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I. Oysters: Inside and Out

Summary

This activity explores the physical characteristics that make oysters 

efficient filter feeders through an investigation into oyster external 

and internal anatomy. They will design a water filter and test its 

function with dirty water, then investigate the ecosystem services 

that oyster reefs provide to organisms that depend on oyster reefs.

Learning Objectives

Students will be able to:

• Identify the form and function of oyster anatomy that make 

oysters efficient filter feeders.

• Compare oyster filter feeding anatomy with student-created 

filters. 

K-12 Oysters in the Chesapeake Bay

Module 2

Grade Level: Middle 

School 

Teaching Time: 3-4 class 

periods

Materials:

Live oysters and oyster clumps

5-10 gal aquarium

Small plastic cups

Rubber bins

Dip nets

Bucket

Magnifying glasses

Hand sanitizer

Paper towels

Organism identification key

If available: 

Compound microscope

Plastic culture dish

Dissecting microscopes

Life in the Chesapeake Bay 3rd 

edition, Alice Jane Lippson and 

Robert L. Lippson

Build a Better Filter Activity

List may vary:

• Rubber bands

• Cotton balls

• Sand 

• Coffee filter

• Sponges 

• Straws 

• Tape 

• Paper towel strips

• Clips

• Toilet paper
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• Explain the importance of oysters and oyster reef habitats to the Chesapeake Bay

• Examine and identify organisms living in the oyster reef community

Background Information

Oysters have remained relatively unchanged for 190 million years. This mollusk is found 

throughout much of the Bay in water depths up to 100 feet, although today they are rarely 

found below 30 feet. The adaptive nature of the oyster in a changing estuarine environment 

has allowed it to become extremely successful. This success is also due to its simple anatomy 

and it ecological niche. 

Oysters alter the sediments below them through their biodeposits, which add organic matter

to the sediments below. Biodeposits consist of feces (partially digested food) and pseudofeces 

(undigested food that has not passed through their gut). The biodeposits are then subject to 

decomposition by aerobic bacteria. The resulting dissolved nutrients are recycled back into the 

water.

Aquatic reefs are complex, diverse communities made of densely packed oysters. Healthy reefs 

form when oyster larvae attach to adult oysters, and layers of oysters grow upward and 

outward. Hundreds of aquatic animals find food and shelter in oyster reefs. With their many 

nooks and crannies, reefs provide a safe haven for small fish and invertebrates to hide from 

predators. Larger species, including white perch, striped bass and blue crabs visit reefs to 

breed and find food. Reefs are the largest source of hard surface on the Bay’s bottom, which is 

otherwise mostly covered with soft sediment. Oyster larvae, sponges, and barnacles are just a 

few of the many invertebrates that live attached to hard surfaces. Piers, rocks, jetties, wrecks, 

and pilings are similar to aquatic reefs. They provide hard surfaces for invertebrates and 

attract larger predators in search of food. 

(http://www.chesapeakebay.net/fieldguide/categories/category/aquatic_reefs_pilings)

Oyster reefs are important in stabilizing exposed marsh edges. The presence of an oyster reef helps 

prevent bank erosion and the loss of marsh grasses. The energy of natural and man-made waves (e.g., 

the wake from boats) is dissipated as the waves are refracted off of the complex structure of the oyster 

reef. In many areas along the east coast of the United States, oyster habitats have declined dramatically 

in recent years. Overharvesting, habitat destruction, and oyster diseases are only some of the causes. 

Non-point source pollutants and suspended sediment negatively affect oysters. Oyster reefs also suffer 

over time if oysters are removed, but no shells returned to the reef areas on which new oysters can set 

and grow.
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Key Words

Abiotic - All non-living factors within an environment, including physical, chemical, and time (e.g., 

seasonal, daylight, etc.) components.

Bacteria - Diverse group of single cell organisms important in decomposition, nitrogen fixation, 

and disease.

Biotic - All living factors within an environment

Bivalve - Marine or freshwater mollusk that has two shells.

Cilia - Hair-like structures used for the movement of particles or fluids in certain cells of more 

advanced organisms.

Commensal organism - Organisms that rely on a host for a benefit, but does not harm or 

benefit the host (i.e., an oyster bar provides protection for crabs and a hard substrate for 

barnacle settlement).

Digestive gland - The gland responsible for the production of digestive enzymes.

Esophagus - Tube that connects the mouth with the stomach

Gills - The gills are the largest organ in the oyster’s body, and consists of four folds of tissue. 

