Figure 34.2 Hypothetical phylogeny of chordates Chapter 34 Vertebrates Figure 34.2 Hypothetical phylogeny of chordates Chordates Craniates Vertebrates Gnathostomes Osteichthyans Lobe-fins Tetrapods Amniotes Milk Amniotic egg Legs Lobed fins Lungs or lung derivatives Jaws, mineralized skeleton Vertebral column Head Brain Notochord Ancestral deuterostome Echinodermata (sister group to chordates) Urochordata (tunicates) Cephalochordata (lamcelets) Myxini (hagfishes) Cephalaspidomorphi (lanpreys) Chondrichthyes (sharks, rays, chimaeras) Actinopterygii (ray-finned fishes) Actinistia (coelacanths) Dipnoi (lungfishes) Amphibia (frogs, salamanders) Reptilia (turtles, snakes, crocodiles, birds) Mammalia (mammals)

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Muscle segments Brain Mouth Anus Dorsal, hollow nerve cord Notochord Muscular, post-anal tail Pharyngeal slits or clefts 4 features seen at some point during development - Notochord – longitudinal, flexible rod between nerve cord & digestive tube - Dorsal, hollow nerve cord - Muscular, post-anal tail - Pharyngeal gill slits

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Notochord – longitudinal, flexible rod between nerve cord & digestive tube Replaced by skeleton in most chordates Present in some invertebrate chordates & primitive vertebrates Dorsal, hollow nerve cord Derived from ectoderm Other animal phyla have a solid nerve cord Becomes brain & spinal cord Muscular, post-anal tail Pharyngeal gill slits Opening behind the mouth so water doesn’t enter digestive tract Modified for gas exchange in aquatic animals Modified for jaw support, hearing & other fcns in terrestrial animals Who are the invertebrate chordates? - Urochordates (tunicates – seas squirts)

Urochordata Cephalochordata Myxini Cephalaspidomorphi Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Figure 34.4 A tunicate, a urochordate (a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized). (b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious. (c) A tunicate larva is a free- swimming but nonfeeding “tadpole” in which all four chief characters of chordates are evident. Tunic Pharynx with numerous slits Atrium Excurrent siphon Incurrent siphon to mouth Stomach Esophagus Intestine Anus Excurrent siphon Pharynx with slits Notochord Tail Dorsal, hollow nerve cord Incurrent siphon Muscle segments - Most are sessile, marine organisms on rocks, docks, & boats - Squirt when disturbed

Chapter 34 Vertebrates Who are the invertebrate chordates? 1. What are the characteristics of chordates? Notochord – longitudinal, flexible rod between nerve cord & digestive tube Replaced by skeleton in most chordates Present in some invertebrate chordates & primitive vertebrates Dorsal, hollow nerve cord Derived from ectoderm Other animal phyla have a solid nerve cord Becomes brain & spinal cord Muscular, post-anal tail Pharyngeal gill slits Opening behind the mouth so water doesn’t enter digestive tract Modified for gas exchange in aquatic animals Modified for jaw support, hearing & other fcns in terrestrial animals Who are the invertebrate chordates? - Urochordates (tunicates – seas squirts) - Cephalochordates

Urochordata Cephalochordata Myxini Cephalaspidomorphi Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Figure 34.5 The lancelet Branchiostoma, a cephalochordate Tentacle Mouth Pharyngeal slits Atrium Digestive tract Atriopore Segmental muscles Anus Notochord Dorsal, hollow nerve cord Tail 2 cm All features present in adult Swim like a fish

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? Hagfish & lampreys – agnathans – without a jaw Hagfish – scavengers Lamprey – tongue for rasping Both lack paired appendages

Figure 34.10 A sea lamprey

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? Hagfish & lampreys – agnathans – without a jaw Hagfish – scavengers Lamprey – tongue for rasping Both lack paired appendages How did the jaw evolve? Modification of skeletal rods that support gill slits Natural selection favored “grasping” Mouth Gill slits Cranium Skeletal rods

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? Modification of skeletal rods that support gill slits Natural selection favored “grasping” 5. What are the 2 groups of fish? Chondrichthyes – cartilaginous fish – sharks & rays Flexible endoskeleton Cartilage derived secondarily as ancestors had bony skeletons Lateral line system – detects electrical fields from muscles of nearby fish 3 different ways of birth within chondrichthyes Oviparous – egg laying Viviparous – live birth Ovoviviparous – eggs stay in oviduct where embryos develop into young that are hatched into the uterus Cloaca – common opening for reproductive & excretory tract Osteichthyes – bony fish

Figure 34.15 Chondrichthyans (a) Blacktip reef shark (Carcharhinus melanopterus). Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins. (b) Southern stingray (Dasyatis americana). Most rays are flattened bottom-dwellers that crush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into their gaping mouth. (c) Spotted ratfish (Hydrolagus colliei). Ratfishes, or chimaeras, typically live at depths greater than 80 m and feed on shrimps, molluscs, and sea urchins. Some species have a poisonous spine at the front of their dorsal fin. Pectoral fins Pelvic fins

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? Modification of skeletal rods that support gill slits Natural selection favored “grasping” 5. What are the 2 groups of fish? Chondrichthyes – cartilaginous fish – sharks & rays Osteichthyes – bony fish Mucus glands for reduced swimming friction Operculum – protective flap that covers gills Swim bladder – air sac that helps control buoyancy Most are oviparous with external fertilization 3 groups Ray-finned Lobe-finned Lungfish

