Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science

Guide Index

Big Picture

Echoes in the Night

Rat Soup

Bee Lines

Champion Chompers

Bridge That Changed the World

Viewer Challenge
in the classroom
TEACHING GUIDES


EXPEDITION PANAMA: Rat Soup


A MAN, A PLAN, A CANAL -- PANAMA!

The building of the Panama Canal is considered one of the world's greatest engineering feats. Begun over 100 years ago, the 50-mile waterway took the efforts of two nations and more than 25,000 lives to complete. When the U.S. took over the canal project in 1904, American engineer John Stevens developed a plan to dig a canal not at sea level, but one that would raise ships up and over Panama with a system of locks and gates. This ingenious design required much less excavation. The design depends on a plentiful supply of fresh water for its operation.

Curriculum Links
Related Activities
Activity 1: Locks in Action
Activity 2: Know Your Watershed
For Further Thought
Paca Parade



CURRICULUM LINKS


BIOLOGY


mammals,
vertebrates
GENERAL
SCIENCE


animal behavior
EARTH
SCIENCE


ecology, erosion,
watersheds
LIFE
SCIENCE


mammals
PHYSICAL
SCIENCE


water pressure
SOCIAL
SCIENCE


Central America

TECHNOLOGY

dams and locks,
engineering




RELATED SHOWS AND ACTIVITIES
Dragon Science (Show 602): "Dams and Dolphins"



ACTIVITY 1: LOCKS IN ACTION

The Panama Canal begins at sea level, rises as it crosses the isthmus, then returns again to sea level. A system of lock chambers is used to raise and lower vessels along this up-and-down journey. Here's a simple model that demonstrates how locks work.

OBJECTIVE

Use modeling to understand how locks work.

MATERIALS
  • small, clear plastic drawer or organizer, about 2" x 2" x 6", with removable dividers
  • waterproof modeling clay
  • small toy boat (or a boat molded from clay)
  • small cup
  • food coloring (optional)
PROCEDURE
  1. Take one small plastic organizer with two inserts and identify the plastic slots into which the dividers will be inserted.

  2. Roll out six thin strips of waterproof clay. Place the clay into the slot guides on either side of the drawer. Place another strip of clay along the bottom of the drawer. The U-shaped clay will produce a waterproof seal between the dividers and the drawer.

  3. Slide the dividers into position, making sure the clay seals any gaps.

  4. Carefully pour water into each of the three separate chambers so that the levels are as shown above. If you wish, add several drops of food coloring to the water to make the levels more visible.

  5. Place a toy boat onto the surface of the lower chamber. Then use a small cup to carefully remove (and discard) water from the center lock chamber. Continue removing water until the water level matches the first chamber.

  6. Gently open (slide out) the lower gate. Move the boat forward into the lock chamber. Reinsert the lower gate, making sure that the seal is once again waterproof.

  7. Carefully add water to the center lock chamber until the water's surface reaches the higher water level of the last chamber.

  8. Slide out the upper gate and move the boat into the upper portion of the "river." Replace the upper gate.
QUESTIONS
  1. How is this model's operation similar to the actual lock system seen on Frontiers? How is it different?

  2. What keeps the gate sealed in the lock seen on Frontiers?

  3. Why is the water level within the center lock chamber, and not within either of the two adjoining compartments, raised and lowered?
ANSWERS
  1. Accept all reasonable answers.
  2. Water pressure.
  3. The adjoining compartments are usually part of a large expanse of water.
DESIGN CHALLENGES
  1. Suppose the boat was going from the high water level to the low water level. Create a series of drawings to illustrate the sequence of events that would allow the boat to move through the lock.

  2. The gates used in the canal are based on a design engineered by Leonardo da Vinci. Can you design a different model of a lock gate? Once you've designed a new gate, try building a model of it.
GEOGRAPHY AND HISTORY CONNECTIONS
  1. Use the timeline in the Big Picture in this guide as a starting point for a more elaborate timeline that shows the contributions of France, Panama and the U.S. to the building of the canal. You'll find more information on the Web or in the library.

  2. Trace the route of the Panama Canal on a map. Use clay or other materials to build a model on a piece of plywood. Label the bodies of water surrounding Panama.

  3. Find other examples of an isthmus on a world map or globe.

  4. Why did people in the 1800s want to build a canal through Central America?

    See a photo gallery and a Java animation of the canal in operation at http://www. pananet.com/pancanal/pcc.htm.


ACTIVITY 2: KNOW YOUR WATERSHED

A watershed (sometimes called a drainage area) is an area of land that is drained by a river or stream. Water flows across or under the land on its way to a stream, river or lake. Streams flow to rivers and eventually to the ocean. The watershed ecosystem around the Panama Canal has been disturbed by introduced grasses and slash-and-burn agricultural methods. Your watershed may have to contend with its own problems.

Use a topographic or physical map to identify your watershed. (One option is to use the "Surf Your Watershed" Web site, which will help you locate your watershed by clicking on a state map. Start at www.epa.gov/surf/.) Can you trace the complete route of drainage from your street to the ocean?

Many local conservation groups sponsor watershed programs. Some schools are involved in projects that monitor water quality and are helping to clean up watersheds. Find out what environmental groups are doing near you.



FOR FURTHER THOUGHT
  1. Illustrate the cycle of rainfall and evaporation in the Panama Canal watershed.

  2. Explain how slash-and-burn agriculture affects the land.

  3. The demonstration pilot program to raise paca is one way scientists are working with local communities to enable people to find local solutions to problems of deforestation. Can you brainstorm any other solutions that involve local people?

  4. Find items at your supermarket or health food store made from rain forest products.


PACA PARADE

The paca (Agouti paca) is a large, nearly tailless rodent about 2 1/2 feet long with white spots that lives in forests of Central and South America. A popular item on the menu, it has practically been hunted to extinction. With domestication of the paca, people in these regions look forward to once again buying paca meat at the market.






 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.