Classifying Commercial Marine Species
Click here to download & print the Descriptions of Organisms, Pictures of Organisms, and Classification Worksheet in Adobe Acrobat format.*

Objectives

  • To introduce some of the commercial marine species caught in Magdalena Bay
  • To have students develop a classification system for animals of Magdalena Bay
  • To introduce the classification system used worldwide

 

Vocabulary

  • taxonomy

 

Background

Scientists classify animals with similar features to help them identify and study the millions of plants and animals in the world. This process is called taxonomy. Those animals with backbones, including fish, reptiles, mammals, and birds, are called vertebrates. Scientists place vertebrates in the phylum, or category, Chordata.

Chordates have a rod-like structure, called a notochord, that serves as an internal skeleton. In most Chordates, this notochord is replaced by a backbone. Chordates also have a tail and gill pouches at some stage in their development, sometimes only as embryos. Scientists divide the phylum Chordata into several categories, called classes. Classes found in the Magdalena Bay area include:

Chondrichthyes: Instead of a bony backbone, these animals have skeletons made of cartilage. They do not have air bladders. Sharks, sting rays and skates are Chondrichthites.

Osteichthyes: These animals are fish with bone skeletons. They usually have an air bladder. Osteichthites include trout, mullet, snapper, halibut, triggerfish and tuna.

Mollusca is another phylum well-represented in Magdalena Bay. They are usually aquatic and soft-bodied with a hard shell and a muscular foot that they use to move. Their bodies are one part, not segmented. Classes of Mollusca in Magdalena Bay include:

Bivalvia: These animals have two shells and no distinct heads. Oysters, clams, mussels, and scallops are all bivalves.

Gastropoda: These animals are asymmetrical and usually have a spiral shell. They also have one or two tentacles. Snails, slugs, and abalone are Gastropods.

Cephalopoda: These animals have a "head-foot" with 8-10 arms or many tentacles. Their mouths have two horny jaws, and they have well-developed eyes and nervous systems. Most Cephalopods have ink glands. Octopuses, squids and nautilus are Cephalopods.

The student researchers also study the Arthropoda phylum. These animals are segmented and have paired, jointed appendages. They have an external skeleton called an exoskeleton and are related to insects. Crustacea, a class within this phylum, are mostly aquatic animals with two pairs of antennae and compound eyes. Lobsters, crabs, and shrimp are Crustaceans.

 

Materials

 

Activity

  1. Introduce taxonomy and explain why scientists use it. (Do not introduce the scientific names and characteristics of the phylums and classes now.)
  2. Explain to students that they will be classifying animals that are found in Magdalena Bay and are harvested by fishermen. The goal is to create groups according to the animals’ characteristics.
  3. Hand out Classification, Pictures of Organisms and Descriptions of Organisms Worksheets.
  4. Have students cut the Pictures of Organisms sheet so that each picture is separate. Tell the students they can use space #19 to create an animal to fit in one of their categories.
  5. Have students look at the pictures and read the descriptions. Have them divide the animals into two groups based on a similar or a different trait.
  6. Have students write the traits that they used on lines A and B of the Classification Worksheet (for example: A = animals that swim, B = animals that do not swim). Have them list the organisms under the appropriate trait. They may need to draw more lines.
  7. Have students divide group A into two smaller categories based on another trait using the lines provided (lines C and D).
  8. Have students divide group B into smaller categories using the lines provided.
  9. Have students divide groups C, D, E, and F. They may draw more lines if necessary.
  10. Have students explain how they classified the organisms.
  11. Read the Background to introduce how scientists classify these same animals. Compare the students’ classification systems to the established system. Remind students that all of the animals they learned about in this activity are harvested by fishermen of Magdalena Bay.

 

Extend the Activity

Go to a fish market or the seafood counter at a grocery store and find out the names of the organisms sold there and where they come from.

 

* If you do not have Adobe Acrobat reader, download it for free from www.adobe.com