Figure 34.16 Anatomy of a trout, an aquatic osteichthyan Nostril Brain Spinal cord Swim bladder Dorsal fin Adipose fin (characteristic of trout) Caudal fin Cut edge of operculum Gills Heart Liver Kidney Stomach Intestine Gonad Anus Urinary bladder Lateral line Anal fin Pelvic fin

Figure 34.17 Ray-finned fishes (class Actinopterygii) (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 34.18 A coelacanth (Latimeria) – lobe-finned

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? Modification of skeletal rods that support gill slits Natural selection favored “grasping” 5. What are the 2 groups of fish? Chondrichthyes – cartilaginous fish – sharks & rays Osteichthyes – bony fish Mucus glands for reduced swimming friction Operculum – protective flap that covers gills Swim bladder – air sac that helps control buoyancy Most are oviparous with external fertilization 3 groups Ray-finned Lobe-finned Lungfish live in oxygen-poor lakes Gave rise to amphibians

Figure 34.20 The origin of tetrapods Amniotes Amphibians Greerpeton Hynerpeton lchthyostega Acanthostega Metaxygnathus Elginerpeton Eusthenopteron Panderichthys Lungfishes Coelacanths Ray-finned fishes Paleozoic Silurian Devonian Carboniferous Permian To present 420 415 400 385 370 355 340 325 310 295 280 265 Millions of years ago

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? What are the 2 groups of fish? How did amphibians evolve? By natural selection from lungfish Escape predators & get more food (insects & other invertebrates) Amphibian characteristics Moist skin for gas exchange Live in damp environs “2 lives” – metamorphosis in shape & environment external fertilization Shell-less egg 3 orders

Urochordata Cephalochordata Myxini Cephalaspidomorphi Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Figure 34.21 Amphibians (a) Order Urodela. Urodeles (salamanders) retain their tail as adults. (b) Order Anura. Anurans, such as this poison arrow frog, lack a tail as adults. (c) Order Apoda. Apodans, or caecilians, are legless, mainly burrowing amphibians.

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? What are the 2 groups of fish? How did amphibians evolve? By natural selection from lungfish Escape predators & get more food (insects & other invertebrates) Amphibian characteristics Moist skin for gas exchange Live in damp environs “2 lives” – metamorphosis in shape & environment external fertilization Shell-less egg 3 orders What adaptation led to further development on land? - Amniotic egg

Figure 34.24 The amniotic egg (from the embryo) Shell Albumen Yolk (nutrients) Amniotic cavity with amniotic fluid Embryo 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”). 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. Amnion. The amnion protects the embryo in a fluid-filled cavity that cushions against mechanical shock. 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. Extraembryonic membranes

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? What are the 2 groups of fish? How did amphibians evolve? What adaptation led to further development on land? Amniotic egg Characteristics of reptiles Scales with keratin (waterproofing) No gas exchange thru skin – lungs – turtles can thru moist cloaca Internal fertilization Most are oviparous but some are viviparous Ectothermic aka “cold-blooded”

Figure 34.23 A phylogeny of amniotes Synapsids Ancestral amniote Reptiles Diapsids Archosaurs Saurischians Lepidosaurs Dinosaurs Parareptiles Turtles Crocodilians Pterosaurs Ornithischian dinosaurs Saurischian dinosaurs other than birds Birds Plesiosaurs Ichthyosaurs Tuatara Squamates Mammals

Figure 34.27 Extant reptiles (other than birds) (a) Tuatara (Sphenodon punctatus) (c) Wagler’s pit viper (Tropidolaemus wagleri), a snake (d) Eastern box turtle (Terrapene carolina carolina) (e) American alligator (Alligator mississipiensis) (b) Australian thorny devil lizard (Moloch horridus)

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? What are the 2 groups of fish? How did amphibians evolve? What adaptation led to further development on land? What adaptations led to flight?

Figure 34.28 Form fits function: the avian wing and feather (a) wing (b) Bone structure Finger 1 (c) Feather structure Shaft Barb Barbule Hook Vane Forearm Wrist Palm Finger 3 Finger 2

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Who are the invertebrate chordates? Who were the first vertebrates/craniates? How did the jaw evolve? What are the 2 groups of fish? How did amphibians evolve? What adaptation led to further development on land? What adaptations led to flight? Honey-combed bones Wings Feathers – flight & down Large breast muscle anchored to keel Large motor area of brain – coordination for flight Other characteristics Keratin beak High metabolism & endothermic Complex behaviors 9. What is the origin of birds?

Figure 34.29 Artist’s reconstruction of Archaeopteryx, the earliest known bird Toothed beak Airfoil wing with contour feathers Long tail with many vertebrae Wing claw Weak flyer - tree dwelling glider

Chapter 34 Vertebrates What adaptation led to further development on land? What adaptations led to flight? What is the origin of birds? What are the characteristics of mammals? Mammary glands that produce milk Diaphragm Hair with fat under skin Mostly viviparous, some oviparous Internal fertilization Larger brains Extensive parental care 3 groups Monotremes – egg layers Placentals – longer pregnancy, embryo within uterus Marsupials – born early & complete embryonic development in pouch

Figure 34.35 Evolutionary convergence of marsupials and eutherians (placental mammals) Marsupial mammals Eutherian mammals Plantigale Marsupial mole Sugar glider Wombat Tasmanian devil Kangaroo Deer mouse Mole Woodchuck Flying squirrel Wolverine Patagonian cavy