What term refers to a low level of difference in physical appearance between males and females?

The term that refers to a low level of difference in physical appearance between males and females is "low sexual dimorphism." Sexual dimorphism describes the physical differences between the sexes of a species, which can include differences in size, coloration, or morphology. When sexual dimorphism is low, it indicates that males and females look quite similar to each other, exhibiting few pronounced physical differences.

In various species, low sexual dimorphism is often found in contexts where males and females share similar roles, such as in certain bird species where both sexes are similarly sized and colored. This can reflect behavioral or ecological strategies where distinct sexual traits do not confer a significant advantage in survival or reproduction.

Other terms in the choices refer to different concepts altogether. High sexual dimorphism would indicate a significant difference in appearance between the sexes. Gender fluidity pertains to the range of gender identities that do not fit within traditional binary notions of male and female. Sexual selection is a mode of natural selection where certain traits evolve because they are advantageous in attracting mates, rather than being strictly tied to survival. Understanding these distinctions is crucial in the context of evolutionary biology and sexual reproduction.