Molly loves early mornings but Patrick has a hard time waking up before ten each day. Molly and Patrick have different circadian rhythms
melatonin schedules.
biological clocks.
chronotypes.

chronotypes

Explanation:

Chronotype is the behavior and preferred bodily and psychological schedule of one’s activity and sleep. It regulates what is the best time for someone to sleep during the day. The people who usually function at the night (like Patrick) prefer the eveningness and delayed sleeping period, while people who easily wake up and do their tasks early (like Molly) are more into morningness and advanced sleep periods.

Most people are flexible, and their schedules and types change in accordance with age, life stage, events, and tasks. However, chronotype also affects our traits, productivity, and effectiveness of our performance, and relaying which type is the best of us we can raise our productivity.

"social stratification refers to the way people are ranked and ordered in society. in western societies, stratification is primarily seen and understood as a result of socioeconomic status, which produces a hierarchy in which access to resources, and possession of them, increases from the lower to the upper strata"