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VERTEBRATES Vertebrates belong to the subphylum Vertebrata of the Phylum Chordata. Vertebrates include fish, amphibians, reptiles, birds, and mammals. Remember that all chordates, including vertebrates, Share four main characteristics which include: a) dorsal nerve cord (spinal cord / brain) b) notochord (backbone) c) gill slits or pouches (gills / lungs) d) post-anal tail (kept by most vertebrates) The backbone, which surrounds the spinal cord, is made up of bony segments called VERTEBRAE. The vertebrates have an endoskeleton which has two main parts: 1.) Axial Skeleton – It is made up of the vertebral column, skull, and rib cage. It supports the body and protects the spinal column, brain, and other internal organs. 2.) Appendicular Skeleton – It is made up of the appendage bones and the wide flattened girdles to which they are attached. It is attached to the axial skeleton. Other vertebrate characteristics include a welldeveloped brain and sensory organs, a closed circulatory system, and a multi-chambered heart. FISHES Inhabit nearly every type of aquatic environment on Earth Characteristics of all fish: 1. breathe using gills as a fish takes water in through its mouth, water passes over the gills and then out through slits at the side of the fish 2. have 2 chambered hearts one chamber receives oxygen-poor blood from the body tissues the other chamber pumps blood directly to the capillaries of the gills, where oxygen is picked up and carbon dioxide releases 3. reproduce sexually fertilization & development is external in MOST fishes eggs & sperm can be released directly into the water, or deposited in more protected areas 4. highly developed sensory systems have eyes that allow them to see objects & contrast between light and dark in the water, but the amount of vision varies among fishes fishes can be grouped into 4 classes: Super Class Agnatha: - jawless fish - have smooth, scaleless skin & long cylindrical body - have cartilaginous skeleton, - no vertebral column - only vertebrates to retain notochord through all stages of their life 1. Class Cephalaspidomorphi: lampreys most are parasites that hitch rides on their hosts, often killing its host as it sucks out its victim’s body fluids 2. Class Myxini: hagfish bottom dwellers that spend most of their time hiding in mud and sand scavenger that eats fish that are already dead or dying 3. CLASS CHONDRICHTHYES: (cartilage fish) - includes sharks, rays, & skates - have hinged jaws and paired fins - have internal fertilization - skates deposit fertilized eggs on the ocean floor - some female sharks & rays carry developing young inside their bodies - have a lateral line system that enables them to sense objects and changes in their environment - is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water Sharks: - would sink if they did not swim continuously because they are denser than water (also suffocate if water not moving over gills) - have tough, leathery skin that is covered with PLACOID SCALES - mouth is lined with 6-20 rows of sharp teeth which continuously form and move forward to replace lost or worn teeth - have a screw-like membrane, called a SPIRAL VALVE, which extends through the centre of the intestine. It slows the movement of food to give more time for digestion - have a large, oily liver that can make up nearly 20% of its total body weight (liver oil is lighter than water and gives sharks buoyancy) 4. CLASS OSTEICHTHYES (bony fish) - includes: i)ray-finned fish (salmon, guppies, tuna) - fan-like moveable fins made of thin membrane supported by bony rays - use their paired pectoral and pelvic fins to steer, brake, move up and down, and even swim backwards - skin is covered with thin, round scales, called CYCLOID SCALES, which overlap like shingles (can determine age by counting rings of scales) - mucus covers scales giving the fish a slimy surface - have a thin-walled sac in the abdominal cavity filled with gas called a SWIM BLADDER dissolved gases in the blood diffuse into & out of the swim bladder as the bladder fills up, the fish rises and when it deflates, the fish sinks - have four pairs of gills & each set of gills is covered by a protective flap of tissue called an OPERCULUM - Unlike sharks, can pump water through their gills even when motionless - also have a lateral line system that detect changes in pressure and vibrations in water - have two pairs of nostrils as well as chemical receptors scattered over their head and body. Smell usually gives fish their first clues about food, mates, and enemies - most have separate sexes and fertilization is external ii) lobe-finned fish (lungfish & coelacanth)