Introduction to Phylum Chordata

General Characteristics Best known of all animal phyla. Consists of only about 45,000 species. Includes the vertebrates and two groups of invertebrates known as lancelets and tunicates. All have bilateral symmetry.

General Characteristics (continued) 4 characteristics appear in all of them at some stage of their development: 1.A single, dorsal nerve cord. 2.A dorsal rod of cartilage called a notochord 3.Pharyngeal (gill) slits, and 4.A tail.

General Characteristics (Continued) The notochord serves as a structure to which muscles can attach. It enables increased strength and flexible movement. It was an important evolutionary advancement. Phylum chordata is broken into 3 subphyla: – Subphylum Cephalochordata (lancelets), – Subphylum Urochordata (tunicates), – Subphylum Vertebrata (vertebrates).

General Characteristics Subphylum Vertebrate is composed of 7 classes: 1.Class Agnatha (jawless fish, including lampreys and hagfish), 2.Class Chondrichthyes (cartilaginous fish, including sharks, rays, and skates), 3.Class Osteichthyes (bony fish, including perch, salmon, eels, and sea horses), 4.Class Amphibia (amphibians, including frogs, toads, and salamanders), 5.Class Reptilia (reptiles, including lizards, alligators, crocodiles, turtles, and snakes), 6.Class Aves (birds, including penguins and ostriches), and 7.Class Mammalia (mammals, including bats and humans).

Subphylum Vertebrata Found on land and in fresh and marine waters. Notochord replaced by cartilage or bone, forming segmented vertebral column (the backbone). Important evolutionary advancement: allowed for great size, powerful movement. Have distinct head and brain inside a skull, another important evolutionary advancement.

Subphylum Vertebrata Gill slits may remain or be modified into other structures during development. Hollow dorsal nerve cord remains, protected by backbone. Vertebrata refers to the vertebrate (segments of backbone) surrounding dorsal nerve cord. About 43,700 species.

Evolution of Vertebrates Summarized Jawless fishes were the first vertebrates. Lampreys and hagfishes are the only surviving jawless fishes. Sharks were among the first vertebrates to have jaws, which allow them to bite. Sharks have a lightweight skeleton of cartilage. They also have streamlined bodies and paired fins, which allow for fast swimming with better control. Bony fishes have a heavier skeleton of bone and a swim bladder, which provides buoyancy.

Evolution of Vertebrates Summarized Amphibians (frogs, toads and salamanders) were the first vertebrates to live on land. However, they lack watertight eggs and so cannot reproduce in environments in which their eggs would dry out.

Evolution of Vertebrates Summarized Each of the adaptations that allowed amphibians to lead a terrestrial existence was refined in reptiles. Reptiles (snakes, lizards, turtles, crocodiles, and alligators) replaced amphibians as a large terrestrial vertebrates. Once reason that reptiles were successful on land is that their dry skin prevents water loss. Another reason is that reptile eggs are watertight, preventing the embryo against drying.

Evolution of Vertebrates Summarized Mammals evolved at the same time the dinosaurs first appeared. Birds evolved from dinosaurs. Feathers on birds and fur on mammals are adaptations that enabled these groups of animals to survive the dramatic global cooling that took place 65 million years ago, when the dinosaurs disappeared.

Evolution of Vertebrates Summarized There are three groups of mammals. Monotremes are mammals that lay eggs. The duckbill platypus is a monotreme. Marsupials suckle their young, which are born after a short period of development, in an external pouch. Koalas and opossums are marsupials. Placental mammals nourish their developing embryos by means of a placenta, a structure that transfers nutrients from the mother’s blood directly to the growing embryo.

Subphylum Cephalochordata Blade-shaped, marine animals known as lancelets. Live in warm, shallow waters. Have no internal skeleton. Keep their notochord, dorsal nerve cord, gill slits, and tail throughout their life. Use their muscular tail to wriggle backward into the sand. Use cilia to draw water into their pharynx through their mouth. Food particles in the water are trapped as the water passes through the numerous slits in the pharynx. The food enters the intestine to be digested, while the water leaves the body through an opening called the atriopore. About 2 dozen species.

Subphylum Urochordata Barrel-shaped, marine animals known as tunicates or sea squirts. Live on the sea bottom – sessile. Have no internal skeleton. Bodies are covered by a tough covering, or tunic. Adults have no notochord, dorsal nerve cord, or tail. Most are sessile. Propelled by the beating of cilia, water enters the body through an incurrent siphon, passes through slits in the pharynx, and exists through an excurrent siphon. Food that is filtered by the pharynx moves into the stomach Undigested materials leaves via the anus, which empties into the excurrent siphon. Tunicates are hermaphrodites. About 1,250 species.

Subphylum Vertebrata Notochord is replaced with a backbone or vertebrae – bone or cartilage that surround and protect the nerve cord. Includes sharks, bony fishes, amphibians, birds, and mammals Stop for Animal Activity

Subphylum Vertebrata Notes How did you do?

Class Agnatha: Jawless Lack true jaws Snakelike bodies Skeleton of cartilage Smooth skin with scales Ectothermic and oviparous Includes Lampreys and Hagfish

Subphylum Vertebrata

Class Agnatha: Lamprey

Class Agnatha: Hagfish

Class Chondrichthyes: Cartilaginous Fishes Skeleton made of cartilage Hinged jaw, paired fins, toothlike scales cover body Ectothermic Some are oviparous, most are ovoviviparous Includes sharks, rays, and skates

Class Chondrichthyes: Sawfish

Class Chondrichthyes: Blue-spotted Ray

Class Chondrichthyes: Brown shark

Class Chondrichthyes: Whale shark

Class Osteichthyes: Bony Fishes Skeleton of bone Hinged jaws, paired fins Overlapping scales Air bladder Ectothermic Oviparous Including salmon, trout, perch, carp and eels

Class Osteichthyes: Hippo tang

Osteichthyes: Lungfish

Osteichthyes: Common Dolphifish

Osteichthyes: Yellow perch

Class Amphibia: Soft eggs Moist thin skin, No scales Four limbs If present, feet lack claws are often webbed Most undergo metamorphosis Most use gills, lungs and skin for respiration 3-chambered heart Oviparous: eggs most remain moist Ectothermic

Class Amphibia: Tadpole

Class Amphibia: Eastern Tiger salamander

Class Amphibia: Northern Cricket Frog

Class Amphibia: Green Climbing Toad

Class Reptilia: Amniotic egg Dry skin and a scale covered body Four limbs (except snakes) Live and reproduce on land Amniotic eggs (eggs that contain layers of specialized membranes) Lungs and a 3-chambered heart with a partially divided ventricle Ectothermic Most are oviparous but some are ovoviviparous (python snakes and garter snakes)

Class Reptilia: Black Mamba

Class Reptilia: Komodo Dragon

Class Reptilia: Albino Chinese Soft- shelled turtle

Class Reptilia: American Crocodile

Class Reptilia: American Alligator

Class Aves: Wings/Feathers Birds that have wings and feathers Feathers are essential for flight and insulation Forelimbs are modified into pair of wings Lightweight rigid skeleton Endothermic; rapid metabolism allows for flight Lungs associated with air sacs All oviparous 4-chambered heart needed for flight

Class Aves: Ostrich

Class Mammalia: Produce milk Placental development and mammary glands that produce milk Hair or fur Endothermic 4 chambered heart Most are viviparous

Class Mammalia: Platypus

Class Mammalia: Vampire bat

Class Mammalia: Sperm whale

Class Mammalia: White-tailed Deer (fawn)