Most body parts contribute to at least one racial score. Take human face, which contributes to human, ausar, kathrit, ovir, etc. etc. racial scores. When your score for any particular race is above a threshold, you qualify as having that race as "what race you are". If multiple races qualify, the race with the highest score is chosen. If no races qualify, you are defined as a "alien hybrid".
As a side note: most variants for races (such as tiger shark for shark) generally have less point contribution per body part, but have a defining feature that grant a large bonus to that score, and a corresponding penalty to the more generalized race, if and only if your generalized race score would be above a threshold.
If you want to see how this works in real time, go play CoC Xianxia. The appearance window has a submenu that displays all your racial score. Toss around transformations and you can see how some common body parts affect many scores, and how some related scores (such as harpy and phoenix) interact with each other.