It adds bases in only one direction.
Provide a list? Ill edit my answer till then
In terms of parasites vs hosts, it is an organism in which the parasite resides and normally feeds + reproduces.
For a fish to be buoyant, or float, it must displace less water or the same amount of water as its own body mass. ... Many fish use swim bladders to help them with quick depth changes. These bladders fill with air to help fish rise or release air so fish can sink, often in conjunction with forward movement.
