Some Characteristics of the protist realm Are the microscopic size of the organisms that compose it and its asexual and sexual reproduction.
The protist kingdom is a diverse group of eukaryotic organisms. These are unicellular, some are colonial or multicellular. They do not have specialized tissue organization. Simple cellular organization distinguishes protists from other Eukaryotes .
The cell body of protists contains a nucleus that is well defined and organelles with membranes. Some have flagella or cilia for locomotion. Reproduction in protists is both asexual and sexual. They live in any environment with water.
Protist organisms were considered the first eukaryotic forms of life, predecessors of plants, animals and fungi. Eukaryotes are organisms whose cells have organelles with Membranes , Which is opposed to prokaryotes, simple nucleus-lacking cells. All prokaryotes are found in the Monera kingdom .
Scientists occasionally call the protist realm"the multifunctional realm"because it is made up of organisms that really do not belong to any other. Some time ago the unicellular amoebas and algae were classified in the same way in a simple taxonomic classification; The protist realm.
However, the emergence of better genetic information has led to a clearer understanding of the evolutionary relationships between different types of protist groups and systematic classification has become obsolete. The understanding of protists and their history continues to be a subject of scientific discovery and discussion.
Protist Kingdom Highlights
1- Protists are eukaryotic organisms
A eukaryote is an organism with a complex cell in which the genetic material is organized inside a nuclear membrane or nucleus.
Eukaryotes comprise animals, plants and fungi, which are mostly multicellular, as well as several groups that are collectively classified as protists (which are usually unicellular).
In contrast, prokaryotes are organisms such as bacteria lacking nucleus and other complex cellular structures. Eukaryotes share a common origin, and are commonly treated formally as a superreinus. Eukaryotes have more in common with Prokaryotes archean Than with prokaryotic bacteria.
Asexual and sexual reproduction
Most protists reproduce through asexual mechanisms according to Simpson. This may include binary fusion where a parental cell divides into two identical cells or multiple fusion where the parental cell increases to multiple identical cells.
However, Simpson added that most protists also have some kind of sexual cycle, however, this is only well documented in some groups.
3 - Eukaryotic cells
Like all eukaryotic cells, protists have a characteristic central compartment called the nucleus that houses their genetic material. They also have a specialized cellular machinery called organelles that perform functions defined within the cell.
Photosynthetic protists, like various types of algae, contain plastids. These organelles serve as the site where the photosynthesis (The process of absorbing sunlight to produce nutrients in the form of carbohydrates).
The plastids of some protists are similar to those of plants. According to Simpson, other protists have plastids that differ in color, repertoire of photosynthetic pigments and in the number of membranes enclosed by the organelle.
4- Diverse nutrition
Protists get nutrition in a number of ways. According to Simpson, protists can be photosynthetic or Heterotrophs (Organisms that seek sources of food of external origin in organic form).
In contrast, heterotrophic protists have two categories: phagotrophs and osmotrophs. Phagotrophs use their cell body to surround and chew their food, often other cells while the osmotrophs absorb nutrients from the environment. According to some scientists some photosynthetic forms are also phagotrophic.
5- Aquatic or wet habitat
Protists live mostly in water or wet land. They can also be found on land where water exists or can even be found in humans.
6- Cellular respiration
Cellular respiration occurs primarily through the aerobic process, but some protists living in animal digestive tracts function strictly under the anaerobic process.
This type of breathing differs from the daily ventilation of humans or animals. This breath is a chemical process in which energy is released from food substances, such as glucose or sugars.
Aerobic respiration needs oxygen to function. Most of the chemical reactions involved in the process occur in narrow objects within the cytoplasm, called mitochondria.
7- Locomotion varied
While some protists are not mobile, others exhibit locomotion through different methods. Some protists have flagella or cilia. These organelles are protuberances formed through specialized clusters of microtubules that move protists through the moist environment.
Other protists move through temporary extensions of their cytoplasm known as pseudopodia. These extensions also allow protists to capture other organisms from which they feed.
Types of protists
Some protists have the ability to make their own food while others rely on other organisms to eat. For this reason, protists are commonly grouped into"animal type protists","plant type protists"and"fungi type protists".
Protists of the animal type
Prototistas heterótrofos consume other organisms to obtain their energy. These protists are called protozoans meaning"the first animal." Protists eat through a process called"phagocytosis."
Under this process they surround their food with their cell membranes and trap it inside a vacuole. The Amoebae Y Paramecia Are both heterotrophic protists, as well as Plasmodium , The protist parasite that causes malaria.
Protists of the Plantae type
The protists Autotrophs Are like plants that use photosynthesis to make their own food. These protists are algae that include red, brown, and green algae, as well as Diatom , Dinoflagellata Y Eugenia . Some algae have complex life cycles.
Protists of the fungi type
These protists are usually a bright yellow or orange color. They do not obtain energy heretrofically or autotrophically, but nevertheless, as well as the fungi, these absorb nutrients from their surroundings.
These protists live in decomposed wood where they form multinucleated masses of cytoplasm that can be moved using pseudopods. These types of protists ingest bacteria and other organisms using phagocytosis.
Classification: from protozoan to protist
The classification in the history of the protists traces our understanding of these various organisms.
Often complex, the long history of protist classification was introduced into two terms, still used today, within the scientific lexicon: protozoan and protist. However, the meaning of these two terms has developed over time.
The observable living world was some time ago divided between plants and animals. But the discovery of several microscopic organisms (including those we know as protists and bacteria) brought with them the need to understand what they were and where they fit taxonomically.
The first instinct of scientists relates these organisms to plants and animals by their morphological characteristics. The term protozoan meaning"first animal"was introduced by the naturalist Georg A. Goldfuss in 1920, according to an article published by the International Journal of Microbiology.
This term was used to describe a collection of organisms including corals. In 1845, the protozoan was established as a phylum of the Animal Kingdom by the German scientist Carl Theodor von Seibold.
This phylum included certain cilia and amoebas which were described by von Seibold as simple cell animals.
In 1860, the protozoan concept was further refined and then raised to the level of a taxonomic realm by paleontologist Richard Owen. The members of this kingdom Protozoa , According to Owen's vision, had characteristics common to plants and animals.
However, behind each of these classifications implied that protozoa were rudimentary versions of plants and animals, and that there was no scientific evidence of the evolutionary relationships between these organisms (International Microbiology, 1999).
In the present day,"protozoa"is a term of convenience used in reference to a phylum of protists and not to a taxonomic group.
The protist term meaning"first of all or primordial"was introduced in 1866 by the German scientist Ernst Haeckel . He suggested the protist group as a third taxonomic kingdom, in addition to the kingdom of plants and animal. This would group all the primitive forms of organisms, including bacteria.
References
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- Barnes, Richard Stephen Kent (2001). The Invertebrates: A Synthesis . Wiley-Blackwell. P. 41.
- The Flagellates. Unity, diversity and evolution . Ed.: Barry S. C. Leadbeater and J. C. Green Taylor and Francis, London 2000, p. 3.
- O'Malley, M.A.; Simpson, A.G. B.; Roger, A.J. (2012). "The other eukaryotes in light of evolutionary protistology". Biology & Philosophy . 28 (2): 299-330.
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