A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ ...

Among other functions, the Notch signaling pathway forestalls the process of myogenesis in animals. The Notch signaling pathway is a pathway in animals by which two adjacent cells within an organism use a protein named ...

Johann Friedrich Meckel and Antoine Etienne Reynaud Augustin Serres developed in the early 1800s the basic principles of what later became called the Meckel-Serres Law. Meckel and Serres both argued that fetal deformities ...

To study human evolution, researchers sometimes use microstructures found in human teeth and their knowledge of the processes by which those structures grow. Human fetusus begin to develop teeth in utero. As teeth grow, ...

Dinosaur egg parataxonomy is a classification system that organizes dinosaur eggs by descriptive features such as shape, size, and shell thickness. Though egg parataxonomy originated in the nineteenth century, Zi-Kui Zhao ...

The Y-chromosome is one of a pair of chromosomes that determine the genetic sex of individuals in mammals, some insects, and some plants. In the nineteenth and twentieth centuries, the development of new microscopic and ...