2. Key Characteristics of Modern Fishes 1. Gills—obtain oxygen from oxygen gas dissolved in water 2. Single-loop blood circulation—blood is pumped from the heart to the capillaries in the gills. 3. Vertebral column (backbone)—made up of cartilage or bone.

3. Gills Gills are made up of rows of gill filaments— fingerlike projections through which gases enter and leave the blood. At the rear of the cheek cavity is an opening called a gill slit. Gill Filaments

4. In countercurrent flow, water passes over the gills in one direction as blood flows in the opposite direction through capillaries in the gills. Gill Filaments Capillary networks in filament Gill filaments Water Artery Vein

5. Circulation of Blood The chamber-pump heart can be thought of as a tube with four chambers in a row. 1. Sinus venosus—this collection chamber acts to reduce the resistance of blood flow into the heart. 2. Atrium—blood from sinus venosus fills this large chamber, which has thin, muscular walls.

6. 3. Ventricle—third chamber is a thick- walled pump with enough muscle tissue to contract strongly, forcing blood to flow through the gills and eventually to the rest of the body. 4. Conus arteriosus—this chamber is a second pump that smoothes the pulsation and adds still more force.

7. Heart Gills Aorta Capillary network

8. Kidney Most vertebrates have about 2/3 water. The salt concentration of sea water is 3 times that of the tissue of a marine bony fish. Kidneys are organs made up of thousands of nephrons—tublelike units that regulate the body’s salt and water balance and remove metabolic wastes from the blood.

9. Reproduction In a process called spawning, male and female gametes are release near one another in the water. Numerous eggs are released, external fertilization occurs and more than likely most fish become food, however some do survive!

10. Reproduction Sharks, rays and skates have internal fertilization. During mating, the male uses the claspers to insert sperm into the female. Eggs develop inside female and are born alive, most of the time.

11. Jawless Fishes Lampreys and hagfishes have scaless, eel- like bodies within multiple gill slits and unpaired fins. Skeletons are made up of cartilage. Lampreys prey on living fishes.

12. Cartilaginous Fishes Skeletons are made of cartilage strengthened by the mineral calcium carbonate. Sharks have 6 to 10 rows of teeth and might go through 20,000 teeth during its life.

13. Bony Fishes Structural Adaptations that contribute to success: 1. Lateral line system—a sensory system that extends along each side of a bony fish’s body. 2. Gill cover—most bony fishes have a hard plate, an operculum, that covers the gills on each side of the head.

14. 3. Swim bladder—bony fishes contain a special gas sac called the swim bladder. They can regulate the gas and thus regulate their buoyancy.

15. Ray-Finned Bony Fish Their fins are supported by bony structures called rays. Teleosts—(95%) most advanced, have highly mobile fins, very thin scales, and completely symmetrical tails.

16. Lobe-Finned Bony Fishes Have paired fins; bones are connected to joints; bony rays are found only at the tips of each lobed fin; muscles in each lobe move independently from one another. Coelacanth—thought to be extinct until found in 1938 (can reach up to 3 m long)

17. Key Characteristics: 1. Legs 2. Lungs 3. Double-loop circulation 4. Partially divided heart 5. Cutaneous respiration

18. A Frog Eyes Tympanic membrane Tongue Lungs Calls Legs Vocal cords Heart Liver Intestine Fat bodies Backbone

19. Lungs An internal, baglike respiratory organ that allows oxygen and carbon dioxide to be exchanged between the air and the bloodstream.

20. Double-loop circulation Amphibians have a pair of blood vessels not found in fishes, the pulmonary veins— carry oxygen-rich blood from the amphibian’s lungs to its heart.

21. Circulation of Blood A dividing wall known as the septum separates the amphibian atrium into right and left halves.

22. Frogs and Toads Order: Anura Environment: deserts to rain forests, valleys to mountains, and ponds to puddles. Body: adapted for jumping Frog Toad

23. Fertilized eggs Young, legless tadpoles live off yolk stored in their bodies. Tadpoles with legs feed on plants in the water. Young frogs have structures needed for life on land. Adult frog Reproduction in Frogs— metamorphosis

24. Salamanders Salamanders have elongated bodies, long tails, and smooth, moist skin. They perform external fertilization, they do not undergo metamorphosis.

25. Caecilians are a highly specialized group of tropical, burrowing amphibians with small, bony scales embedded in their skin. Internal fertilization—the female may bear live young or lay eggs that develop externally.