Along with the mantle, it is the chief organ of respiration. They create water currents, collect 

food particles, and move food particles to the labial palps for further sorting. 

Hemocyte - Blood cell found in the circulatory fluid of the oyster. There are different types 

that perform a wide variety of functions from defense to nutrient transport.

Hermaphroditic - Possessing functioning male and female reproductive organs.

Mantle - Two fleshy folds of tissue that cover the internal organs of the oyster and are always 

in contact with the shells, but not attached to them. Its principal role is the formation of the 

shell.

Mollusk - Animals with soft unsegmented bodies usually enclosed in a calcareous shell.

Omnivorous - Organisms that consume a variety of plant and animal materials. 

Parasitic organisms - Organisms that rely on a host for resources, and as a result are harmful.

Pericardial cavity - Cavity containing the heart. 

Phytoplankton - Diverse group of minute plants that drift freely within the water column.

Pseudofeces - Undigested food that has not passed through an oyster’s gut.

Sessile – An organism that is permanently attached to a hard surface and not freely moving.

Shucking - Opening an oyster.

Stomach - A large sac-like organ that is divided into two chambers used in the digestion and 

sorting of food particles.

Tentacles - Small sensory organs attached to the edge of the mantle used for the detection of 

environmental stimuli.

Umbo - The pointed and oldest part of the oyster.

Valves - The two shells of the oyster.

Watermen - Individuals who earn an income from harvesting aquatic resources.

Zooplankton - Diverse group of minute animals that drift freely in the water.
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Activity Procedure

Engagement

Class Demonstration: Place 6-8 live oysters in a 5-10 gallon fish tank, and fill with no more 

than 5 gallons of Bay water. Take a picture of the water when the oysters are placed into the 

tank, and let the oysters sit in the tank for the rest of the lesson time and compare the water 

at the end. Alternatively, you can show the following demonstration video from the 

Chesapeake Bay Foundation.

http://www.cbf.org/about-the-bay/more-than-just-the-bay/creatures-of-the-chesapeake/easternoyster

Discussion questions: 

• What effect did the oyster have on the water? 

• What did the oyster do to the sediment in the water? 

• What is the impact of many oysters on a larger body of water?

Note: Under optimal temperature and salinity conditions, a single oyster may filter as much as 

15 liters of water per hour, up to 1500 times its body volume. Spread over an entire reef, for 

an entire day, the potential for oysters to improve water clarity is immense.

Exploration 

Students work in teams to design and build their own 

water filtering system, collect data, and compare their 

results with other teams. Take a few minutes to review 

the engineering design process with your students. It is a 

series of steps that engineering teams use to guide 

them as they solve problems. The design process is 

cyclical, meaning that engineers repeat the steps as 

many times as needed, making improvements along 

the way. Two key themes of the engineering design 

process are teamwork and design. 

Information and this diagram are from 

https://www.teachengineering.org/k12engineering/designprocess#Improve

Consider using one of these activities from NASA for your water filtration design activity. 

https://www.nasa.gov/pdf/146846main_Cleaning_Water_Educator.pdf
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Student page is here: https://www.nasa.gov/pdf/146847main_Cleaning_Water_Student.pdf

You might also consider this activity using empty 2 liter bottles.

http://www.jpl.nasa.gov/edu/teach/activity/water-filtration-challenge/

Build a better filter

• Teams of students plan and present a blueprint for a simple filter that will best clean 

dirty water. Once the blueprint has been approved by the instructor, teams collect the 

appropriate materials and build their filter. 

• They will test their filter with 2 cups of “polluted water” after construction.

• The teams can let their filter work for 5 minutes. 

• After 5 minutes, the amount of clean water is measured and a sample poured into a 

clear specimen cut for comparison to other teams. 

• Students should complete the Student Data Sheet 1.

Explanation 

Oyster Internal and External Anatomy: 

(from Estuaries 101 Curriculum, Activity 6, http://estuaries.noaa.gov/teachers/pdf/06_oysters_tg.pdf)

For this activity, you will need to purchase either preserved oysters from a biological supply 

house or fresh oysters from a supermarket fish department. If you live near an estuary or 

marine site, perhaps you can collect the oysters yourself. If you buy preserved oyster 

specimens, you should review and follow safety rules for class dissection of prepared 

specimens. Special safety procedures are always taken when using preserved specimens in 

class. 

You will need to clean up properly afterward as all materials exposed to preservatives must be 

considered contaminated. In addition, students will be handling oysters, oyster shells, and 

oyster knives in this activity. It is important for you to know if anyone in your class (or classes) 

has a shellfish allergy. For some students, this allergy can be life threatening. Opening oysters 

may be hazardous for your students. You may want to open the oysters yourself ahead of 

time. This can help decrease the need for your students to use a scalpel or knife. 

