The viability and function of cells are indeed vital in keeping an organism, from unicellular bacteria to a multicellular organism, fully efficient.
Cells, due to its variations and complexity, allow men to reach milestones unimaginable before. Considering its minute nature, who would have thought that it is the source of major leaps performed by man? From simple tasks like cooking to complex ones like designing nuclear warheads and constructing skyscrapers, all these are made possible by this basic unit.
Since the height of Greek's search for knowledge, these complexities were tried to be explained. Astounding for them as it seems, mere observations led to unfolding little by little of what was really behind this.
The development of an animal from the fusion of two cells has always been a source of wonder. Socrates made first observations as he noted the development of a chick from an egg. For three weeks, he has been noting changes in morphology of the organism from being a yolk to a complete bird as it hatches.
Early scientists tried to explain this phenomenon as epigenesis. Epigenesis is the belief that the form of the embryo gradually develops from a formless egg. At present, it was found out that development of an embryo to a multicellular organism is brought about by series of cell divisions as directed by the organism's genome and different cytoplasmic environments of each differentiating cells.
In nearly all cases, multicellular organisms begin from a fertilized egg which would then divide mitotically to the different cells of the body. The study of this development has traditionally been tagged as embryology. However, growth of an organism does not stop until birth. Until death, cells are continually dividing and development continually occurs; skeleton is continually being formed, skin cells are continually being sloughed off, etc. Thus, the field is expanded to what is now known as developmental biology.
It is also important to note that the cells which differentiate are organized into intricate tissues and organs. They are not randomly placed. These are as dictated by the genetic information available to an organism. This differentiation of an organism to an ordered form is known as morphogenesis.
However, there are also cues by which cells are signaled to stop cell division. This is necessary when form has been achieved. If not, we would be considered malformed. For example, a cancer cell has lost its ability to terminate growth. Continuous division leads to tumors which is generally a malformation. Thus, there has to be a way by which morphogenesis is regulated. This is still made possible by the information contained in the DNA.
More so, outside factors should be considered when development is brought to light. Cues from the environment are also important consideration as this has grave effects on development of an organism. Environment, as a factor, plays a key role in contributing to how an organism develops and thus, brings about slight variations and individuality to organisms.
