1. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Classes of Fishes Scientists have grouped fishes into three classes based on their body structure. Jawless fishes Cartilaginous fishes Bony fishes

2. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Classes of Fishes Jawless fishes Hagfish and lampreys Eel-like bodies that lack scales, paired fins, or a bony skeleton Have gills and other characteristics of fish Hagfish feed on soft-bodied invertebrates or dead fish, are known for producing large quantities of slime to escape predators. Lampreys are parasites that attach to and feed on other fishes.

3. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Classes of Fishes Cartilaginous fishes All cartilaginous fishes have skeletons made of cartilage. Sharks: most have several rows of sharp teeth, streamlined shape, strong swimming muscles, placoid scales Skates and rays: adapted for life on the bottom of the sea with flattened bodies and enlarged pectoral fins

4. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Classes of Fishes Bony fishes There are two groups of bony fishes: the ray-finned fishes and the lobe- finned fishes. Most fishes today are ray-finned fishes, with fins that are thin membranes supported by thin, spinelike rays. Only 8 living species of lobe-finned fishes, which have muscular, jointed lobes for fins. Lobe-finned fishes may have been the ancestor of tetrapods, four-footed animals with legs that have feet and toes that have joints.

5. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Evolution of Fishes First fishes First jawless, toothless fishes fed on organic materials from the ocean floor Jawless filter feeders appeared next in the fossil record

6. Diversity of Today’s Fishes Copyright © McGraw-Hill Education Ecology of Fishes Habitat alteration Fishes are an important source of food in all aquatic ecosystems Dams and other obstructions interfere with migration in fish, drastically reducing population sizes Pollution Numbers and diversities of fish decline when their habitats are polluted When suitable conditions return, sometimes populations rebound.