Every living entity is made up of cells. Cells are the basic building blocks of all living organisms in terms of structural, functional, and biological units. The number of cells, however, varies with respect to different organisms and can be classified into two types -
Cells function differently in unicellular and multicellular organisms. Unicellular organisms accumulate all the cellular activities within a single cell. Examples of unicellular organisms include bacteria, protists, yeast, and so on. Multicellular organisms carry out specific cell activities through a well-defined group of cells.
The arrangement of cells is much simpler in unicellular organisms, whereas multicellular organisms found it complex to arrange cells. The differences are classified based on several parameters -
|Parameters||Unicellular Organisms||Multicellular Organisms|
|Definition||It’s a cellular organism with internal units all accumulated into a single cell||It’s a cellular organism with internal units all taken up by groups of cells assigned to different specialized functions|
|Complexity||Simple cell body Organization||Complex cell body Organization|
|Function||A single cell performs all necessary life processes||Groups of cells are divided into their functionalities and groups of cells take up different life processes|
|Shape||Irregular formation in structure||Structure is well defined|
|Size||Comparatively smaller than multicellular organisms i.e., they are microscopic||Comparatively larger than unicellular organisms i.e., they are macroscopic|
|Cellular structure||Both Prokaryotes and Eukaryotes||Only in the form of Eukaryotes.|
|Nature||These organisms are heterotrophs in nature||These organisms can be both heterotrophs and autotrophs in nature|
|Lifespan||These organisms have comparatively shorter life spans||These organisms have comparatively longer life spans|
|Evolution||These organisms are the oldest forms of life dating back to over 4 million years ago||These organisms are comparatively newer and more complex forms of life derived from prokaryotes|
|Differentiation||There is no differentiation in the cell as there are only single cells performing all units||The cell differentiation exists as there are groups of cells that perform different functional units|
|Functional segment||All the functional units are divided under an organelle level||All the functional units are divided at cellular, tissue, organs level|
|Reproduction||The dominant form of reproduction is asexual, although there are some unicellular organisms that take part in sexual reproduction||The multicellular organisms reproduce sexually as well as asexually|
|Reproduction process||The process of reproduction can be either by budding and by binary fission||The process of reproduction is occurred by gamete fusion|
|Efficiency||The efficiency of the functional units is low||The efficiency of the functional units is high|
|Regeneration||These organisms are capable of regenerating at a greater rate in comparison to the multicellular organisms||These organisms regenerate much slower or have a lower rate of regeneration in comparison to the unicellular organisms|
|Consequences||If the cell is injured, the whole organism dies||If a cell is injured, the organism does not die as it is being supported and replaced by various other cell groups|
|Examples||Amoeba, Paramecium, Plasmodium, Yeast, Algae, Euglena Fungi, Protozoans||Vertebrates, Invertebrates, gymnosperms, angiosperms, plants|
When discussing the cellular structures of organisms, one should take into account that not all cellular structures are similar, as they have their own classifications based on their physical, functional, and biological units. In cellular organisms, the type classification can be made with accordance to the difference in the above-mentioned parameters, they are called as follows,
Prokaryotic cells lack a well-defined nucleus and membrane-bound cell organelles. These are the primitive or early forms of cellular organisms. Examples of prokaryotes are bacteria, blue-green algae, nostoc, mycoplasma, salmonella, etc. Among prokaryotes, bacteria are the most common and they multiply very fast as part of their reproduction. They are single-celled organisms with a very low lifespan.
Eukaryotic cells are cells with an organized nucleus that is enveloped by membrane-bound organelles. They are more evolved than their predecessor cells. Some eukaryotic cells found in nature are fungi, plants, animals, protists. The genetic material of eukaryotic cells is organized in the form of chromosomes. They form organisms by grouping various different cells for different functional units to sustain life. Due to the nature of grouping, it is possible for the organism to evolve into more complex species.