Developmental Biology studies the initiation and construction of organisms rather than their maintenance.It is a science of becoming, a science of process.
Formation of orderly body from a single cell by passing through various stages is called Development.
That formation takes place according to the instructions which are encoded in genes and transmitted from parents.
Objectives of Development
Development accomplishes two major objectives.
First, it generates cellular diversity and order within the individual organism.
Secondly, it ensures continuity of life from one generation to the next.
Basic concepts in Developmental Biology
1- Differentiation
A single cell, the fertilized egg, gives rise to hundreds of different types of cell types- muscles cells, epidermal cells, neurons, lens cells, lymphocytes, blood cells, fat cells and so on.
The generation of this cellular diversity is called differentiation.How can this identical set of genetic instruction produce different types of cells?
2-Morphogenesis
The creation of ordered form is called morphogenesis, and it involves coordinating cell growth, cell migration and cell death.
It involves how can the cells are not randomly distributed but rather, they become organized into intricates tissues and organs. During development, cells divide, migrate and die . Tissues folds and separate. For example, our fingers are always at tips of our hands , never in the middle of arms.
3-Growth
The permanent increase in size of an organism is called growth.If each in our face were to undergo just one more cell division, we would be considered horribly malformed. Our arms are generally the same size on both sides of body. How is cell division so tightly regulated?
4-Reproduction
The sperm and egg are very specialized cells, and only they can transmit the instructions for making an organism from one generation to the next.
5-Regeneration
Formation of lost body parts is called regeneration. Some organisms can regenerate their entire body.
Many reptiles can regenerates their tails. Mammals are generally poor at regeneration, yet there are some cells in their bodies- stem cells- that are able to form new structures even in adults.
6-Evolution
Evolution involves inherited changes in development.
7-Environmental Integration
The development of many organisms is influenced by cues from the environment that surrounds the embryo or larvae.
The sex of many species of turtles, for instance, depends on the temperature the embryo experiences while in the egg.
Moreover, certain chemicals in the environment can disrupt normal development , causing malformations in adult.