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Spin, Spin, Spin

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TEACHING GUIDES


Spiders!:
Spin, Spin, Spin


Danish arachnologist Fritz Vollrath studies spiders that exist only inside his computers. Vollrath's cyberspiders spin webs and even mate. By observing the behavior of these digital spiders, Vollrath is learning more about how and why spiders build webs. Watching successive generations of cyberspiders spin their webs is giving scientists an unexpected window into evolution.

Curriculum Links
National Science Education Standards
Related Frontiers Shows and Activities
Activity 1: What Webs We Weave
Activity 2: Web Research Lab
Challenge: Could You Survive as a Spider?




CURRICULUM LINKS


BIOLOGY/
LIFE SCIENCE


arachnids, diversity, evolution, invertebrates

CHEMISTRY


spider silk

COMPUTER
SCIENCE


 

GENETICS


 

PHYSICAL
SCIENCE


tensions and forces

TECHNOLOGY


computer modeling




NATIONAL SCIENCE EDUCATION STANDARDS

SCIENCE AS INQUIRY/PHYSICAL SCIENCE
5-8,
9-12:
Motions and Forces
LIFE SCIENCE
5-8: Structure and Function in Living Systems, Reproduction and Heredity, Regulation and Behavior, Diversity and Adaptations of Organisms
9-12: Molecular Basis of Heredity, Biological Evolution, Behavior of Organisms
SCIENCE AND TECHNOLOGY
5-8,
9-12:
Abilities of Technological Design, Understanding About Science and Technology
SCIENCE IN PERSONAL AND SOCIAL PERSPECTIVES
5-8: Science and Technology in Society
9-12: Science and Technology in Local, National and Global Challenges
HISTORY AND NATURE OF SCIENCE
5-8: Science as a Human Endeavor, Nature of Science
9-12: Science as a Human Endeavor, Nature of Scientific Knowledge




RELATED FRONTIERS SHOWS AND ACTIVITIES



ACTIVITY 1: WHAT WEBS WE WEAVE

Like other spiders that weave webs, orb weavers are nearly blind. Despite their poor vision, they spin intricate, exquisite webs to trap their prey. To find out just how spiders plan and build their webs, arachnologist Fritz Vollrath programs digital spiders to simulate the behavior and web-building strategies of orb-weaving spiders in nature.

Researchers studying spider behavior often use orb-web spiders for their subjects. For example, scientists might watch as a spider builds a web in a frame, then turn the frame in another direction or upside-down to find out how the spider responds. Spiders have also accompanied astronauts on NASA flights to test the effects of microgravity on web-building.

Given the dexterity of your fingers and the fact that your vision is probably superior to that of a spider's, what kind of webs can you weave? In this activity, you'll build a model of a spider web.


MATERIALS
  • string (about 300cm per web)
  • 12" x 12" x 1/4" wooden board
  • 4 short nails
Note: Instead of building the web with nails, you might wish to experiment with using glue to attach the threads

PROCEDURE

  1. CONSTRUCT THE FRAMEWORK THREADS:
    Two inches in from each corner, hammer nails into the board to serve as supports to which you'll attach the framework threads. Tie the beginning of your string to point A and pull it to point B. Wrap the string around point B and pull it to point C. Wrap the string around point C and pull it to point D. Wrap the string around point D and pull the string back to point A and tie a knot.


  2. CONSTRUCT THE RADIAL THREADS:
    About two inches over from point A, tie a new length of string. Draw it across the framework and tie it to the framework thread diagonal to this point. This is the first radial thread. Tie another string in the center of the framework between points A and B. Draw it across to the opposite framework and tie it. Tie a third radial two inches left of point B and draw it across in a diagonal, crossing the first and second radials. Repeat these steps to lay down radials between points B and C. Lay down a total of six radials. Make sure radials meet in the center, or hub, of the web.


  3. CONSTRUCT THE SPIRAL:
    Tie a new section of string to the center of the web. Loop it over and under each radial in a spiral, radiating out until you get to the framework. Tie the end of the spiral off at the framework. You may want to glue your spiral to the radial threads at key points to reinforce your web.
EXTENSIONS

  1. Watch Frontiers and note the steps an orb-weaving spider follows to make a web. How does the spider's procedure compare with yours?

