☔️ Water series: The primordial soup of life: oceans water: Difference between revisions

===Body salinity strategies===

There must be a good reason to keep the same salinity on the inside and the outside, as it asks for energy to regulate your internal salinity instead of letting it depend from the surrounding sea water. On the contrary, vertebrate fishes<ref>Most fishes that we know and see in our plates are bony fishes, from sardines to trout.</ref>, with their ability to isolate their inside from the outside, conquered new unclaimed areas consisting on fresh waters. Without this skin and regulation tactics, they would simply dilute in rivers, unable to fight the osmotic laws that would push their inside highly salted water outside in the less salted water (a jellyfish in fresh water will dissolve). However, water must be absorbed to run through the fish gills<ref>Gills are sort of semi-outer lungs that most marine life uses to filter the sea water and extract dissolved oxygen from it, either by the force of the currents, by moving (ram ventilation) or breathing.

source: https://en.wikipedia.org/wiki/Gill</ref> so that fishes can extract the oxygen they need to live. This means that breathing basically disrupts their body salinity, and that’s why fresh water fishes reject large amount of water by peeing to stay salty. On the other hand, sea fishes reject salt filtered by their gills while drinking a lot of sea water to prevent their salinity to rise. We are closer to the first ones, as we get the desired amount of salt from our savoury food, while peeing unsalted water.<ref name="boeuf" />