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Biological patterns such as animal markings, the segmentation of animals, and phyllotaxis are formed in different ways. [2]In developmental biology, pattern formation describes the mechanism by which initially equivalent cells in a developing tissue in an embryo assume complex forms and functions. [3]
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
Evolutionary embryology is the expansion of comparative embryology by the ideas of Charles Darwin. Similarly to Karl Ernst von Baer 's principles that explained why many species often appear similar to one another in early developmental stages, Darwin argued that the relationship between groups can be determined based upon common embryonic and ...
First attested in English in the mid-14c., the word embryon derives from Medieval Latin embryo, itself from Greek ἔμβρυον (embruon), lit. "young one", [1] which is the neuter of ἔμβρυος (embruos), lit. "growing in", [2] from ἐν (en), "in" [3] and βρύω (bruō), "swell, be full"; [4] the proper Latinized form of the Greek term would be embryum.
A History of Embryology is a 1934 book by Joseph Needham. [1] The book is based on lectures on Speculation, Observation, and Experiment. The same lectures were then compiled and released as a book published. [2] The works contain several sections dedicated to Spagyric. The book shows the development of embryological thought and scientific ...
This results in a series of zones becoming set up, arranged at progressively greater distance from the signaling center. In each zone a different combination of developmental control genes is upregulated. [22] These genes encode transcription factors which upregulate new combinations of gene activity in each region. Among other functions, these ...
Embryology is the subdivision of developmental biology that studies embryos and their development. The main article for this category is Embryology . Contents
For example, German biologist and philosopher Ernst Haeckel proposed that all organisms went through a "re-run" of evolution he said that 'ontogeny repeats phylogeny' while in development. Haeckel believed that to become a mammal , an embryo had to begin as a single-celled organism, then evolve into a fish, then an amphibian, a reptile, and ...