Phylum Chordata “Vertebrates” Kingdom Animalia Phylum Chordata “Vertebrates”

Phylum Chordata “Vertebrates Organisms in this phylum are segmented animals with four distinctive features Dorsal hollow nerve cord Stiff notochord Pharyngeal slits behind the mouth Muscular post-anal tail Coelom Bilateral symmetry Phylum Chordata “Vertebrates

Simplest Chordates The simplest chordates are tunicates and lancelets. These are marine invertebrates POST-ANAL TAIL DORSAL, HOLLOW NERVE CORD Tunicates PHARYNGEAL SLITS Muscle segments Mouth Simplest Chordates NOTOCHORD LARVA

Simplest Chordates Lancelets DORSAL, HOLLOW NERVE CORD NOTOCHORD Head Mouth Simplest Chordates Water exit Pharynx Anus POST-ANAL TAIL PHARYNGEAL SLITS Digestive tract Segmental muscles

Vertebrates A skull and a backbone are hallmarks of vertebrates Most chordates are vertebrates. Their endoskeletons include a skull. Their backbone is composed of vertebrae. Vertebrae Backbone Skull Vertebrates A skull and a backbone are hallmarks of vertebrates

Vertebrates Most vertebrates have hinged jaws. Exception: Lampreys lack hinged jaws. They are classified as agnathans. Jaws evolved by the modification of skeletal supports of the gill slits. Gill slits Skeletal rods Skull Vertebrates Most vertebrates have hinged jaws. Mouth

Class Chondrichthyes Cartilaginous Fish Fish are jawed vertebrates with gills and paired fins. Cartilaginous fish diverged before bony skeletons appeared. Examples: Shark and ray Class Chondrichthyes Cartilaginous Fish

Class Osteichthyes Bony fish Bony fishes are more diverse and have more mobile fins operculi that move water over the gills a buoyant swim bladder BONY SKELETON OPERCULUM Class Osteichthyes Bony fish Gills SWIM BLADDER

Class Osteichthyes Three sub-classes of bony fish: Ray-finned Lobe-finned Lungfish Evolutionary evidence suggests that tetrapods evolved from lobe-finned fish. Rainbow trout, a ray-fin Coelacanth, a lobe-fin Class Osteichthyes

Air-breathing lungfishes that developed skeleton-reinforced appendages probably gave rise to the first amphibians. Bones supporting gills Typical tetrapod limb skeleton

Class Amphibia 1st Land Vertebrates Class Amphibia is represented today by: frogs toads Salamanders Their limbs allow them to move on land. However, amphibian larvae must develop in water. Class Amphibia 1st Land Vertebrates

Class Amphibia Key Characteristics: Body Temperature: Ectotherms – obtain their body heat from the external environment Reproduction: Females lay eggs in water, and males fertilize. Eggs do not have shells or outer coverings. Examples: Frogs and toads Salamanders and newts Caecilians (worm-like animal burrows in soil) Class Amphibia

Class Reptilia 1st amniotic egg Reptiles have more terrestrial adaptations than amphibians. Class Reptilia is able to live on land due to: waterproof scales a shelled, amniotic egg Modern reptiles are still ectotherms. They warm their bodies by absorbing heat from the environment. Class Reptilia 1st amniotic egg

Class Aves 1st Endotherms Class Aves has: scales amniotic eggs Wings Feathers an endothermic metabolism hollow bones a highly efficient circulatory system Wing claw (like reptile) Teeth (like reptile) Class Aves 1st Endotherms Feathers Long tail with many vertebrae (like reptile)

Class Aves Birds share many characteristics in common with reptiles. Scientists believe that birds’ feathers are evolved scales. Consider the scaly skin of birds’ feet. Class Aves

Class Mammalia Mammals also evolved from reptiles. Mammals are endothermic. There are two unique mammalian characteristics: Hair, which insulates the body Mammary glands, which produce milk that nourishes their young. Class Mammalia

Class Mammalia Monotremes Monotremes: a few mammals lay eggs Example: duck-billed platypus Class Mammalia Monotremes

Class Mammalia Marsupials Marsupials have a short gestation. The tiny offspring complete development attached to the mother’s nipple, usually inside a pouch. Example: kangaroos Class Mammalia Marsupials

Class Mammalia Placental Mammals Most mammals are eutherians, also called placentals, They have a relatively long gestation. Complete embryonic development occurs within the mother. Class Mammalia Placental Mammals

Phylogeny of the Animal Kingdom A traditional phylogenetic tree is based on patterns of embryonic development and some fundamental structures. Phylogeny of the Animal Kingdom

Porifera Platyhelminthes Mollusca Arthropoda Chordata Present day Cnidaria Nematoda Annelida Echinodermata Pseudocoelom PROTOSTOMES Coelom from cell masses DEUTEROSTOMES Coelom from digestive tube No body cavity True coelom Body cavity Radial symmetry Bilateral symmetry No true tissues True tissues Ancestral protists