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Difference Between Unicellular And Multicellular Organisms

Difference Between Unicellular And Multicellular Organisms

The difference between unicellular and multicellular organisms is majorly due to the difference in the composition, function, and arrangement of the cells. The unicellular organisms contain a single cell whereas the multicellular organisms contain multiple cells.

Unicellular organisms conciliate all the cellular activities by a single cell, while 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.

Difference Between Unicellular And Multicellular Organisms


Character Unicellular Organisms Multicellular Organisms
Cell A unicellular organism contains a single cell. A multicellular organism contains multiple cells.
Shape It is irregular in shape. The shape is well-defined.
Size It is small in size. It is comparatively large in size.
Nature Unicellular organisms are Microscopic. Multicellular organisms is Macroscopic.
Cell type It includes organisms having both prokaryotic and eukaryotic cell types. It includes organisms comprising only eukaryotic cell types.
Cell organization The cell organization is simple. The cell organization is complex.
Cell differentiation Generally absent, but unicellular yeasts may undergo differentiation Specialized cell differentiation occurs
Life span The life span is short. The life span is longer.
Evolution The oldest life forms evolved 3.8-4 billion years ago These evolved from the prokaryotes
Operational efficiency Operational efficiency is low. Operational efficiency is high.
Reproduction Reproduction occurs via budding and binary fission. Reproduction occurs via gamete fusion.
Regeneration ability Unicellular organisms show a greater tendency to regenerate. Multicellular organism shows low regeneration ability.
Examples Bacteria, Protozoans, Unicellular amoeba, etc. Humans, Animals, Plants, etc.

Both unicellular and multicellular organisms are the two major categories of the cell-type, depending on the numbers, shape, and size of cells.

  • Unicellular organisms have small size single-cell, whereas multicellular organisms contain large-sized multiple cells.
  • The arrangement of cells in the unicellular organisms is simple than the multicellular organisms.
  • Unicellular organisms are microscopic, they are only visible under the microscope, whereas multicellular organisms are macroscopic, thus, it can be detected with the naked eye.
  • Unicellular organisms consist of both prokaryotic (bacteria, archaea) and eukaryotic (Protozoa, unicellular algae, unicellular fungi,) cell type microorganisms.
  • The life span of unicellular organisms is short as compared to the multicellular organisms due to the high workload.
  • Unicellular organisms have low operational efficiency as compared to multicellular species.
  • Unicellular organisms generally do not go through any cell differentiation, except unicellular yeasts. While multicellular organisms go through categorized cell division to form differentiated cells, which can perform particular tasks.
  • The unicellular organisms are immortal, as they are capable of regeneration whereas multicellular organisms lose the regeneration ability for cell growth and differentiation of cells aging.

Unicellular Organisms

Unicellular organisms can be defined as the living-organisms, which consist of only a single cell. This single cell is capable to perform different life processes or cellular activities. It consists of prokaryotic organisms like bacteria and archaea, and eukaryotic organisms like protozoa, unicellular algae, and unicellular fungi.

Features of Unicellular Organisms

The main feature of a unicellular organism is that they are microscopic. It cannot be easily observed through the naked eye. Most of the organisms commonly reproduce via asexual methods like fragmentation, budding, and binary fission, whereas few of them can also reproduce sexually via conjugation. Due to single-cell composition, the arrangement of the cell is quite simple. These organisms can develop well in extreme heat, acidity, salinity, etc.

Multicellular Organisms

Multicellular organisms can be defined as living-organisms, which consist of multiple cells. With these distinct cell organelles it is capable to perform different life processes or separate cellular activities inside a body. It only consists of eukaryotic organisms like insects, animals, birds, humans, etc.

Features of Multicellular Organisms

The main feature of a multicellular organism is that these are macroscopic. It is easily noticeable through the open eye. Most of the organisms commonly reproduce via sexual methods (by the formation of zygote), whereas few members few of them can also reproduce asexual means like budding, spore formation, etc. Due to the multiple cell composition, the arrangement of cells is quite complex. The size of these organisms increases as the numbers of cells increases.

Similarities Between Unicellular And Multicellular Organisms

  • Both single and multi-celled organisms embrace a functional unit of life, known as “Cells”.
  • Both of them consist of plasma membrane and cytoplasm.
  • They carry similar features by containing DNA and ribosomes for the gene expression.
  • The process of cell division typically occurs commonly through mitosis or meiosis.
  • They need cellular energy to function.


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