Fishes By : Jessica Martinez & Gabriela Perez
What is a Fish? • Aquatic vertebrates • Characterized by fins, gills, and scales. • For almost every general statement there is an exception. • Chordates • Over 24,000 living species.
Form and Function • Adaptations to surviving life underwater include various modes of feeding, specialized structures for gas exchange, and paired fins for locomotion.
Form and function continued.. • Feeding: - Fishes vary in feeding styles. There are herbivores, carnivores, parasites, filter feeders, and detritus feeders. - Food enters through the fishes‘ mouth, passes through the esophagus, into the stomach to be broken down. In most fishes, it then goes into the pyloric ceca to be processes furthermore. . • Respiration: - Gills are the major structure used for respiration. The gills are made of filaments contain a network of capillaries that provide a large surface area for exchange for oxygen and carbon dioxide. - The water is pulled through the mouth, passed over the gill filaments, and pushing oxygen-poor water out through the pharynx. • Circulation: - Fishes have a one way circulatory system that passes blood from the heart to the gills , which then passes it to the rest of the body in a single loop. - Heart consists of 4 parts : sinus, venosus, atrium, and the ventricle. • Excretion: - Fishes get rid of their nitrogenous waste in a form of ammonia. - Some of it diffuses through the gills. Others are removed by kidney and excretory organs. • Response -Have well-developed nervous systems around the brain. -The brain consists of six parts: Olfactory bulb, cerebrum, optic lobe, cerebellum, and the medulla oblonganta. -They have a lateral line system that helps them sense motion of other fishes or prey that are moving nearby.
Form and Function Continued.. • Movement: - Most move by alternately contracting paired sets of muscles on either sides of the backbone. This then creates an “S” shaped curve throughout their body - Then, with the help of the fins, it propels the fish forward. - Most fishes that have dense bones have an internal gas filed organ called a swim bladder that adjust their buoyancy to float. • Reproduction: - Reproduced sexually - Eggs are fertilized either internally or externally , depending on the species. - There are three different modes of fish reproduction: • Oviparous: When the embryos hatch outside of the mother’s bodies, and obtain nutrition from the yolk of the egg. (example: Salmon) • Ovoviviparous: When the eggs remain in the mother’s body after fertilization, obtain their nutrition from the yolk of the egg, and are “born alive”. (example: Guppies) • Viviparous: When the embryo stays in the mother’s body and, like mammals, obtain nutrition from their own mother’s body and are born alive. (example: Sharks)
Groups of Fishes • Fishes are grouped into three major categories according to their body structures.
Jawless Fishes • Have no teeth or jaws. • They lack vertebrae; are made up of cartilage. • 2 classes: • Lampreys: filter feeders when larvae and parasites as adults. • Hagfishes: Feed on dead and dying fish; they have six hearts and can regularly tie themselves into knots!
Sharks and Their Relatives • Class: Chondrichthyes • Includes sharks, rays, skates , and a few uncommon fish. • These fishes are built entirely of cartilage. • They have tooth-like scales that make their skin rough. • Sharks have thousands of teeth and are continuously replacing worn out or lost teeth. • Some sharks, however, have flat teeth and others have teeth so tiny that they are practically useless. • MOST SHARKS DO NOT ATTACK PEOPLE • Skates and rays are more diverse than sharks. • Some feed on bottom-dwelling invertebrates by using their mouths as powerful vacuums. The largest rays feed on floating plankton. • Skates and rays often glide through the ocean using their large, wing like pectoral fins.
Bony Fishes • Class: Osteichthyes • Skeletons are made up bones. • Most living bony fishes are part of the ray-finned fishes: slender bony spines that are connected to tissues to form fins. • Only seven species of bony fishes are not classified as ray-finned fish. They are instead into the lobe-finned subclass. • Lobe-filled fishes include lungfishes(fresh water fish) and coelacanth (marine fish).