Phylum Chordata

• General characteristics: notochord (flexible cord down back), dorsal nerve cord (nerves down back), pharyngeal slits (gill slits), postanal tail (tail that goes past anus)
• name means cord
• subphylum Vertebrata (human, cat, fish, bird, reptiles): notochord developed into backbone consisting of vertebrae, endoskeleton present in bone or cartilage, closed circulatory system, all skeletons built on similar plan
• the seven major classes of subphylum Vertebrata: Class Agnatha (Lamprey), Class Chondrichthyes (sharks, skates, and rays), Class Osteichthyes (Perch, Salmon, Cod), Class Amphibia (Frog, Salamander), Class Reptilia (Snakes, Lizards), Class Aves (birds), Class Mammalia (Humans, Apes, Cat, Rat)
• Complete digestive system and coelom.
• Three stages: i. Mechanical digestion (food is broken down by teeth), ii. chemical breakdown (food is chemically broken down by enzymes in the gut), iii. uptake of nutrients (intestines) into the circulatory system
• Aquatic organisms rely on gills to move oxygen-rich across densely packed blood vessels
• terrestrial organisms have either respiration through their skin (some Amphibians), or developed lung tissues to allow internal respirations (Reptiles, birds, mammals)
• all vertebrates have a closed circulatory system (blood contained entirely within blood vessels)
• as vertebrates advance through the later phyla, circulatory systems become more advanced, with dual pumps and a four-chambered heart
• closed circulation: system of arteries, veins, arterioles, venules and capillaries which distribute blood and exchange waste products. (veins always bring blood to the heart, arteries always takes blood away from the heart)
• the circulatory system has many functions such as: cooling and warming of the body, transport of wastes away from cells (CO2, nitrogenous compounds), transport of goods to the cells (O2, glucose)
• Excretory system [remove liquid and nitrogenous waste, (urea + ammonia)]: occurs across nephrons (functional unit) located in the kidneys
• kidneys function to remove excess water and nitrogenous wastes from the blood
• urine is sterile and mostly water, should not contain proteins or glucose (diabetes)
• two kidneys per individual (only need one)
• all vertebrates have a strongly developed nervous system, with a complex brain and specialized sensory apparatus. The spinal cord carries nerve impulses to and from the body.
• CNS: Central nervous system (brain and spinal cord)
• PNS: Peripheral nervous system (all other)
• All vertebrates have two sexes. male: testis is the site of sperm production, female: ovaries is the site of egg production, both gonads regulate hormone levels which control secondary sexual characteristics.
• Class Agnatha - one of the most ancient species of fish: jawless fish- circular ring of teeth around the mouth grinds into prey, eel-like with no scales or fins, most of this class are extinct (surviving examples include the Hagfish and Lampreys)
• Class Chondrichthyes - sharks, skates, and rays: boneless fish - skeleton made only of cartilage, tooth-like scales, paired fins, no swim bladder, lots of teeth
• Class Osteichthyes - bony fish: skeleton made of bone, flat overlapping scales, has a swim bladder (controls height in water), varied adaptions for different life styles (poison spines, wing-like fins, suction cups), examples include (cod, salmon, trout).
• Class Amphibia - Amphibians that demonstrate the water-to-land transition in their life cycle: Amphibians live on land, but lay their eggs in water (adults have lungs, but larva have gills), larva (tadpoles) are herbivorous, but adults are carnivorous, has a cloaca - single opening for eggs/sperm, solid waste, and urine, metamorphosis, examples include salamanders, frogs, and caecilians
• Class Reptilia - organisms that do not require water for reproduction: first organisms to produce an Amniotic egg. This contains a fluid-filled space around the embryo as well as a large yolk-sack to feed the developing embryo (hard-shelled egg). Well-developed lungs, dry, scale-less skin, examples include crocodiles, turtles, lizards, and snakes
• Class Aves - feathers are the key to flight: evolved from bipedal dinosaurs, front limbs modified into wings, feathers, hollow-lightweight bones, highly efficient respiration, no teeth - birds use a muscular crop and gizzard to moisten and grind their prey before digestion, examples: eagles, geese, penguins, ostrich, hummingbirds
• Class Mammalia - hair and mammary glands: mammals are homeothermic (maintain body temperature), highly developed kidneys, sweat glands, and highly developed nervous systems, mammary glands allow mammals to produce milk to feed their offspring, examples include monotremes (platypus), marsupials (kangaroo, koala), placental (mice, dogs, whales, humans)