chondrichthyes contains sharks, rays, skates, sawfishes, and chimaeras. The skeletons of these fishes are built entirely of cartilage. Many sharks have thousands of teeth arranged in several rows. Most species of sharks do not attack people. Copyright Pearson Prentice Hall

Groups of Fishes Some skates and rays feed on bottom-dwelling invertebrates. The largest rays eat floating plankton. Skates and rays glide through the sea with their large, winglike pectoral fins. Many skates and rays cover themselves with sand and rest on the ocean floor. Copyright Pearson Prentice Hall

Groups of Fishes Bony Fishes Bony fishes make up the class Osteichthyes. Their skeletons are made of bone. Almost all living bony fishes are ray-finned fishes. “Ray-finned” refers to the slender bony spines, or rays, that are connected by a thin layer of skin to form the fins. Copyright Pearson Prentice Hall

Groups of Fishes Only seven living species of bony fishes are not classified as ray-finned fishes. These are the lobe-finned fishes, a subclass that includes lungfishes and the coelacanth. The fleshy fins of lobe-finned fishes have support bones. Some of these bones are jointed. Copyright Pearson Prentice Hall

Ecology of Fishes Some fishes spend most of their lives in the ocean but migrate to fresh water to breed. These fish are called anadromous. Salmon are anadromous. Photo credit: ©Ralph A. Clevenger/CORBIS Copyright Pearson Prentice Hall

30-2 Copyright Pearson Prentice Hall

30-2 A characteristic of almost all fish is a notocord as an adult. the presence of scales. a skeleton made of cartilage. the lack of jaws. Copyright Pearson Prentice Hall

30-2 Fishes whose eggs hatch outside the mother’s body are ovoviviparous. oviparous. viviparous. parous. Copyright Pearson Prentice Hall

30-2 Salmon are anadromous fishes that spend their lives in the sea. spend their lives in rivers or streams. migrate to the sea in order to spawn. migrate to rivers and streams to spawn. Copyright Pearson Prentice Hall

30-2 An example of a fish that is a filter feeder as a larva and a parasite as an adult is a shark. skate. lamprey. lungfish. Copyright Pearson Prentice Hall

30-2 Most members of the class containing sharks and rays are characterized by a cartilaginous skeleton. a bony skeleton. a single operculum over the gills. no swim bladder. Copyright Pearson Prentice Hall

END OF SECTION

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