Fishes Ch. 30.2

 More than 2/3 of the Earth’s surface is water  No matter where there is water, there is some sort of fish living in the water

 Fishes are aquatic vertebrates that have pair fins, scales, and gills  However, there is a large variation between species of fish  Catfish don’t have scales  One reason for variation is due to the many different classes of fish  (KPCOFGS) What is a Fish?

 First vertebrates to evolve  Probably evolved from common invertebrate ancestors  Evolution of jaws and pair fins were important developments Evolution of Fishes

 Jawless  Bodies were armored with bony plates  Late Cambrian period (~510 mya) The first fishes

 Between mya, fishes underwent major adaptive radiation.  Species emerged were jawless with small amounts of armor  Ancestors of modern hagfish and lampreys  Armored fish became extinct 360 mya The Age of Fishes

 Jaws are a useful adaptation  Jaws hold teeth and muscle and so food is more than just small particles  Eat a wider variety of foods  Paired fins = pectoral and pelvic fins  Give more body movement control  Tail fins give more greater thrust in swimming Arrival of Jaws and Paired Fins

 Divided into 2 groups:  Cartilaginous fish (sharks and rays)  Bony fish (other fish) The Rise of Modern Fishes

 Evolved and adapted for:  Various modes of feeding  Specialized structures for gas exchange  Paired fins for movement Form and Function in Fishes

 Fish have a variety of ways to feed (i.e. herbivores, carnivores, parasites, filter feeders, etc).  Some fish use multiple ways to eat in order to survive  Digestion is somewhat complex (see diagram on webpage)

 Gas exchange is via the gills  Made of feathery, threadlike structures (filaments)  The network provides for a large surface area  Circulation – closed circulatory system  Heart pumps blood in a single loop (heart  gills  body  back to heart

 Excretion: rid nitrogenous waste as ammonia  Some diffuse it through the gills, others have kidneys  Response: fish have a well developed nervous system  Cerebrum processes the sense of smell  Cerebellum coordinates body movements  Medulla oblongata controls the functioning of many internal organs

 Have well developed eyes that see color  Have strong sense of taste and smell  Lateral line system helps a fish detect vibrations in the water that help with sensing when prey are swimming around

 Movement: alternate paired sets of muscles on either side of their backbone (S shaped curve)  Fins will help propel the fish forward  Swim bladders are gas filled; help fish adjust their buoyancy

 Reproduction: eggs are fertilized internally or externally  Oviparous – eggs hatched outside the body  Ovoviviparous – eggs stay in the mother’s body and use yolk for nourishment  Viviparous – eggs stay in mother’s body and obtain nourihment directly from the mother  ONLINE PRACTICE ACTIVITY

 3 main classifications of fish:  Jawless: no true teeth or jaws, made of cartilage, no vertebrate, notochords as adults  Lampreys, hagfish  Condrichthyes (cartilaginous): skeletons made of cartilage  Sharks, rays, skates  Osteichthyes (bony): skeletons made of bones; ray finned (slender, bony spines)  Lobed finned (fleshy fins)