Chapters 41– 45 Modern Biology

1. Chapters 41– 45 Modern Biology Vertebrates

2. Overview: Half a Billion Years of Backbones • By the end of the Cambrian period, some 540 million years ago • An astonishing variety of animals inhabited Earth’s oceans • One of these types of animals • Gave rise to vertebrates, one of the most successful groups of animals

3. Figure 34.1 • The animals called vertebrates • Get their name from vertebrae, the series of bones that make up the backbone

4. There are approximately 52,000 species of vertebrates • Which include the largest organisms ever to live on the Earth

5. Vertebrates are a subphylum of the phylum Chordata • Not ALL chordates are vertebrates! • Two groups of chordates, the urochordates and cephalochordates, never develop a hard internal skeleton (invertebrate)

6. Chordates Craniates Vertebrates Gnathostomes Osteichthyans Lobe-fins Tetrapods Amniotes Echinodermata(sister group to chordates) Chondrichthyes(sharks, rays, chimaeras) Cephalaspidomorphi(lampreys) Amphibia(frogs, salamanders) Cephalochordata(lancelets) Reptilia(turtles, snakes,crocodiles, birds) Actinopterygii(ray-finned fishes) Urochordata(tunicates) Actinistia(coelacanths) Dipnoi(lungfishes) Myxini(hagfishes) Mammalia(mammals) Milk Amniotic egg Legs Lobed fins Lungs or lung derivatives Jaws, mineralized skeleton Vertebral column Head Brain Notochord Ancestral deuterostome Figure 34.2 • A hypothetical phylogeny of chordates

7. Dorsal,hollownerve cord Brain Notochord Musclesegments Mouth Anus Pharyngealslits or clefts Muscular,post-anal tail Figure 34.3 Derived Characters of Chordates • All chordates share a set of derived characters • Although some species possess some of these traits only during embryonic development

8. Notochord • The notochord • Is a longitudinal, flexible rod located between the digestive tube and the nerve cord • Provides skeletal support throughout most of the length of a chordate • In most vertebrates, a more complex, jointed skeleton develops • And the adult retains only remnants of the embryonic notochord

9. Dorsal, Hollow Nerve Cord • The nerve cord of a chordate embryo • Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord • Develops into the central nervous system: the brain and the spinal cord

10. Pharyngeal Slits or Clefts • In most chordates, grooves in the pharynx called pharyngeal clefts • Develop into slits that open to the outside of the body • These pharyngeal slits • Function as suspension-feeding structures in many invertebrate chordates • Are modified for gas exchange in aquatic vertebrates • Develop into parts of the ear, head, and neck in terrestrial vertebrates

11. Muscular, Post-Anal Tail • Chordates have a tail extending posterior to the anus • Although in many species it is lost during embryonic development • The chordate tail contains skeletal elements and muscles • And it provides much of the propelling force in many aquatic species

12. Incurrentsiphonto mouth Excurrentsiphon Excurrent siphon Atrium Pharynxwith numerousslits Anus Intestine Tunic Esophagus Stomach (b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious. (a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized). Figure 34.4a, b Tunicates, subphylum Urochordata • Belong to the deepest-branching lineage of chordates • Are marine suspension feeders commonly called sea squirts Purple tunicate colony

13. Notochord Dorsal, hollownerve cord Tail Excurrent siphon Musclesegments Incurrentsiphon Intestine Stomach Atrium Pharynx with slits (c) A tunicate larva is a free-swimming butnonfeeding “tadpole” in which all fourchief characters of chordates are evident. • Tunicates most resemble chordates during their larval stage • Which may be as brief as a few minutes Figure 34.4c

14. Tentacle 2 cm Mouth Pharyngeal slits Atrium Notochord Digestive tract Atriopore Dorsal, hollownerve cord Segmentalmuscles Anus Tail Figure 34.5 Lancelets, subphylum Cephalochordata • Known as lancelets, or amphioxus, (from the Greek for "both [ends] pointed"), they are small, eel-like, animals that spend much of their time buried in sand. • In Asia, they are harvested commercially for food that is eaten by both humans and domesticated animals.

