The positive and negative effects of amoeba for humans and in nature.

Positive qualities:
Euglens feed on bacteria and cleanse water bodies from pollution, bacteria and decaying substances.
They also multiply rapidly and serve as food for fish and other aquatic life.
Carry out photosynthesis thereby reducing the amount of carbon dioxide, and vice versa increasing oxygen with water.
Another useful thing is that by the number of these protozoa, you can determine the degree of water pollution.

Negative influence:
They are causative agents of diseases.
There are a large number of amoebas that cause disease in animals and humans.
For example, ciliates are embedded in the skin of fish, which leads to their death.