administration student task rubric student work technical quality
Dichotomous Key 2
Administration Procedures
Contributed by: New York State Alternative Assessment in Science Project (NYSED)


Students use a dichotomous key to identify unknown fictitious organisms.

The task is designed to be completed by individual students. However, you may wish to have students complete question #1 in small cooperative groups, and then have students work individually to complete questions 2-4.

This activity is to be used as an assessment after students have been exposed to the use of a dichotomous key, and therefore know what the term "dichotomous" refers to, and how it is used. There are 13 species of "Triangulum" pictured on the species sheet that goes with the student directions for the task. It is suggested that each student (or student group) identifies any three of the species in the time allotted to complete the task.

This task is designed to take students approximately 15-25 minutes to complete.

Overall Task Content Area:

Life Science

Specific Knowledge Areas:

Populations/Biological evolution

Performance Expectations:

  • conducting investigations
  • using equipment
  • gathering, organizing, and representing data
  • formulating conclusions from investigational data
  • applying scientific principles to develop explanations and solve new problems

National Science Education Standards:

8 A SI 1: Abilities necessary to do scientific inquiry: Grades 5-8
1.4 Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description - providing causes for effects and establishing relationships based on evidence and logical argument. This standards requires a subject knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge.

8 C LS 5: Diversity and adaptations of organisms: Grades 5-8
5.1 Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

(Use the "hot" link on the PALS home page to check the full text of related National Science Education Standards, if desired.)

National Council of Teachers of Mathematics:

PS2: Solve problems that arise in mathematics and in other contexts:
Grades 6-8

General Instructions to the Teacher:

This task is designed to take students approximately 15-25 minutes to complete. An expanded version in which students identify all 13 species of Triangulum on the species sheet would require approximately 45 minutes to complete.

This task can be used in conjunction with other (similar) performance tasks by having students (or student groups) rotate between stations. Since this task may take only 20 minutes or less for students to complete, the teacher will have to decide how best to use the remaining time in a typical class period.

If students are to work in groups, group assignments should be made in advance.


At this station students should have:

  • metric rulers

Advance Preparation:

  • N/A


  • Be careful.
  • Teachers and students should always exercise appropriate safety precautions and utilize appropriate laboratory safety procedures and equipment when working on science performance tasks.


  • N/A


©1997-2005 SRI International. All rights reserved. Terms of Use