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3. Fishes and Amphibians Chapter 33 Table of Contents Section 1 The Fish Body Section 2 Today’s Fishes Section 3 Amphibians

4. Chapter 33 Section 1 The Fish Body Objectives • Describethe characteristics of modern fishes. • Summarizehow fish obtain oxygen. • Summarizehow blood circulates through a fish. • Contrasthow marine and freshwater fishes balance their salt and water content. • Describetwo methods of reproduction in fishes.

5. Chapter 33 Section 1 The Fish Body Characteristics of Fish

6. Chapter 33 Section 1 The Fish Body Key Characteristics of Modern Fishes • All fishes share certain key characteristics: 1. Gills. Fishes normally obtain oxygen from water with their gills. 2. Single-loop blood circulation. Blood is pumped from the heart to the gills through the body and back to the heart again. 3. Vertebral column (backbone). All fishes have an internal skeleton made of either cartilage or bone, with a vertebral column surrounding the spinal cord.

7. Chapter 33 Section 1 The Fish Body Gills • The major respiratory organ of a fish is the gill. Gills are made up of rows of gillfilaments—fingerlike projections through which gases enter and leave the blood. • The gill filaments hang like curtains between a fish’s mouth and cheeks. At the rear of the cheek cavity is an opening called a gill slit. • In countercurrent flow, water passes over the gills in one direction as blood flows in the opposite direction through capillaries in the gills.

8. Chapter 33 Section 1 The Fish Body Respiration in Fishes

9. Chapter 33 Section 1 The Fish Body Parts of Fish Gills and Countercurrent Flow

10. Chapter 33 Section 1 The Fish Body Circulation of Blood • Fishes have a simple chamber-pump heart: 1. Sinus venosus. This collection chamber acts to reduce the resistance of blood flow into the heart. 2. Atrium. Blood from the sinus venosus fills this large chamber, which has thin, muscular walls. 3. Ventricle. Contractions of the ventricle pump the blood toward the gills. 4. Conus arteriosus. This chamber is a second pump that smoothes the pulsations and adds still more force.

11. Chapter 33 Section 1 The Fish Body Fish Heart Structure

12. Chapter 33 Section 1 The Fish Body Fish Heart and Single-Loop Circulation

13. Chapter 33 Section 1 The Fish Body Kidneys • Although the gills play a major role in maintaining a fish’s salt and water balance, another key element is a pair of kidneys. • Kidneys are organs made up of thousands of nephrons. Nephrons are tubelike units that regulate the body’s salt and water balance and remove metabolic wastes from the blood. • Excess water and bodily wastes leave the kidneys in the form of a fluid called urine.

14. Chapter 33 Section 1 The Fish Body Fish Kidneys

15. Chapter 33 Section 1 The Fish Body Parts of a Nephron

16. Chapter 33 Section 1 The Fish Body Reproduction • The sexes are separate in most fishes, and generally fertilization takes place externally. • In a process called spawning, male and female gametes are released near one another in the water. A yolk sac within each egg contains nutrients the developing embryo will need for growth. • The eggs of sharks, skates, and rays are fertilized inside the female’s body.

17. Chapter 33 Section 2 Today’s Fishes Objectives • Distinguishbetween the three general categories of modern fishes. • Describethe major external and internal characteristics of the yellow perch. • Summarizefeatures of bony fishes.

18. Chapter 33 Section 2 Today’s Fishes Jawless Fishes • Lampreys and hagfishes have scaleless, eel-like bodies with multiple gill slits and unpaired fins. • Their skeletons are made of cartilage, a strong fibrous connective tissue, and both kinds of fishes retain their notochord into adulthood. • Hagfishes are scavengers of dead and dying animals on the ocean bottom. • Most lampreys are parasitic on other living fishes.

19. Chapter 33 Section 2 Today’s Fishes Cartilaginous Fishes • Sharks, skates, and rays are cartilaginous fishes. Their skeletons are made of cartilage strengthened by the mineral calcium carbonate. • The shark’s light, streamlined body allows it to move quickly through the water in search of prey. Its skin contains cone-shaped placoid scales, which give the skin a rough texture. • Two smaller groups of cartilaginous fishes, the skates and rays, have flattened bodies that are well adapted to life on the sea floor.

20. Chapter 33 Section 2 Today’s Fishes Characteristics of Bony Fish

21. Chapter 33 Section 2 Today’s Fishes Bony Fishes • Jawless and cartilaginous fishes are not as diverse as bony fishes, which are the most numerous of all the fishes. • Bony fishes have a fully developed lateral line system. The lateral line is a sensory system that extends along each side of a bony fish’s body. • The lateral line system also enables a fish to detect a motionless object by the movement of water deflected by that object.

22. Chapter 33 Section 2 Today’s Fishes Lateral Line in Fishes

23. Chapter 33 Section 2 Today’s Fishes Lateral Line System

24. Chapter 33 Section 2 Today’s Fishes Bony Fishes, continued • Most bony fishes have a hard plate, an operculum, that covers the gills on each side of the head. • Movements of certain muscles and of the opercula permit a bony fish to draw water over the gills, which enables the fish to take in oxygen.

