Imagine you are a biologist with the task of genetically engineering a cow to survive on an alien planet. The planet has twice the gravity of Earth, the partial pressure of O2 is twice as high as that of Earth, and the partial pressure of CO2 is 100 times that of Earth. The planet is very dry, with an extremely low relative humidity. What changes would you make to the circulatory and respiratory

Question

systems to accommodate these differences and allow your cow to function?

What will be an ideal response?

Answer 1

Gravity: The circulatory system will have to work harder to pump blood against gravity. The student might suggest higher blood pressure, a stronger heart and vessel linings, and more valves in the veins and lymph vessels of the legs. O2: The greater abundance of O2 will make delivery to the tissues easier. A hemoglobin molecule could have a lower affinity for O2, which would still allow it to pick up oxygen under these conditions and drop it off in the tissues more readily. This increased energy supply may make it easier to do the work needed to move around against gravity. CO2: The increased CO2 will tend to make the blood more acidic, and this problem could be addressed with buffers or changes in the properties of other proteins to allow them to function at a lower pH. The CO2 sensors of the brain and blood vessels will have to be adjusted so that they are less sensitive to CO2 . Finally, the respiratory system will have to have some adjustments to prevent excess water loss. Making it more closed, with longer and more elaborate nasal and bronchial passages (as with camels) might help. Keep an open mind while grading this one, and you might enjoy the responses.