You may choose to open one oyster as a demonstration so that students see how the adductor 

holds the oyster’s two valves together. 

Have students examine the anatomy of the oyster and take notes on the shape, color, and 

texture of the oyster’s shell and the oyster's interior organs on Student Data Sheet 2
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Procedure 

1. Distribute copies of Student Data Sheet 2: Oyster Dissection. Discuss the importance of 

lab safety, particularly having to do with using the scalpel or knife and with the possible 

exposure to chemical preservatives.

2. Students assemble in small groups and put on their gloves, goggles, and lab aprons. 

Each student group will be given an oyster to dissect. 

3. Have students use the scalpel or knife to gently slice along the adductor (hinge) of the 

oyster. Again, you may prefer to do this yourself ahead of time so that students do not 

need to open the oysters themselves. At minimum, demonstrate the proper way of 

separating the valves. 

4. Students have a simple diagram of oyster anatomy on Student Data Sheet 2 and are 

asked to identify and describe the oyster body parts shown.

5. Properly dispose of all specimens and contaminated materials when the exercise is 

finished.

6. Discuss with the students why the anatomy of an oyster makes the oyster well-suited 

to live in an oyster reef. Oyster anatomy is typical of any bivalve. Discuss the function 

of the different oyster body parts.

Alternatively, the following online activities allow students to observe and investigate the 

anatomy of the oysters. 

Resource: http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/index.htm

External Anatomy - http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/lab_e.htm

Internal Anatomy - http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/lab_i.htm

Short on time? These videos may be useful. 

Dissecting the Eastern Oyster -

http://www.bing.com/videos/search?q=oyster+anatomy+videos&qpvt=oyster+anatomy+video

s&view=detail&mid=F684D64842EB7123159EF684D64842EB7123159E&FORM=VRDGAR

Behind the Shell -

http://www.bing.com/videos/search?q=oyster+anatomy+videos&qpvt=oyster+anatomy+video

s&view=detail&mid=2CE3A373772B247991DA2CE3A373772B247991DA&FORM=VRDGAR
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Extension

Investigate an oyster reef

(Compiled in 2012 by education staff at the Chesapeake Bay National Estuarine Research Reserve in Virginia for 

use in the B-WET Chesapeake Studies in the Classroom program)

Oyster reefs are built primarily by the eastern oyster, Crassostrea virginica, through successive 

reproduction and settlement of larvae onto existing reef structure. Oyster reefs are formed in 

the intertidal zone when oysters grow on a hard foundation or substrate, such as dead shells. 

This process forms clusters of oysters which join together creating an elaborate threedimensional group. The structure of an oyster reef provides a place for many estuarine species 

to seek refuge from predators and provides a habitat for organisms that thrive in brackish 

water. Students will examine different species found on an oyster reef in the Chesapeake Bay;

use a microscope and a dichotomous key to help them determine the different organisms 

being viewed, and; draw conclusions based on the observed adaptations of the organisms 

about how the organism utilizes the oyster reef. They will also practice scientific sketching and 

become familiar with how to use a field guide and dichotomous key. 

http://www.chesapeakebay.net/fieldguide/categories/category/aquatic_reefs_pilings

Oyster reefs perform important functions, such as: 

• Provide habitats for plants, fish and invertebrates

• Provide breeding, feeding, and nursery grounds for fish, crustaceans, other 

invertebrates, and birds species 

• Create a hard structure that is used as a place of refuge against larger predators 

• Provide a place for sessile organisms to attach to 

• Assist in cycling nutrients for marine organisms to utilize 

• Maintain water quality and stabilizing sediments 

• Protect coastal areas from erosion 

By performing these functions, reefs are able to support important local and commercial 

fisheries, as well as maintain species of plants and animals’ diversity and abundance. If the 

health of the reef is degraded in any way, it can affect the functioning of this habitat, such as 

its’ ability to filter sediments, and cycle nutrients for reef organisms, or provide a healthy 

nursery and breeding grounds for organisms. (http://www.oyster-restoration.org/wpcontent/uploads/2012/07/CoenLuckRestMonitoring.pdf)

1. Have the students share what information they already know about the Bay. Be sure to 

explain that the Chesapeake Bay is an estuary, a semi-enclosed body of water where the rivers 

meet the sea. Because the Chesapeake Bay is an estuary, it has brackish water, a mixture of 
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salt and fresh water. Animals that live in the Chesapeake Bay must be able to thrive in brackish 

water.

