2.  Dogfish because they turn their head side to side when they swim  Spiny because they have spines near their fins

3.  K: Animalia  P: Chordata  SP: Vertebrata  C: Condrichthyes  O: Squaliformes  F: Squalidae  G: Squalus  S: S. acanthius

4.  Sharks have been around for over 300 million years  There are over 300 species of sharks

5.  Head: broad, flattened  Trunk: fusiform in shape to help with locomotion  Tail: compressed laterally, principal organ of locomotion

6.  Rostrum: pointed snout at the anterior end of the body, helps overcome water resistance  Nares: external nostrils, located on ventral surface of rostrum, used to detect odors in the water  Jaws: on underside of head, sharp pointed teeth in rows (replaceable),

7.  Spiracle: modified gill slit, serves in water intake when jaws are grasping food  Eyes: immovable eyelid, can not focus on one object simultaneously  Lateral Line: extends from spiracle to tail, receptor for vibrations and pressure changes

8.  Pectoral Fins: located ventrolaterally behind the gill slits, helps with manuvering and keeping shark horizontal in water  Pelvic fins: located ventrolaterally at the end of the trunk  Dorsal Fins: unpaired, located on the dorsomedial line, 1 st behind pectoral fin other behind the pelvic line

9.  Caudal fin: major part of tail, consists of dorsal lobe and ventral lobe of unequal size  Mouth: located subterminally  Teeth: modified placoid scales, arranged in rows, can be replaced

10.  Endolymphatic Pores: lead to endolymphatic duct, used in equilibrium  Ampullae of Lorenzini: pores in the skin at the top and bottom of head › Functions: electrical potential; hydrostatic pressure, temp gradient, salinity gradient

11.  Claspers: modified copulatory organs located on the edges of the pelvic fin in adult male sharks  Cloaca: common exit for the digestive, urinary and reproductive systems  Papilla: Males- urogenital papilla, exit for urine and sperm; Females-urinary papilla, exit for urine only

12.  Abdominal Pore: located on the lateral edges of the cloaca, serves as outlets for excess coelomic fluid

13.  Placoid Scales: modifications of teeth, embedded in skin pointing caudally  Development is very similar to teeth in higher vertebrates, including humans http://1.bp.blogspot.com/_D6I3F3P3x_4/S9iyOaQ5N9I/AAAAAAAAAFg/6Jfa3MUF3L4/s400/placoid+scale.jpg