Level can be increased by earning XP (Experience Points), which are given upon completing a match, based on the amount of kills and time survived. Achieving certain Level milestones will unlock ability to obtain DNA for more Animals.
Rewards
After a match that results in the player reaching Level 10 and every 10th level after, the player will receive DNA corresponding to one of the animal types which the respective level unlocks (levels which do not have corresponding animal unlocks will just multiply whatever the random DNA drop the player receives at the end of the match). Time survived determines the base amount of DNA earned, and a bonus of either 2, 3, or 4 times the DNA is applied to the drop.