Choose words from the box to complete the sentences. Write the words on the lines. (malaria) (parasites) (Plasmodium) (symbiotic) (Trichonympha) (mutualists)

Protists interact with the environment in many ways. Many protists are 1. . They live in 2. relationships with host organisms that provide a benefit to both protists and hosts. For example, the protist 3. lives in the guts of termites and gives the termites their ability to digest wood. In contrast, some protists are 4. that harm or kill their hosts. The protist 5. can infect the human bloodstream and cause 6. , killing a million people per year.