2. There are many unique habitats found along the Chesapeake Bay. Have the students list a 

few (e.g., oyster reef, salt marsh, mud flat, sea grass bed, etc.). Explain that they will be closely 

examining an oyster reef community by using microscopes, a dichotomous key, and a field 

guide. Be sure students understand that community is a group of organisms living and 

interacting with one another in a particular environment. By the end of the lab, students 

should be able to describe how the organisms living in the oyster reef function as a 

community, and why oysters and oyster reefs are important to the Chesapeake Bay. Explain 

how to use the dichotomous key:

http://www.vims.edu/cbnerr/_docs/education_docs/habitatcageactivity.pdf

Choose an organism that most students are familiar with, for example an oyster, and work 

through the dichotomous key step by step as a class. Be sure everyone practices how to use 

the key. Review microscope and lab safety. Remind students that they are handling glass, 

shells, which could be sharp, and live animals that need to be handled carefully.

3. Students will use their dichotomous key to identify what organism they are looking at 

through the microscope. Students will write the name and sketch a picture of the organism in 

Student Data Sheet #3. Students will research their organism in the field guide and write down 

several adaptations or characteristics it has, to share with the class.

4. Students will identify and repeat the above steps for at least three organisms living in the 

oyster reef (or as time permits).

5. As students identify an organism, have them write the name of the organism on the board.

Additional students should add to the list, but only with organisms not already listed on the 

board. This will create a comprehensive list of what the entire class was able to identify.

Students should complete the following questions:

1. Was it easy or hard to find the organisms living on the oyster shell? (Students should be 

able to explain that some organisms were easier to see then others, but by using a microscope 

they could see the organisms more clearly.)

2. What external characteristics did a lot of the organisms share? (Same color, relatively small,

blend in with the oyster shell, etc.)

3. What is the difference between sessile and motile organisms? Name an example of each. 

How does this affect their survival in an estuary? (A sessile organism is one which is not free to 

move about; it is attached to the substrate, for example a barnacle or an anemone. A motile 

organism is able to freely move, for example, a polychaete worm or mud crab. Because sessile
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organisms cannot freely move about, they must have the ability to find food another way. 

Sessile organisms have adapted to this obstacle by finding food through processes such as 

suspension feeding or filter feeding. While motile organisms are able to freely move about the 

oyster reef, at times they may appear to be more exposed to predators than sessile organisms. 

Successful motile organisms in an oyster reef typically have excellent camouflage that allows 

them to blend in with the habitat.)

4. What does the oyster reef provide for these organisms? (Habitat, protection, food, place to

reproduce, etc.)

5. Why are oysters important to the Chesapeake Bay? (Help to filter water, provide food for

humans and other organism, provide a habitat for many organisms, help the economy, etc.)

Page 31 references a large poster of an oyster reef. You can go to the link provided and 

discuss the organisms on the poster, or use it as a reference for this activity. Alternatively, you 

can print a large poster-sized copy for classroom use. 

Possible animals that might be found on an oyster reef:

Mud Crab: A small dark brown or black crab about the size of a quarter that lives in the nooks 

and crevices of the oyster shells.

Blenny: A small fish that has a feathery dorsal ridge (top fin). It is brown and black in color.

Naked Goby: A small fish that has big eyes, the body is scales and it is greenish in coloration 

with narrow pale cross bars along its sides.

Grass Shrimp: A small translucent shrimp that lives among the oysters

Oyster Toad Fish: Slightly larger than the blenny with large bulging eyes, pale yellow in 

coloration with brown spots on the body. Its mouth is large with sharp teeth, and whiskers.

Amphipods: A small crustacean related to a pill bug on land. An amphipod lies and moves on 

its side (flattened laterally) with jointed appendages; less than half an inch in size.

Barnacle: There are three different species of barnacles that grow in the Bay. It’s an animal 

that lives inside a three-sided shell. To feed, the barnacle will stick out its feathery like 

appendage (arm) and wave it about to capture small particles floating in the water.

Evaluation 

• Dissection questions on Student Data Sheet 1, Oyster Internal and External Anatomy 

pages.

• Student designs and results for Build a Better Filter (Student Data Sheet 2).

• Student observations of organisms from an oyster reef. (Student Data Sheet 3).

