1. The problem asks: "Taylor's dad is building a terrarium for his lizards. The number of lizards will determine how many shelves the terrarium will have. What is the independent variable?" 2. In any relationship, the independent variable is the one that you can control or choose freely, and it affects the dependent variable. 3. Here, the number of lizards determines the number of shelves, so the number of lizards is the independent variable. 4. The number of shelves depends on the number of lizards, so shelves is the dependent variable. 5. Therefore, the independent variable is the number of lizards. Final answer: The independent variable is the number of lizards.