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Project title or topic of activity

Physiology and Physics of Diving

Author(s): Elena Ruiz

Date: Fall 1999


Summary of Activity
50-100 words

This laboratory activity is designed for children in middle school grades sixth through eighth. Activities aim to encourage students to find answers for themselves. The activities include a math-worksheet, new vocabulary and the construction of learning models. Each model fulfills a different purpose: The dive depth model allows students to put their educated guess to workÉlater establishing the true or false perceptions of diving capabilities of marine animals and humans. The lung model allows students to make a lung out of plastic, play with it, and gain an understanding of its function through introspection. The model of the bends helps demonstrate the accumulation of nitrogen bubbles in bones and muscles. The pressure model shows how air is compressed when pressure is applied. At long last, the density model points out the difference between dense and lighter materials. All of the models are set up to be engaging, allowing students to come up with answers to complicated scientific questions rather than just being told the facts. These activities intend to expand the student's knowledge on many subjects such as, math, physics, and physiology all at once in a painless, fun and exciting manner.


Grade levels

grades levels 6-8th.

General description or introduction
The scientific principles that the activity is founded on.

Scientific Principals Included in the Lesson Plan:

  • Marine animals have special adaptations that allow them to deep-sea dive.
  • Positive buoyancy is needed by marine animals to help them float.
  • Humans attempt to dive deep in the ocean comes with great difficulties totally unlike the great ease with which marine animals take to diving.
  • The human respiratory system consists of nose, mouth, throat, trachea (windpipe), and lungs. It gets oxygen from the air via the lungs. When one inhales, oxygen comes into the lungs. When one exhales carbon dioxide is expelled from the lungs through you nose or mouth. In the lungs air sacs called alveoli bring air into contact with blood passing through tiny blood vessels.
  • Decompression sickness known as "the bends" and acute mountain sickness is brought on by the decrease in atmospheric pressure.
  • Pressure increases with depth and decreases with altitude.
  • Terrestrial organisms are under 1 atmosphere of pressure. Pressure increases 1 ATM with every 33ft (about 10m) of water. Marine organisms are under more pressure because water is denser than air. Density equals mass divided by volume.
  • Cooling seawater becomes denser whereas, freshwater becomes less dense as it cools.

Background information

Diving capability of marine animals is amazing. For example, the emperor penguins can dive approximately 700 meters, weddell seals 1000 meters, elephant seals 1,800 meters, and sperm whales 2,200 meters. These diving capacities are achieved through adapted mechanisms they have for deep-sea dives. Some of these mechanisms include: faster breathing, circulating blood exclusively to the brain and heart, streamlining of their bodies, having heavy bones, collapsible lungs, and more hemoglobin/myoglobin proteins for oxygen transport. On the contrary, to increase buoyancy some marine animals substitute light ions for heavy ones in internal fluids, store lipids, or have gas-filled floats.

Humans lack the adaptive mechanisms mentioned and can not deep-sea dive with the same great ease or performance seen in marine animals. One of the many mechanisms that humans lack is the spontaneous collapsible lung seen in marine animals. Humans have a lung with a rib cage and diaphragm that moves in rhythm to breathing. Breathing allows flow of oxygen from the nose or mouth to the trachea, bronchial tubes and ultimately the lungs. Each bronchial tube goes into a lung and continues to branch into smaller tubes. The smaller tubes end in air sacs called alveoli. Capillaries surround alveoli where oxygen exchange takes place. Although, human lungs are magnificent, they are not well suited for deep-sea diving. Largely, humans must then contend with their physical constraints. The pressure at depth is so massive that it can collapse a human lung and force all remaining oxygen out. Worst of all when a diver ascends to the surface the decrease in pressure can cause decompression sickness, known as "the bends". " The bends" cause nitrogen bubbles to amass in the bones and muscles causing severe pain. Similarly, increasing altitude often produces acute mountain sickness (AMS) causing headaches, shortness of breath, nausea, and dizziness. All of these symptoms stem from a lower oxygen pressure.