15. Tunicates and lancelets are marine suspension feeders • They retain the characteristics of the chordate body plan as adults • Never really develop an endoskeleton • True vertebrates did not come along until later • Subphylum Vertebrata • Classes: • Agnatha – the jawless fish • Chondrichthyes – the cartilaginous, jawed fish • Osteichthyes – bony fish • Amphibia • Reptilia • Aves • Mammalia

16. 5 mm (b) Haikouichthys.Haikouichthys had a skull and thus is considered a true craniate. Figure 34.8b During the Cambrian explosion, 530 million years ago A skull, brain, eyes, and other sensory organs evolved • In other Cambrian rocks • Paleontologists have found fossils of even more advanced chordates, such as Haikouichthys • Vertebrates have an endoskeleton: • Vertebrae enclosing a spinal cord • An elaborate skull • Cartilage and/or bone

17. Slime glands Figure 34.9 Agnatha • The least advanced vertebrate lineage that still survives • There are two groups of jawless fish (sometimes called cyclostomes), the lampreys and the hagfish, with about 100 species between them. • In addition to the absence of jaws, Agnatha are characterized by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches.

18. Figure 34.10 • Lampreys are jawless vertebrates • Inhabiting various marine and freshwater habitats • Parasitize other fish

19. (a) Blacktip reef shark (Carcharhinus melanopterus).Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins. Pelvic fins Pectoral fins (b) Southern stingray (Dasyatis americana).Most rays are flattened bottom-dwellers thatcrush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into their gaping mouth. Figure 34.15a, b Class Chondrichthyes • The largest and most diverse subclass • Includes the sharks and rays

20. Chondrichthyans (Sharks, Rays, and Their Relatives) • Members of class Chondrichthyes • Have a skeleton that is composed primarily of cartilage • Jaws, with teeth

21. (c) Spotted ratfish(Hydrolagus colliei). Ratfishes, or chimaeras, typically live at depths greaterthan 80 m and feed on shrimps, molluscs, and sea urchins. Some species have a poisonous spine at the front of their dorsal fin. Figure 34.15c • A second subclass • Is composed of a few dozen species of ratfishes

22. Most sharks • Have a streamlined body and are swift swimmers • Have acute senses Mako Nurse shark Hammerhead Whale shark – the largest fish in the sea

23. Ray-Finned Fishes and Lobe-Fins • The vast majority of vertebrates • Belong to a group called Osteichthyes • Are the vertebrates we informally call fishes • Nearly all living osteichthyans • Have a bony endoskeleton • Jaws, teeth, flat overlapping scales • Control their buoyancy with an air sac known as a swim bladder

24. Adipose fin(characteristic oftrout) Dorsal fin Caudal fin Swim bladder Spinal cord Brain Nostril Cut edge of operculum Anal fin Gills Anus Gonad Liver Heart Lateral line Stomach Urinary bladder Kidney Intestine Pelvic fin Figure 34.16 • Fishes breathe by drawing water over four or five pairs of gills • Located in chambers covered by a protective bony flap called the operculum

25. (a) Yellowfin tuna (Thunnus albacares), a fast-swimming, schooling fish that is an important commercial fish worldwide (b) Clownfish (Amphiprion ocellaris), a mutualistic symbiont of sea anemones (c) Sea horse (Hippocampus ramulosus), unusual in the animal kingdom in that the male carries the young during their embryonic development (d) Fine-spotted moray eel (Gymnothorax dovii), a predator that ambushes prey from crevices in its coral reef habitat Figure 34.17a–d Ray-Finned Fishes Includes nearly all the familiar aquatic osteichthyans

26. The fins, supported mainly by long, flexible rays • Are modified for maneuvering, defense, and other functions

27. Figure 34.18 Lobe-Fins • Have muscular pelvic and pectoral fins • Include coelacanths, lungfishes, and tetrapods

28. Evolution: Lungfish • Modern lungfish in Africa, South America, and Australia are able to survive when their pools dry up by burrowing into the mud and sealing themselves within a mucous-lined burrow. During this time, they breathe air through their swim bladder instead of through their gills, and reduce their metabolic rate dramatically.

29. Evolution: “Walking” fish Mudskippers: By using their highly modified pectoral (swimming) fins much like legs. And by flipping their bodies, they can "skip" across the mud (and water), which is a great way to avoid predators. They are poor swimmers, and will also use these fins to walk underwater Northern Snakehead:can breathe air, live outside of water for several days, where it might wriggle its way to other bodies of water. Considered invasive in places.

