Development
From a biological perspective, development can be defined as a process through which a living organism changes from a simple life to more complicated life forms. This involves transformation from a single cell to a more complex multicellular organism. Through the process of development, an organism is able to grow, develop different body structures such as limbs. In addition, they are also able to develop different body processes such as respiration and reproduction amongst many others. Some biologists also describe the development as a gradual change in the size, shape and roles of an organism during its life. During such changes, its genetic makings, referred to as genotypes, are transformed into more developed systems, called phenotype. According to different philosophical views, development takes place in virtually all things, in both physical and biological beings. This viewpoint can be traced back during the earliest philosophical days. Although most detailed aspects of development still remains anonymous, some of the major features have become clear to scientists. Biological anatomy and physiological concepts has been used to explain the process of development.
Modern biological science on development looks into the influence of cell evolution, differentiation and morphogenesis. Moreover, morphogenesis is a term used to describe a process that results into the growth of tissues, organs and anatomy. In addition, it also used to refer to the process of regeneration and aging. Cell differentiation is the creation of various kinds of cells from a single cell, also known as the zygote or the spore. The creation of different cell types like sperm cells, nerve cells and epithelial cells among others arises from several intermediary or less differentiated cells. A cell develops into a certain cell type by preserving some specific configuration of gene expression. This is based on controlling genes such as genes for transcription factors and signaling proteins. These genes can be involved in self-propagating circuits found in the gene regulatory system. The circuits are understood to be comprised of several cells that interconnect with each other. Outside indicators can alter the expressions of genes by stimulating a receptor, which activates a motioning cascade affecting the transcription factor. For instance, the extraction of the development factors from myoblasts makes them stop separating and rather differentiate into muscle cells.
In all living organisms, development process takes place in different stages. The first stage, which involves the formation of germ layers, is called gastrulation. Differentiation as well as growth of the various body organs and systems the takes place. These stages are classified into phases of embryogenesis and organogenesis. The former includes the periods of cleavage and gastrulation while the latter is a period of the creation of the organs and different organ systems. Cleavage is simply the early period during which the division of the fertilized eggs takes place while gastrulation is the process of formation of a double-layered cup of cells. The inner layer and the outer layer of cells are known as ectoderm and endoderm respectively. Another third layer that develops in between the two layers is called mesoderm. It differentiates into muscles, blood and blood vessels, the heart, reproductive organs, the spleen and the kidney. Finally, the endoderm segregates into cells that coat the digestive tract, respiratory systems, the liver, gallbladder and the pancreas. Therefore, development simply involves the process of differentiation of cells into more complex structures.
