Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 18 Intro to Chordates: Fish

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Our own phylum, Chordata, is distinguished by four features Chordates, phylum Chordata have –A dorsal hollow ner ve cord –A stiff notochord –Pharyngeal slits –A muscular post-anal tail

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Characteristics of Chordates Muscle segments Mouth Pharyngeal pouches Anus Tail What Is a Chordate? Hollow nerve cord Notochord

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The notochord is a long supporting rod that runs through the body just below the nerve cord. What Is a Chordate? Notochord

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Pharyngeal pouches are paired structures in the throat (pharynx) region. Pharyngeal pouches What Is a Chordate?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The tail can contain bone and muscle and is used for swimming by many aquatic species. Tail What Is a Chordate?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Most Chordates Are Vertebrates –About 96 percent of all chordate species are vertebrates. –Most vertebrates have a vertebral column, or backbone. –In vertebrates, the dorsal, hollow nerve cord is called the spinal cord. What Is a Chordate?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings As a vertebrate embryo develops, the front end of the spinal cord grows into a brain. The backbone is made of individual segments called vertebrae. In addition to support, vertebrae enclose and protect the spinal cord. What Is a Chordate?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Phylogeny of Chordates What Is a Chordate? Chordates Craniates Vertebrates Jawed vertebrates Tetrapods Amniotes Milk Amniotic egg Legs Lobed fins Lungs or lung derivatives Jaws Vertebral column Head Brain Ancestral chordate Tunicates Lancelets Hagfishes Lampreys Sharks, rays Ray-finned fishes Lobe-fins Amphibians Reptiles Mammals

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Jawed ver tebrates with gills and paired fins include sharks, ray-finned fishes, and lobe-fins Three lineages of jawed ver tebrates with gills and paired fins –Are commonly called fishes

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings What Is a Fish? Fishes are aquatic vertebrates. Most fishes have paired fins, scales, and gills. Anal fin Eye Mouth Dorsal fin Caudal fin Operculum (gill cover) Pelvic fin Pectoral fin Lateral lineScales

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Fishes Fishes and nonvertebrate chordates probably evolved from common invertebrate ancestors. The evolution of jaws and the evolution of paired fins were important developments during the rise of fishes.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Fishes The Arrival of Jaws and Paired Fins –The evolution of jaws in fish was extremely useful. –Jaws with muscles and teeth made it possible for fish to eat a wider variety of foods. –Animals with jaws can also defend themselves by biting.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Fishes Fishes evolved paired pectoral (anterior) and pelvic (posterior) fins. These fins were attached to girdles—structures of cartilage or bone that support the fins. Cartilage is a strong tissue that supports the body and is softer and more flexible than bone.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Fishes Paired fins gave fishes more control of body movement. Tail fins and powerful muscles gave fishes greater thrust when swimming.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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 © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Fishes Respiration –Most fishes exchange gases using gills located on either side of the pharynx. Gills

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Fishes –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 © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Fishes 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 © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Fishes Excretion –Fishes eliminate nitrogenous wastes in the form of ammonia. –Some wastes diffuse through the gills into the surrounding water.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Fishes Many bony fishes have an internal, gas-filled organ called a swim bladder that adjusts their buoyancy. Swim bladder

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Groups of Fishes What are the three main groups of fishes?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings All living fishes can be classified into three groups: jawless fishes, cartilaginous fishes, and bony fishes. Groups of Fish

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 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. Groups of Fish

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Modern jawless fishes are divided into two classes: lampreys and hagfishes. Lamprey Groups of Fishes

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chondrichthyans –Have a flexible skeleton made of car tilage –Include sharks and rays Figure 18.17A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ray-finned Fishes The ray-finned fishes have –A skeleton reinforced with a hard matrix of calcium phosphate –Operculi that move water over the gills –A buoyant swim bladder Gills Bony skeleton Dorsal fin Anal fin Swim bladder Heart Pectoral fin Operculum Pelvic fin Rainbow trout, a ray-fin Figure 18.17B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Lobe-fins The lobe-fin fishes –Have muscular fins suppor ted by bones Figure 18.17C