Biology 9700 · AS & A Level · Respiration

Respiration — practice question

An investigation was done to find out how temperature affects oxygen consumption in the lizard, Sauromalus hispidus. Because this lizard’s body temperature changes with the surrounding temperature, several lizards were fitted with small airtight masks that covered their heads. Air was passed into the mask through one tube and removed through another. By comparing the oxygen concentration of the inhaled air with that of the exhaled air, the researchers could determine the lizards’ oxygen consumption rate. Each lizard’s oxygen consumption rate was measured while it was resting and while it was running. The measurements were taken at a range of temperatures from $15^\circ\text{C}$ to $40^\circ\text{C}$. Fig. 4.1 presents the results.
(a)

Using Fig. 4.1, describe how temperature affects the oxygen consumption rate of the lizard when it is resting and when it is running.

(a(i))[4]

Running causes rapid ATP use by muscle cells in the legs and heart of a lizard. With reference to the processes occurring inside a mitochondrion, explain why a faster rate of ATP use requires a higher rate of oxygen consumption.

(a(ii))[3]

Describe the way temperature affects the oxygen consumption rate in Sauromalus when it is at rest.

(b(i))[2]

The oxygen debts were determined using the masks described in (a). Suggest which measurements were taken, and how those measurements were used to work out the oxygen debt.

(b(ii))[3]

Compare the oxygen debt accumulated by a running Varanus with that of a running Sauromalus.

(b(iii))[3]

Varanus is a swift carnivore. Sauromalus is a slow herbivore. Explain how the results in Table 4.1 show that Varanus is well suited to its mode of life.

(b(iv))[2]

Most lizards, including Sauromalus, have very simple lungs without alveoli. Varanus, however, has lungs that are more mammal-like, with many air sacs similar to the alveoli of human lungs. Suggest how this difference could explain the differences in the oxygen debts of Sauromalus and Varanus shown in Table 4.1.

(iii)[3]

Varanus is a swift carnivore. Sauromalus is a slow herbivore. Explain how the data in Table 4.1 show that Varanus is well suited to its mode of life.

(iv)[2]

Most lizards, including Sauromalus, possess very simple lungs with no alveoli. Varanus, by contrast, has lungs that are more mammal-like, containing many air sacs similar to the alveoli of human lungs. Suggest how this difference could explain the differences in the oxygen debts of Sauromalus and Varanus shown in Table 4.1.

Worked solution & mark scheme

This 22-mark question has a full step-by-step worked solution and mark scheme.

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI