Chapter 24

1. Chapter 24 Animal Diversity II: Vertebrates

2. An Evolutionary Tree of Some Major Animal Phyla Fig. 23-1

3. Chapter 24 At a Glance • 24.1 What Are the Key Features of Chordates(脊索动物)? • 24.2 Which Clades Make Up the Chordates? • 24.3 What Are the Major Groups of Vertebrates(脊椎动物)?

4. 24.1 What Are the Key Features of Chordates? • All chordates have four distinctive structures • A notochord(脊索): a stiff flexible rod extending the length of the body • A dorsal, hollow nerve cord(神经管):lies above the digestive tract and expands anteriorly to form the brain • Pharyngeal gill slits(咽鳃裂): located in the pharynx that may form respiratory organs or may appear as grooves • A post-anal tail(肛后尾): the chordate tail extends past the anus

5. 24.1 What Are the Key Features of Chordates? • Humans are members of the phylum Chordata • In humans, the chordate features are best seen during embryonic development, but later, we lose our notochord, gill slits, and tails • Only the dorsal nerve cord is retained in post embryonic human development

6. Chordate Features in the Human eye heart liver tail limb bud (future leg) gill slit limb bud (future arm) Fig. 24-2

7. An Evolutionary Tree of the Chordates Craniates Vertebrates Tetrapods Petromyzontiformes (lampreys) Reptilia (turtles, snakes crocodiles, birds) Cephalochordata (lancelets) Actinopterygii (ray-finned fish) Chondrichthyes (sharks, rays) Amphibia (frogs, salamanders) Actinistia (coelacanths) Urochordata (tunicates) Dipnoi (lungfishes) Myxini (hagfishes) Mammalia (mammals) Hair, milk Amniotic egg Limbs Lobed fins Lungs Jaws Vertebral column Skull Dorsal nerve cord, notochord, pharyngeal gill slits, post-anal tail Fig. 24-1

9. 24.2 Which Clades Make Up the Chordates? • The chordates include three clades • The lancelets(文昌鱼类)头索动物亚门(Cephalochordata) • The tunicates(被囊类)尾索动物亚门(Urochodata) • The craniates (有头类) 脊椎动物亚门(Vertebata) vertebrates

10. 24.2 Which Clades Make Up the Chordates? • Lancelets are marine filter-feeders • Lancelets are small, fishlike, invertebrate chordates that retain all the four chordate features as adults • Lancelets live half-buried in the sand, with only the anterior end of their bodies exposed • Food particles are drawn into the mouth by pharyngeal cilia(纤毛) and are then transported to the digestive tract

11. Invertebrate Chordates nerve cord notochord gut muscle segments tail mouth anus gill slits (a) Lancelet Fig. 24-3a

13. 24.2 Which Clades Make Up the Chordates? • Tunicates include sea squirts(海鞘) and salps(樽海鞘) • Tunicates (sea squirts) live in a marine environment • The larvae are motile and exhibit all key chordate features • Adults are sessile filter-feeders that have lost their tail and notochord • Barrel-shaped tunicates, known as salps, live in the open ocean and move by contracting an encircling band of muscle that propels the organism forward

14. Invertebrate Chordates incurrent siphon (water enters) excurrent siphon (water exits) atrial opening tail mouth anus gill slits nerve cord attachment points gut gill slits notochord larva (b) Tunicate heart gut gonad adult Fig. 24-3b

16. Author Animation: Lancelets and Tunicates

17. 24.2 Which Clades Make Up the Chordates? • Craniates have a skull • The craniates include all chordates that have a skull that encloses a brain • This group includes the hagfish and the vertebrates—animals in which the embryonic notochord is replaced during development by a backbone, or vertebral column(脊柱), composed of bone(硬骨) or cartilage(软骨) (which resembles bone, but is more flexible)

18. 24.2 Which Clades Make Up the Chordates? • Hagfishes are slimy residents of the ocean floor • They lack jaws • They are exclusively marine, and live near the ocean floor • They feed primarily on worms • They secrete massive quantities of slime as a defense against predators

19. 24.2 Which Clades Make Up the Chordates? • Hagfishes are slimy residents of the ocean floor (continued) • They respire using gills, have a two-chambered heart, and are ectothermic(变温动物的) (they rely on heat from the outside environment to regulate body temperature) • They lack a true backbone, and thus are not a true vertebrate but have a rudimentary braincase • They represent the chordate group that is most closely related to the vertebrates

