Webster's defines an animal as: "any of a kingdom (Animalia) of living things including many-celled organisms and often many of the single-celled ones (such as protozoans) that typically differ from plants in having cells without cellulose walls, in lacking chlorophyll and the capacity for photosynthesis, in requiring more complex food materials (such as proteins), in being organized to a greater degree of complexity, and in having the capacity for spontaneous movement and rapid motor responses to stimulation".

• So Siggy is a plant because she has chlorophyll and can photosynthesize.
• So Siggy is an animal because she needs "more complex food materials" and has "rapid motor responses to stimulation".