The number of cells present in the body and their cellular functions make the organisms specialized from others. Based on the cell number of the body, the organisms have been divided in to two types unicellular and multicellular organisms. the major difference between unicellular and multicellular organisms has been given bellow
Unicellular vs Multicellular organisms
1. Unicellular organism.
Body:- Body is made up of single cell and contains every organelle in its cytoplasm.
Cell division: For cell division the energy from its cellular organelles and uses low level of energy consumption.
Metabolism: In single cell organisms every process carried out in cytoplasm. A single cell carries out all the metabolic processes of organism.
Cellular exposure: The cell body is exposed to the environment on all sides and this feature provide the benefit to uptake the nutrients and protection from surrounding area.
Size: A unicellular organism cannot attain a large size of its body because of the limit imposed by surface area to volume ratio
Life span: This organisms show very short lifespan due to high metabolic rate and reproduction.
Power of division: Power of division is not lost because one cell replicates to two duplicate cells
Regeneration: The concept of regeneration in unicellular organisms makes no sense because in these organisms one cell dies, the whole organism is gone.
Partition of role: In unicellular organisms there is no cellular compartments and different types of cells to share the developmental and metabolic roles. The cell has the same role for itself and the organism
Death: Death rate is very high compared to multicellular organisms because in unicellular organism a simple cellular injury can cause total organism death.
2. Multicellular organisms
Body: body is made up of various types of cells which are responsible for specific function.
Cell division: Division of labour can be at cellular, tissue, organ and organ system level. It gives high degree of operational efficiency.
Partition of role: Different cells are specialized to perform different functions like reproduction, mobility or locomotion, respiration, digestion, sensing and consumption of nutrients etc.
Cellular exposure: Only outer cells are specialized to face the environment and provide the protection for total body. Inner cells are responsible for other cellular functions.
Death: Injury or death of some cells does not affect the organisms because the damaged cells can be replaced by new cells.
Size: A multicellular organisms can show changes in body size by increasing the number of small cells.
Life span: Lifespan is long in this organism because sharing of cellular processes for specialized cells.
Power of division: Certain specialized cells lose power of division because some cells only have the feature for reproduction.
Regeneration: The capacity of regeneration decreases with increasing specialization.
Dual role of cell: Every cell in the organism perform the dual role. One for themselves and other for the whole organism. This feature also shows the major difference between unicellular and multicellular organisms.