Pressure is the acting force on a unit area. Terrestrial organisms are under 1 atmosphere (ATM) of pressure. Pressure increases 1 ATM with every 33 ft (approx.10m) of water. Marine organisms are under more pressure because water is denser than air. Higher pressure is related to greater density. Density grows as unvarying mass is confined to a smaller volume. In fact, seawater becomes denser as it cools given that molecules move slower and pack closer together. Freshwater does the opposite it becomes denser as it cools and then at 4C and below it freezes and expands. The expansion causes molecules to take up less space resulting in lighter ice. To summarize, seawater becomes denser as it cools while freshwater becomes lighter.

Credit for the activity

  • Math-worksheetÉ. Original idea by Elena Ruiz with help from Heather Bleakley
  • Dive Depth ModelÉ.Original idea by Elena Ruiz, derived from looking at pangea model in marine biology classroom.
  • Lung ModelÉ. Idea from a science book provided by Dr. Mangin. I forgot to ask for the information like author, title and publication date.
  • The model of the bendsÉ.Idea from the "Big Blue Ocean" by Bill Nye, Copyright- September 1999 by Little Bear Company in co-operation with Walt-Disney.
  • The pressure modelÉ.Idea from the Marine Biology Classroom.
  • The density modelÉ. Idea from College Physics Text by Jerry D.Wilson,Copyright-1994 Prentice-hall, Inc.

Estimated time to do the activity


Goals of Activity:

Goal A
Understand the underlining adaptations that allow marine animals to deep-sea dive.

Goal B
Understand how lungs function.

Goal C
Understand what causes the bends and mountain sickness

Goal D
Understand math and physics behind atmospheric pressure.


National Science Education Standards. (NSES)

Two content standards that this lesson plan covers:

Standard 1
Life Science Content Standard For grades 5-8
Structure and living systems
"The human organism has systems for digestion, respiration , reproduction, circulation, excretetion, movement, control, and coordination, and for protection for protection from disease. These systems interact with one another."---This lesson plan covers human respiration.

Standard 2
Life Science Content Standard For grades 5-8
Diversity and adaptation of organism
"Biological evolution accounts for the diversity of species developed through gradual process over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occuring variations in populations. Biological adaptations include changes in structure, behaviors, or physiology that enhance survival and reproductive success in a particular environment."------The lesson plan covers marine animals mechanistic adaptations for deep-sea diving.


Materials Needed

  • Dive Depth Model-Cut out pictures of the following: human diver, northern fur seal, bottlenose dolphin, emperor penguin, weddell seal, leatherback sea turtle, northern elephant seal, sperm whale.
  • Construction paper,
  • scissors,
  • glue.
  • Access to chalkboard,
  • chalk and sticky magnet tape or double-sided tape.
  • Lung Model-2L plastic bottle,
  • three-way hose connector,
  • modeling clay,
  • 2rubber bands,
  • plastic tube,
  • 3 small balloons and scissors.
  • The Bends Model-two six pack unopened plastic 16oz soda bottles,
  • access to place where there is no fret of making a mess preferably the outdoors.
  • Pressure Model- 2L soda bottle,
  • 1.75L of water,
  • 1ml glass vial.
  • Density Model- 12 oz unopened Classic Coke Can and Diet Coke Can,
  • 10-15 gallon fish tank,
  • 10-15 gallons of water.
  • Math worksheet-scratch paper and pencil.


Have all materials ready to use. Attempt to make and use all of the models before hand. For the dive depth model make sure that all of your pictures are cut out, glued unto construction paper and that the sticky magnet/double-sided tape works. In addition, to having clearly marked on the chalk board a scale showing depth of the ocean by 200m increments. Then students forming groups of four can construct the lung model. Following bends model experiment should be carried out in a place where there is no fret of making a mess by students in-groups of two. Prior to class the instructor should build the pressure model due to the time consuming and tricky set up. Finally, the density model should have an appropriate sized fish tank of about 10-15 gallon filled with water and ready to go. The math worksheet explaining pressure and density can be consulted throughout the class period. In short, be prepared and don't forget to have fun.

