Final answer:
The question involves the identification of age or sex in animals, indicating that certain animal species may be easier to age than sex, and vice versa. Typical cases include species of fish and birds where age or sex determination poses different levels of difficulty.
Step-by-step explanation:
The question seems to be referring to the difficulty of determining age or sex in certain animals or organisms. It hints at particular types of animals where one of these characteristics can be identified but not the other. Although the specific animals or organisms are not provided in the blank spaces, there are some instances where this statement would be true. For example, with some species of fish, it can be relatively easier to determine age by examining scales or otoliths (ear stones), but sexing them might be more difficult without invasive methods. In contrast, certain bird species can be sexed easily by their plumage (feathers), but aging them precisely can be more challenging once they are adults and their plumage characteristics change minimally with age.