Getty/Jason Hosking. A niche is a term that is used in ecological biology to define an organism's role in an ecosystem. Not only does a niche include the environment a given organism lives in, it also includes the organism's job in that environment.
Perilymph (also known as Cotunnius' liquid, and liquor cotunnii) is an extracellular fluid located within the cochlea (part of the inner ear) in two of its three compartments: the scala tympani and scala vestibuli. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid. The major cation (positively charged ion) in perilymph is sodium: The values of sodium and potassium concentration in the perilymph are 138 mM and 6.9 mM, respectively.
2. The right atrium contracts and pumps the blood through the tricuspid valve and into the right ventricle. 3. The right ventricle then pumps blood through the pulmonary artery into the lungs. 4. In the lungs, tiny blood vessels called capillaries absorb carbon diox-ide from the blood and replace it with oxygen. 5. Oxygenated blood then flows through the pulmonary vein and into the left atrium. 6.