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Skeletons of radiolarians, marine protozoaSkeletons of radiolarians, marine protozoa Like bacteria, protists are microscopic, single-celled organisms. But unlike bacteria, each protist has its genetic material (DNA) wrapped inside a bag-like membrane to form the nucleus, or control centre, of the cell. Protists live mainly in water or in damp places. They can be parasites living inside plants and animals, including humans. Some are like tiny plants (protophyta), such as algae, absorbing their energy from sunlight and their raw materials for growth from the water around them. Others are like minute animals (protozoa), for example amoebae, which move around and consume food particles such as bacteria.

Kinds of protist

An amoeba, a type of protozoaAn amoeba, a type of protozoaAn amoeba devouring bacteria An amoeba devouring bacteria Some protists have a rigid, case-like cell wall around them. Some protozoans, the foraminiferans and radiolarians, have skeletons with beautiful shapes and patterns. Others have no rigid case and can take up any shape. The amoeba, for example, has no definite shape. It moves by flowing along like a plastic bag full of jelly. A few protists cause diseases, such as plasmodia, which produce malaria.

Euglena, a single-celled flagellateEuglena, a single-celled flagellate 

There are an estimated 36,400 different types of protozoans.

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