Animals like plants need the sun and all people will tell you that if the sun is out for weeks, they feel depressed and sad. The Sun gives us tone and the image of the cock that launches his cororico at dawn, we sing more readily under the Sun than in the rain, although the song says.
The Sun also unconsciously influences our internal “clocks”. We have at the base of the brain a small gland called the pineal gland. In the presence of the Sun (which she “feels” through our eyes and our skin), she emits a substance called melatonin. This gland regulates the rhythm of your sleep and the number of hours that you remain awake.
But if you live in a cave for several months, as there is no Sun to regulate the rhythm of the day and night, your body use other references and will invent a new rhythm of life that will either 17 hours is more than 30 hours instead of the usual 24 hours.
Your body will change rhythm automatically according to the need of your organs and you will not feel more tired anymore. But it is certain that if you stay locked up without seeing the Sun for a year or more, your body will weaken, mainly the bones of your skeleton that need vitamin D, the one you make when your skin turns brown in the sun.
The animals also follow the rhythm of the day and the night. Most of them have diurnal life, like you and me, and sleep during the night. But the owl, for example, wakes up in the evening and lives at night, like the owl or the great duke. Other animals, such as groundhogs, hedgehogs and bears, even take advantage of winter to hibernate and save energy. They hide in burrows or caves and sleep deeply for several months. They will only wake up in the spring to eat and breed.
And what about plants? In the 18th century, the Swedish botanist Carl von Linné discovered that some plants were opening at the same time as the Sun. Thus, the orange marigold opens its petals at 9 o’clock in the morning, the lady-of-eleven-hour opens at 11 am and the night-owl opens her corolla at 5 pm.
Other plants literally follow the movement of the Sun like the sunflower that always turns to the Sun where the daisy closes when there is no Sun. In contrast, some green plants do not like the sun much. For example, Christmas roses or ferns will grow much faster and have more beautiful colors if they live in the shade.
Finally, some plants are not interested at all in the position of the Sun and live at their own pace. This is how the bamboo that feeds the panda flowers once every 30 or 70 years. These archaic plants or flowers, however, need the sun to breathe and ensure photosynthesis, to convert carbon dioxide into essential oxygen for life.