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Dichotomous Key
Administration Procedures

8th Grade Performance Task
Contributed by: New York State Education Department (NYSED)
NYS Alternative Assessment in Science Project (1996)


Students use a dichotomous key to identify unknown fictitious organisms.

This task assesses students' abilities to classify, and hypothesize about and interpret data.

Note: 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.

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

Overall Task Content Area:

Life Science

Specific Knowledge Areas:

Populations and ecosystems

Performance Expectations:

  • using equipment
  • gathering, organizing, and representing data
  • formulating conclusions from investigational data

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.

Students will be working individually during this exercise.

Students should be ready to work as soon as the period begins. The materials should be set out at each lab station, if possible. A central supply area, if needed, should be easily accessible. All supplies should be clearly labeled.

Materials for "Dichotomous Key":


Advance Preparation:



  • 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.


Dichotomous Key 2


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