In addition, it is observed across a number of widely different species, including some invertebrates that do not have a similar blood coagulation system. It is a highly sulfated glycosaminoglycan. It has the highest negative charge density of any known biological molecule. Evolutionary conservation
In addition to the bovine and porcine tissue from which pharmaceutical-grade heparin is commonly extracted, it has also been extracted and characterized from:

The biological activity of heparin within species 6–11 is unclear and further supports the idea that the main physiological role of heparin is not anticoagulation. These species do not possess any blood coagulation system similar to that present within the species listed 1–5. The above list also demonstrates how heparin has been highly evolutionarily conserved, with molecules of a similar structure being produced by a broad range of organisms belonging to many different phyla. Pharmacology
In nature, heparin is a polymer of varying chain size. Unfractionated heparin (UFH) as a pharmaceutical is heparin that has not been fractionated to sequester the fraction of molecules with low molecular weight. In contrast, low-molecular-weight heparin (LMWH) has undergone fractionation for the purpose of making its pharmacodynamics more predictable. Often either UFH or LMWH can be used; in some situations one or the other is preferable. Mechanism of action
Heparin binds to the enzyme inhibitor antithrombin III (AT), causing a conformational change that results in its activation through an increase in the flexibility of its reactive site loop. The activated AT then inactivates thrombin, factor Xa and other proteases.
An estimated 75% of volcanic eruptive volume is generated by submarine eruptions near mid ocean ridges alone, however problems detecting deep sea volcanics meant they remained virtually unknown until advances in the 1990s made it possible to observe them.Submarine eruptions may produce seamounts, which may break the surface and form volcanic islands. Submarine volcanism is driven by various processes. Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface. Eruptions associated with subducting zones, meanwhile, are driven by subducting plates that add volatiles to the rising plate, lowering its melting point. Each process generates different rock; mid-ocean ridge volcanics are primarily basaltic, whereas subduction flows are mostly calc-alkaline, and more explosive and viscous.Spreading rates along mid-ocean ridges vary widely, from 2 cm (0.8 in) per year at the Mid-Atlantic Ridge, to up to 16 cm (6 in) along the East Pacific Rise. Higher spreading rates are a probable cause for higher levels of volcanism. The technology for studying seamount eruptions did not exist until advancements in hydrophone technology made it possible to "listen" to acoustic waves, known as T-waves, released by submarine earthquakes associated with submarine volcanic eruptions. The reason for this is that land-based seismometers cannot detect sea-based earthquakes below a magnitude of 4, but acoustic waves travel well in water and over long periods of time.