Billions of protozoa, such as these radiolarians, live in the sea as plankton. As they die, the tiny skeletons of the dead...Read More >>Billions of protozoa, such as these radiolarians, live in the sea as plankton. As they die, the tiny skeletons of the dead radiolarians sink and form the thick, muddy ooze on the seabed. 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 is a type of protozoa, with no definite shape.An amoeba devours bacteria and algae by turning parts of its body into "arms" that engulf the organism.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 flagellate, a type of protist. Species of Euglena are found in both fresh and salt waters. They may...Read More >>Euglena, a single-celled flagellate, a type of protist. Species of Euglena are found in both fresh and salt waters. They may bloom in numbers sufficient to colour the surface of stagnant ponds green. Euglena is widely studied in laboratories as a "model organism". The scale bar shows a measure of 25 microns (millionths of a metre).
There are an estimated 36,400 different types of protozoans.
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