Biology of development. Evolution

Developmental biology deals with the only thing uniting all the question: how a single cell can develop into a Mature organism? In humans, this conversion occurs whenever a single fertilized egg develops into a person with more than 1013-1014 cells, several hundred distinct cell types and dozens of fabrics. This process should occur in a reliable and predictable manner and within a certain time frame.

Developmental biology is rooted in embryology, based on observations and surgical manipulations on the developing organisms. Early embryological studies in the XIX and early XX centuries in an easily accessible embryos of amphibians and birds showed that the embryo develops from a single cell, and identified many of the fundamental processes of development. Much later introduction to embryology molecular biology and genetics has transformed the area, allowing scientists to study and manage the development using a large variety of powerful biochemical and molecular methods.

One of the most important topics in developmental biology — its connection with the study of evolution. Early in development the embryos of many species are very similar to each other. As you continue development of signs, shared between species, consistently turn to the more specialized, common to a smaller number of more closely related species.

Comparison of embryo characteristics among and within evolutionary related organisms shows that specific signs of development (e.g., fingers) that are specific for certain groups of animals (e.g., primates), there are based on less specific features that are common to large groups of organisms (e.g., mammals), in turn, ascending to the structures observed in even larger groups of organisms (e.g., vertebrates). The structures of different organisms are called homologous if they develop from structures present in the common ancestor. the four different types, allowing us to trace back to their common ancestor, having a common sign, and functional shoulder and arm. Molecular evolutionary mechanisms that created these structures of the limb, common to all four modern species.

Stem not less than not every similarity is a consequence of homology. Evolutionary studies also recognize the existence of similar structures that look alike but arose independently from each other in different ways when it is impossible to detect a common ancestor with that structure. Molecular paths that generate the same structure, evolutionary remain rare.

In the example shown in the figure, the structure of bat wings and birds have arisen in the course of evolution, independently, facilitating the task of moving through the air. The evolutionary path of these two animals have a common ancestor with a simple structure similar to a wing, from which bats and birds inherited the wings. On the contrary, it’s easy to see that birds have for the formation of wings developed additional education in the limbs, while bat wings have evolved with the use of fingers, connected by an intermediate tissue. Such a situation is called convergent, or convergent evolution.

Evolutionary conservation of developmental processes is critical for studies of human development, because for obvious ethical reasons, the vast majority of such studies cannot be performed on humans. Thus, to understand the observations of the evolution, for the study of normal and abnormal development processes scientists use animal models. The possibility to extend the obtained results to humans is completely dependent on the survival in the evolution of mechanisms of development and the existence of homologous structures.