1. The population of native white-clawed crayfish in English rivers is decreasing due to an increasing population of American imported signal crayfish.

Figure 1 shows a white-clawed crayfish.

Figure 1

(i) Which term is used to describe the American imported signal crayfish now that it is living in English rivers?

(1)

☐ A Indigenous species

☐ B Non-indigenous species

☐ C Non-invasive species

☐ D Pathogenic species

(ii) American imported signal crayfish may eat white-clawed crayfish.

Explain one other reason why the increasing population of American imported signal crayfish may have caused the decrease in white-clawed crayfish.

(2)

(iii) The Environment Agency is developing methods of increasing the population of white-clawed crayfish in English rivers.

Which term describes these methods?

(1)

☐ A Mutation

☐ B Conservation

☐ C Predation

☐ D Mutualism

(iv) White-clawed crayfish cannot survive in rivers with a low concentration of oxygen.

Explain how eutrophication can cause the population of white-clawed crayfish to decrease.

(3)