- Biological rhythms that happen across one day are circadian rhythms.
- For example, in human brains there is a timing mechanism called a biological clock which regulates the things that occur in our body over a 24 hour period and can be influenced by environmental factors such as light intensity.
- This includes the release of hormones such as Melatonin. This usually happens around 10pm at night as Melatonin makes us feel sleepy. However, in the morning Melatonin levels drop so we wake up. That is why we are sleepy at night and alert in the morning.
- Our biological clock needs regular exposure to day and night to keep with the 24 hour cycle. When we travel across the globe the day-night cycle there is different than the one the body was using. This can cause a person to feel less alert and less able to think clearly which is jet lag.
- Flowers, such as daisies, close at night and open during the daytime. This makes sure the insects can visit them for pollination in the day and the seeds are protected from the wind and cold at night. Flowers only produce nectar during the daytime when the insects are likely to visit the flowers.
- Stomata open in the day and close at night.