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Wild Indonesia classroom resources

Why Do Elephants Have Big Feet?

Lesson Objectives
Related National Standards
Tools and Materials Needed
Teaching Strategy
Video Segments
Procedure

Assessment Recommendations
Extensions and Adaptations

Subjects: Zoology, biological/environmental interactions, life science, physical science, mathematics

Grade Level: Middle school and above.

Lesson Objectives

Students will understand how an organism's adaptations give it advantages in particular environments. In this lesson, students will calculate the amount of pressure exerted by the foot of an elephant and a human. Finally, students will relate the concept of pressure per square inch to calculate the mass of a car.

By the end of this activity, students will:

  1. Understand how the adaptation of foot size better allows some animals to live in their environment.
  2. Calculate the pressure per square inch under the feet of two animals.
  3. Determine the amount of force that several types of land can support.
  4. Understand how the size of a foot allows some animals to better survive in an area.
  5. Calculate the weight of a car from the area of tire touching the ground.

Related National Standards from the McRel Standards Database at

http://www.mcrel.org/standards-benchmarks/

Science

  1. Knows that plants and animals have features that help them live in different environments
  2. Knows basic ideas related to biological evolution (e.g., diversity of species is developed through gradual processes over many generations; biological adaptations, such as changes in structure, behavior, or physiology, allow some species to enhance their reproductive success and survival in a particular environment)
  3. Knows that natural selection leads to organisms that are well suited for survival in particular environments, so that when an environment changes, some inherited characteristics become more or less advantageous or neutral, and chance alone can result in characteristics having no survival or reproductive value

Tools and Materials Needed

  1. Copy of the program "Wild Indonesia"
  2. Cutout of elephant foot and duck foot
  3. Rulers and unlined paper OR a pre-made square inch grid
  4. Tire pressure gauge
  5. Piece of 2 X 4 wood
  6. Bathroom scale
  7. Several bricks

Estimated Time to Complete Lesson

Two days, excluding time to watch the video. The three video segments will take 3 hours to complete. The activities can be done in one class period. An additional class period is desirable to discuss results and identify other adaptations.

Teaching Strategy

Background Information

Both plants and animals have changed throughout time to better adapt themselves to survival in their environment. This is especially evident on the 17,000 islands of Indonesia and the Galapagos Islands off the coast of Equador where it was first noticed in the shape of bird beaks. In Indonesia, some of the adaptations are so specialized that the animal can only live on one island out of the whole chain. At various times in the video, teachers should freeze the film and have their classes identify various adaptations seen on individual animals.

In this set of activities we will be examining one adaptation, foot size at it relates to elephants and water birds. As you watch the video, focus on the animals' feet and habitat. Both the foot type and the body weight affect how an animal would exist on a certain type of land.

Different types of land react differently to the masses that are placed on them. If too great a mass is placed on a type of land, it will sink into the land to some degree. A practical application of this occurs when building houses. If a house is placed on weak land such as varved clay, it will cause the land to begin to depress and slide down which may damage and destroy the house. Sand will compress and the structures on it will begin to lean without appropriate foundations. We can demonstrate the strength of the land by making several land types and looking for the impressions caused by putting masses on the end of a 2 X 4 beam placed on the area as described in the "extensions" section.

Two animals, the elephant and man (the student) are examined to determine the effect of the foot size on distribution of mass. If the mass were not well distributed, the elephants would sink into most surfaces. Students will have had the experience of walking on a surface where their feet have sunk into the earth and become stuck.

The effect of weight distribution is further examined by taking a "modern elephant" and a car, and determining both the pressure it exerts and its mass from the area of the wheels touching the surface.

Video Segments (all from Episode 1)

06:35 Asian elephants walk along jungle trail. Film informs us that they weigh 5 tons.

12:50 Short segment that shows webbed feet of ducks.

17:00 Segment showing Asian Tiger walking. There are several close ups of the foot pads. This tiger weighs about 400 pounds.

49:20 Note the curved claws of the tree kangaroos that make it difficult to walk on flat land but allow them to grasp branches.

Procedure

  1. Watch the Wild Indonesia video series. Stop the tape occasionally and identify characteristics of various animals. Concentrate attention on adaptations that allow animals to survive in their environment. Examples are the hand-like feet of the monkeys, the tails that wrap around tree branches that act as extra hands, and coloration. Also note the types of land that various animals live in-swamps, seashores, dry land and rocks.

  2. Have students calculate the total surface area of the elephant foot touching the ground and the pounds of elephant that each square inch supports. Watch the video segment at 6:35 in episode one relating to elephants. Note the mass of the elephants (5 tons) and discuss the body adaptations that would be necessary to support that much weight. An elephant foot is roughly circular and the circumference is approximately one-half that of the shoulder height of the animal. Given that the average adult elephant height is about 13 feet, students may calculate the area of a foot by using the formula Circumference = pi times diameter. For an elephant with a shoulder height of 13 feet, this would be about 2 feet or 24 inches. By using the formula for the area of a circle, area = pi times the radius squared, the number of square inches of one elephant foot touching the ground is found to be Area = 3.14X12 squared or about 452 square inches. Since elephants have four feet, the total area supporting the elephant while standing is about 1800 square inches. Dividing the number of pounds in an elephant (about 10,000) by the surface area gives a value of about 5.5 pounds being supported by each square inch. Elephants have big feet to distribute the weight.

  3. Have students measure the length and width of their foot and determine the amount of pressure that they exert when walking.

  4. Compare the pressure exerted by an elephant to that produced by a car. Using a tire pressure gauge, find the tire pressure of a car. This is the amount of pressure that each square inch of the tire places on the roadway as the car travels. Compare this to the pressure exerted by the elephant. Use these results to discuss why cars use large tires to drive in sand and muddy areas.

  5. By sliding sheets of paper under the edges of the tires as far as they will go all sides and then moving the car, the number of square inches of tire touching the pavement can be seen and measured. The mass of the car can be calculated by multiplying the number of square inches of tire contacting the pavement by the air pressure in the tires. Since most cars have similar tire pressures, a graph may be produced that relates square inches tire contact with the pavement to the mass of a car.

Helpful Web Site

The Elephant Repository
http://elephant.elehost.com/
This site has both information and links about elephants.

Assessment Recommendations

Students may be assessed though their participation in the class discussion and participation in the activities. Teams of students will write a paragraph describing the support that various land types provide. Teams of students will also measure the area of a tire touching the ground for various cars in the parking lot and use a measurement of the air pressure in the tires to determine the mass of the car. These activities would be assessed in an objective fashion.

Extensions/Adaptations

  1. Discuss the strength of various types of land. Prepare in advance, or have student groups prepare, several sample plots of land that measure about 1 foot by 1 foot square and about 1 foot deep--sand, large gravel (rocky soil), soft dirt (the plot is prepared like garden soil), regular grassy yard and one plot that is soft dirt that is saturated with water (swamp). Students will take a short section (about 3 foot) of 1 X 1 or 2 X 4 lumber and place vertically in the middle of the plot. One brick is placed on the top of the wood and the depression that is made is measured. This is repeated with 2, 3 and 4 bricks. Once the bricks are weighed, students may construct a graph showing how mass relates to depression for each land type.

  2. Students may be assigned an animal to research to determine body mass and foot size and area of habitation. Students would then make a small bulletin board panel describing their animal and the adaptations they have that better allow survival and the amount of pressure that their feet exert when walking.

  3. Students can be assigned other items to determine mass and pressure relationships for presentation to the class. Some items include ice skates, roller skates, 18 wheel trucks and smaller package trucks.


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