External Anatomy


Instructional Level: High School

Driving Question(s):

How do environmental, ecosystem and anthrogenic impacts influence or interact with the anatomical structures and functions of the eastern oyster and related conservation and restoration efforts of this keystone species?



Oysters grow their own individual set of shells (valves) and as a result, no two oysters look alike and thus have own unique shape and form.  These shells are mainly composed of calcium carbonate and are produced by the mantle that puts down the shell in layers.  Along with providing protection for the oyster, these shells provide shelter and a hard substrate for other organisms to attach and grow.  Oysters are the only organism to provide a hard reef-like structure in the Chesapeake Bay, playing an essential part of the bay ecosystem.

This activity combines a hands-on exploration with an online resource.  Teachers can walk through the activity with the entire class or students can work independently.  An offline resource is also available for download to a local computer.


Students will:

  1. Identify the external and internal features of the valves as it relates to the anatomy of the oyster.
  2. Hypothesize about the orientation and symmetry of the oyster.

Lesson Materials

Per Student or Lab Group:

  • Paired oyster shells (enough for 1 pair/student or pair of students)
  • Computer access
  • External Anatomy Worksheet
  • Stereomicroscope (optional)
  • Large Magnifying glass (optional)



  1. If not doing engagement titled “Shell Activity“  make sure students have paired oyster shells from a single oyster.  Students can work independently or in pairs (based on the number of paired oysters you have available).


  1. Give each student(s) a set of paired oyster shells.
  2. Give students 2 minutes to write down observations of the shell characteristics, these observations can include inferences.
  3. Have students share their observations and/or inferences and record for classroom use.
  4. As a class or independently, have students access and complete the external anatomy lab


Working in their group, have students discuss comparative anatomy related to one of the following:

  1. How are the shells of the oyster different from those of another bivalve (clam, mussel, scallop)?
  2. Shells are composed on calcium carbonate (CaCO3).  Calciums comes from the salt in the ocean, where does the carbon in the carbonate come from? See Acid Test for the Great Shellfish Bay?, Chesapeake Quarterly, March 2012, Vol 11, Num 1.


  1. Have students complete the External Anatomy Worksheet (assessment of the major external features).
  2. Have students share their sketches for peer to peer evaluation.
  3. Provide opportunity for students to explain their sketch using critical thinking and reasoning skills.


Next General Science Standards

Performance Expectation:  HS-LS1-2   

  • SEP: Developing and Using Models
    • Modeling in 9–12 builds on K–8 experiences and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds.
      • Develop and use a model based on evidence to illustrate the relationships between systems or between components of a system.
  • DCI: Structure and Function
    • Multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a component of the next level.
  • CCC: Systems and System Models
    • Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions— including energy, matter, and information flows—within and between systems at different scales. 

Performance Expectation:  HS-LS2-6

  • SEP: Engaging in Argument from Evidence
    • Engaging in argument from evidence in 9–12 builds on K–8 experiences and progresses to using appropriate and sufficient evidence and scientific reasoning to defend and critique claims and explanations about the natural and designed world(s). Arguments may also come from current scientific or historical episodes in science.
      • Evaluate the claims, evidence, and reasoning behind currently accepted explanations or solutions to determine the merits of arguments.
  • DCI: Ecosystem Dynamics, Functioning, and Resilience
    • A complex set of interactions within an ecosystem can keep its numbers and types of organisms relatively constant over long periods of time under stable conditions. If a modest biological or physical disturbance to an ecosystem occurs, it may return to its more or less original status (i.e., the ecosystem is resilient), as opposed to becoming a very different ecosystem. Extreme fluctuations in conditions or the size of any population, however, can challenge the functioning of ecosystems in terms of resources and habitat availability. 
  • CCC: Stability and Change
    • Much of science deals with constructing explanations of how things change and how they remain stable.

Maryland E-Lit Standards

  • None


External Anatomy Lab

External Anatomy Worksheet

Acid Test for the Great Shellfish Bay?, Chesapeake Quarterly, March 2012, Vol 11, Num 1

**Use of images with permission, J. Adam Frederick**

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