Holoaden Holoaden Holoaden (common name: highland frogs) is a small genus of craugastorid frogs endemic to southeastern Brazil. "Holoaden" is the type genus of subfamily Holoadeninae that was erected in 2008 and placed in family Strabomantidae, erected at the same time. Before that, it was in Brachycephalidae. However, later research has led the whole Strabomantidae, Holoadeninae included, to become included in Craugastoridae. This arrangement is not followed by all, and the AmphibiaWeb still keeps Holoadeninae, and consequently "Holoaden", in Strabomantidae. "Holoaden" grow to snout–vent length at most. Head is narrower than the body. Differentiated tympanic membrane and tympanic annulus are absent.
Cell membrane concentration in order to equilibrate the membrane. It is considered a passive transport process because it does not require energy and is propelled by the concentration gradient created by each side of the membrane. Such a concentration gradient across a semipermeable membrane sets up an osmotic flow for the water. Osmosis, in biological systems involves a solvent, moving through a semipermeable membrane similarly to passive diffusion as the solvent still moves with the concentration gradient and requires no energy. While water is the most common solvent in cell, it can also be other liquids as well as supercritical liquids and