The XP curve every Survival skill follows, how XP is earned and capped, and what happens on level up.
Skill levels on Survival work the same way for every skill: you start at level 1 with 0 XP, each action listed on the skill's page grants a small amount of XP, and you level up when your XP for the current level reaches the amount shown below. Mining, Farming, Forestry, Fishing and Slayer share one XP table; see Skills for the overview.
Each skill keeps its own level and its own XP bar. Skills never share XP.
XP is added to the current level's bar. When the bar reaches the amount required for that level, the surplus carries over and you move up one level. A large XP gain can skip several levels at once.
Each skill's XP table has 137 levels, and there is no entry beyond level 137. The skill tree menu shows levels 1 to 90.
XP is saved a few seconds after you gain it, so it is kept when you log out.