Survival in the Land of Batzilla

Courtesy of Judy Day, NCSU
Revised by Shawn Reintjes, The Science House, 2007

Teacher Pages

Introduction

 Teacher Reads to Class:

In the movie, “Jurassic Park” it is made chillingly clear that Tyrannosaurs respond to movement and not to shapes. To avoid being a Tyranno-meal a smaller creature had to stay motionless. Present day animals use size, motion, shape, and color to stay out of the notice of predators. A good example is the snowshoe rabbit, whose winter coat helps it disappear into the white snow background. However, some predators, such as bats, detect their prey through sounds that we cannot hear. How would a prey animal escape the notice of such a predator?

In an ecological system some animals show adaptations that allow them to escape the notice of a predator, either by their size, coloring or motion. These adaptations occur even when the prey does not scientifically understand the science of sound or sight.

Background information for Teachers:

In your science teaching you might have used an ultrasonic motion detector-an “electronic bat” for measurements of position and velocity. The detector is connected to a computer and measures the distance and velocity of an object or person that crosses the detector’s field. The thought came to mind- “What if the ultrasonic detector really was a predatory bat?” What kinds of animals could escape its notice or camouflage themselves from the notice of the electronic bat? Can we investigate through experimentation and reasoning and deduce what types of animals would be most likely to survive?

Below is a guided student inquiry into the workings of an ultrasonic motion detector. The students are led to study something they cannot see, hear, feel, or taste, but only can be detected through the output of the computer. In the process the students must design strategies to avoid becoming prey of the predatory “Batzilla.”

This inquiry was written for students in grades 6-12. However, the motion detector has been successfully used with students in grades 3- college. The format is a guided inquiry that is based around a general goal. The focus is centered on three major questions:

1.     How does Batzilla detect its prey?

2.     What factors hinder prey detection?

3.     Can you design a prey that is least likely to be detected by Batzilla?

Provided is a list of questions to guide students’ investigations and two hypotheses (inspirations) that lead to other questions. These investigations lead to the final challenge of survival- nature’s version of a final exam.     

This activity is best done over two days.

Day One: The students explore the detection capabilities of Batzilla and ways to confuse or avoid the detection of Batzilla.

Day Two:The students design and construct a model of an animal that would stand a good chance of avoiding becoming a bat meal. You may want to assign the design as a homework project upon completion of the first day activity.

Notes:

  • There are no unusual safety hazards with this experiment.
  • A wide range of materials should be available to allow maximum exploration. You could instruct the students to bring in their own materials to construct their model animal.
  • The instructions are written for a Macintosh using Vernier equipment and Vernier software. You can modify the instructions to fit your equipment. This activity can be done using CBL instead of the microcomputers.

Answers to some of the problems:

 This investigation is fun to perform and leads to many questions about subjects from physics to ecology. The final challenge is an exercise in applying the science learned to a design problem (technological design). The investigation is performed using Vernier Motion Detector and LabPro with the computer. The detector was able to detect objects in a line of site within a cone of 10-11degrees to either side of straight ahead. The motion detector could not discriminate objects closer than 0.4 meters to the sensor nor further away than 5.5 meters. Objects greater than 4 meters away created lots of erroneous signals, but still could be detected. The motion detector was very sensitive and could detect an object 1 cm in diameter from as far away as 1.8 meters. Several objects were constructed of foam and cardboard to study the effect of absorption and reflection of sound waves. It was discovered that it is possible to absorb and reflect sound waves away from the detector. Not difference was noticed when experiments were conducted in dark versus light rooms or when operated in a noisy versus quiet room, though when two motion detectors were set up facing each other it created interference and false readings.

The Details of the Electronic Bat

The Vernier Motion Detector emits short bursts of ultrasonic sound waves ( about 40 kHz) from the gold foil of the transducer. These waves fill a cone-shaped area said to be about 15-20 degrees off the axis of the centerline of the beam. The Motion Detector then “listens” for the echo of these ultrasonic waves returning to it. The equipment measures how long it takes for the ultrasonic waves to make the trip from the motion detector to an object and back. Using this time and the speed of sound in air ( which is 343 m/s), the distance to the nearest object is determined. The sensitivity of the echo detection circuitry automatically increases, in steps, every few milliseconds as the ultrasound travels outward. This is to allow for echoes being weaker from distant objects.

Tips:

  1. Many hard, reflective surfaces can cause sound waves to bounce around the room.
  2. Putting a cloth over an object can minimize sound reflection.
  3. Other sources of ultrasonic waves in the same frequency range as the motion detector can cause erroneous readings. (Frequency- around 40kHz)
  4. Irregular reflecting surfaces sometimes cause waves to be reflected back and sometimes not. Results are erratic.

