Materials Included In Kit

Prelab Preparation

Use the black line masters to make enough copies of all materials for individual student use.

Safety Precautions

This activity is considered nonhazardous. Follow all standard laboratory safety guidelines.

Disposal

The master copies of the Dichotomous Key to Norits, Norits Drawing Sheet and Norits Classification Worksheet should be saved for future use.

Teacher Tips

• Not all terms in the Norits Dichotomous Key are defined but in the context of the activity, students will be able to formulate definitions and make key decisions without much help. (This also illustrates one of the major problems encountered when using real dichotomous keys.)

• All materials are reusable.
• This activity is an excellent first day activity for introducing taxonomic keys. It can be completed in one class period. After using the key to the Norits, it will be an easy transition to dichotomous keys for real organisms.
• Have other taxonomic keys available and use them after the Norits experience.
• The activity worksheet is easily scored and incorporated into your evaluation scheme. The numbered pathways and the drawing in question 5 will easily reveal if a student is having trouble with the concepts in the activity. The activity materials can be easily adapted for evaluation purposes at the end of student work with taxonomic keys.

Sample Data

Answers to Questions

1. What characteristics do all Norits seem to have in common?
   

   All seem to have a shake and shake spots as well as other key body parts, such as felt(s), apus, mora and prop(s).
   

2. What characteristic do biologists seem to feel is most important when classifying Norits?
   

   The segmentation of the mora is a key first division that divides the Nortis genus from the Rossi genus.
   

3. Why might the key used to classify Norits ever change?
   

   As new anatomical, genetic, behavioral or other data are collected more important relationships might be revealed.
   

4. How might observing living Norits affect how they might be classified?
   

   Behaviors might become more important than structural makeup. Will Nortis breed with Rossi, for example?
   

5. Draw a picture of what a Rossi multiops might look like.

Introduction

Life has been found in a water sample from the planet Norad. Biologists, in an attempt to organize their writings and descriptions of the organisms, have named and classified them. Learn how to use a dichotomous key as you identify the Norits from Norad.

Concepts

• Classification

• Binomial nomenclature
• Taxonomy
• Dichotomous keys

Background

The number and different kinds of organisms in the world is mind-boggling. Keeping track of all the various species and trying to identify relationships between them presents a great challenge. Imagine trying to identify relationships between organisms as diverse as giraffes, microbes, fish and oak trees. Just trying to sort out one species, such as ants, is a real challenge. Biologists like to group “like things” with “like things,” that is, put them into logical categories. The question becomes—what logic, whose logic and what is logical? The field of biology that identifies and classifies organisms into categories is called taxonomy.

Taxonomists analyze shared characteristics to determine possible relationships between organisms. As more and more information is collected about various species, the relationships (categories) often change. The field of taxonomy is a changing one and one that often results in serious disagreements.

The general classification system that biologists use today is based upon a system developed in the mid-1700s by a Swedish biologist named Carl von Linnaeus. He established a system of groups he called taxa (singular taxon). Each taxon is a category into which related organisms are placed. Thus, the name taxonomy. Linnaeus ranked taxa from the broadest, most general groups to the smallest, most specific groups.

The broadest, most general group was called a kingdom. Kingdoms are divided into groups called phyla. Within each phylum there are groups called classes. Classes are then divided into orders. Orders are divided into families. Families are divided into genera. Finally genera are divided into species.

Linnaeus proposed further to use a binominal nomenclature system for naming each species. Each species has a two-part name. First there is the genus name and this is followed by the species name. The genus name is capitalized and the species name is not. Both words of the name are printed in italics or underlined. For example, the biological name for the animal we commonly call the lion is Panthera leo. The tiger is Panthera tigris while the house cat is Felis catus.

The complete classification of the three cats is shown in Table 1.

Which of these cats are most closely related?

Materials

Safety Precautions

This activity is considered nonhazardous. Follow all standard laboratory safety guidelines.

Procedure

1. Study the basic anatomy of a Norit as shown in Figure 1.

2. Choose a Norit from the Norits Drawings Sheet and use the Dichotomous Key to Norits to identify (name) the Norit. Start at step 1 and read the two choices (dichotomous) and determine which description best describes the Norit you are looking at.
3. Select the choice that best fits the Norit, and follow the direction given at the end of the line (e.g., Go to number 9). Record the numbers of the path you follow as you work through the key for the Norit.
4. Eventually you will run out of choices and you will arrive at the “scientific” name for the Norit in question. Record the name on your Norits Classification Worksheet.
5. Key each of the organisms A–J from the Nortis Drawings Sheet similarly. Record each numbered pathway and the name of each organism.
6. Answer the five questions on the Norits Classification Worksheet.

Student Worksheet PDF

10256_Student1.pdf