Lesson 1: Cell Phone Network Introduction

This is the first lesson of the Introduction to Systems Module. In this lesson, students learn about systems by participating in an cell phone network activity. A network is a system of interconnected parts. These parts may be organisms, genes, molecules, etc…Nodes are the parts of a network, and edges are the relationships between those parts of the network


See the NGSS listed in the left-hand menu. When applicable, connections to 21st Century Learning Skills and other published standards are also included in the chart below. In addition, for this lesson, here is a breakdown of:

What Students Learn
  • A network is a system of interconnected parts. These parts may be organisms, genes, molecules, etc…
  • Nodes are the parts of a network, and edges are the relationships between those parts of the network
  • A network shows the flow of something through a system, including information (cell phone network), energy (food web), etc…
What Students Do
  • Students create and analyze a cell phone network.
  • Students use a computer program (Cytoscape) track flow of information through a network
  • Students use a computer program (Cytoscape) to interpret the impact of removing nodes on a network


  1. Warm-up: see slide 1 in power point Network Intro and Cell Phone Activity (PowerPoint | Google Slides)
    • Pre-assess student understanding using this worksheet. (Word Doc | Google Doc)
    • Once you have collected the student worksheets, lead a class discussion based on the two questions listed below.  Goal: connect the idea of networks to previous knowledge. Some things they may come up with: computer networks, etc…
    • Describe what you think the word “network” means.
    • Give at least 2 examples of a “network”
  2. Introduce concept of networks: see slides #2 – 7 in power point. Concepts to introduce: what is a network, what is a node, what is an edge, what are some examples of networks in biology?Key concepts: many things in biology may be represented as networks. A network is made of the individual parts of the system and the interactions between those parts of the system. We will use the word “nodes” to represent the parts of the system, and “edges” to represent the interactions. A food web is used as an example of a network, and students should have previous experience with food webs from middle school.

Use slides #8-13 to provide students with an overview of the cell phone activity you will be completing in class. Diagram should include both the number/letter label for each student as well as names for each student (see slide 9). The names of their classmates don’t get used later on in class, it just makes the activity a little more fun and functions as a get to know your classmates activity.

Direction of arrows in a network is a very important concept. Often interactions work in just one direction. Emphasize this using cell phone examples in slides 10 and 11

Why the “rules for network” (slide 12)? Most kids have experience with cell phones in real life, and they know its easy to add numbers to phone books or to call back someone who called you, so this is a pre-emptive strike against kids who say “Why can’t I just…?” The third rule is an attempt to get kids to talk to each other, avoiding a situation where one student collects all of the information cards and creates the poster by him/herself. This activity should be a lesson in teamwork as well as networks!

Slide 13 is an overview of what will be happening in the class. This is an important slide! There is a lot of moving around and switching groups in this activity, so it is important to give students a preview of what they will be doing.


After reviewing the PowerPoint, pass out one cell phone card to each student (PDF – see Advanced Prep for detailed instructions). Consider giving card 3E to the person you want to be the “hub”. Also, consider passing out a copy of the instructions document at this time (Word Doc | Google Doc). You will have already given an overview of the instructions, so you may not need to go over the instructions with them. Inform students that you expect them to refer to their handout first before they ask you for help with “what to do next.” You may want to leave the PowerPoint slide with the instructions posted during the activity (slide #13 of Network Intro and Cell Phone Activity, PowerPoint | Google Slides).

Another Idea: you may not find it necessary to pass out instructions to the students at all – the PowerPoint may have given your students enough information to complete the task on their own. Whether or not to hand instructions to each student is up to the teacher, it may be necessary for some classes but not necessary for others. You may wish to simply print a class set of 12 instructions, and place one at each of the stations (7 for the numbered stations and 5 for the lettered stations). Another option that works for some classes is to have each group use whiteboards instead of butcher paper.

Inform students that there is some information on the cell phone student cards that is unnecessary for today’s lesson: the actual phone number (this is just for fun, they do not actually need this piece of information), and the information on the carrier, roaming, etc… This information is what the Cytoscape simulation is based on, but there are no questions written which require the students to use this info in lesson 1.

Extension idea: you may choose to add some challenge questions using that extra info (carriers, etc) and see if they can answer them using their paper network. This might enhance their appreciation of Cytoscape when they get to use it in lesson 2!

