October 24, 2012
Specific Purpose: To inform my audience about the different classifications of fish. Central Idea: Fish are classified by their different characteristics which sorts them into different classes like Agnatha, Chondrichthyes, and Osteichthyes. Introduction
I. Classification of living things helps people to understand how living organisms may or may not be related to each other. A. The system of classification we use today was invented 200 years ago by Carl Linnaeus. B. Carl Linnaeus system of classification groups organisms by their characteristics or features they have in common. II. According to the book Vertebrate Biology by ORR Robert; Fish, mammals, reptiles, birds, and amphibians are classified together as vertebrates because they all have an internal backbone. III. In researching this particular topic, I learned that the most important characteristics used in fish classification are the type of bone in their skeleton, the gill structure, the number and shape of fins, and the type of scales. IV. Now I will introduce you to the characteristics and the three different classes of fish. “Jawless (Agnatha), Cartilaginous (Chondrichthyes), and Bony Fish (Osteichthyes). Body
I. The Agnatha class is the oldest group, similar to fish but with some different characteristics. A. As explained in The Evolution of Vertebrate Design, certain characteristics like lacking jaws is what classified fish to this class. 1. The Agnatha class lacks an internal bone skeleton, jaws, and paired fins. 2. Instead of jaws, they have circular toothed mouths called cyclostomic. Which they use to suck blood from the side of their prey. 3. They have a smooth, scale less skin which is soft to the touch. B. There are two living groups of Agnatha the lampreys and Hagfish 1. Lamprey have a single dorsal nostril, a pineal eye, three fins (anterior, posterior,...