Classification of Organisms - Catholic Texts

BIO Lab 17: Classification of Organisms

Classification of Organisms

And God said: Let the earth bring forth the living creature in its kind, Cattle and creeping things, and beasts of the earth, according to their kinds.

And it was so done....And God saw that is was good. Genesis 1:24-25

Introduction

Scientists have an overwhelming task when attempting to classify organisms. Several factors can be considered in separating one organism from another: physical characteristics; mode of locomotion; physiological traits; biochemical analyses; and others.

Carolus Linnaeus developed a classification system in the eighteenth century, a form of which is still used today. The Linnaean Classification System formalized the science of taxonomy ? the science of grouping, describing, identifying and classifying all microorganisms, plants and animals.

The Linnaean Classification is hierarchical with the greatest number of subjects in the first group or taxon, and increasingly more specific and narrow in the last group or taxon. Linnaeus also named organisms according to a binomial system and is known as binomial nomenclature. Individual organisms are given a Latin name with two parts. The first Latin name identifies the Genus (and is capitalized). The second name identifies the Species and is specific to the unique organism. For example, the gray wolf has the scientific Latin name, Canis lupus or C. lupus.

Learning Objectives:

? Use of a dichotomous key to classify organisms ? Sort objects into groups based on similarities

Materials Required:

From Biology Kit

Keys provided Appendices

Student Supplied

Scissors

Experiment Part 1? Using a Dichotomous Key

Introduction ?

Many nature field guides have been written to assist the naturalist in identifying specimens encountered in the field. They typically use dichotomous keys. A dichotomous key is used to identify organisms. The word "dichotomous" is Greek: dikho ? meaning "in two"; and, temnein ? meaning "to cut". A dichotomous key is a flow chart in which a trait is examined, and specimens are split into two distinct groups each time.

?2016 Catholic Initiatives in Math and Science, LLC

All Rights Reserved

1

BIO Lab 17: Classification of Organisms

For example, look at the Partial Dichotomous Key for Insects below. This flowchart was used for an insect (pictured to the left) to determine which Order in which it belonged. The, first question asked in the flowchart was ? "Are the wings functional?". The "Yes" answer led to the second question ? "Are there scaled wing coiled mouthparts?". Here, the "No" answer led to the third question ? "How many pairs of wings?". When the answer, "3 pairs", was given, the Order could be established as Diptera. By repeating this process with the appropriate dichotomous keys, groups of organisms may be divided into distinct and related categories.

Table 1 in the Lab Report is a sample of a dichotomous key used to place insects into Orders.

It is identical to the flowchart. Notice that Question #1 asks about the presence/absence of functional wings. You will work with this key in Part 1 below.

PROCEDURE ? Part 1

1. Identify the Order of Sample 1 ? Place the figure of Sample 1 (found in Appendix A) in front of you ? Use the Dichotomous Key in Table 1 of the Lab Report ? Start at 1a and 1b of Table 1 Determine whether 1a or 1b provides the better description Under "Your Notes" column, note which choices were made Follow the closest match to the next number specified Continue following the key until the Order is identified Record the results in Table 2

?2016 Catholic Initiatives in Math and Science, LLC

All Rights Reserved

2

BIO Lab 17: Classification of Organisms

2. Identify the Order of Sample 2 ? Place the figure of Sample 2 (found in Appendix A) in front of you ? Use the Dichotomous Key in Table 1 ? Repeat the steps that you used in step 1 to identify the insect

3. Proceed to Part 2

Experiment Part 2? Sorting Objects

Introduction ?

When scientists sort organisms, they typically place them in categories according to physical characteristics. Those organisms sharing a physical characteristic (or characteristics) will be placed in a group. In this experiment, you will sort fasteners into groups according to similarities in physical features. If you are part of a class, you may want to share your results with others.

Note: Be on the lookout for a sample that may have similar physical characteristics, but has a different function from the other objects!

PROCEDURE ? Part 2 ? Sorting objects

1. Obtain the set of object photographs found in Appendix B

2. Cut out the 18 samples and place them in front of you so that you can see them all

The coins are only placed in the photographs to give an idea of size. The objects of interest are NOT the coins!

3. Pick up one sample object ? Find other samples that seem most similar to the one you have in your hand ? Place these cut-out objects in a pile clearly separated from the others ? In Table 3, write down the sample names and the properties shared between them

4. Pick up another sample object from the main pile ? Find samples that share physical characteristics to this sample ? Place these in another separate pile ? In Table 3, write down the sample names and the shared properties

5. Continue sorting until all 18 objects are in a group ? You do not need to have all rows filled in the table provided ? It is acceptable to have only one sample in a group

6. OPTIONAL: Share your findings with others in your class

7. Perform Data Analyses and Conclusions

?2016 Catholic Initiatives in Math and Science, LLC

All Rights Reserved

3

BIO Lab 17: Classification of Organisms

The coins are only placed in the photographs to give an idea of size. The objects of interest are NOT the coins!

?2016 Catholic Initiatives in Math and Science, LLC

All Rights Reserved

4

BIO Lab 17: Classification of Organisms

?2016 Catholic Initiatives in Math and Science, LLC

All Rights Reserved

5

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download