Step-by-Step Procedure for the Activity

The dive depth model- Cut out picture of the following, human diver, northern fur seal, bottlenose dolphin, emperor penguin, weddell seal, leatherback turtle, northern elephant seal, sperm whale. These pictures can be found in magazines or in the internet. Once pictures have been found and cut out then they can be glued unto construction paper. On the backside of the construction paper apply a small piece of sticky magnet or double- sided tape. The chalkboard should be marked showing a scale starting at 200m- 2200 m with noted increments of 200m. The model is now ready for use and students can put the pictures on the chalkboard based on their educated guess as to the different deep-sea diving capacities of the human and marine animals. The following are the approximate diving capacities: human diver 200m, northern fur seal 400m, bottlenose dolphin 700m, emperor penguin 700m, weddell seal 1000m, leatherback turtle1300m, northern elephant seal 1800m, sperm whale 2200m.

The lung model-Place the plastic tube around the opening of the hose connector. Use the modeling clay to make an airtight seal. Then put the two balloons around the other openings of the hose connector and secure them with rubber bands. Check to see if the link between the connector and the balloons is airtight. Next using scissors, make a smooth cut off the bottom of the plastic bottle. Place the balloons and connectors inside the bottle and with modeling clay fasten the hose connector and plastic tube to the neck of the bottle. Again, make sure to have an airtight seal. Afterward, tie a knot in the neck of the third balloon and cut it crosswise in half. Stretch the knotted part of the balloon over the lower end of the bottle. Secure the balloon as tight as possible so that is resembles a drum skin. The balloon at the bottom represents the diaphragm. Finally, hold the balloon its knot and pull it down. The diaphragm also moves down when you inhale lowering the air pressure inside the lungs and causing air to be sucked in from the outside. The other two balloons should expand, just like your lungs.

The model of the bends- Get an unopened 16oz-soda bottle that contains carbonated soda. Shake it up vigorously twists the cap gently letting a bit of air escape then twist the bottle cap shut and airtight. Observe the bubbles forming inside the soda bottle. This illustrates the accumulation of nitrogen bubbles in the tissues that cause the bends in human divers.

The pressure model-Obtain an empty 2L-soda bottle and fill it with 1.75L of water. Then place a small glass vial inside upside down letting some water enter it. Next cap the soda bottle airtight. Squeeze the soda bottle and observe how the glass vial moves up and down. Notice how the glass vial fills with more water and less air as the soda bottle is squeezed. This illustrates how air is compressed when pressure is applied.

The density model- Obtain an unopened 12oz can of Classic Coke and one of Diet Coke. Put the soda cans into a 10-15 gallon tank full of water. Notice how the Classic Coke sinks and the Diet Coke floats. This takes place because the density of the Diet Coke is less than that of the water, while the Classic Coke has a greater density. This helps in understanding density and also buoyancy.

Images, work sheets, additional web pages

{none available}

Items for discussion or conclusion

1st question

What are other cool things that marine animals do that humans cannot do?

2nd question
What ideas do you have to improve research in the depth of the ocean?

3rd question
What are animals that live in the different depth layers of the ocean? Why do they live there? How do they live there?

4th question
What is G-Force?


At the end of the lesson plan students should be able to: Name a couple of things that help make marine animals better suited for deep sea diving. Tell about lung function, the bends and acute mountain sickness. In addition to, fully understanding the concept of pressure and density. Some questions one could ask through out the activity or as a form of evaluating their progress are the following: What mechanism do marine animals have for deep-sea diving that humans do not have? What is atmospheric pressure, and what is it in the mountains vs. the deep seaÉdoes it increase or decrease? How do our lungs work? Do we breathe oxygen or carbon dioxide? Is seawater denser as it cools or as it heats? Is ice more or less dense than liquid water? Why? What are the bends? Overall, children should enjoy all of the activities and be allowed to explore the possible answers to the scientific topics discussed. Learning perhaps that science is logical, Comprehensible and really cool!

Beyond the Activity
Further activities which relate to and extend the complexity of the experiment.

Web Resources
A web address with information on the topic of the activity.

Web Address

Additional References

Magazine: American Scientist, Volume 85