The Animal Kingdom: The Deuterostomes Chapter 30 The Animal Kingdom: The Deuterostomes

Main branches of deuterostomes Echinoderms Hemichordates (marine deuterostomes with three-part body, including proboscis, collar, trunk) Acorn worms Chordates

Characteristics of echinoderms Spiny “skin” Water vascular system Tube feet Endoskeleton Larvae Bilateral symmetry Adults Pentaradial symmetry

Class Crinoidea Oral surface is turned upward Some crinoids are sessile Class includes Sea lilies Feather stars

Crinoidea: feather star

Class Asteroidea Central disk with five or more arms Tube feet for location Members are sea stars

Class Ophiuroidea Longer, more slender arms than members of Asteroidea Arms are used for locomotion No suckers on tube feet Members are brittle stars

Ophiuroidea: daisy brittle star

Class Echinoidea No arms Solid shell Covered with spines Members are Sea urchins Sand dollars

Echinoidea: sand dollar

Class Holothuroidea Mouth is surrounded by a circle of modified tube feet that serve as tentacles Members are sea cucumbers

Holothuroidea: sea cucumber

Phylum Chordata At some time in their life cycle, all chordates have Notochord Dorsal, tubular nerve chord Pharyngeal slits Postanal tail

Generalized chordate body plan

Subphyla of phylum Chordata Urochordata Cephalochordata Vertebrata

Invertebrate chordates Tunicates (subphylum Urochordata) Are suspension-feeding marine animals with tunics Larvae have typical chordate characteristics and are free-swimming

Tunicates (subphylum Urochordata), cont. Adults of most groups are sessile suspension feeders

Tunicate body plan: lateral view of an adult tunicate

Tunicate body plan: internal structure of a larval tunicate (lateral view)

Invertebrate chordates Lancelets (subphylum Cephalochordata) Small Segmented Fishlike Exhibit chordate characteristics

Cephalochordate body plan: lancelet

Evolution of chordates Tunicates were probably first to evolve Subphyla Cephalochordata and Vertebrata considered sister taxa by some Common ancestor probably resembled tunicate larva

Evolutionary relationships of vertebrates

Shared derived characters of vertebrates Verytebral column Cranium Neural crest cells Pronounced cephalization Muscles attached to endoskeleton

Major groups of jawless fishes Ostracoderms (extinct) Agnathans Hagfishes (class Cephalaspidomorphi) Lamprey (class Myxini) or Craniates Vertebrates Hagfishes (systematist designation referring to invertebrate character of hagfishes)

Three lampreys attached to a carp Suction-cup mouth of adult lamprey

Evolution of jawed fishes and amphibians Class Chondrichthyes Jaws Two pairs of fins Placoid scales

Structure of a placoid scale

Class Chondrichthyes, cont. Sharks Many species ovoviparous Some species oviparous Few species vivaparous Rays Skates Oviparous

Internal structure of a shark

Bony fishes Class Actinopterygii Class Actinistia Class Dipnoi Ray-finned fishes Class Actinistia Coelacanths Class Dipnoi Lungfishes

Perch, a representative bony fish

During the Devonian, bony fishes gave rise to Actinopterygii Lungs modified as a swim bladder Evolved into modern bony fishes Sarcopterygii evolved into Lungfishes Coelacanths

Sarcopterygii, cont. Coelacanths and lungfishes apparently preadapted for life on land Lungfish may have given rise to tetrapods First successful tetrapods labyrinthodonts (ancestors of frogs and salamanders)

Diver swimming with coelacanth

An artist’s conception of labyrinthodonts

Class Amphibia Use moist skin as well as lungs for gas exchange Three-chambered heart Systemic and pulmonary circulations Most return to water to reproduce

Class Amphibia, cont. Salamanders Frogs (tadpoles undergo metamorphosis) Toads Caecilians

Modern reptiles: Chelonia mydas

Vertebrate adaptations to terrestrial life Amniotic egg: amnion forms fluid-filled sac around embryo Body covering that retards water loss Physiological mechanisms to conserve water

Modern reptiles: Crocodilia niloticus

Class Reptilia is paraphyletic Dinosaurs Turtles Lizards Snakes Alligators Birds sometimes included

Modern reptiles: Basiliscus plumifrons

Reptiles Internal fertilization Most secrete a protective shell around egg Embryo develops protective membranes, including amnion, to retain moisture

Reptiles, cont. Dry skin with horny scales Lungs with many changers Three-chambered heart with some separation of oxygen-rich and oxygen-poor blood

Paleontological discovery of feathered dinosaurs Many biologists consider birds to be feathered dinosaurs; they classify as diapsids Birds Most reptiles

Caudipteryx (headless)

Reconstruction of Archaeopteryx

Birds: adaptations for powered flight Feathers Wings Light, hollow bones with air spaces Four-chambered heart Very efficient lungs

Birds: adaptations for powered flight, cont. High metabolic rate Constant body temperature Excrete solid metabolic wastes Well-developed nervous system Excellent vision and hearing

Mammals Hair Mammary glands Differentiated teeth Three middle-ear bones Constant body temperature Highly-developed nervous system Muscular diaphragm

Convergent evolution in placental and marsupial mammals

Monotremes (subclass Holotheria) Oviparous Duck-billed platypus Spiny anteater

Marsupials (subclass Metatheria) Young are born in an embryonic stage and complete their development in marsupium Kangaroos Opossums

Macropius giganteus Macropius giganteus soon after birth

Placental mammals (subclass Eutheria) Placenta permitting development within the uterus Living placental mammals are classified into circa sixteen orders