25. Chapter 33 Section 2 Today’s Fishes Bony Fishes, continued • Bony fishes contain a special gas sac called a swim bladder. • By adjusting the gas content of the swim bladder, bony fishes can regulate their buoyancy. • As the swim bladder fills, the fish rises, and as it empties, the fish sinks.

26. Chapter 33 Section 2 Today’s Fishes Swim Bladder

27. Chapter 33 Section 2 Today’s Fishes External Structure of Fish—Yellow Perch

28. Chapter 33 Section 2 Today’s Fishes Internal Structure of Fish—Yellow Perch

29. Chapter 33 Section 2 Today’s Fishes Anatomy of a Bony Fish

30. Chapter 33 Section 2 Today’s Fishes Ray-Finned Bony Fishes • Ray-finned bony fishes comprise the vast majority of living fishes. • Their fins are supported by bony structures called rays. • Teleosts are the most advanced of the rayfinned bony fishes. Teleosts have highly mobile fins, very thin scales, and completely symmetrical tails.

31. Chapter 33 Section 2 Today’s Fishes Ray-Finned Fishes

32. Chapter 33 Section 2 Today’s Fishes Teleost

33. Chapter 33 Section 2 Today’s Fishes Ray-Finned Bony Fishes • Ray-finned bony fishes comprise the vast majority of living fishes. • Their fins are supported by bony structures called rays. • Teleosts are the most advanced of the rayfinned bony fishes. Teleosts have highly mobile fins, very thin scales, and completely symmetrical tails.

34. Chapter 33 Section 2 Today’s Fishes Lobe-Finned Bony Fishes • Only seven species of lobe-finned fishes survive today. One species is the coelacanth and the other six species are all lungfishes. • In many lobe-finned fishes, each fin consists of a long, fleshy, muscular lobe that is supported by a central core of bones. • The ancestor of the amphibians most likely was a third type of lobe-finned fish that is now extinct.

35. Chapter 33 Section 3 Amphibians Objectives • Summarizethe external and internal structures of the Eastern Lubber grasshopper. • Comparecomplete and incomplete metamorphosis. • Describethe characteristics of insects.

36. Chapter 33 Section 3 Amphibians Characteristics of Amphibians

37. Chapter 33 Section 3 Amphibians Key Characteristics of Modern Amphibians • Most amphibians share five key characteristics: 1. Legs 2. Lungs 3. Double-loop circulation 4. Partially divided heart 5. Cutaneous respiration

38. Chapter 33 Section 3 Amphibians Key Characteristics of Modern Amphibians, continued Lungs • A lung is an internal, baglike respiratory organ that allows oxygen and carbon dioxide to be exchanged between the air and the bloodstream. • In amphibians, the lungs are hardly more than sacs with folds on their inner membrane that increase their surface area. • Many amphibians also obtain oxygen through their thin, moist skin.

39. Chapter 33 Section 3 Amphibians Amphibian Lung Structure

40. Chapter 33 Section 3 Amphibians Respiration in Amphibians

41. Chapter 33 Section 3 Amphibians Key Characteristics of Modern Amphibians, continued Double-Loop Circulation • As amphibians evolved and became active on land, their circulatory system changed, resulting in a second circulatory loop. • Amphibians have a pair of blood vessels not found in fishes, the pulmonary veins. The pulmonary veins carry oxygen-rich blood from the amphibian’s lungs to its heart. • The heart pumps the oxygen-rich blood to the rest of the body.

42. Chapter 33 Section 3 Amphibians Key Characteristics of Modern Amphibians, continued Double-Loop Circulation • Circulation in fishes involves a single loop. Amphibians have a second loop that goes from the heart to the lungs and back to the heart.

43. Chapter 33 Section 3 Amphibians Key Characteristics of Modern Amphibians, continued Circulation of Blood • A dividing wall known as the septum separates the amphibian atrium into right and left halves. • The septum prevents the complete mixing of oxygen-rich and oxygen-poor blood as each enters the heart. • A number of amphibians have a spiral valve that divides the conus arteriosus. The spiral valve also helps to keep the two streams of blood separate as they leave the heart.

44. Chapter 33 Section 3 Amphibians Amphibian Heart Structure

45. Chapter 33 Section 3 Amphibians Frog Heart and Double-Loop Circulation

46. Chapter 33 Section 3 Amphibians Types of Amphibians

47. Chapter 33 Section 3 Amphibians Frogs and Toads • The order Anura is made up of frogs and toads that live in environments ranging from deserts to rain forests, valleys to mountains, and ponds to puddles. • Adult anurans are carnivorous, eating a wide variety of small prey. • The frog body, particularly its skeleton, is adapted for jumping, and its long muscular legs provide the power.

48. Chapter 33 Section 3 Amphibians External Structure of a Frog—Leopard Frog

49. Chapter 33 Section 3 Amphibians Internal Structure of a Frog—Leopard Frog

50. Chapter 33 Section 3 Amphibians Anatomy of a Frog