State one substance that plants produce using nitrate ions.
Describe the effects of excess fertiliser on aquatic ecosystems.
Describe the differences in the populations of the species in river A and in river B in Table 6.1.
Suggest which species in Table 6.1 has the lowest tolerance to pollution.
Complete the sentences so they describe the data shown in Fig. 6.1. Overall, the population size increased and then fell. In 1998, the population size of red king crabs was [BLANK]. The largest population size of red king crabs was in the year [BLANK]. The population size in 1995 was the same as the population size in [BLANK].
Using the data in Fig. 6.1, calculate the percentage rise in the red king crab population between 1995 and 1999. Give your answer to the nearest whole number.