The great diversity of living beings that have inhabited the planet since time immemorial is enormous. There are larger or smaller organisms, with some habits or others, some more primitive, others more evolved … Of all these living beings we can make two large groups into which to classify them: unicellular and multicellular living beings.
In Green Ecologist we are going to clarify these concepts, so if you want to know more, do not miss this article in which we tell you what are unicellular and multicellular organisms, with examples and their differences, through a comparative table of differences between unicellular and multicellular organisms.
The living things or unicellular organisms, as their own name makes us think, are those that are formed solely by single cell in which all the vital functions necessary for life are produced. For this reason, they are mostly microscopic organisms, but there are some unicellular living beings that can reach large sizes of up to 20 centimeters, such as xenophiophores, a type of foraminifera, commonly called "living sand", of marine life mainly with a shell formed by one or more chambers.
Most single-celled beings are prokaryotic cellsIn other words, cells that do not have a nucleus, their genetic material is not enveloped and "enclosed" by a membrane, but rather it is dispersed throughout the cytoplasm, like bacteria. However, there are other unicellular organisms, such as protozoa, that do have a nucleus. These types of cells are called eukaryotic cells, which have a more complex structural organization and reach larger sizes than prokaryotic cells. Here you can learn more about eukaryotic and prokaryotic cells.
Unicellular living beings can reproduce both sexually (through conjugation) and asexually depending on the organism to which we refer. There are several strategies for asexual reproduction, as they are:
These beings are considered the most primitive beings, since its system is simpler than that of multicellular beings, which we will comment on later. In addition, currently contrary to what they may seem, they represent the most living things that inhabit our planet and live in very remote places where other forms of life cannot develop.
Single-celled organisms have representatives of some kingdoms of living things as they are:
Some more concrete examples of single-celled organisms, within the great variety, are:
You may be interested in these other articles on Bacteria, good allies of ecology and Types of bacteria. In addition, we recommend you watch this video about protists, to learn more about these single-celled organisms.
The multicellular living beings, as its name indicates and in contrast to unicellular living beings, are those that are made up of two or more eukaryotic cells. Therefore, they present a greater complexity than unicellular organisms in terms of the functions they perform.
These multicellular organisms arose from a primitive single-celled organism. Although the process by which this leap to multicellularity occurred is one of the great unknowns and there are several hypotheses in this regard, the truth is that it is known that it occurred 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, such as the zygote, which is the cell resulting from the union of male and female sex gametes in fertilization. This cell divides and multiplies giving rise to a multicellular organism whose cells will undergo differentiation processes and will work independently and together, forming tissues, organs and systems that will make up the individual's body. In some simpler groups of species, such as sponges, true tissues do not form and their cells function more independently.
Cells of multicellular organisms reproduce asexually Through two processes: mitosis, daughter cells identical to the mother cell and with the same number of chromosomes originate; and meiosis, typical of 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 a great diversity of multicellular organisms, although we must remember that unicellular living beings widely exceed this multicellular diversity. Even so, if we want to put some examples of multicellular living things we find a wide range that ranges from fungi to animals and plants:
After knowing what they are and several examples of unicellular and multicellular organisms, we will discuss in a little more detail how they differ. These are the main differences between unicellular and multicellular organisms:
Here below you can see the comparative table of differences between unicellular and multicellular organisms.
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