Unicellular and multicellular organisms: examples and differences

The living beings or unicellular organismsas their own name makes us think, they are those that are formed only by A single cell in which all the vital functions necessary for life occur. For this reason, they are mostly microscopic organismsbut there are some unicellular living beings that can reach large sizes of up to 20 centimeters, such as xenophioforos, a type of foraminifera, commonly called “living sand”, marine life mainly with a shell formed by one or several cameras.

Most unicellular beings are prokaryotic cellsthat is, cells that have no core, their genetic material is not wrapped and “locked” by a membrane, but is scattered by the cytoplasm, such as bacteria. However, there are other unicellular organisms, such as protozoa, which do have a core. This type of cells are called eukaryotic cellswhich have a more complex structural organization and reach longer sizes than prokaryotic cells. Here you can learn more about eukaryotic and prokaryotic cells.

Unicellular living beings can be reproduced both sexual (through conjugation) and asexually depending on the organism to which we refer. There are several strategies of asexual reproductionsuch as:

• Binary bipartition or fission. The nucleus and cytoplasm of the cell is divided by giving rise to two identical daughter cells.
• Gemation in yeasts. The nucleus is divided and separated from the stem cell with a portion of the cytoplasm generated by the daughter cell.
• The sporulation. The nucleus is divided several times and each of them will generate a spore that will be released when the stem cell membrane will be broken.

These beings are considered The most primitive beingsbecause its system is simpler than that of multicellular beings, which we will discuss later. In addition, contrary to what they may seem, they represent the majority of living beings that inhabit our planet and live in very remote places where other life forms cannot be developed.

Unicellular organizations have representatives of some Kingdoms of living beings as they are:

• The Monera Kingdom, formed by unicellular bacteria.
• Some organisms of the Protist kingdom.
• The yeasts of the Fungi Kingdom.

Some most concrete examples of unicellular organismswithin the great existing variety, are:

• Yeasts like Saccharomyces Cerevisaethe yeast used in beer.
• Escherichia colibacteria.
• Toxoplasma gondiiProtozoo responsible for toxoplasmosis.
• Tripanosoma Cruzi, Protozoo causing Chagas disease.
• Trichomonas vaginalis.
• Candida Albicansfungus responsible for candidiasis.
• Mycobacterium tuberulosis, bacteria responsible for tuberculosis.
• Neisseria gonorreaebacteria that cause gonorrhea.
• Pneumoniae mycoplasmabacteria responsible for pneumonia.
• Clostridium botulinumbacteria that causes botulism.
• Pneumococci (bacteria).
• Staphylococci (bacteria).
• Dinoflagelladas (Protist).
• Some unicellular algae such as diatoms.
• Paramecios (Protist).

You may be interested in this other article on types of bacteria. In addition, we recommend watching this video about the protists, so you can learn more about these unicellular organisms.

https://www.youtube.com/watch?v=5YFRVB86m4

The Pluricellular living beingsas the name implies and as opposed to unicellular living beings, they are those that are formed by two or more eukaryotic cells. They present, therefore, a greater complexity than the unicellular organisms in terms of the functions they develop.

These multicellular organisms emerged from a primitive unicellular organism. Although the process by this leap to multicellularity is one of the great unknowns and there are several hypotheses in this regard, the truth is that it is known that it happened several times simultaneously in different evolutionary groups of various organisms, such as animals, land plants, algae and fungi.

In itself, all current multicellular organisms come from a single cell, that is, they begin their life being unicellular as, for example, the zygote that is the cell resulting from the union of male and female sexual gametes in fertilization. This cell is divided and multiplied giving rise to a multicellular organism whose cells will suffer differentiation processes and will work in a non -independent and joint way forming tissues, organs and systems that will compose the body of the individual. In some groups of simpler species, such as sponges, true tissues are formed and their cells work with greater independence.

The cells of multicellular organisms reproduce asexually Through two processes: mythosis, daughter cells identical to the stem cell and with the same number of chromosomes are originated; and the meiosis, typical of the reproductive cells whose purpose is to originate the gametes, the sex cells, with half of the genetic endowment. The reproduction of multicellular organisms is also very varied and can be sexual reproduction or asexual reproduction.

There is one Great diversity of multicellular organismsAlthough we must remember that unicellular living beings widely exceed this multicellular diversity. Even so, if we want to put some Examples of multicellular living beings We find a wide range that covers from fungi to animals and plants:

• All The animals vertebrates, which belong to the animal kingdom, such as mammals, birds, reptiles, amphibians, fish, and all invertebrate organisms, such as sponges, anélidos, arthropods, etc.
• Within plants and algae We can find green algae, red algae, brown algae and all the variety of land plants, such as mosses, liver plants, angiosperms or gymnosperms, among many other groups.
• All Fungiexcept unicellular yeasts.

After knowing what they are and several examples of unicellular and multicellular organisms, we go on to comment with a little more detail how they differ. These are the main differences between unicellular and multicellular organisms:

• The main difference, as we have already mentioned from the beginning, is the amount of cells that these living beings have. The unicellular have only one and the multicellular have more.
• Unicellular organisms can be part of the group of prokaryotes and eukaryotes, while multicellular organisms are only part of eukaryotic living beings.
• There is a difference in the size of the unicellular and multicellular organisms, being mostly the first of smaller than the latter.
• Unicellular living beings have more resistance to extreme environmental conditions than multicellular.
• Unicellular living beings do not make up complex structures, such as tissues, organs and systems, while multicellular do.

Down here you can see the Comparative table of differences between unicellular and multicellular organisms.

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