Definition: a thin membranous, sometimes alveolated sac in the dorsal portion of the abdominal cavity. Contains a varying mixture of gases, not identical to the composition of air.
Definition: A taxon is Endangered when the best available evidence indicates that it meets any of the \r\ncriteria A to E for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.
Definition: A shallow stretch of a river or stream, where the current is above the average stream velocity and where the water forms small rippled waves as a result. It often consists of a rocky bed of gravels or other small stones.
Definition: The benthopelagic zone biome comprises regions of the marine water column which usually coincide with the benthic boundary layer (BBL) - the layer of isothermal and isohaline water contiguous to the sea floor. A general reversal in the declining gradient of pelagic biomass may be observed here, perhaps explained by viable nutrition on the sea floor being resuspended by bottom currents. This zone typically extends 100 m above the seafloor, but may reach upto1000 m during benthic storms.
Definition: A habitat that is in or on a body of water containing low concentrations of dissolved salts and other total dissolved solids (<0.5 grams dissolved salts per litre).
Definition: Capable of creating a new organism by combining the genetic material of two gametes, which may come from two parent organisms or from a single organism, in the case of self-fertilizing hermaphrodites.
Definition: National Museum of Natural History, Smithsonian Institution (USNM), Washington, District of Columbia, USA.\r\nNMNH and USNM both refer to the National Museum of Natural History. Collections are associated with one or the other acronym. US, the US National Herbarium, is a collection within the National Museum of Natural History. URL for main institutional website, http://www.mnh.si.edu/rc/\r\nURL for institutional specimen catalog, http://collections.mnh.si.edu/
Definition: Relative to pinhole eyes, lens eyes have greatly improved resolution and image brightness. The lens converges incoming rays of light, thereby reducing the angle over which each photoreceptor receives light, and forming an image focused on the retina. Most lens eyes have "accommodation"; they can focus an image either by physically moving the lens toward or away from the retina or by using eye muscles to adjust the shape of the lens.