20. Hagfishes Fig. 24-4

21. 24.2 Which Clades Make Up the Chordates? • Several adaptations have allowed vertebrates to successfully invade most habitats • The presence of an internal skeleton that can grow and repair itself allowed for greater size and mobility, enabling these animals to invade most habitats • Jaws evolved to allow these animals to exploit a much wider range of food sources than jawless animals that preceded them • The development of paired appendages (fins, legs, wings) helped to stabilize movement • The increased size and complexity of the brain and sensory structures allowed these animals to perceive their environment in detail and to respond in a variety of ways

22. 24.2 What Are the Major Groups of Vertebrates? • Today, vertebrates include the following groups: • Lampreys(七鳃鳗) • Cartilaginous fishes (软骨鱼) • Ray-finned fishes (辐鳍鱼) • Coelacanths(腔棘鱼) • Lungfishes (肺鱼) • Amphibians (两栖类) • Reptiles (爬行类) • Mammals (哺乳类) 鸟类(Aves)??

23. 24.2 What Are the Major Groups of Vertebrates? • Some lampreys parasitize fish • Like hagfishes, lampreys are jawless • They have a large rounded sucker that surrounds the mouth • Their spinal cord is protected by cartilaginous segments • They live in both fresh and salt waters • Marine forms must return to fresh water to spawn

24. 24.2 What Are the Major Groups of Vertebrates? • Some lampreys parasitize fish (continued) • Some lamprey species are parasitic • A lamprey will attach to a host with its suckerlike mouth • It has rasping teeth on its tongue, which are used to excavate a hole in the hosts body wall through which the lamprey sucks blood and body fluids

25. Lampreys Fig. 24-5

26. 24.2 What Are the Major Groups of Vertebrates? • Cartilaginous fishes are marine predators • They are of the class Chondrichthyes, and include sharks(鲨),skates (鳐), and rays(魟) • Most are marine • They possess jaws and a cartilaginous skeleton • Their body is protected by a leathery skin embedded with tiny scales

27. 24.2 What Are the Major Groups of Vertebrates? • Cartilaginous fishes are marine predators (continued) • They respire using gills • They possess a two-chambered heart • They have internal fertilization, in which the male deposits sperm directly into a female’s reproductive tract • They tend to sink when they stop swimming because they lack a swim bladder

28. 24.2 What Are the Major Groups of Vertebrates? • Cartilaginous fishes are marine predators (continued) • While some sharks feed by filtering plankton from the water, most are predators of larger prey such as fishes, marine mammals, sea turtles, crabs, or squid • Many have several rows of razor-sharp teeth • The back rows move forward as the front teeth are lost • Most sharks avoid humans, but some can be dangerous; in 2008, there were 59 documented attacks in the world, four of them fatal

29. 24.2 What Are the Major Groups of Vertebrates? • Cartilaginous fishes are marine predators (continued) • Skates and rays are mostly bottom dwellers with flattened bodies, wing-shaped fins, and thin tails • Some have a spine near the base of the tail that is capable of inflicting dangerous wounds • Others produce an electrical shock that can stun prey

30. Cartilaginous Fishes Skate Fig. 24-6

31. 24.2 What Are the Major Groups of Vertebrates? • Ray-finned fishes are the most diverse vertebrates • Bony fish are found in nearly every watery habitat, both freshwater and marine • This group includes: • Ray-finned fishes, such as the angler fish, the moray eel, and the sea horse • Lobe-finned fishes, which include the lungfish and the coelacanth

32. 24.2 What Are the Major Groups of Vertebrates? • The ray-finned fishes are the most diverse and abundant group of vertebrates • They are distinguished by the structure of their fins, which are formed by webs of skin supported by bony spines • They have a bony skeleton • Their skin is covered with interlocking scales • They have a two-chambered heart • Their gills are for respiration • Most have a swim bladder that allows them to float effortlessly at any level in the water

33. 24.2 What Are the Major Groups of Vertebrates? • The ray-finned fishes are the most diverse and abundant group of vertebrates (continued) • They are an important human food source • Populations of almost all economically important ray-finned fish species have declined drastically due to increased efficiency in their capture by humans • Large predatory fish such as the tuna have been reduced to 10% of their original population sizes due to overfishing

