Which term refers to the character states involved in evolutionary biology, such as "hair present" or "hair absent"?

The term that accurately describes the traits or conditions that can exist for a particular characteristic in evolutionary biology, such as "hair present" or "hair absent," is known as character states. Character states provide information about the various forms a given trait can take—essentially categorizing the observable traits of organisms within a specific lineage.

In this context, each character state represents a different manifestation of a genetic trait, allowing researchers to analyze similarities and differences among species. Understanding these states is crucial for constructing phylogenetic trees and for studies involving evolutionary relationships, as they reflect the evolutionary history and adaptations of organisms over time.

The other terms may relate to aspects of biological characteristics but do not specifically denote the variations of observable traits in the same way. For instance, while "phenotype states" might seem relevant—given that phenotypes encompass the observable characteristics resulting from both genetic and environmental factors—they do not exclusively refer to the specific alternative forms of a trait that character states do. Similarly, "characteristic states" and "genotypic expressions" focus on broader or different aspects of biological functionality and inheritance rather than the direct comparison of specific traits like the presence or absence of hair.