Virtual Systematics Lab: Introduction to Systematics Worksheet

Learning Goal: To learn how biologists classify species based on their evolutionary relationships.
Prerequisite Knowledge: Before beginning this lab, you should be familiar with these concepts: • why biologists today use the three-domain system of classification • how evolutionary trees depict biologists’ understandings about the evolutionary relationships among groups of organisms
Introduction: Almost every place on Earth, from the surface of your skin to the bottom of the ocean, is teeming with living things. To keep track of the vast diversity of life, biologists historically named and classified organisms according to their appearance. The system of categorizing organisms is known as taxonomy. Today, scientists classify organisms into taxonomic groups (taxa) according to their evolutionary history. This discipline is known as systematics.
The Virtual Systematics Lab features a collection of pictures and descriptions of diverse species that represent major evolutionary pathways. In the Systematics Lab, you can explore five different taxonomic classification schemes that biologists have used--from the traditional Linnaean scheme to the current three-domain system.
In this activity, you will learn how to use the Virtual Systematics Lab to identify the characteristics that various organisms share and to determine the relatedness of different taxa.

Part A
Enter the Systematics Lab Room by clicking the button. Then, follow the lab procedure.
[pic]
|Lab Procedure |
|Locate the main window of the Systematics Lab Room--it is the large white box that shows taxonomic pathways, commonly known as|
|evolutionary trees. |

What three taxa appear in the main window when you first enter the Systematics Lab Room? At what level of classification are these three taxa?

|ANSWER: |

The three taxa that appear when the lab opens are: Archaea, Bacteria, and Eukarya. All three of these titles are domain names which is the first tier in the classification process followed by kingdom, phylum, class, order, family, genus, species, and sub-species.

Part B
|Locate the Traits box at the lower left of your computer screen. Then, roll over the name Archaea on the main window and |
|notice that information about that selected group appears in the Traits box. |
|Click on the term peptidoglycan in the Traits box, and notice that its definition appears in the Glossary box directly above |
|the Traits box. |
|Roll over the other two names in the main window to find out about their traits. Click on any unfamiliar terms to learn their |
|definitions. |

List one trait for each of these three taxa that distinguishes it from the others.

|ANSWER: |

Each of the domain names listed have special traits. Archaea, for example, have cell walls that lack peptidoglycan, a polymer found in the cell walls of prokaryotes. The cell walls of Bacteria, however, do contain peptidoglycan. Eukarya, oddly, can be either multicellular or unicellular.

Part C
|Click on the name Eukarya in the main window. Notice the two boxes below the main window that are titled “Included” and |
|“Excluded.” The information in these boxes indicates which species are included and which are excluded from the group you |
|selected. You can select either Pictures or Text as a way to view the included and excluded species. |

Which of these organisms are included in Eukarya? Select all that apply.

ANSWER:

__x__ Yeast

__x__ C. elegans

_x___ Ponderosa pine

____ E. coli
| | |

Part D
|When you clicked on Eukarya in the main window, the names of the five supergroups of eukaryotes appeared, reflecting one |
|current hypothesis of eukaryote evolution. Click on Unikonta, which is the supergroup that includes animals. |
|Continue to click on the groups in this sequence until you get to the phylum Chordata: |
|Opisthokonta > Metazoa > Eumetazoa > Bilateria > Deuterostomia > Chordata |
|Using the Included and Excluded boxes beneath the main window, use a trial-and-error approach to click through the groups |
|under phylum Chordata until you’ve found classes Mammalia and Reptilia. |

What groups did you click through to get to classes Mammalia and Reptilia?

|ANSWER: |

The phylum groups I had to click through are as follows: Chordata, Craniata, Vertebrata, Gnathostomata, Osteichthyes, Sarcopterygii, Tetrapoda and Amniota. This brought us to the class groups Mammalia and Reptilia.

Part E
|Click on Mammalia. Use the Included box to identify some animals included in this class. |
|Now, click on Reptilia and use the Included box to identify some animals included in this class. |

Which two of the following species are more closely related: red-eared slider, vampire bat, American alligator?

|ANSWER: |

The red-eared slider and the American alligator are both included in the Reptilia group and so they would be more closely related.

Part F
|Click on class Reptilia, and continue to click on the groups in this sequence until you get to the order Saurischia: |
|Diapsida > Archosauria > Dinosauria > Saurischia |
|Now, click through the different branches contained within Saurischia. |

Are all of the saurischians extinct? Explain.

|ANSWER: |

No not all of the saurischians are extinct. Some of them are such as the brontosaurus and t-rex. However, there are still some of them that still exist today such as chickens and ostriches.

Part G
Here’s how you can use the Lab Book to examine multiple branches of a tree at the same time.
|Drag the tree in the main window to the right until you get back to where you had selected Deuterostomia in step 7. |
|Now, instead of Deuterostomia, click on Ecdysozoa. Then, click on these taxa in this sequence: |
|Arthropoda > Hexapoda > Insecta > Isoptera > Rhinotermitidae > Reticulitermes |

What is the common name of the species you have arrived at?

|ANSWER: |

The only organism in the included area is the termite so that is the common name for the class reticulitermes.

Part H
|Click the Save button located above the left side of the main window. This will save this view of this particular branch of |
|this tree to the Lab Book. You can save as many opened branches to the Lab Book as you like, and they will remain saved until |
|you exit the lab room or close your Internet browser window. |
|Now, drag the tree window back to where you had selected Arthropoda in step 14. This time, click through these taxa in this |
|sequence: |
|Arthropoda > Crustacea > Malacostraca > Decapoda > Nephropidae > Homarus |

What is the common name of the species you have arrived at?

|ANSWER: |

The only name in the included section is the American lobster.

Part I
|Click the Save button to save this branch to the Lab Book. |
|Now, click on the red Lab Book next to the clipboard on the lab bench. Open either of the trees you saved by clicking on the |
|tree icon in front of its title. |
|On the left-hand page where the opened tree appears, right-click (or Ctrl-click) on the tree, and select Copy Data. |
|Next, open the other tree, and then right-click (or Ctrl-click) on the left-hand page. Select Paste Data. Using the scroll |
|bar, you should see the two trees, one above the other. |
|Select both trees by command- or Ctrl-clicking on both. Then, click Combine Trees in the upper left corner of the Lab Book. |
|The two trees will merge so that the point at which their lineages diverged is more obvious. |

What is the name and level of the taxon where the two species’ lineages diverge?

|ANSWER: |

Both species branch off of the Arthropoda taxon.

Part J
Think It Over
In one sentence, summarize how these two species are related and what distinguishes them taxonomically.

|ANSWER: |

The two species follow the same lineage until they reach the arthropoda taxon and then one continues in the crustacea taxon while the other continues in the hexapoda taxon. One is a crustacean, American lobster, and the other is an insect, termite.