30. Bonessupportinggills Tetrapodlimbskeleton Figure 34.19 The Origin of Tetrapods • In one lineage of lobe-fins • The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life

31. Millions of years ago 420 370 340 310 295 280 265 415 400 385 355 325 Silurian Devonian Carboniferous Permian To present Paleozoic Ray-finned fishes Coelacanths Lungfishes Eusthenopteron Panderichthys Elginerpeton Metaxygnathus Acanthostega lchthyostega Hynerpeton Greerpeton Amphibians Amniotes Figure 34.20 • Extraordinary fossil discoveries over the past 20 years • Have allowed paleontologists to reconstruct the origin of tetrapods

32. Amphibians • Class Amphibia • Is represented by about 4,800 species of organisms • Most amphibians • Have moist, thin skin that complements the lungs in gas exchange • Must lay eggs in water • Young are very fish-like

33. (b) The tadpole is an aquatic herbivore witha fishlike tail and internal gills. (c) During metamorphosis, the gills and tail are resorbed, andwalking legs develop. (a) The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and would desiccate in air. Figure 34.22a–c • Amphibian means “two lives” • A reference to the metamorphosis of an aquatic larva into a terrestrial adult

34. (a) Order Urodela. Urodeles (salamanders) retain their tail as adults. Figure 34.21a Order Urodela • Includes salamanders, which have tails

35. (b) Order Anura. Anurans, such as this poison arrow frog, lack a tail as adults. Figure 34.21b Order Anura • Includes frogs and toads, which lack tails as adults

36. (c) Order Apoda. Apodans, or caecilians, are legless, mainly burrowing amphibians. Figure 34.21c Order Apoda • Includes caecilians, which are legless and resemble worms

37. Evolution: More complete land-dwellers • “Amniotes” include reptiles, birds, and the mammals • Requires a terrestrially adapted egg • contains specialized membranes that protect the embryo • Amniotes also have other terrestrial adaptations • Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs

38. dinosaurs other Saurischian than birds Ornithischiandinosaurs Crocodilians Ichthyosaurs Plesiosaurs Squamates Mammals Pterosaurs Parareptiles Tuatara Turtles Birds Saurischians Dinosaurs Lepidosaurs Archosaurs Synapsids Diapsids Reptiles Ancestralamniote Figure 34.23 • A phylogeny of amniotes

39. Chorion. The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell. Allantois. The allantois is a disposal sac for certain metabolic wastes pro- duced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ. Extraembryonic membranes Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”). Amnion. The amnion protectsthe embryo in a fluid-filled cavity that cushions againstmechanical shock. Embryo Amniotic cavitywith amniotic fluid Yolk (nutrients) Albumen Shell Figure 34.24 The Amniote Egg • The extraembryonic membranes • Have various functions

40. Reptiles • The reptile group includes • The tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs

41. Early Amniotes: the dinosaurs • The oldest reptilian fossils • Date to about 300 million years ago • Included large herbivores and eventually carnivorous predators • Their ability to spend all their lives on land quickly led to their domination

42. Figure 34.25 • Reptiles • Have scales that create a waterproof barrier • Lay shelled eggs on land

43. Most reptiles are ectothermic • Absorbing external heat as the main source of body heat • Birds are endothermic • Capable of keeping the body warm through metabolism

44. (a) Tuatara (Sphenodon punctatus) Figure 34.27a Lepidosaurs • One surviving lineage of lepidosaurs • Is represented by two species of lizard-like reptiles called tuatara

45. Figure 34.27b (b) Australian thorny devil lizard (Moloch horridus) Order Squamata • lizards and snakes are lepidosaurs • Lizards • Are the most numerous and diverse reptiles, apart from birds

46. (c) Wagler’s pit viper (Tropidolaemus wagleri), a snake Figure 34.27c Order Squamata • Snakes are legless lepidosaurs • That evolved from lizards

47. Order Chelonia • Turtles • Are the most distinctive group of reptiles alive today • Some turtles have adapted to deserts • And others live entirely in ponds and rivers • All turtles have a boxlike shell • Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs

48. Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina) • Tortoises are generally turtles with high domed shells and elephantine legs. Totally terrestrial, they do not swim well and are likely to drown in deep water. • Turtles are usually marine, with generally flattened, leathery, circular shells and flipper-feet for swimming. Some water turtles never leave that element. • Terrapins are generally water turtles that frequent swampy areas and estuaries. Webbing between their toes, and spending time basking on land are characteristic.

49. Figure 34.27e (e) American alligator (Alligator mississipiensis) Alligators and Crocodiles • Crocodilians • Belong to an archosaur lineage that dates back to the late Triassic

50. The crocodile’s head tends to run to a very narrow breadth from the eyes to the nostrils and the general color throughout the body and head is grayish. The crocodile is the only one of the three that is found mainly in salt water. The alligator’s head is somewhat broadened at the snout. The head of the caiman is more like that of the alligator but is not so broad. Alligators and caimans are greenish-black in general coloration. American alligator Nile crocodile caimen