Ancestral deuterostome Notochord Brain Head Vertebral column Gnathostomes

Ancestral deuterostome Notochord Brain Head Vertebral column Gnathostomes Osteichthyans Lobe-fins Tetrapods Amniotes Jaws, mineralized skeleton Legs Lobed fins Lungs or lung derivatives Mammalia (mammals) Reptilia (turtles, snakes, crocodiles, birds) Amphibia (frogs, salamanders) Dipnoi (lungfishes) Actinistia (coelacanths) Actinopterygii (ray-finned fishes) Chondrichthyes (sharks, rays, chimaeras) Cephalaspidomorphi (lanpreys) Myxini (hagfishes) Cephalochordata (lamcelets) Urochordata (tunicates) Echinodermata (sister group to chordates) Chapter 34 Vertebrates Figure 34. 2 Hypothetical phylogeny of chordates Craniates Vertebrates Milk Amniotic egg

Chapter 34 Vertebrates 1. What are the characteristics of chordates? Dorsal, hollow nerve cord Muscle segments Brain Notochord Mouth Anus 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 2. Who are the invertebrate chordates? - Urochordates (tunicates – seas squirts)

Mammalia Reptilia Amphibia Dipnoi Actinistia Actinopterygii Chondrichthyes Cephalaspidomorphi Myxini Cephalochordata Urochordata

Figure 34. 4 A tunicate, a urochordate Incurrent siphon to mouth Notochord Excurrent siphon Dorsal, hollow nerve cord Excurrent siphon Tail Excurrent siphon Atrium Pharynx with numerous slits Tunic Incurrent siphon Intestine Stomach Atrium Anus Intestine Esophagus Stomach (a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized). Muscle segments (b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious. Pharynx with slits (c) A tunicate larva is a freeswimming but nonfeeding “tadpole” in which all four chief characters of chordates are evident. - Most are sessile, marine organisms on rocks, docks, & boats - Squirt when disturbed

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 2. Who are the invertebrate chordates? - Urochordates (tunicates – seas squirts) - Cephalochordates

Mammalia Reptilia Amphibia Dipnoi Actinistia Actinopterygii Chondrichthyes Cephalaspidomorphi Myxini Cephalochordata Urochordata

Figure 34. 5 The lancelet Branchiostoma, a cephalochordate Tentacle 2 cm Mouth Pharyngeal slits Atrium Notochord Digestive tract Atriopore Dorsal, hollow nerve cord Segmental muscles Anus Tail -All features present in adult -Swim like a fish

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. 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? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? - Hagfish & lampreys – agnathans – without a jaw - Hagfish – scavengers - Lamprey – tongue for rasping - Both lack paired appendages 4. How did the jaw evolve? - Modification of skeletal rods that support gill slits - Natural selection favored “grasping” Gill slits Cranium Mouth Skeletal rods

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? - Modification of skeletal rods that support gill slits - Natural selection favored “grasping” 1. 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 movement 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? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? - Modification of skeletal rods that support gill slits - Natural selection favored “grasping” 1. 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 Dorsal fin Adipose fin (characteristic of trout) Swim bladder Spinal cord Nostril Cut edge of operculum Caudal fin Brain Gills Heart Gonad Urinary Anus bladder Liver Kidney Intestine Stomach Pelvic fin Anal fin Lateral line

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? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? - Modification of skeletal rods that support gill slits - Natural selection favored “grasping” 1. 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 Millions of years ago 420 415 Silurian 400 385 370 355 Devonian 340 325 310 295 Carboniferous 280 265 Permian Paleozoic Ray-finned fishes Coelacanths Lungfishes Eusthenopteron Panderichthys Elginerpeton Metaxygnathus Acanthostega lchthyostega Hynerpeton Greerpeton Amphibians Amniotes To present

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. 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

Mammalia Reptilia Amphibia Dipnoi Actinistia Actinopterygii Chondrichthyes Cephalaspidomorphi Myxini Cephalochordata Urochordata

Figure 34. 21 Amphibians (a) Order Urodela. Urodeles (salamanders) retain their tail as adults. (b) Order Anurans, such as this poison arrow frog, lack a tail as adults. (c) Order Apodans, or caecilians, are legless, mainly burrowing amphibians.

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. 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 7. What adaptation led to further development on land? - Amniotic egg

Figure 34. 24 The amniotic egg Extraembryonic membranes (from Allantois. The allantois is a disposal sac for certain metabolic wastes produced 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. the embryo) 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. 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”). Embryo Amniotic cavity with amniotic fluid Yolk (nutrients) Albumen Shell

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. How did amphibians evolve? 7. What adaptation led to further development on land? - Amniotic egg - Characteristics of reptiles - Scales with keratin (waterproofing) - No gas exchange thru skin – lungs – turtles also thru moist cloaca - Internal fertilization - Most are oviparous but some are viviparous - Ectothermic aka “cold-blooded”

Diapsids Reptiles Ancestral amniote als Ma mm ua ma tes Sq ra ata Tu au rs thy os Ich sa urs sio Ple Bir ds Sa ur din ischi an os tha aurs n b oth ird er s au rs Or nit din hisc os hia au n rs ros Pte od ilia ns Cr oc rtle s Tu les ep ti Pa rar Figure 34. 23 A phylogeny of amniotes Saurischians Dinosaurs Lepidosaurs Archosaurs Synapsids

Figure 34. 27 Extant reptiles (other than birds) (b) Australian thorny devil lizard (Moloch horridus) (a) Tuatara (Sphenodon punctatus) (c) Wagler’s pit viper (Tropidolaemus wagleri), a snake (d) Eastern box turtle (Terrapene carolina) (e) American alligator (Alligator mississipiensis)

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. How did amphibians evolve? 7. What adaptation led to further development on land? 8. What adaptations led to flight?

Figure 34. 28 Form fits function: the avian wing and feather Finger 1 (b) Bone structure Palm (a) wing Finger 2 Forearm Wrist Finger 3 Shaft Vane Shaft Barbule Hook (c) Feather structure

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. How did amphibians evolve? 7. What adaptation led to further development on land? 8. 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 Wing claw Toothed beak Airfoil wing with contour feathers Long tail with many vertebrae Weak flyer - tree dwelling glider

Chapter 34 Vertebrates 1. What are the characteristics of chordates? 2. Who are the invertebrate chordates? 3. Who were the first vertebrates/craniates? 4. How did the jaw evolve? 5. What are the 2 groups of fish? 6. How did amphibians evolve? 7. What adaptation led to further development on land? 8. What adaptations led to flight? 9. What is the origin of birds? 10. 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 Plantigale Marsupial mole Eutherian mammals Deer mouse Mole Sugar glider Flying squirrel Wombat Woodchuck Tasmanian devil Kangaroo Wolverine Patagonian cavy