PHYLUM CHORDATA: Subphylum vertebrata There are three basic characteristics that distinguish Phylum Chordata from all other animal phyla: The presence of a flexible, rod-like, internal supporting structure called a notochord. It runs the length of the organisms near the dorsal surface. In vertebrates it is replaced during embryonic development by cartilage or bone The presence of a hollow dorsal nerve cord. This lies just above the notochord. This tube will eventually form the brain and spinal cord of the adult. Gill slits are present at some time in development. These are paired openings in the wall of the pharynx. In some vertebrates, gill slits are only seen in the embryo. In others such as fish they are present and function during respiration for life Vertebrates 1. They are a subphylum under the Phylum Chordata. This means they possess a dorsal nerve cord, notochord, and gill slits at the embryo stage. 2. Vertebrates are the most numerous (95%) and most complex of all chordates. 3. Possess a backbone. The vertebrae surround and protect the nerve chord. Vertebrae develop from and replaces the notochord. 4. Anterior part of the dorsal, hollow nerve cord is enlarged into a brain (cephalization). The cerebrum has increased in size and is more complex. 5. The body is usually divided into head, neck, and trunk. The head contains the brain and various sense organs. 6. A tail is present at some stage of development. 7. Jointed internal skeleton (endoskeleton). 8. Two pairs of appendages. 9. There is a ventral with two to four chambers. The circulatory system is closed, and red blood cells contain hemoglobin to bond to oxygen. 10. In aquatic vertebrates, gas exchange takes place in gills. In land vertebrates, it occurs in the lungs. 11. Large coelom containing increasingly complex organ systems. 12. The body covering, the skin, is made up of at least two layers: the epidermis and the dermis. The skin often forms other structures such as glands, scales, feathers, hair, nails, claws, horns and hoofs. VERTEBRATES Group includes 7 classes: agnatha (jawless) FISH chondrichthyes (cartilaginous) osteichthyes (bony) amphibia (e.g. frog) reptilia (e.g. alligator) aves (e.g. eagle) mammalia (e.g. human) 1
Vertebrate Respiration Fish: The only vertebrate adapted to live their lives solely in water. Oxygen is obtained from water by way of gills Water travels over and through gills allowing O 2 and CO 2 to be exchanged between the water outside their bodies and their blood inside. Vertebrate Respiration (con t) Reptiles, Birds, and Mammals: Have lung based respiratory systems used to obtain oxygen from air Functional units of lungs are known as alveoli Their main function in the lung is to transport oxygen into the blood stream and remove carbon dioxide Vertebrate Respiration (con t) Amphibians: Utilise lungs and their skin to carry out gas exchange However because their lives commence in water they also utilize gills Vertebrate Circulation There are 3 types of circulatory pathways: Fish: Blood flows through a two chambered in a one way circuit pathway Amphibians and most reptiles: Blood flows through a three chambered into a two circuit pathway Crocodiles, birds and mammals: Blood flows through a four chambered that is completely separated into right and left halves. Right half pumps blood to the lungs (deoxygenated) Left pumps blood to the rest of body (oxygenated) 2
Vertebrate Reproduction External fertilization: Sperm and egg meet outside the bodies of the parents Fish and frogs Internal fertilization: Sperm and egg meet inside the bodies of the parents Reptiles, birds and mammals Reptiles and birds lay eggs Mammals are the only vertebrate where embryo development occurs internally Some exceptions duckbill platypus and marsupials Class Agnatha VERTEBRATE CLASSES jawless fish that are smooth and shiny tube shaped, 1 metre long approx. 60 species of lampreys and hagfish scavengers and parasites Hagfish bore holes in dead and dying fish lampreys often latch on to other fish with their sucker like mouths Class Agnatha (con t) Endoskeleton made of cartilage Respiratory system made of 6-14 pairs of gills Reproduce sexually with externally fertilization Excretory system composed of 2 kidneys, 2 ureters, a bladder and a urinary opening Class Chondrichthyes Cartilaginous fish, have scales Approx. 850 species Includes sharks, rays and skates 3
Class Chondrichthyes (con t) Endoskeleton of cartilage not bone, flexible Respiratory system made of 5-7 pairs of gills Reproduce sexually with primarily internal fertilization no parental care Excretory system composed of 2 kidneys, 2 ureters, a bladder and a urinary opening Class Osteichthyes Bony fish Most numerous of all vertebrates Approx 20000 species Includes trout and herring Have a swim bladder which is an internal organ used for buoyancy All have a lateral line Sense organ that is sensitive to pressure change in the water and can detect nearby movement Detects vibrations and movements to detect predators and prey Class Osteichthyes (con t) Endoskeleton made of cartilage and bone Respiratory system made of gills which are covered by an opercuclum Reproduce sexually with external fertilization and external development Excretory system made of 2 kidneys, 2 ureters, a bladder and urinary opening Class Amphibia Includes approx 4000 species of frogs, toads, newts and salamanders Undergo metamorphosis Change in life stages Larval stage begin life in water and breathe using gills. Adult stage live life on land and use lungs and skin for respiration Class Amphibia (con t) Endoskeleton made of cartilage and bone Respiratory system consists of thin, gas-permeable skin and the gills and as amphibian larvae develop, the gills degenerate, and paired lungs develop Three chambered with little blood mixing Reproduce sexually with fertilization and development occurring externally Excretory systems made of 2 kidneys, 2 ureters, a bladder, and a cloaca A common opening for the release of urine and feces Class Reptilia Approx 4000 species including snakes, alligators, crocodiles, and turtles Have skin made of keratin which is impermeable to water 4
Class Reptilia (con t) Endoskeleton made of bone and cartilage, Respiratory system uses lungs to breathe Three chambered Excretory system lacks a bladder Reproduce sexually with fertilization occurring internally while development occurs externally lay eggs Class Aves Approx 9000 species of birds Three types of feathers Down: insulation Contour: Shape and color Quill: Flight Class Aves (con t) Structurally adapted for flight; have hollow bones that are equipped with air sacs. Respiratory systems consists of lungs and air sacs; air is moved in and out of the respiratory system through pressure changes in the air sacs. Circulatory system controlled by a 4 chambered with a septum; blood does not mix Reproduction is sexual with fertilization occurring internally and development externally Lay eggs Excretory systems similar to reptiles Class Mammalia Most developed of all vertebrates Includes humans, monkeys, whales Have hair and mammary glands Class Mammalia (con t) Endoskeleton made of bone and cartilage Respiratory system consists of lungs to breathe, obtain oxygen from air Circulatory system controlled by 4 chambered with a septum Excretory system made of 2 kidneys, 2 ureters, bladder and a urethra Class Mammalia (con t) Reproduction is sexual with fertilization internal and development occurring both internally and externally Three types of mammals Monotremes: lay eggs and incubate like birds (platypus, anteater) Marsupials: pouched mammals with partial external development and nourished externally (kangaroos, opossums) Placentals: Placentae and umbilical cord for internal development 5