Student Page 

Survival in the Land of Batzilla

            In a jungle far, far away, the many animals live a happy existence, marred only by the nightly excursions of the giant predatory monsters, the Batzilla! Somehow the flying Batzillas are able to sense their victims in the dark and then swoop rapidly down to attack without warning. You are a field biologist studying the ecology of the jungle. You want to understand the predatory behavior of the Batzillas and also what types of strategies their prey might use to escape detection. Fortunately you have been able to capture a live Batzilla and to attach it to a computer sensor that registers its brain waves. The computer makes a graph of the waves showing the position of any object sensed by the captive Batzilla. You can use the graph to perform tests to understand how Batzilla detects its prey. From that understanding you should be able to construct some model animal(s) that would be to live in the jungle without becoming Batzilla meals (too often)!

            This research program is divided into four parts. The first part assumes that you know nothing about how Batzilla detects its prey. The next two parts are based on two possible hypotheses about Batzilla physiology. There are, no doubt, other possible hypotheses you may wish to explore if time allows. Testing these hypotheses is an important prelude to the final challenge of survival, which is the last part of your research program.

I. The Beginning: (You know nothing about how the Batzillas detect their prey.)

Possible questions to consider and investigate through experimentation-

  1. How far away does the prey have to be from Batzilla to avoid detection?
  2. Does this distance depend on the size of the prey?
  3. How accurately and precisely does Batzilla sense the distance to its prey?
  4. Can a prey animal get close enough to touch the Batzilla without being detected?
  5. Does the prey need to be directly in front of the Batzilla to be detected? If not, how far off to the side does it have to move to be out of range?
  6. Does the prey have to be moving to be detected or can Batzilla detect the prey if it lies motionless?
  7. Can a Batzilla (like Superman) detect prey through an obstacle? Can the prey hide behind a tree?
  8. Can the Batzilla detect prey better in the dark or in sunlight? Or is there a difference?

II. A Hypothesis-“Batzillas use some kind of invisible ray that is similar to sound.”

More Questions:

  1. Can your hear the Batzilla when it is looking at you?
  2. If you make a lot of noise does it confuse the Batzilla? Are there any special sounds that would distract it?

 

 

Another Hypothesis-“Batzillas use a type of sonar that uses sound at frequencies higher than what humans can hear.”

More ideas to ponder:

  1. Some objects or surfaces absorb sound very well and some reflect sound well. What types of materials are best to use to escape the notice of Batzilla?
  2. Some shapes bounce sounds in odd directions that might confuse the sonar. Think of the design of the Stealth Fighter, which helps it elude radar detection.
  3. What is the range of lengths of ultrasonic waves in air? Is there any advantage in having dimensions comparable to the wavelength of Batzilla’s sonar signals?

Additional information: http://members.aol.com/bats4kids/echo.htm

III. The Final Challenge of Survival!

Life in the jungle is a competition, a test of the survival of the fittest. You and your lab partner are to use what you have learned about the ways of Batzilla to construct a model animal that might have a chance of evading the Batzilla’s keen senses. You can use any materials that are available to you. The animal must have dimensions of at least 20cm by 20cm by 20cm. It must have a mass of at least one-half kilogram. You may suspend your animal from a string to move it within the range of Batzilla. The “animal” that can make the closest approach to Batzilla without being detected is the animal that would be most likely to escape being its next meal.

LabPro Directions and Set-Up:

Equipment / Materials:

  • Computer
  • LabPro
  • Motion sensor
  • LoggerPro software
  • Meter sticks
  • String
  • Various sized objects
  • Poster board
  • Foam
  • Other Materials the students may want to explore

Computer Set Up

Connect the LabPro to the computer and to a power supply.

Connect the Motion Sensor ("Batzilla") to the Dig/Sonic 1 port on the LabPro.

Turn on the computer.

Open the LoggerPro program.

Under the Experiment menu choose Show Sensors and select the Motion Detector in the appropriate port.

Computer Use

  • Wake up Batzilla by clicking the Collect button. His "brain waves" will appear on the screen.

  • You can sometimes get a better look at Batzilla"s brain waves by selecting Autoscale Graph under the Analyze menu to make the graph more readable.

  • You may want to change the maximum distance on Batzilla's brain wave display. Do this by clicking on the number on top most number on the y axis. The number will become highlighted and can be changed by typing in the desired value and hitting return.

[1] Pictures are copyright free courtesy of KidZone
http://www.kidzone.ws/animals/bats/photos.htm

Return to Inquiry with Technology

 
     

Contact Us ____ Site Map____ Search____ Home _____Copyright 2006 The Science House