to be defined as carnivorous, a plant must first exhibit an adaptation of some trait specifically for the attraction, capture, or digestion of prey. only one trait needs to have evolved that fits this adaptive requirement, as many current carnivorous plant genera lack some of the above-mentioned attributes. the second requirement is the ability to absorb nutrients from dead prey and gain a fitness advantage from the integration of these derived nutrients (mostly amino acids and ammonium ions) either through increased growth or pollen and/or seed production. however, plants that may opportunistically utilize nutrients from dead animals without specifically seeking and capturing fauna are excluded from the carnivorous definition. the second requirement also differentiates carnivory from defensive plant characteristics that may kill or incapacitate insects without the advantage of nutrient absorption. due to the observation that many currently classified carnivores lack digestive enzymes for breaking down nutrients and instead rely upon mutualistic and symbiotic relationships with bacteria, ants, or insect, this adaptation has been added to the carnivorous definition. despite this, there are cases where plants appear carnivorous, in that they fulfill some of the above definition, but are not truly carnivorous. some botanists argue that there is a spectrum of carnivory found in plants: from completely non-carnivorous plants like cabbages, to borderline carnivores, to unspecialised and simple traps, like "heliamphora", to extremely specialised and complex traps, like that of the venus flytrap.