Classroom management tip: it is important to have time limits for each of the segments of this activity. Announce time limits beforehand, write them on the board, and/or you may wish to have a signal such as a bell because this activity can get loud!
Students will fill out names on their cell phone cards.  Allow students to mingle in the classroom, give them 3 minutes to find the names of all of the people in their phone book.

Purpose: to get students to mingle and learn each other’s names. Emphasize that on the poster you want to see both number/letter labels and actual student names from their classmates.

Note: if you do not have 35 students, it would be a good idea to come up with fake names for the students who are missing from the network. You can write these names on the white board. If no one was assigned 7A or 6A, for example, write on the white board 7A = Jesse, 6A = Tommy, etc… If you do not do this, each group will come up with different fake names and that gets confusing when you try to compare networks!!

Students will meet with their numbered groups to begin network drawing. See Cell Phone advanced prep 1 (Word Doc | Google Doc) for info on what should be ready at each station. Documents you should have photocopied and ready to go: Information Sheet for A, B, and C (Word Doc | Google Doc), Information Collecting Sheets (Word Doc | Google Doc). Also, just in case it is needed for student make up, or some other purpose, here is the complete information sheet for all, A-E groups (Word Doc | Google Doc).

Important notes for teacher: make sure that students recognize that their drawing at this point will be incomplete. For example, they may know that 4a can call student 5b but they do not know the name of student 5b. Students will be tempted to “make up” additional information (such as a fake name for person 5b). Therefore, it is important to emphasize that they will obtain this information later, and that the network they draw at this point should ONLY include information that they KNOW.

Each numbered group will be creating one network poster. Remind students to use pens and color so their poster will be easy to read. Students are all expected to participate in the drawing (this is emphasized in the instructions). Students have done this successfully by splitting up portions of the network between group members, or by assigning different tasks: such as reader, node drawer, edge drawer, decorator/color specialist.


Suggested break point if required due to class time


Students will meet with lettered groups to collect all additional information needed to complete network. Post the instructions from the PowerPoint (slide #13) to guide students. Use of the “information collecting sheets” should smooth this portion of the lesson, because students will know exactly what information they need to find out. Remind them again that they need information on names as well as number/letters, and they should not be making up any names. Each number/letter is assigned to an actual classmate, and any numbers that are unassigned are named on the white board.

Students will meet with their numbered groups again to finish network drawing.


Using handout Intro to Networks Student Questions (Word Doc | Google Doc), students will analyze the cell phone network they have just created and will answer questions about routes of information flow through the system. See Intro to networks Teacher KEY (Word Doc | Google Doc) for answers. Tell students that when they are completely done with their network, they should raise their hands. The teacher can then check on the poster to see if it looks complete, and then pass out the introduction to networks questions. Keep in mind that the students will need to use their poster to answer the questions, so these questions need to be done in class. There is a suggested homework assignment which students can work on in class when finished with the intro to networks questions. This HW is to create a challenge question about the cell phone network. Encourage them to write a question which is tricky, inform students that they can use any information given on the cell phone cards (carrier, roaming, email, photo capacity). Inform students that these questions will be shuffled, and given out to another group tomorrow as a challenge (during the Cytoscape activity). The goal is to have students analyze the creation they just made, and to observe how information can flow through the system from one node (person/cell phone) to another distant node.

A secondary goal is for them to analyze a paper version of the network, so they can compare and contrast this analysis with the analysis that can be completed using a computer program (Cytoscape). They should see, after the next lesson, that you can answer more complex questions about large networks using computers.


Career Connection


How will I know they know

  • Cell phone poster: were students able to successfully create a linked network? (group assignment)
  • Cell phone questions: were students able to answer analysis questions about their network? (individual assignment)
  • Cell phone homework: were students able to create a thoughtful challenge question about the network? (individual assignment)
  • Networks quiz: are students able to create a network, and track the flow of energy through a network? (quiz)



A potential assignment would be for students to create their own network based on something else in their life. A family tree, perhaps, using the relationship “is the child of”, or a tree showing their social group, using the relationship “is friends with”. Challenge students to think about what the nodes in the network would be (people, computers, phones, etc…) and what the relationships, or edges, should be. Keep in mind that in today’s network, the nodes were student cell phones, and the edges were the relationship “can call”. Also view the Extension Activity that also can serve as a further lead in to Lesson 2 (Word Doc | Google Doc).