Part A

Setting Up the Experiment

1. In your lab report, make a data table similar to the one shown on the facing page.

2. Use a glass-marking pencil to label three beakers "A" "B" and "C". Also, write your initials on the beakers.

3. Add 500 mL of pond water to each beaker.

4. ^ ^ ^ CAUTION Put on a ^r ^r ^r lab apron and safety goggles. If you get thyroxine on your skin or clothing, rinse with water while calling to your teacher. If you get thyroxine in your eyes, immediately flush them with water at the eyewash station while calling to your teacher.

5. Use a graduated cylinder to measure 10 mL of thyroxine solution. Add the 10 mL of solution to beaker A. Measure and add 5 mL of thyroxine solution to beaker B.

6. Add equal amounts (about 1 mL) of strained spinach to beakers A, B, and C.

7. Place a sheet of graph paper, ruled side up, under a Petri dish.

8. CAUTION You will be working with live ^^ animals. Handle them with care, and follow directions carefully. Catch a tadpole with a fish net, and place the tadpole in the Petri dish. Measure the tadpole's total length, tail length, and body length in millimeters by counting the number of squares that it covers on the graph paper. Then, place the tadpole in beaker A.

Repeat step 8 with two more tadpoles. Average the total length, tail length, and body length of the three tadpoles that you placed in beaker A. In your data table, record the average measurements under the column labeled "Beaker A."

10. Repeat step 8 with three more tadpoles, this time placing the tadpoles in beaker B. Average the total length, tail length, and body length of the three tadpoles. Record your average measurements in your data table under "Beaker B."

11. Repeat step 8 with three more tadpoles. Place these three tadpoles in beaker C. Average the total length, tail length, and body length of the three tadpoles. Record your average measurements in your data table under "Beaker C." You should have measured a total of nine tadpoles and placed three in each beaker.

12. j^.. Clean up your materials, and wash your hands before leaving the lab.

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