UNICELLULAR AND MULTICELLULAR ORGANISMS

Every living particle is composed of cells. In terms of functional, biological and structural terms, the cells are said to be the fundamental building units of all living organisms. The quantity in which these cells are present differs with different organisms and is distinguished into unicellular and multicellular organisms. In unicellular and multicellular organisms the functioning of cells varies to different levels. In context with the unicellular creatures, the entire functioning is done by only one cell, which modifies and adapts to complete tasks, whereas a multicellular organism possesses many cells that are specialized to perform various functions that help the organisms thrive in all situations.

A BRIEF ABOUT UNICELLULAR AND MULTICELLULAR ENTITIES

Unicellular organisms consist of, for example, yeasts, bacteria, protists etc. For instance, a paramecium is referred to as a unicellular organism that has a slipper shape that is present in pond water. The paramecium ingests the food in the water and it gets stored and ingested into organelles called food vacuoles. The normal and efficient functioning of the cell is kept up by the supply of nutrients from the food moving through the cytoplasm to the organelles present around it. 

Multicellular organisms are made up of more than one number of cells. These cells modify, adapt and specialize as per the type of function they have to perform. The cells in the human body like nerve cells, muscle cells, skin cells, blood cells and other varieties of cells differentiate early in the developmental process to perform a variety of functions. The structure of the cell is dependent on the type of function it has to perform. For instance, the nerve cells have appendage-like structures known as dendrites plus axons that are responsible for creating connections with nerve cells to do actions like muscle contraction, send signals to target organs, or receive a sensory stimulus.  Outer skin cells form flattened stacks that protect the body from the environment. Whereas the structure of a muscle cell is slender and thin that are collectively present to perform muscle contraction. 

In cellular organisms, the classification can be done based on the distinguishing features of the above-mentioned characteristics; they are known as follows, Prokaryotes and Eukaryotes.

HOW DO WE DISTINGUISH BETWEEN UNICELLULAR AND MULTICELLULAR ORGANISMS?

The differences can be drawn between the two types of organisms in light of several parameters described as follows.

BASED ON – THE COMPLEXITY OF BODY ORGANISATION

The multicellular organisms have a comparatively complex type of body organisation whereas unicellular organisms have relatively simpler body cell organisation.

BASED ON – SIZE AND SHAPE

Unicellular organisms have an irregular boundary or form. In terms of size, they are microscopic i.e. smaller than their other counterparts. The multicellular organisms have a well-defined structure and are comparatively large in size or macroscopic.

BASED ON – THE PRESENCE OR ABSENCE OF DIFFERENTIATION/ MATURATION

The single cell in the unicellular organisms doesn’t undergo any maturation or differentiation; rather it is the single cell that has to perform the entire functions required for the normal lifespan of the organism.

There is a process of differentiation in the eukaryotic cell as the different cells are ought to perform different parameters of functions. 

BASED ON – THE TYPE OF REPRODUCTION AND WAYS

The dominant way of reproduction in unicellular organisms is generally asexual. But some forms of one-celled creatures also show sexual reproduction. 

The asexual ways to reproduce can be through binary fission, fragmentation or budding.

On the other hand, multicellular organisms reproduce both via asexual and sexual types of reproduction.

To achieve sexual reproduction, the fusion of gametes is crucial. After the male gamete fuses with the female gamete, fertilisation takes place. 

BASED ON – THE LEVEL OF FUNCTIONING 

Usually, the unicellular organisms have their division of functional units at the organelle level. The multicellular organisms have their functional unit classified at three levels namely the cellular level, the tissue level and the organ level.

BASED ON – THE RATE OF EFFICIENCY 

The one-celled creatures are relatively less efficient owing to having only one cell to perform various functions at different parameters. Simply, the functional units in them are less efficient.

In multicellular organisms, they have various cells differentiated to take up numerous functions at various parameters, hence more efficiency of the functional units is relatively possible, unlike its other counterpart.

CONCLUSION 

When we look around our surroundings we observe a variety of organisms. Not only us, even on the surface of the skin or inside your digestive or organ tract, but a huge number of different microorganisms also reside there. This is how we are home to approximately 100 trillion bacterial cells and structures. We can infer that our body is acting as an ecosystem. 

The surroundings and nature consist of both unicellular and multicellular organisms. 

All the cellular structures can be categorised further into two broad segments namely, eukaryotes and prokaryotes. Unicellular organisms have only a single cell composition. Multicellular organisms are made up of more than one number of cells.