Protists are mostly microscopic unicellular, or single-celled, organisms. The cells of protists have a nucleus and are highly organized with specialized cells parts called organelles. Protists are classified, along with plants, animals, and fungi, as eukaryotes.
There are many diverse organisms which are considered to be protists including algae, amoebas, and ciliates such as paramecium. Protists are basically all the eukaryotic organisms that are not animals, plants, or fungi. Protists usually form colonies consisting of one or a couple of distinct kinds of cells. Multicellular protists may include brown algae and certain red algae.
Cells of protists have a nucleus which contains their genetic material. Organelles inside the cells carry out defined functions within the cell. For example, it is here where some protists receive energy from the sun to produce nutrients through a process called photosynthesis. Most protists also have mitochondria, another organelle, which generates energy for the cells to use. The exception is those that live in environments lacking oxygen.
Finally, most protists reproduce asexually, which can include binary fission where a parent splits into two identical cells or multiple fission, where the parent produces multiple identical cells. Some protists may have another sexual cycle, but have only been found in a few groups.
1. Amoeba proteusAmoeba proteus is closely related to the giant amoebae, which can be commonly found at science supply stores. The small protozoan uses tentacles called pseudopodia to move. They are very well known for these tentacular protuberances. It occupies freshwater environments and feeds on other protozoans, algae, and other smaller amoebae. Under a microscope, they may appear in a variety of colors.
2. Euglena gracilis
Euglena is the best known and most often studied member of the class Euglenoidea, which is a diverse group containing hundreds of species. They are found in fresh and salt waters, and are abundant in quiet inland waters. This is where they may bloom in large numbers sufficient to color the surface of ponds and ditches green and red.
3. Paramecium aurelia
They are unicellular organisms belonging to the genus Paramecium. They are covered with cilia which help them with feeding and movement. They can reproduce sexually and asexually, or by the process of endomixis. The paramecium demonstrates a strong sex reaction where groups of cluster together and emerge in conjugant pairs. The pairing may last up to 12 hours, at which time the micronucleus of each organism is exchanged.
The Five Kingdoms
Function of the Vacuole