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Activity: What is a Fish?
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
Table of Contents


  • Table 4.1
  • Pen or pencil



  1. Imagine that someone who has never seen a fish before asks you to teach him or her about fish. What would you tell them? Answer the question by writing down your own definition of what a fish is.
  2. Compare your definition with a group of your peers’ definitions and work together to refine your definition of a fish. Record your groups’ definition of a fish.
  3. Consider the examples of different animals in Table 4.1. For each example, answer the following questions in the table:
    1. Based on your groups’ definition, is this animal a fish?
    2. Do you want to change your fish definition based on this example, and if so, how?
  4. Use Table 4.1 to help you modify your written definition so that it is your best description of a fish.
    1. Look back over the organisms in the list. If you think they are fish, then make sure they fit your definition.
    2. If you think they are not fish, make sure the wording of your definition excludes them. For example, shrimp fit the definition of “an aquatic animal that breathes with gills.” Since a shrimp is not a fish, you would need to modify this definition to exclude shrimp.


Activity Questions
  1. As you developed your group definition of a fish in Step 2,
    1. what ideas did your group have that you had not thought of?
    2. how did you change your mind about your original definition?
  2. Describe how your definition of a fish changed as you worked through Table 4.1.
  3. Why do you think it is so challenging to define what a fish is?
  4. Why do you think that some animals are called fish when they are not really a fish, for example, jellyfish?
  5. Give your best definition of a fish.
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.