34. The Diversity of Ray-Finned Fishes Fig. 24-7

35. 24.2 What Are the Major Groups of Vertebrates? • Coelacanths(腔棘鱼) and lungfishes have lobed fins(叶状鳍) • Both coelacanths and lungfishes have fleshy fins that contain rod-shaped bones surrounded by a thick layer of muscle • This shared trait is indicative of the groups shared ancestry, although the lineages have been evolving separately for hundreds of millions of years • Some of these modified fleshy fins could be used to drag the fish from a drying puddle to a deeper pool • This gave rise to the first vertebrates to invade land—the amphibians • Some of the lineages of lobefins left descendents that survive today and are the tetrapods(四足类) (amphibians, reptiles, and mammals)

36. 24.2 What Are the Major Groups of Vertebrates? • Lungfish are found in freshwater habitats • They tend to live in stagnant waters low in oxygen • They have both gills and lungs • Lungs allow them to supplement their supply of oxygen by breathing air directly

37. 24.2 What Are the Major Groups of Vertebrates? • Lungfish are found in freshwater habitats (continued) • Some species of lungfish can survive even if the water dries up • They burrow into the mud • They seal themselves in a mucus-lined chamber and breathe through lungs as their metabolic rate slows • They resume their underwater way of life when the rains return and the pool refills

38. Lungfishes are Lobe-Finned Fish Fig. 24-8

39. 矛尾鱼Latimeria chalumnae 是唯一现生的总鳍鱼类，于1938年渔民在南部非洲东南沿海首次捕获。

40. 24.2 What Are the Major Groups of Vertebrates? • Amphibians live a double life • This group includes frogs(蛙), toads(蟾), salamanders(蝾螈), and caecilians(蚓螈) • The double life of amphibians • Amphibians begin life adapted to an aquatic environment (e.g., tadpoles have gills) • They later mature into semi-terrestrial adults with lungs

41. 24.2 What Are the Major Groups of Vertebrates? • Amphibians • Amphibians have a three-chambered heart • Most adults respire through lungs and moist skin • Most have four limbs • They reproduce sexually using external fertilization

42. 24.2 What Are the Major Groups of Vertebrates? • Most amphibians are confined to moist habitats • Their skin must be kept moist to avoid desiccation when out of water • Their breeding behavior and use of external fertilization requires water • The male sperm swim to the female eggs • The eggs, protected only by a jelly-like coating, are vulnerable to water loss • The larvae, such as the tadpoles of some frogs and toads, develop in water

43. 24.2 What Are the Major Groups of Vertebrates? • Amphibians are represented by the frogs, toads, salamanders, and caecilians • Frogs and toads undergo a metamorphosis(变态) during their life cycle, starting out as aquatic tadpoles and developing into terrestrial hopping adults • Salamanders have lizard-like bodies with four legs and a long tail • They begin life as aquatic larvae with gills that are retained in adulthood by some species, while others metamorphose into terrestrial adults • Caecilians are limbless burrowing amphibians that resemble an earthworm and can be up to 5 feet long; they have small eyes and limited vision

44. Amphibian Means Double Life Fig. 24-9

45. 24.2 What Are the Major Groups of Vertebrates? • Reptiles belong to the class Reptilia and are adapted for life on land • These animals evolved from an amphibian ancestor about 250 million years ago • Reptiles include lizards, snakes, alligators, crocodiles, turtles, and birds • They respire exclusively through lungs

46. The Diversity of Reptiles Fig. 24-10

47. 24.2 What Are the Major Groups of Vertebrates? • Reptiles are adapted for life on land (continued) • There are three notable adaptations that allowed the reptiles freedom from their aquatic origins • They have tough scaly skin that protects the body and resists water loss • They have internal fertilization, where the male deposits sperm in the female’s body • They have evolved a shelled amniotic egg(羊膜卵), which encapsulates the embryo in a liquid-filled membrane, the amnion(羊膜), which prevents the embryo from drying out on land

48. 24.2 What Are the Major Groups of Vertebrates? • Reptiles are adapted for life on land (continued) • All reptiles have modified three- or four-chambered hearts, which separate oxygenated and deoxygenated blood more effectively than do amphibian hearts • All reptiles have more efficient lungs than do amphibians and do not use their skin as a respiratory organ • The reptile skeleton provides better support and more efficient movement on land than do those of amphibians

49. The Amniotic Egg Fig. 24-11

50. 24.2 What Are the Major Groups of Vertebrates? • Reptiles are represented by lizards, snakes, alligators, crocodiles, turtles, and birds • Lizards and snakes form a common lineage whose ancestors had limbs and whose representatives are mostly predators