Oysters & Organisms Lessons



Class Periods




Subject Areas


Students will watch a video of oysters filtering a tank to motivate their work. They will then do a lab where they will investigate which objects float and which objects do not. They will use that demonstration to discuss how oysters filter water.


  • What is density?

  • How do we find the density of a substance?

  • Why is the idea of density important to studying oysters?

Materials and Resources


  • Beaker of water
  • Piece of a candle
  • Small rock
  • Oyster Shell
  • Scale
  • Graduated cylinders

Before you get started

Tips for Teachers

Computer with YouTube access/projector.

Tips for Teachers

  • If your time is limited, rather than calculating density, you can simply give the students the densities of the objects and have them see if they float or sink.

  • Make sure your graduated cylinders are wide enough to drop the objects in, so that you can see how much water they displace.

  • For the object that floats (the candle), the students will need to push the candle until it is just submerged in order to calculate the volume. You can use a pencil for this.

  • If students struggle with ratios, there is an ratio and proportions practice sheet with oyster connections that might be fun.


An adult oyster can filter up to 5 liters or 1.3 gallons on water an hour. That’s equal to 60 two-liter soda bottles a day, for just one oyster! Historically, oysters could filter the Chesapeake Bay’s entire water volume in less than a week.  Today, with 1% of the oyster population left in the Chesapeake Bay, it would take oysters nearly a year.

Oysters are filter feeders, meaning they eat by pumping large volumes of water through their body.  Water is pumped over the oyster’s gills through the beating of cilia.  Plankton, algae and other particles become trapped in the mucus of the gills.  From there these particles are transported to the oyster esophagus and stomach to be eaten and digested.

Once the oyster removes all nutrients, indigestible material is expelled as “pseudofeces” through the anus.  The pseudofeces are expelled from the oyster’s shell via a rapid closing of valves. The expelled particles swirl through the water and resemble a smoke ring.  These smoke rings are an indication that oysters are filtering the water and doing what they are meant to do. (http://baybackpack.com/blog/how_does_an_oyster_filter_water)

Instruction Plan



Watch this movie:




Why do you think the water with oysters  is so much clearer than the water without oysters? What do you think the oysters are doing?



Explain that the way the oysters filter the water has to do with density and that students will do a density lab to explore it.

Show the students the candle, rock and oyster shell. Ask the students to make a hypothesis. Which objects do they think will float and which do they think will sink? Ask them WHY an object would float or sink?



There are two options for this section:


Pass out the “Density Lab” handout.

  1. Define density: Mass/Volume. Define Mass and Volume.

  2. Find the density of each object. Find the mass by weighing the object and the volume by seeing how much water it displaces in the graduated cylinder.

  3. Calculate the density of each object.

  4. Test your hypothesis

  5. Discuss WHY an object would float or sink based on the density of water.

OPTION 2: (much shorter)

  1. Define density: Mass/Volume. Define Mass and Volume.

  2. Tell students the densities of the three substances: Oysters: 1.5-2 g/mL Candle Wax: .93 g/mL Rock: This varies based on the type. 2.3-5 g/mL (for an exact answer, look up the kind of rock you have or calculate the density)

  3. Tell students that the density of water is 1 g/mL. Ask them to hypothesize        based on the densities which will float and which will sink.

  4. Have them test their hypothesis in a beaker of water. Finally, discuss WHY an object would float or sink based on the density of water.  



If oyster shells are more dense than water, they will sink. Why is this important? As oysters feed, they process water and filter through what is inside. Using their cilia, they draw water in and “sort” particles into two categories: food and waste. Any particles that they can’t eat, they release as pseudofeces. Due to the density of pseudofeces (which is made out of the same material as oyster shells), these then sink into the benthic layer below and no longer pollute the water. This is how oysters filter.

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Which of the following objects from the harbor do you think will be discarded and which will be food for the oyster?

  1. Algae

  2. Sewage

  3. Plankton

  4. Small pieces of plastic

  5. Bacteria

Explain how density is important to the filtration that oysters do.


CCLS - ELA Science & Technical Subjects

    • Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
    • Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic.
    • Integrate information presented in different media or formats (e.g., visually, quantitatively) as well as in words to develop a coherent understanding of a topic or issue.

CCLS - Mathematics

    • Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities.
    • Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations.
    • Compute unit rates associated with ratios of fractions, including ratios of lengths, areas and other quantities measured in like or different units.

NGSS - Disciplinary Core Ideas

  • LS2.A: Interdependent Relationships in Ecosystems

    • Growth of organisms and population increases are limited by access to resources.
  • LS2.C: Ecosystem Dynamics, Functioning, and Resilience

    • Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions to any physical or biological component of an ecosystem can lead to shifts in all its populations.
  • PS1.A: Structure and Properties of Matter

    • Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals).

NYC Science Scope & Sequence - Units

  • Grade 6, Unit 2

    • Weather and Atmosphere
  • Grade 6, Unit 3

    • Diversity of Life
  • Grade 6, Unit 4

    • Interdependence
  • Grade 7, Unit 4

    • Dynamic Equilibrium: Other Organisms
  • Grade 8, Unit 4

    • Humans and the Environment: Needs and Tradeoffs

NYS Science Standards - Key Ideas

  • LE Key Idea 1

    • Living things are both similar to and different from each other and from nonliving things.
  • LE Key Idea 3

    • Individual organisms and species change over time.
  • LE Key Idea 5

    • Organisms maintain a dynamic equilibrium that sustains life.
  • LE Key Idea 6

    • Plants and animals depend on each other and their physical environment.
  • LE Key Idea 7

    • Human decisions and activities have had a profound impact on the physical and living environment

NYS Science Standards - Major Understandings

    • Living things are composed of cells. Cells provide structure and carry on major functions to sustain life. Cells are usually microscopic in size.
    • Cells are organized for more effective functioning in multicellular organisms. Levels of organization for structure and function of a multicellular organism include cells, tissues, organs, and organ systems.
    • Multicellular animals often have similar organs and specialized systems for carrying out major life activities.
    • The excretory system functions in the disposal of dissolved waste molecules, the elimination of liquid and gaseous wastes, and the removal of excess heat energy.
    • Animals and plants have a great variety of body plans and internal structures that contribute to their ability to maintain a balanced condition.
    • All organisms require energy to survive. The amount of energy needed and the method for obtaining this energy vary among cells. Some cells use oxygen to release the energy stored in food.
    • Herbivores obtain energy from plants. Carnivores obtain energy from animals. Omnivores obtain energy from both plants and animals. Decomposers, such as bacteria and fungi, obtain energy by consuming wastes and/or dead organisms.H
    • Food provides molecules that serve as fuel and building material for all organisms. All living things, including plants, must release energy from their food, using it to carry on their life processes.
    • Foods contain a variety of substances, which include carbohydrates, fats, vitamins, proteins, minerals, and water. Each substance is vital to the survival of the organism.