Which of the following refers to a skin graft that is made up of tissue from one species and grafted onto another species?

A skin graft made up of tissue from one species and grafted onto another species is referred to as a xenograft. This type of graft is typically used in various medical settings, particularly in situations where human tissue is either not available or not suitable for grafting, thus animal tissue is utilized.

In the context of grafting, there are different classifications based on the source of the graft. An autograft involves tissue taken from the patient's own body, an allograft refers to tissue taken from a donor of the same species but not genetically identical, and an isograft involves grafting tissue between genetically identical individuals, such as identical twins. Each of these graft types is relevant in clinical practice, but for the situation described in the question, a xenograft is the correct terminology.