1 Some DMMs can simultaneously measure and display the ac and dc components of a signal. 2  The DMM display can show results three ways (see illustration below): 3  The ac portion of the signal appears in the primary display and the dc portion in the smaller secondary display.
Each lichen specie is one alga species plus one fungus. The alga, a microscopic green plant, makes the food for the duo, while the fungus, a non-green plant, gives the pair support and soaks up moisture.
Some have suggested that this is a type of lichen, arguing that a mutualism between an alga and a fungus is by definition a lichen. However, others have argued that in a true lichen the fungus is the exobiont, that is it encloses the alga and forms the conspicuous part of the thallus.