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Chapter 18- Fish

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1 Chapter 18- Fish

2 Vertebrate Chordates Phylum Chordata- internal skeleton of cartilage or bone; vertebrae surrounding the dorsal nerve cord (develops from notochord). Fish Aquatic Gills Fins;covered in scales Pectoral fins- located on anterior portion Pelvic fins – located on posterior portion Dorsal fin – located on dorsal area Caudal fin- tail fin Post anal fin – sticks out past the cloaca Two-chambered heart All vertebrates developed from fish Fins developed into jointed appendages Ectothermic

3 Gills Pharyngeal pouch – Small pocket at the back of throat that becomes the gills Rows of gill filaments (fingerlike projections through which gases enter and leave the blood) Gill slit- Opening at rear of the cheek Operculum- Covers gills and draws water into fish’s mouth Countercurrent flow- Water passes over gills in one direction as blood flows in opposite direction through capillaries 85% extraction of dissolved oxygen from water

4 Blood Circulation Heart pumps blood to the gills
Sinus venosus- Collects oxygen-poor blood from body Atrium- Delivers to ventricle Ventricle- Pumps blood to gills Conus arteriosus- Smooths flow of blood Oxygen-rich blood leaves gills to go to the rest of the organs

5 Fish Heart Structure

6 Kidneys and Reproduction
Kidneys- Organs made of 1,000s of nephrons Nephron- Tube-like unit regulates the body’s salt and water balance and removes waste from blood Excess water and waste-urine Reproduction Most separate sexes External fertilization (spawning) Yolk sacks supply nutrients-stay attached to hatchlings Large numbers of eggs released to ensure some survive Sharks, skates, and rays have internal fertilization Claspers- Male organs used to insert sperm into female

7 Subphylum Hyperotreti
Class Myxini Hagfish Craniata- Partial cranium (skull); no vertebrae Cartilage skeleton Lack jaws 4 pairs of tentacles around mouth

8 Subphylum Vertebrata 43,700 species
Skeleton (cartilage or bone); grows as the animal grows Complete digestive system and a large coelom Closed circulatory system Respiration by: gills, lungs, and in some cases, moist skin

9 Class Cephalasidomorphi- Lampreys
Agnatha ("no jaws") or the Cyclostomata ("round mouth"). Long, eel-like, jawless fish No paired fins Free-swimming predators Hatch in freshwater; Some migrate to the sea, return to freshwater to reproduce

10 Range of Lamprey in n. America

11 Fish Trivia

12 Ostracoderms First were Placoderms- extinct Heavy armor plated
Strong jaws-modified gill arches Paired pectoral and pelvic fins allow for better escape and predation

13 Gnathostomata Jaws evolved from anterior pair of pharyngeal arches
The skeletal supports for the pharyngeal slits More efficient gill ventilation and capture and ingestion of food Paired appendages

14 Class Osteichthyes- Bony fish
20,000 species Marine and freshwater Lateral line system- Sensory system extending on each side Sensory cells with cilia detect vibrations to allow a fish to perceive its position in the water Optic tectum – Area in a fish’s brain that receives and processes info from visual, auditory and lateral line systems Two groups: the lobe-finned (Sarcopterygii) and ray-finned fish (Actinopterygii)

15 Sarcopterygii: Lobe-finned fish
6 species of lungfish Found in stagnant or freshwater ponds Africa, South America, and Australia. 1 species of coelacanth deep oceans crossopterygian fish Muscular fins with large, jointed bones attaching the fins to the body Become limbs of amphibians during evolutionary descent

16 Lung Fish & Coelacanth

17 Actinopterygii: Ray-finned fish
Thin, bony supports with radiating bones Filter feeders and predators Swim bladder- a gas-filled sac that regulates buoyancy and depth External fertilization Teleosts- 95% of all living fish Examples: tuna, bass, perch, catfish, eels, and trout

18 Trout, Swordfish, and Flounder

19 Eel

20 Class Chondrichthyes 850 species of skates, rays, and sharks
Jaws, lots of teeth, paired fins, and a cartilage endoskeleton 5 to 7 gill slits on both sides of the pharynx lack gill covers

21 Class Chondrichthyes- Sharks
Teeth of sharks are enlarged scales Largest sharks are filter feeders (Basking and whale sharks) Most sharks are fast-swimming, open-sea predators

22 Basking and Whale Sharks

23 Class Chondrichthyes (Elasmobranchia)- Rays and Skates
Family Rajidae of the order Rajiformes Live on ocean floor Pectoral fins enlarged into wing-like fins Swim slowly Venomous spine Countershading- Bottom is lighter while top is darker Electric ray stun with over 300 volts Rays are live-bearing while skates are egg laying

24 Sawfish Sawfish rays have large anterior "saw" -use to slash through schools of fish

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