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Objectives

Students should be able to:

  1. Understand the broad concept of taxonomy
  2. Understand some important systematic approaches, especially Cladistics Phylogenetics, or simply Cladistics.
  3. Describe the species concept
  4. Define and describe taxonomic groups and hierarchies
  5. Construction and use of taxonomic key
  6. Understand nomenclature, classification, and identification of organisms

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Introduction

Classification

The essence of systematics or taxonomy is embodied in the appreciation of evolutionary relationships amongst the more than 1.5 million biological species already known to man. Systematists seek to understand the diversity of life, and to reconstruct the evolutionary or phylogenetic relationship amongst the different kinds of organisms that lived in the past or are currently cohabiting the earth.

Systematists traditionally use evidences derived from fossil record and morphological and anatomical studies of extant organisms to reconstruct phylogeny. Today, molecular biology such as amino acid sequences of proteins and nucleotide sequences of DNA and RNA, provide powerful tools for systematics.

Cladistics

 

The concept of Cladistics was pioneered in 1950 by a German entomologist named Willi Hennig, who published a short book in which he proposed the basic ideas that changed taxonomy. The term Cladistics takes its name from the concept of a "clade", which Hennig defined as a group of organisms related by common descent.

The objective of cladistics is to classify organisms according to their evolutionary relationships, and that the way to discern these relationships is to determine what characters are primitive and which are considered derived characters. The former are those attributes of an organism, which all members of the group have in common to one another. Commonly shared or primitive characters shared by all members of the group in question are called symplesiomorphic.

Derived characters are relatively recent in evolutionary appearance, and are also considered advanced traits that only appear in a few members of the group. Cladistics taxonomy makes the assumption that the appearance of derived characters may provide information to evolutionary relationships.

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Pre-lab Activities

This section is intended to guide student towards a brief but meaningful survey of relevant taxonomic literature. It should be useful in helping you appreciate the purpose of the exercises involved in the following sections.

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Pre-Laboratory Activity #1 - Linne Biography

Click on Access Science (from the LRC Homepage) and find a biography of Carl von Linné. Print it out, read it, it will help you with your Pre-Lab Questions. Attach it to your Pre-Lab Questions

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Pre-Laboratory Activity #2 - Sample Dichotomous Key

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Sample Dichotomous Key - Download and print out this key.

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Pre-Laboratory Activity #3 - Data Collection Sheet

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Data Collection Sheet - Systematics - Download and print out this sheet.

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Pre-Laboratory Activity #4 - Using Dichotomous Keys

Dichotomous keys are useful for rapid and correct identification of various species. You will be using two keys, one for plants and the other for animals. The first is a dichotomous key for some common trees in the winter condition. The second is a pictorial key for the identification of fleas. Download and print out all of the following:

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Dichotomous Key for Trees in the Winter Condition - Download and print out this key.

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Key to Fleas - Courtesy of U.S. Public Health Service

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Aid to Flea Identification

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Flea #1

SIPH001B.GIF
Major external features of a flea, Siphonaptera
Resolution 1168x1161x2, 38,747 bytes
Submitted by: I. Livingston
Displayed at 1:2
Image courtesy of BIODIDAC, University of Ottawa, Canada
12 January 2004
 

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Flea #2

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Flea #3

Image courtesy of:
Public Health Image Library (PHIL)
Centers for Disease Control and Prevention
1600 Clifton Rd.
Atlanta, GA 30333 U.S.A
http://phil.cdc.gov/phil/default.asp
12 January 2004
 

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Pre-Lab Questions (Html version)      Pre-Lab Questions (Word version)

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The Laboratory Activities and Data Collection

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Lab Activity #1 - Species Description

Materials:

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Numbered specimen

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Data Collection Sheet - Downloaded and printed out


Procedures:

  1. Examine one of the specimens provided and write your own description of that specimen. Remember to use only features that appear to have biological significance. (See Pre-lab question  concerning biological features)

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Lab Activity #2 - Species Classification

Materials:

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Data Collection Sheet - Downloaded and printed out


Procedures:

  1. Provide a complete classification of the three specimens provided. Include all the hierarchical levels from Domain to Species. You may have to search this information in some published material, the Learning Resources Center, or the World Wide Web.

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Lab Activity #3 - Using Dichotomous Keys - Plants

Materials:

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Dichotomous Key - Downloaded and printed out

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Assortment of tree twigs

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Data Collection Sheet - Downloaded and printed out

Procedures:

  1. Obtain the tree twigs that you need to identify.

  2. Using the dichotomous key, identify the tree species.

  3. Place the information requested on the Data Collection Sheet.

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Lab Activity #4 - Using Dichotomous Keys -  Animals

Materials:

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Pictorial key for common fleas

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3 Flea pictures

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Aid to Flea Identification

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Data Collection Sheet

Procedures:

  1. Using the flea key and aid to flea identification, identify the three fleas shown in the pictures.

  2. Place your identification of the fleas on the Data Collection Sheet.

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Lab Activity #5 - Constructing a Simple Dichotomous Key

Materials:

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Sample Key - Downloaded and printed out for study


Procedures:

  1. You are provided with five organisms. Using the sample key and the steps provided below, construct a dichotomous key with which someone unfamiliar with the group can identify the five organisms.

    1. Select any obvious features or differences in the same feature that divide the organisms into two dichotomous groups (couplet).
    2. Select another feature that further subdivides each of the two dichotomous groups formed above into two dichotomous groups and so on.

    3. Repeat the above procedure as necessary to construct another couplet thus, distinguishing each member of the group.

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Lab Activity #6 - Cladistics

Materials:

bulletCladogram - Downloaded and printed out
bulletData Collection Sheet - Downloaded and printed out

Procedures:

  1. Follow the procedures as they appear on the Cladogram.

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Post-lab Activity and Data Analysis

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Results and Analysis

Below are listed the activities you performed in lab and the results and analysis materials that are to be given to the instructor.

  1. Completed Data Collection Sheet

  2. Post-Lab Questions - Answered

  3. Any other materials requested by the instructor

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Post-Lab Questions (Html format)        Post-Lab Questions (Word format)

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