Final answer:
The regulatory subsystem's in-season activities include various physiological changes and behaviors such as hibernation, molting, and hormone production, which are responses to environmental changes associated with different seasons.
Step-by-step explanation:
The term 'regulatory subsystem' suggests you're referring to biological systems, possibly within the context of homeostasis or the nervous and endocrine systems. These subsystems are responsible for maintaining the internal environment of an organism. In the regulatory subsystem, in-season activities could refer to physiological changes or behaviors that occur in response to environmental changes associated with different seasons. Examples of such in-season regulatory activities include hibernation in animals during winter, molting in birds for breeding season, or the production of hormones like melatonin influenced by the length of day and night. All these actions are regulated to ensure the organism adapts to the seasonal variations for survival.