How has DNA sequencing affected the science of classifying organisms?

Lab 6: Taxonomy


Pre-Lab Questions

1. Use the following classifications to determine which organism is least related out of the three. Explain your rationale. (1 pts)

The Eastern Newt is the least related organism out of the three. While all three are classified into the same domain, kingdom, phylum and class the Eastern Newt is in a different order than the American Green Tree Frog and the European Fire-Bellied Toad.

2. How has DNA sequencing affected the science of classifying organisms? (1 pts)

DNA sequencing has allowed for the comparison of genes at the molecular level as opposed to physical traits at the organism level. Physical traits can be misleading when classifying how related two organisms are. DNA sequencing can also trace relatedness through generations and more accurately assess how closely related two organisms are.

3. You are on vacation and see an organism that you do not recognize. Discuss what possible steps you can take to classify it. (1 pts)

The organism’s physical features can be used to compare it to known organisms. Some physiological features can even possibly be used to help classify it.


Experiment 1: Dichotomous Key Practice Level American Green Tree

Fro  g

European Fire-

Bellied Toadinomial Name

Table 3: Dichotomous Key Results

(2 pts each)

Post-Lab Questions

1. What do you notice about the options of each step as they go from number one up. (1 pt)

The options become more and more specific.

2. How does your answer from question one relate to the Linnaean classification system? (1 pts)

The dichotomous key options became more and more specific as they came closer to identifying the organism just like the classification system starts as a broad category (i.e, animal kingdom) and becomes more specific until a unique species is classified (i.e., species).

Experiment 2: Classification of Organisms

The flow chart questions will lead you to the correct classification of the organisms into their respective kingdoms. Table 2, shown above, has an error in your lab manual–sunflowers do not have motility. Most of you saw the discrepancy and went with the answer you got from the flow chart. For the blanks in the completed table (above), that’s because those answers are variable, and not necessary to identify that organism using the given flow chart. (3 pts)

Post-Lab Questions

1. Did this series of questions correctly organize each organism? Why or why not? (2)

Yes. If the questions in the “tree” were answered correctly, each organism should end up in the correct kingdom.

2. What additional questions would you ask to further categorize the items within the domains and kingdoms (Hint: think about other organisms in the kingdom and what makes them different than the examples used here)? (2 pts)

Your answers will vary, but you should have brainstormed other organisms that belong to each domain or kingdom. For example, fish are also in the animal kingdom – how do fish differ from bears (gills instead of lungs, live in water, etc.)? What makes types of protists different from each other (shape, form of motion, etc.)?

3. What questions would you have asked of the ones that you answered about when classifying the organisms? (2 pts)

Answers will vary.


· Bacteria: Is it a membrane bound organelle?

· Fungi: Is it a yeast or mold?

· Plantae: Does it have a cell wall?

· Animalia: Is it multicellular?

· Protista: Is it a eukaryote, but, not an animal, plant, or fungi?

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