<p>Chapter 31: Fishes and Amphibians Section 1: Fishes What is a Fish?  Fishes and other vertebrates have at some time during their development a notochord, a hollow dorsal nerve cord, and pharyngeal slits  In most vertebrates, the notochord is replaced during development by a backbone, or ______, which encloses and protects much of the nerve cord  In addition, most vertebrates have two sets of ______, a ______with a ventral heart, and either ______for breathing  Fishes can be defined as aquatic vertebrates that are characterized by scales, fins, and pharyngeal gills  There are so many fishes, living and extinct, that their correct scientific classification is complicated  For our purposes, we can say that the living fishes fall into three main groups: ______, ______, and ______o Sharks and their relatives are also known as ______because their skeletons are made up of soft, flexible cartilage rather than bone Evolution of Fishes  Fishes are the most primitive living vertebrates  The first fishes were odd-looking jawless creatures whose bodies were covered with ______o Lived in the oceans of the late ______(540 MYA) o For over 100 MY, fishes retained the basic armored jawless body plan o Then, during the Ordovician and Silurian periods, fishes underwent a major adaptive radiation . Jawless fishes – ______. Jawless fishes – ______ Still others were armored fishes that possessed a feeding adaptation that would revolutionize vertebrate evolution: ______ Jawless fishes are limited to eating small particles of food  Jaws made it possible for vertebrates to nibble on plants, munch on other animals, and defend themselves by ______ Also evolved ______o More control over their movement Form and Function in Fishes  Fishes have entered many environments and evolved adaptations that enable them to survive a tremendous variety of conditions Feeding  Every mode of feeding is seen in fishes o Herbivores, Carnivores, Parasites, Filter feeders, Detritus feeders  A single fish may exhibit several modes of feeding, depending on ______ The adaptations for feeding in fishes are often remarkable o ______o ______ Most fish do not chew their food  Instead, they tear their food into chunks or swallow their prey whole  From the mouth food passes through the esophagus and into the stomach, where it is partially broken down  In many fishes, the food is further processed in the ______, which are located at the point where the stomach and the intestine meet o Secrete digestive enzymes and absorb nutrients from the digested food  The intestine receives partially digested food from the stomach and pyloric ceca and completes the process of digestion and nutrient absorption  Any materials that remain undigested after passing through the intestine are eliminated through the anus Respiration  Most fishes breathe with ______that are located on either side of the ______ Most fishes breathe by pumping water through the mouth, over the gill filaments, and out through slits in the sides of the pharynx  A number of fishes have an adaptation that allows them to survive in ______or in areas where bodies of water often dry up  They have specialized organs that serve as lungs by obtaining oxygen from the air o Modified ______. Swim bladder is a ______Internal Transport  Typically have ______with a heart that pumps blood around the body  The heart consists of two muscular pumping chambers o ______o ______. Pumps blood out of the heart into a muscular vessel called the ______Excretion  Most fishes get rid of nitrogenous wastes in the form of ______ Some wastes diffuses through the gills into the surrounding water  Others are removed by the ______, which are excretory organs composed of many tubules that filter nitrogenous wastes from the blood and concentrate them  Kidneys help fishes control the ______</p><p>Response  Fishes have a fairly well-developed nervous system organized around a ______ The most anterior parts of a fish’s brain are the ______, which are connected by stalks to the two lobes of the cerebrum  Cerebrum – sense of smell, taking care of young, exploring environment  The ______process information from the eyes  The ______coordinates body movements  The ______controls many internal organ functions and maintains balance  Posterior to the brain is the spinal cord  In cartilaginous and bony fishes, the spinal cord is enclosed and protected by the vertebral column  Between each set of vertebrae, a pair of ______exits the cord and connects with ______</p><p> Most fishes have superbly designed sense organs that collect information about their environment  ______ Most fishes have ears inside their head, but they cannot hear sounds well o ______Reproduction  Most fishes have separate male and female sexes  A number of fishes are born as males but change to females as they grow older  Many fishes are ______o ______. External fertilization  Some species of fishes are ______o Young develop inside the mother’s body but are not directly nourished by the mother’s body  Other species are ______o ______Jawless Fishes  Divided into two classes o ______. Only vertebrates that do not have backbones as adults . Instead, their long, snakelike bodies are supported by a ______Lampreys  ______ Adult’s head is completely taken up by a circular sucking disk with a round jawless mouth in the center  Live by attaching themselves to fishes and scraping away at the skin with their ______ Then suck up tissues and body fluids  Rarely kill their host, but do leave it in a weakened condition with a large open wound that is ______Hagfishes  Most primitive vertebrates alive today  Pinkish-gray wormlike bodies  4 – 6 short tentacles around the mouth  Lack ______ Do have light detecting regions scattered around their body  Feed on dead and dying fish by using a toothed tongue to scrape a hole into the fish’s side  Peculiar traits o Secrete incredible amounts of ______o Have ______hearts o Open circulatory system o Tie themselves into ______Sharks and Their Relatives  Class ______ Contains sharks, rays, skates, etc.  All members have an endoskeleton made entirely of ______ ______living shark species o Curved tails, torpedo shaped bodies, and rounded snouts o Enormous number of ______. 3000 arranged in 6 – 20 rows  Not all sharks attack people  Some are ______ Others have flat teeth adapted for crushing the shells of mollusks and crustaceans  Each year more people are killed by lightning than by sharks  Rays and skates are adapted for living on the ocean floor o ______from top to bottom o Swim by flapping their large wing like pectoral fins o Most reach a maximum length of about ______Bony Fishes  Class ______ More species in this class than in any other vertebrate class  About ______of all vertebrates are bony fishes  Somewhere between ______species alive today  Almost all bony fishes belong to the enormous group called the ray-finned fishes  Includes everything from guppies to groupers, salmon, and eels  The name refers to the thin bony spines, or rays, that are connected by a thin layer of skin to form the fins  These fins are adapted to a wide variety of functions  Only seven living species of bony fishes are not classified as ray-finned fishes  These are the ______and the ______ These fishes are of interest because they give us an idea of what the lungs and limbs may have been like in the ancestors of terrestrial vertebrates  The six species of lungfishes alive today are found in Australia, Africa, and South America  When water is available, lungfish use their gills to eliminate carbon dioxide, but they get most of their oxygen by gulping air into a simple sac that functions as a lung  During the dry season, lungfish burrow in the mud and enter a dormant state  The single species of coelacanth alive today is the only surviving member of the lobe-finned fishes  Unlike ray-finned fishes, which have many bones in the bases of their fins, coelacanths have few bones in their fin bases  Attached to those bones are a few large rays that form the fins  Ancient lobe-finned fishes seemed to have lived in swampy areas where shallow pools alternated with mud flats and sand bars  The modern coelacanth lives in water about 70 to 400 meters deep in a relatively small area of ocean off the western coast of Africa  Coelacanths were thought to have disappeared with the dinosaurs about 70 million years ago  In 1938, however, fishermen sailing in the ocean off the coast of Africa caught a coelacanth  Scientists were enormously excited to find living coelacanths because these animals represent a fascinating piece of evolutionary history o The closest thing we known of to the ancestors of all land vertebrates How Fishes Fit into the World  Fishes are vital parts of many biological systems  For many birds and mammals fishes are important ______ As predators and herbivores, fishes help control the populations of the organisms they eat  Since prehistoric times, humans have caught fishes for ______</p><p> For at least 4000 years, humans have also raised fishes in artificial ponds</p>