Biology Chapter Chordates 30 Notes Chordate:An animal that has, for at least some stage of its life, a dorsal, hollow nerve cord, a notochord, pharyngeal pouches, and a tail that extends beyond the anus. Notochord:long supporting rod that runs through the body just below the nerve cord Pharyngeal pouches:paired structures in the throat region. Most chordates are vertebrates. Vertebrae: individual segments in a backbone Endoskeleton: Internal skeleton that contains living as well as dead cells Two Groups: Chordates Tunicates and lancelets Tunicate: filter-feeding chordate that has all chordate characteristics when larvae but has neither a notochord nor a tail as an adult and also attaches itself to a solid surface when an adult. Sea squire: common name for tunicate Lancelets: small nonvertebrate chordate that does not have fins or legs but do have a definite head, mouth, pharynx, and gill slits. Fish: aquatic vertebrates with paired fins, scales, and gills Cartilage: strong tissue that supports the body and is softer and more flexible than bone Fish:

Feeding: herbivores, carnivores, parasites, filter feeders, detritus feeders, and combinations of feeding types Digestive tract: food enters the mouth, through the esophagus to the stomach where it is partially broken down. From there it goes to the pyloric ceca which secrete digestive enzymes and absorb the nutrients and then the intestine where even more enzymes are secreted and more nutrients absorbed. Undigested material leaves through the anus. Mouth à stomach à esophagus à esophagus à stomach à pyloric ceca à intestine à anus Fish Respiration: gills located on either side of the pharynx Number of gills: most single but some multiple, like lampreys and sharks Filament: threadlike structure in the gills that is full of capillaries Fish Circulation: closed circulatory system with heart that pumps blood in a single loop. Parts of fish heart: 4 parts – sinus venosus, atrium, ventricle, bulbus arteriosis Vein: blood vessel that returns blood to the heart Artery: blood vessel that carries blood away from the heart Fish Circulation: sinus venosis à atrium à ventricle à bulbus arteriosis à arteries à Arterioles à capillaries (where oxygen exchange occurs) à venules à Veins à sinus venosis Excretion: Nitrogenous waste in the form of ammonia diffuses through the gill or is removed from the blood by the kidneys How do fish handle living in salt water? kidneys help fish control the amount of water in their body by concentrating wastes and returning as much water as possible to the body. How do fish handle living in fresh water? kidneys help fish control the amount of water in their body by diluting wastes and excreting as much dilute urine as possible. Fish nervous system: brain with olfactory bulbs, optic lobes, cerebrum, cerebellum, and medulla oblongata connected to nervous system, highly developed sense organs including eyes, taste, smell, ears that can detect vibrations, lateral line system – sense motion from other fish Swim bladder: internal, gas-filled organ that allows fish to adjust their buoyancy Reproduction: external or internal reproduction Oviparous: form of reproduction where eggs hatch outside the mother’s body Ovoviviparous: from of reproduction where the eggs stay in the mothers body after internal fertilization, hatch inside the mother, and then leave the mother

Viviparous: form of reproduction where internal fertilization procures embryos that are never inside an egg during development Three Groups of Fishes: jawless fishes, cartilaginous fishes, bony fishes Jawless fishes: fish that have no true teeth or jaws, lack vertebrae, and have a skeleton made of cartilage and fiber Lampreys and Hagfish: two jawless fish How does a Lamprey obtain nutrients? A lamprey’s head is a sucking disk with a circular sucking disk in the center, which it uses to attach itself to fish, whales, dolphin. Then the lamprey uses its toothlike structures to scrape at the host tissue and suck up the tissue and body fluids. How does a Hagfish obtain nutrients? a hagfish feeds on dead and dying fish by using a toothed tongue to scrape a hole in a fishes side. Sharks, rays, skates, common fish like sawfish - organisms that belong to the cartilaginous fish category Traits of cartilaginous fish (Chondrichthyes)

Internal skeleton made of cartilage, toothlike scales that make their skin rough Traits of bony fish (Osteoicthyes): skeletons are made of bones Types of bony fish: ray-finned fish, lobe-finned fish How are ray-finned fish different from lobe-finned fish? Ray finned fish has slender bony spines that form fins that are never jointed but lobe-finned fish have fleshy fins and more substantial bones that are sometimes jointed. Two types of lobe-finned fish? lungfish and coelacanth

AMPHIBIANS Characteristics of Amphibians: vertebrates, live in water as larva and on land as an adult, adult breathes with lungs, skin is moist with mucus glands, does NOT have scales, does NOT have claws. Adaptations that allow amphibians to live outside of water: strong bones, lungs and breathing tubes, breastbone forms a body shield to protect internal organs. Three orders of amphibians: frogs, toads, and salamanders

How is amphibian feeding different in the larva and the adult? larva are filter feeders or herbivores that eat algae, adults are strict carnivores Trace the path of food in a frog’s digestive system: mouth à esophagus à stomach à small intestine à large intestine (colon) à cloaca Organs that help a frog digest but are not part of the digestive tract: liver, pancreas, gallbladder What does the liver do to help digestion? Liver produces bile, which helps digest lipids What does the gallbladder do to help digestion? gallbladder stores bile from the liver and releases it when food enters the digestive system What does the pancreas do to help digestion? The pancreas produces enzymes that digest nutrients in the intestine. How is respiration different in the larva of amphibians than the adult form? in most larval amphibians, gas exchange occurs through skin and gills. In adults, lung replace the gills and some gas continues to be exchanges through the skin and the lining of the mouth. In some land salamanders there are no lungs and the only gas exchange is through the skin. Circulation: double loop, closed circulatory system with a single heart Double loop circulation: the fist loop of blood vessels carries oxygen-poor blood from the heart to the lungs and skin, the second loop takes oxygen-rich blood away from the lung and skin and back to the heart. The three chambers of the amphibian heart: right atrium, left atrium, ventricle Excretion: kidneys filter waste from the blood, create urine, pass the urine through ureters into the cloaca or store it in urinary bladder Reproduction: female lays eggs in water and the male fertilizes them externally, a few species of salamanders have internal fertilizations. Tadpoles: common term for frog larvae Nictating membrane: moveable membrane located inside the regular eyelid, which can be closed over the eye Tympanic membrane: eardrums located on the side of the frog’s head Three groups of amphibians: salamanders, frogs and toads, caecilians

Salamanders (Urodela) and newts: long bodies and tails, most have four legs, larva and adults are carnivores, some keep gills all their lives, live under rocks and rotting logs Frogs and toads (Anura): Amphibians with the ability to jump What is the difference between a frog and toad? frogs have long legs that make lengthy jumps, are most tied to water, and have smoother skin, toads have shorter legs that make smaller jumps, are less tied to water, and have bumpier skin. Caecilians (Apoda) legless amphibians that live in water or burrow in most soil, and have fishlike scales embedded in their skin, which makes them an exception to the amphibian definition For that last few decades, populations of amphibians have been decreasing, sometimes drastically. Nobody knows why but disease and environmental factors affecting amphibian populations are being researched.