  2. The shape of an orb web is considered an example of an Archimedes' spiral (named after the Greek mathematician who studied spirals extensively), because it spirals out in an even manner. Other spiral shapes found in nature include the fossilized ammonite, a sunflower and a spiral galaxy. Can you find other examples?

  3. The spiral is the sticky part of the spider's web. Scientists do not agree about why spiders can avoid becoming trapped in their own webs. Use the Internet to research theories about why spiders don't get stuck in their own webs.


ACTIVITY 2: WEB RESEARCH LAB

As you see on Frontiers, some types of spiders rely on webs to help catch their prey. Some webs catch insects, while others are designed to catch birds and bats!

Spiders have had 400 million years to perfect their silk, known for its elasticity and strength. Silk is secreted by the silk glands or spinnerets. Many species produce up to seven different kinds of silk, each with different properties, each produced by a different silk gland. There are silks for different parts of a web, for egg sacs and for snares, but the strongest kind is dragline silk, used to make the frame of a web and the line a spider uses to dangle from its web. Scientists and engineers are very interested in synthesizing spider silk, which they hope could be used for parachutes, bullet-proof vests and even surgical sutures.

In this activity, you'll define properties of different threads and then use your results to select the best thread to design a web to capture a specific prey. You'll first need to test various types of thread to see which is the strongest.


MATERIALS
  • thread test set-up made from a piece of 2" x 4" board and 4 screw hooks. Set this between two tables (see diagram below)
  • samples of thread from fabric store (Select threads made from different fibers, with a mix of thickness and elasticity.)
  • hooked mass set 10g to 1000g (If not available, devise a paper clip hook with fishing weights.)
PROCEDURE

  1. Measure approximately 20cm of each thread to be tested. Assign a number to each thread so that you can keep track of which is which. Create a data table like the one below and record the number and material of each thread.

  2. Tie a loop in each end of the thread. Loop one end of the thread around one of the screw hooks so it hangs freely (see test set-up diagram above).

  3. Begin with the lightest mass and carefully hang it on the first thread to test it. If the thread does not break, add more mass. Repeat until the thread breaks.

  4. In your data table, record the greatest mass the thread supports without breaking. Record any other observations you make.

    TEST # MATERIAL MASS NOTES
    1. Rayon 500g Stretched 2 cm
    2. Cotton 450g  
    3. Elastic 650g Stretched 20 cm
    4.      
    5.      
    6.      
    7.      
  5. Repeat Steps 2 through 4 for each thread sample.
QUESTIONS

  1. Which thread supported the most mass? The least?

  2. Which thread would be the best to catch large prey, like a bird or bat? Explain.


CHALLENGE: COULD YOU SURVIVE AS A SPIDER?

For this challenge, you'll need more thread to build webs, a golf ball and a test apparatus to hang webs from (a ring stand and 14cm ring work well). You'll also need to use a balance (pan, triple beam or electronic) to determine the mass of each web. Or, designate the winner as the web using the least thread.

Work in teams of two or more to attempt the following challenges. Webs must be attached to the test apparatus and cannot be adjusted after they are set up.


CHALLENGE 1:
Design the lightest web that will support a golf ball. The team that designs the lightest web to support the ball wins.

CHALLENGE 2:
Design the lightest web that will catch and hold a golf ball dropped from the greatest height. Start with a drop of 20cm for the first trial. If the web catches and holds the golf ball, increase the drop height by 5cm for each additional trial.


QUESTIONS

  1. The challenges required different web designs. How do various spiders' webs differ based on the challenges that nature presents?

  2. You weren't allowed to adjust your web once it was set up. How often do spiders tend to adjust their webs?
EXTENSIONS

  1. Find out the results of a ground-based experiment designed to see how spiders might behave in space: geocities.com/CapeCanaveral/Launchpad/3877/

  2. Conduct your own experiment about the biological clock in orb-weaving spiders: www.cbt.virginia.edu/olh/middle/activ_m/spider.html






 

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