• Exit/Debrief: What are oyster reefs important in the Bay?
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Module References

http://www.mdsg.umd.edu/topics/k-12-lesson-plans/oysters-classroom

http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/index.htm

http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/lab_e.htm

http://ww2.mdsg.umd.edu/interactive_lessons/oysters/anatlab/lab_i.htm

https://e360.yale.edu/digest/a_remarkable_recovery_for_the_oysters_of_chesapeake_bay/4

437/

http://chesapeakebay.noaa.gov/oysters/oyster-reefs

http://www.vims.edu/cbnerr/_docs/education_docs/habitatcageactivity.pdf

www.vims.edu/cbnerr/_docs/education_docs/habitatcageactivity.pdf

http://www.sms.si.edu/irlspec/Oyster_reef.htm

http://www.oyster-restoration.org/wpcontent/uploads/2012/07/CoenLuckRestMonitoring.pdf

Maryland Environmental Literacy Standards

http://marylandpublicschools.org/programs/Documents/Environmental/MDEnvironmentalLitS

tandards.pdf

Additional Resources

http://estuaries.noaa.gov/teachers/pdf/06_oysters_tg.pdf

http://digg.com/video/the-best-way-to-shuck-an-oyster

http://hatchery.hpl.umces.edu/oysters/oysters-life-cycle/

Three Dimensional Learning How the Dimensions

are Addressed.

Core Disciplinary 

Idea(s)

MS-LS1A. Structure and 

Function. Within cells, special 

structures are responsible for 

Students gather 

information about water 

filtration of oysters 
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particular functions. In 

multicellular organisms the 

body is a system of multiple 

interacting sub-systems. 

MS-LS2.A. Interdependent 

Relationships in Ecosystems.

Organisms and populations of 

organisms are dependent on 

their environmental 

interactions, both with other 

living things and with nonliving factors. 

MS-LS2.C. Ecosystem 

Dynamics. The completeness 

or integrity of an ecosystem’s 

biodiversity is often used as a 

measure of its health. 

MS-ETS1.B. Developing 

possible solutions.

through observations of 

live oysters, and then 

investigate the external 

and internal structures 

and systems that 

contribute to the 

successful water filtration 

of oysters as mechanism 

to obtain food. The 

students model the 

filtration system of 

oysters in a design-a-filter 

task, and then they look at 

the organisms that are 

dependent on oyster reefs 

for protection, food, 

breeding places, and 

water quality. Students 

will use the engineering 

design process to create a 

water filtration system.

Science/Engineering 

Practice(s)

Developing and using models.

(Develop a model to describe 

phenomena) Construct an 

explanation using a model or 

representation. Undertake a 

design project to construct 

and/or implement a solution 

that meets specific design 

criteria and constraints. 

Students model complex and 

microscopic structures and 

systems and visualize how 

their function depends on the 

shapes, composition, and 

relationships among its parts.

Students design a solution 

to clean up dirty water 

through various filtration 

systems that mimic how 

oysters efficiently filter 

Chesapeake Bay water. 

Students investigate the 

structures and systems 

that allow an oyster to 

provide valuable 

ecosystem services such 

as water filtration.

Cross-cutting 

Concepts

Cause and Effect - Use cause 

and effect relationships to 

predict phenomena in natural 

or designed systems. 

Students investigate the 

anatomy that allows the 

oyster to be an efficient 

filter feeder.
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Structure and Function.

Complex and microscopic

structures and systems can be 

visualized, models and used to 

describe how their function 

depends on the relationships

among its parts. 

They also look for typical 

oyster anatomy parts, 

which are named similarly 

in the animal kingdom 

based on function. Many 

organs in the oyster serve 

similar functions in other 

animals. 

Ties to Common 

Core

Grades 6-8 Reading 

Standards for Literacy in 

Science and Technical 

Subjects. Follow precisely a 

multistep procedure when 

carrying out experiments, 

taking measurements, or 

performing technical tasks. 

RST.6-8.7 Integrate 

quantitative or technical 

information with a diagram, 

model, graph, or table. 

Students use a multistep 

protocol to investigate the 

external and internal 

structures of the oyster 

and learn to use a 

dichotomous key to 

identify organisms in an 

oyster reef. 

Students will include 

accurate and precise 

descriptions with their 

design diagram. 

Ties to MD 

Environmental 

Literacy Standards

Standard 4: Populations, 

Communities and 

Ecosystems. The student will 

use physical, chemical, 

biological, and ecological 

concepts to analyze and 

explain the interdependence 

of humans and organisms in 

populations, communities,

and ecosystems

Students organize data to 

show the variety of 

organisms and their 

relationships in an oyster 

reef.