Dinosaur metabolism

Directions: For this lab you will be able to download the document and TYPE your answers on it. You can then submit it to Dropbox on Pilot. You will also need to utilize your book and/or Google to help with answering the questions.

Laboratory objective: The purpose of this laboratory is to introduce the student to dinosaur metabolism and what factors cause the debate over whether the dinosaurs were cold or warm blooded.

Laboratory discussion: The debate over whether dinosaurs are warm or cold blooded is a complex one. Many factors such as growth rate, respiration, scaling, and temperature regulation can affect the dinosaur’s metabolism.

Laboratory activities:

Part I: Growth Rates

The curves above represent the body mass (in tons) of the giant crocodilian Deinosuchus (line A) and the ceratopsian Triceratops (dashed line B), both of which are found in the Montana Group deposits of the American West.

1) At what age does Triceratops growth level off?

2) At what age does Deinosuchus growth level off?

3) Which of these reptiles grew at a rate more like a modern mammal (i.e., fast)? [Triceratops | Deinosuchus]

Part II: Dinosaur Respiration (Lungs)

Food is only part of metabolism. Another important aspect is respiration: without oxygen, there isn’t much metabolism!! Recent work by Colleen Farmer, David Carrier, and Elizabeth Brainerd on modern animals has revealed a lot more diversity in vertebrate respiration than previously known. For example, mammalian breath (which uses the ribs plus a muscular diaphragm, but doesn’t use a throat pump) is just plain weird!

Here is a look at some of the techniques used to get air down into the lungs:

• Buccal pumping (swallowing air): used by air-breathing fish and amphibians

• Gular pumping (using an actively pumping throat): used by lizards and crocodilians

• Costal breathing (moving ribs in and out): all amniotes but rib bless frogs

• Diaphragm breathing: mammals

• Hepatic piston (liver pumping): crocodilians

• Air Sac pumping: birds

Interestingly, both crocodilians and birds use their pelvic (hip) muscles in breathing. In the figure on the previous page, A is a modern alligator. When the rectus abdominis muscle contracts it pulls the pubis forward, pushing the liver forward and forcing air out of the lungs (expiration). When the ischiopubic and diaphragmatic muscles contract, it pulls the liver backwards, causing the lungs to expand and draw in air (inspiration). B shows respiration in a pigeon. During inspiration the sternum rotates downward and the longissimus dorsi muscles contracts to pull the tail up: together, these inflate some of the air sacs in the body. During expiration the infrapubic and suprapubic abdominal muscles contract to pull the sternum up and the tail down, pushing air out of the sacs. Below is a drawing showing the air sac system of a bird, in left lateral view. C, I, AT, PT, and AB are different individual air sacs—you don’t need to worry about that level of detail. The bold arrows show how the air sacs invade the vertebrae: