klyvning

Klyvning is a Norwegian term that can refer to several related phenomena in natural sciences, most notably in biology and geology.

In biology, klyvning (embryonal cleavage) describes the rapid mitotic cell divisions that follow fertilization, during which the zygote is partitioned into progressively smaller cells (blastomeres) without overall growth. The process produces two-cell, four-cell, eight-cell stages, then a morula and a blastula. These divisions are controlled by maternal and zygotic gene expression and are characterized by holoblastic or meroblastic cleavage, depending on yolk distribution. Cleavage patterns (radial, spiral, bilateral) vary among species and are important for early development and fate specification.

In geology and mineralogy, klyvning refers to a mineral’s tendency to break along planes of weakness in its crystal structure, yielding smooth, flat surfaces called cleavage planes. Cleavage is influenced by crystal structure, bond strength, and mineral composition, and is described by quality (perfect, good, distinct, indistinct, poor) and by the number and orientation of cleavage directions. It is a key property for mineral identification and is distinguished from fracture, which is an irregular break.

In chemistry or everyday language, the term may appear as a translation of "cleavage," meaning the breaking of chemical bonds, such as in bond cleavage during reactions, hydrolysis, or enzymatic processing. Specific usage depends on the context and field.