Final answer:
Specimens requiring collection at specific times include those related to circadian rhythms like in the Mosenthal test, and for continuous observation in studies like solar astronomy.
Step-by-step explanation:
Specimens that must be collected at specific times of day are often associated with biological processes that follow circadian rhythms, or with scientific studies that require standardization of conditions to ensure accuracy. Examples include the Mosenthal test, which evaluates renal concentrating ability and requires urine samples to be collected every two hours during daylight, and the study of solar astronomers observing the Sun's oscillations, where continuous observation is necessary, therefore specific geographic locations for telescope placement are chosen to optimize observing times.
Biological specimens used for cassette analysis in pharmacological studies also require collection at precise intervals to monitor drug metabolism and distribution over a 24-hour period.