State the names of the two other major groups of vertebrates.
Use Table 1.1 to compare fish, mammals and birds.
Define the term diffusion.
Suggest one adaptation, visible in Fig. 1.1, that shows fish gills are efficient structures for gas exchange by diffusion.
State one type of pollutant that can cause a decrease in the concentration of dissolved oxygen in rivers.
Carry out steps 1 to 3 to work out how increasing the water temperature from 15^{\circ}C to 25^{\circ}C affects gas diffusion distance. Step 1 Find the concentration of dissolved oxygen from Fig. 1.3 at: 15^{\circ}C: [BLANK] mg per dm$^3$ 25^{\circ}C: [BLANK] mg per dm$^3$ Step 2 Use the values from step 1 to find the gas diffusion distances from Fig. 1.2: [BLANK] µm [BLANK] µm Step 3 Calculate the difference in the values from step 2. [BLANK] µm