Differentiation

Differentiation is the process of an unspecialised cell becoming a specialised cell.

Differentiation is the process of an unspecialised cell turning into a specialised cell. In this example, an unspecialised plant cell differentiates into a root hair cell (which is a type of specialised cell).

As a cell differentiates, it gains new sub-cellular structures that allow it to carry out its function as a specialised cell.

For example, as an unspecialised plant cell differentiates into a root hair cell, it greatly increases its number of mitochondria. The large number of mitochondria enable the root hair cell to release large amounts of energy (through respiration) for actively transporting mineral ions into the root (which is part of the root hair cell's function).

Differentiation is crucial to the development of multicellular organisms

As we have seen, multicellular organisms such as plants and animals usually contain many different types of specialised cell.

The cell types found in a plant include xylem cells, phloem cells and root hair cells.

A plant contains many kinds of specialised cells, including xylem cells, phloem cells and root hair cells.

The cell types found in an animal include nerve cells, muscle cells and egg or sperm cells.

However, when a new plant or animal is created through sexual reproduction, the new individual starts out as a single, unspecialised cell, called a zygote.

A zygote is formed when an egg cell and a sperm cell fuse during sexual reproduction. A zygote is an unspecialised cell.

How does a zygote develop into a multicellular organism such as a plant or animal?

How does a zygote, which is a single, unspecialised cell, develop into a multicellular organism containing many different cell types?

Clearly, the number of cells needs to increase. This is achieved through cell division, in which one cell divides to form two. First the zygote divides to form two cells. Then each of those cells divides, giving a total of four cells, and so on. Through many rounds of cell division, the organism eventually reaches the number of cells needed to be fully developed.

Cell division allows a zygote to develop into a multicellular organism.

However, cell division alone is not enough to get from a zygote to a mature multicellular organism. The zygote was an unspecialised cell. If all that had happened was cell division, then we would just have a big pile of unspecialised cells, not a complex multicellular organism with many different cell types.

Therefore, differentiation is crucial to the development of multicellular organisms. During the process of developing from a zygote to a mature organism, unspecialised cells in different parts of the organism differentiate to form different types of specialised cells. This allows the organism to develop all of its different tissues and organs.

Both cell division and differentiation are crucial to the process of a zygote developing into a multicellular organism. Cell division increases the number of cells. Differentiation is the process by which unspecialised cells become specialised.

In plants, some specialised cells can change cell type

Some types of specialised plant cells can change cell type after they have differentiated.

For example, if xylem and phloem cells are damaged, other specialised cells in the same part of the plant can transform into xylem and phloem cells in order to repair the damage.

(This process of changing from one type of specialised cell to another is not differentiation, because differentiation is when an unspecialised cell becomes a specialised cell).

As far as we know, animal cells do not do this. Once an animal cell has differentiated into a specialised cell, it stays as that type of specialised cell until it dies.

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