When taming the standard animal just doesn't cut it. The Bio-Engineer specializes in taking the DNA from one animal and making it into a new animal, or in some cases a much better clone of the original.
As you progress a long this skill tree you will become more adapt at successfully taking the DNA from much higher grade creatures you may run across during your travels.
Another perk to note is the BE (Bio-Engineer) ability to take said DNA sample and apply it to special synth cloth for the aspiring tailor or a food additive for the adept chef.
When doing this, you can grant that cloth / additive with special abilites (i.e Stat bonuses i.e +5 Terrain Negotiation, +5 Creature Harvest, ect) that can be used to make, or rather enhance clothing or food / beverage.