What term describes having two different forms of growth in organisms?

The term that describes having two different forms of growth in organisms is dimorphism. Dimorphism specifically refers to the occurrence of two distinct forms or morphs within a species, which can be seen in various biological contexts. For instance, in some species of plants or animals, males and females may exhibit different physical characteristics, or a species might adopt different forms depending on environmental conditions.

In contrast, polymorphism refers to the presence of multiple forms or variations within a population, which may include several different types rather than just two. Monomorphism, on the other hand, indicates that a species exhibits only a single form or structure. Metamorphism is not a commonly used term in biology with regard to growth forms; it generally refers more to the process of metamorphosis, particularly in the context of transforming from one developmental stage to another, like from a larva to an adult in insects. Thus, dimorphism accurately captures the concept of having two distinct growth forms.