Biology 9700 · AS & A Level · Respiration

Respiration — practice question

An investigation was undertaken to find out how temperature affects the rate of oxygen consumption in the lizard, Sauromalus hispidus. A lizard’s body temperature changes with the surrounding temperature. A number of lizards were fitted with small airtight masks over their heads. Air was passed into the mask through one tube and removed through another. Differences in oxygen concentration between the air supplied for inhalation and the air breathed out allowed the researchers to determine the lizards’ rate of oxygen consumption. Each lizard’s oxygen consumption rate was measured both at rest and while it was running. The measurements were carried out at a range of temperatures from $15^\circ \text{C}$ to $40^\circ \text{C}$. Fig. 4.1 presents the findings.
(a)

Fig. 4.1 gives the results for the rate of oxygen consumption in lizards at rest and while running.

(a(i))[4]

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

(a(ii))[3]

Explain how temperature affects the rate of oxygen consumption in Sauromalus when it is at rest.

(b(i))[2]

The oxygen debts were determined with the masks described in (a). Suggest what measurements were taken, and how these measurements were used to calculate the oxygen debt.

(b(ii))[3]

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

(b(iii))[3]

Varanus is a fast-moving carnivore. Sauromalus is a slow-moving herbivore. Explain how the results in Table 4.1 show that Varanus is well-adapted to its mode of life.

(b(iv))[2]

Most lizards, including Sauromalus, have very simple lungs with no alveoli. Varanus, however, has lungs that are more like those of mammals, containing large numbers of air sacs similar to the alveoli of human lungs. Suggest how this difference could account for the differences in the oxygen debts of Sauromalus and Varanus shown in Table 4.1.

(iii)[3]

Explain how the results in Table 4.1 show that Varanus is well-adapted to its mode of life.

(iv)[2]

Most lizards, including Sauromalus, have very simple lungs with no alveoli. Varanus, however, has lungs that are more like those of mammals, containing large numbers of air sacs similar to the alveoli of human lungs. Suggest how this difference could account for 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