Difference Between Monera and Protista

Main Difference – Monera vs Protista

Monera and Protista are two kingdoms which are found in the classification of organisms on earth. Monera consists of cyanobacteria, archaebacteria and eubacteria whereas Protista consists of protozoans, algae and molds. Some of the organisms in Monera and Protista are heterotrophs whereas some of them are autotrophs. The main difference between Monera and Protista is that unicellular prokaryotes are classified into kingdom Monera whereas unicellular and multicellular eukaryotes, which are not either fungi, plants or animals, are classified into kingdom Protista.

This article explores,

1. What is Monera
– Characteristics, Classification, Organisms
2. What is Protista
– Characteristics, Classification, Organisms
3. What is the difference between Monera and Protista

What is Monera

Monera is the kingdom which contains the least organized unicellular prokaryotic microorganisms on earth. Microorganisms in kingdom Monera play a vital role in nitrogen and carbon cycles. They are metabolically diverse, using a variety of substrates as their energy and carbon sources. Asexual reproduction is identified in monerans, occurring by binary fission, budding and fragmentation. Since monerans are prokaryot, they do not have membrane-bound organelles like the nucleus. Horizontal gene transfer is also found in monerans. Archaebacteria, cyanobacteria and eubacteria are the three domains of kingdom Monera.

Archebacteria

Archebacteria are considered to be evolved just after the first life on earth. Hence, they are called ancient bacteria. Archaebacteria usually live in extreme environments like hot springs, salt lakes, oceans, marshlands and soils. They were also found in human skin, oral cavity and colon as well. Three types of archaebacteria are found: methanogens, halophiles and thermophiles. Methanogens live in oxygen-free environments whereas halophiles live in water with high salt concentrations. Thermophiles live in hot environments.

Eubacteria

Eubacteria are found in almost all habitats like soil, water and in and on large organisms. Some eubacteria generate parasitic and pathogenic effects on their hosts. The cell wall of eubacteria is made up of peptidoglycans and murins. Two types of eubacteria are found: gram positive and gram negative bacteria.

Cyanobacteria

Cyanobacteria are the only photosynthesizing prokaryotes. Photosynthesis occurs in the folds of the outer membranes of cyanobacteria. Cyanobacteria were responsible for the conversion of the reducing atmosphere of early earth into the oxidizing atmosphere. They are found in each and every aquatic habitat from fresh water to ocean. Cyanobacteria is shown in figure 1.

Figure 1: Cyanobacteria

What is Protista

Protista is the kingdom which contains the second least organized organisms on earth. Protists are eukaryotes, which can be either unicellular or multicellular organism. But, they are neither fungi, plants nor animals. Since protists are eukaryotes, they contain membrane-bound organelles as well as the nucleus. Metabolism of protists depends on the type of organism. Some are autotrophs like algae whereas the others are heterotrophs like euglena and amoeba. Protists can also be parasites. Protists exhibit sexual reproduction by producing gametes and asexual reproduction by binary fission. Algae, protozoans and molds are the two domains of protists.

Algae are plant-like, mostly unicellular organisms. They are autotrophs, containing plastids called chloroplasts. A single cell consists of a large single chloroplast. Three types of algae are found: green algae, red algae and brown algae. Protozoans are the animal-like unicellular microorganisms. They are heterotrophs, engulfing food particles by phagocytosis and digesting them in order to obtain nutrients. Protozoans are capable of moving by the motion of their flagella. Flagellata, Ciliophora, Amoebozoa and Sporozoa are the four types of protozoans. Molds are fungus-like, multicellular eukaryotes. Slime molds and water molds are the two types of molds. Elglena, a protozoan is shown in figure 2.

Figure 2: Euglena

Prokaryotes/Eukaryotes

Monera: Monera are prokaryotes.

Protista: Protista are eukaryotes.

Oragnization

Monera: Monera are less complex microorganisms.

Protista: Protista are complex organisms compared to monerans.

Unicellular/Multicellular

Monera: Monera consist of unicellular microorganisms.

Protista: Protista consist of both unicellular and multicellular organisms.

Size

Monera: Monera contains small microorganisms.

Protista: Organisms in Protista are larger than monerans.

Nucleus

Monera: Monera does not consist of a well-defined nucleus in their cells.

Protista: Protista consist of a well-defined nucleus.

Membrane-bound Organelles

Monera: Monera does not consist of membrane-bound organelles.

Protista: Protista consists of membrane-bound organelles like Golgi apparatus, ER and plastids.

Cilia, Flagella and Psedopodia

Monera: Most monerans do not contain either cilia, flagella or pseudopodia.

Protista: Protista usually contain cilia, flagella and pseudopodia.

Habitat

Monera: Monera are found in almost all the habitats on earth.

Protista: Protista are mainly found in aquatic habitats.

Reproduction

Monera: Monera exhibit asexual reproduction.

Protista: Protista exhibit both sexual and asexual reproduction.

Types

Monera: Archaebacteria, cyanobacteria and eubacteria belong to the kingdom Monera.

Protista: Algae, protozoans and molds belong to the kingdom Protista.

Examples

Monera: Halobacterium, Lokiarchaeum, Thermoproteus, Mycobacteria, Bacillus, Sporohalobacter, Clostridium are the examples of monerans.

Protista: Green algae, red algae, amoeba, euglena, slime molds and water molds are the examples of protists.

Conclusion

Monera and Protista contain the two least organized organisms on earth. Monera consists of unicellular prokaryotes. Protista consist of both unicellular and multicellular eukaryotes. Archaebacteria, cyanobacteria and eubacteria are the three types of monerans. Protozoans, algae and molds are the three types of protists. Monera are found in almost all the habitats on earth. In contrast, protists are mainly found in aquatic habitats. Monera do not have membrane-bound organelles like nucleus, Golgi and ER. But, protists consist of a well-defined nucleus. However, the main difference between Monera and Protista is their organizations of cells in each kingdom.

Reference:
1. Esko, Jeffrey D. “Eubacteria and Archaea.” Essentials of Glycobiology. 2nd edition. U.S. National Library of Medicine, 01 Jan. 1970. Web. 18 Apr. 2017.
2. “Protist Classification and the Kingdoms of Organisms – Journals – NCBI.” National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 18 Apr. 2017.

Image Courtesy:
1. “Tolypothrix (Cyanobacteria)” By Matthewjparker – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “euglena” by schmidty4112 (CC BY 2.0) via Flickr