First secondary biology research on protists
Protists constitute a class of diverse microorganisms. Most of them consist of a single cell that is very small and invisible to the naked eye. The cells of these organisms are characterized by an organized structure that includes a specific nucleus and organelles that perform various vital functions.
Previously, amoeba and unicellular algae were classified within one kingdom known as the Protista kingdom, but the development of genetic studies has provided new data showing the evolutionary relationships between these organisms more precisely, which led to changes in the way they are classified.
Features of protists
Living things in nature are divided into two main categories based on the structure of their cells. The first is prokaryotes, which includes bacteria and archaea, and is characterized by simpler cells. The second is eukaryotes, which includes fungi, plants, and animals, in addition to protists.
Professor Esther Simpson from the Department of Biology at Dalhousie University explains that protists include all eukaryotic organisms that are not classified as animals, plants, or fungi. Simpson also mentions that there are models of multicellular protists found in brown algae and some species of red algae.
Most protists exist in the form of single cells or colonies divided into one or two cell types.
Protist cells
Protist cells, like other complex cells, have a nucleus that stores genetic material that enables them to carry out their vital functions. These cells are also equipped with organelles that play various vital roles. For example, some types of algae are known for their ability to perform photosynthesis thanks to the presence of plastids responsible for this process.
These plastids contain photosynthetic pigments and differ in the number of membranes surrounding them depending on the species, such as diatoms and dinoflagellates, which contribute to the formation of aquatic phytoplankton.
Furthermore, mitochondria are found in most protist cells and are responsible for generating the energy needed for the cell. However, there are exceptions in some protists that live in oxygen-deficient environments.
These protists use an organelle known as a hydrogenosome, which is a modified version of mitochondria that helps produce energy, as is the case in the parasite Trichomonas vaginalis, which causes trichomoniasis in humans.
Species in the kingdom Protista
The kingdom Protista consists of five main groups that include protozoa, which are microscopic organisms that live in water or soil. In addition, there are colloids that are living, gel-like forms that appear in moist places. As for golden algae, it is distinguished by its bright color and has an important biological and environmental role.
The group also includes dinoflagellates, which are known for their unique circular motion. Finally, Euglena algae can live in fresh water and are flexible in their feeding methods.
Nutrition of protists
Protozoa have different ways of obtaining food, and as Simpson notes, they may rely on photosynthesis or subsist anautonomously by consuming organic matter from external sources.
These organisms are divided into two main groups: macrophages, which use their bodies to surround and ingest food, and osmotrophs, which absorb nutrients directly from their surrounding environment.
Simpson elaborates on his explanation, explaining that a few photosynthetic organisms exhibit phagocytic behaviours, and this description applies specifically to most algal dinoglaids, which have their own plastids, but also happily feed on other organisms, which gives them a mixotrophic quality that indicates the diversity and multiplicity of their diets.
