Describe how ultrafiltration occurs in a glomerulus.

Glucose and water are reabsorbed by the proximal convoluted tubule of a nephron.

Put a tick (✓) in the box next to the correct ways in which glucose and water are reabsorbed.

☐ Glucose by active transport and water against a water potential gradient

☐ Glucose by diffusion and water down a water potential gradient

☐ Glucose by facilitated diffusion and active transport and water against a water potential gradient

☐ Glucose by facilitated diffusion and active transport and water down a water potential gradient

The equation shows the relationship between urine concentration in arbitrary units (y) and mean length of the loop of Henle in mm (x).

y = 0.72x + 4

Calculate the mean length of the loop of Henle in an organism that produces urine with a concentration of 16.56 arbitrary units.

Answer = ______________ mm

Scientists investigated the relationship between the thickness of the kidney medulla of different species of mammals and the concentration of their urine.

Figure 1 shows their results.

Explain the pattern shown by the results in Figure 1.