Evaluate and explain how to fix the habitat of a classroom iguana.

In the Iguana Home task, students help troubleshoot and fix the habitat for a classroom iguana named "Iggy." Students first learn about iguanas and their basic needs, and then they work through the task to determine how best to fix Iggy’s wire mesh cage.

Content Area: Design and Systems
Practice: Developing Solutions and Achieving Goals
Learn about content areas and practices
Task Time: 30 minutes
Assessment Year Used: 2014

Students were able to identify design problems and predict the outcomes of design decisions but were less able to explain how a design change could solve a problem.

67%
of students were able to analyze and identify a design problem.
8%
of students successfully explained how a set of design changes could solve a problem.
69%
of students were able to recognize requirements and critique a proposed design solution.
Explore task details by selecting a step below
Step 1
Evaluating the Cage Design to Solve Problem 1
Students consider design solutions and make predictions for solving the problem of Iggy’s cage being too cold.

67% of students correctly identified a cage design requirement that was not met, while 12% were able to use information to identify and explain the best solution.

What Students Did

First, students identify the most likely reason why Iggy is hanging on the heat lamp. The explanation is that Iggy’s home is too cold. Next, students need to select the best solution out of four options and explain why that solution would work best.

Skills Measured

  • Analyze as an initial step for designing or troubleshooting a system and evaluate latter parts of a design cycle.
  • Design or redesign a device or system to address a need.

Student Performance

67% of Students
recognized that Iggy’s home was too cold.
12% of Students
selected and explained how using a stronger heat lamp would be the best design solution.

Related Experience from Student Survey

62% of Students
reported figuring out why something was not working three or more times, outside of school, in order to fix it.
Step 2
Evaluating the Cage Design to Solve Problem 2
Students consider design solutions and make predictions for solving the problem of Iggy being awake and active at night.

66% of students predicted and explained how a design choice would fulfill an unmet need, while 8% of students successfully explained how a set of proposed changes would meet the need in order to solve the design problem.

What Students Did

In this section of the task, students evaluate how to fix the problem with Iggy being active at night.

Skills Measured

  • Analyzing as an initial step for designing or troubleshooting a system.
  • Design or redesign a device or system to address a need.

Student Performance

82% of Students
identified which requirement would determine a design decision.
38% of Students
predicted and explained how a design choice would not meet a particular requirement.
66% of Students
predicted and explained the possible outcomes of a design change.
8% of Students
successfully explained how design problems would be solved by a set of proposed changes.

Related Experience from Student Survey

43% of Students
reported using different tools, materials, or machines three or more times, at school, to see which are best for a given purpose.
Step 3
Testing the Cage Design and Evaluating Alternative Solutions
Students observe Iggy’s behavior to determine whether the proposed cage design solutions solve Iggy’s problems.

83% of students could identify the outcome of making a design change to a system, while 41% of students were able to use information from a model to explain why a specific design change would not be successful.

What Students Did

Students are told that the low temperature problem is not yet solved and they need to evaluate two alternative solutions to make the cage warmer. Students first evaluate and predict whether or not adding plastic sides to the cage will improve the cage’s temperature. Then they need to identify why the alternative solution of adding a plastic top to the cage might work.

Skills Measured

  • Design or redesign a device or system to address a need.
  • Understand and use models to solve engineering design problems.
  • Predict the consequences of design decisions or making changes to a system.

Student Performance

69% of Students
correctly predicted and explained how a design choice would not meet a particular need.
41% of Students
were able to use information from a model system to explain why a design change would not work.
83% of Students
correctly identified how a design change to one part of a system would affect how it functions.

Related Experience from Student Survey

37% of Students
reported building or testing a model three or more times, while at school, to see whether it solves a problem.
Step 4
Redesigning the Cage to Prevent Dehydration
Students select a cage redesign to prevent dehydration.

46% of students correctly identified and explained the best way to meet stated design requirements.

What Students Did

At the end of the task, students are asked to consider which of two options would be best for making sure Iggy does not become dehydrated: 1) another bowl of water or 2) an automatic water-misting system.

Skills Measured

  • Design or redesign a device or system to address a need.

Student Performance

46% of Students
identified and explained the choice that would best meet the stated design goal.

Related Experience from Student Survey

49% of Students
reported using different tools, materials, or machines three or more times, outside of school, to see which are best for a given purpose.
A Closer Look: Students' Abilities to Evaluate Design Options, Predict Outcomes of Design Changes, and Explain Design Solutions
Six percent of students could identify an unmet design requirement, predict the outcome of a design change, and explain how design changes could solve a problem.

Follow the left-most series of blue disks.

Task Step 2 (Question 3): Analyzing a design and identifying an unmet requirement.

82% of students correctly analyzed Iggy’s behavior to identify an unmet cage design requirement.

Task Step 2 (Question 5): Predicting the possible outcome of a proposed design change.

56% of students could identify an unmet design requirement and correctly predict the possible outcome of a proposed design change to Iggy’s cage.

Task Step 2 (Question 6): Explaining how modifying system could solve a problem by meeting design requirements.

6% of students could identify an unmet design requirement, successfully predict the outcome of a design change, and explain how cage design modifications could solve a problem.

Chart with 2 disks. On left:Disk indicating 82% correct. On right, disk indicating 18% incorrect.
Chart with 4 disks. From left to right: Disk indicating 56% correct, disk indicating 26% unsatisfactory, disk indicating 9% correct, disk indicating 8% unsatisfactory.
Disk indicating 6% correct, disk indicating 33% partially correct, disk indicating 17% unsatisfactory, disk indicating 1% correct, disk indicating 12% partially correct, disk indicating 13% unsatisfactory, disk indicating <0.5% correct, disk indicating 4% partially correct, disk indicating 5% unsatisfactory, disk indicating <0.5% correct, disk indicating 2% partially correct, disk indicating 6% unsatisfactory.