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, ...

Implantation is a process in which a developing embryo, moving as a blastocyst through a uterus, makes contact with the uterine wall and remains attached to it until birth. The lining of the uterus (endometrium) prepares ...

Preformationism was a theory of embryological development used in the late seventeenth through the late eighteenth centuries. This theory held that the generation of offspring occurs as a result of an unfolding and growth ...

Tooth enamel contains relics of its formation process, in the form of microstructures, which indicate the incremental way in which it forms. These microstructures, called cross-striations and striae of Retzius, develop as ...

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 ...

Vitamin A (retinol) is an essential vitamin in the daily functioning of human beings that helps regulate cellular differentiation of epithelial tissue. Studies have shown that an excess of vitamin A can affect embryonic ...

Purkinje cells, also called Purkinje neurons, are neurons in vertebrate animals located in the cerebellar cortex of the brain. Purkinje cell bodies are shaped like a flask and have many threadlike extensions called dendrites, ...

Angelman syndrome is a disorder in humans that causes neurological symptoms such as lack of speech, jerky movements, and insomnia. A human cell has two copies of twenty-three chromosomes for a total of forty-six-one copy ...

When scientists discovered a 3.3 million-year-old skeleton of a child of the human lineage (hominin) in 2000, in the village of Hadar, Ethiopia, they were able to study growth and development of Australopithecus afarensis, ...

The one gene-one enzyme hypothesis, proposed by George Wells Beadle in the US in 1941, is the theory that each gene directly produces a single enzyme, which consequently affects an individual step in a metabolic pathway. ...