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# Warm Up: How did the Environment Affect the Body Temperature of Cold-Blooded Dinosaurs?

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Source:
Author: Janice VanCleave

### Problem

How did the environment affect the body temperature of cold-blooded dinosaurs?

### Materials

• large unruled index card
• pencil
• one-hole paper punch
• scissors
• bulb-type thermometer
• timer

### Procedure

1. Fold the index card in half lengthwise and open it again. For fun, draw a dinosaur on one side of the folded card.
2. Use the paper punch to make two holes about 1 inch (2.5 em) apart in the center of the other side of the card.
3. Cut two slits in the paper slightly longer than the width of the thermometer, as shown. Do this by inserting the scissors in each hole and cutting a slit on both sides of the hole.
4. Insert the thermometer through the slits in the card so that the bulb is at the tail end of the dinosaur.
5. Read and record the temperature.
6. Stand the dinosaur card outdoors so that the thermometer is in direct sunlight.
7. After 5 minutes, read and record the temperature again.

### Results

The temperature reading increases when the card is placed in direct sunlight.

### Why?

Ectothermic (cold-blooded) dinosaurs, like ectothermic reptiles of today, were able to increase their body temperature by moving into the sun. The higher temperature reading when the thermometer was placed in the sun indicates that a dinosaur's skin would have received more heat when the animal stood in a sunny area. The blood in the vessels beneath the skin would have warmed, raising the body temperature of the animal.

### Let's Explore

How could ectothermic dinosaurs cool oft? Repeat the experiment twice. First, turn the card so that the head of the dinosaur points directly toward the sun and the thermometer bulb points away from the sun. Then, place the card in a shady area. Science Fair Hint: Take photographs of the card in each position. Prepare a chart using the photos and the temperature in each area. Use the chart as part of a project display.

### Show Time!

1. How did dinosaurs keep warm after sunset? Lying against warm soil may have helped dinosaurs stay warm at night. Determine whether soil, after sunset, cools at a slower rate than does the air above it. Do this by measuring the temperature changes of soil and air in a cold environment. Fill two 12-ounce (360-ml) plastic cups half full with soil. Insert the bulb of a thermometer about 1/2 inch (0.63 cm) beneath the soil in one cup. Stand a second thermometer on the surface of the soil in the second cup. Place both cups side by side in a sunny spot. After 5 minutes, read and record the temperature on both thermometers. Keeping the thermometers in the same position, place the cups in a freezer. After 5 minutes, remove the cups from the freezer and again read and record the temperature on both thermometers.
2. Some ectothermic dinosaurs may have had special physical features that helped them control their body heat. For example, the fossil remains of Spinosaurus show that this animal had long spines of bone projecting upward from the backbone. These spines are thought to have supported a web of skin like a sail. During the cooler part of the day, Spinosaurus could stand with its side to the sun and the blood in the "sail" would heat up like a solar collector. The sun-warmed blood would then carry heat through the animal's body. If the animal became too hot, it could turn the sail away from the sun or move into the shade. Make diagrams or models showing the use of this skin and use them as part of a display.

### Check it Out!

Find out more about the special physical features used to control the body temperature of some dinosaurs. Some scientists think the plates on the back of Stegosaurus may have been used for heat control, not for protection. For more information about these plates and other physical features dinosaurs used for heating and cooling, see pages 117–119 in Dinosaur! by David Norman (New York: Prentice Hall General Reference, 1991).