Marine animals are the general name of heterotrophic organisms in the ocean. There are many categories, and the morphological structure and physiological characteristics of each category can be very different. There are small unicellular protozoa, and large whales that can be more than 30 meters long and weigh more than 190 tons. The following is how marine animals sleep, which I carefully recommend. It's for reference only. Welcome to read!
How do marine animals sleep
Both humans and animals need to sleep. If we can't get a good sleep for a long time due to external interference, we and animals will be physically and mentally tired, and even lead to death. People usually lie down to sleep, but animals sleep in strange positions - wading birds such as herons, storks, cranes and snipes on the edge of the swamp can be independent on one foot, canids such as wolves, dogs and jackals need their ears close to the ground, bats can hang upside down, spiders and monkeys only need to hook their tails on branches... So how do animals in the ocean sleep?
Although animals in the ocean have various sleeping positions, the vast majority of marine animals sleep for a short time and are difficult to be found by humans because of the dual pressure of breathing and natural enemies.
Fish can never close their eyes because they have no eyelids, so they sleep with their eyes open. In order to keep breathing, the operculum will still fan slowly and rhythmically, and occasionally stroke the pectoral fin or caudal fin to keep the body balanced. Fish sleep is like a human nap, some only a few minutes, some even a few seconds, mainly because they must always be vigilant, otherwise they will fall into the mouth of the sneaker.
Dolphins seem to be swimming in the water all day and can't see any sleep time. In fact, their work and rest time is similar to ours. At night, the Dolphin will dive 30 meters underwater and fall asleep quietly, but its tail will still swing every 30 seconds or so. But dolphins are mammals. How do they breathe when they sleep? It turns out that dolphins have great lung capacity and can store oxygen in their blood, so they can no longer surface in dozens of minutes after one breath. This time is enough for them to have a beautiful dream. Of course, dolphins stay alert when they sleep. Scientists have found that the two hemispheres of their brains sleep alternately: when one side is asleep, the other is awake. After a period of time, the two will exchange again. If they are severely stimulated by the outside world, the two hemispheres will wake up at the same time to ensure that they can quickly respond to changes in the outside world.
Seals are different from dolphins. They can live both underwater and on shore. If they choose to sleep on shore, they are similar to terrestrial animals; If you choose to sleep underwater, you have to wake up every time you breathe. Although it seems very uncomfortable to us bystanders, they are used to it.
When octopus is sleeping, it leaves two tentacles scratching around its body, and the other tentacles roll up to rest. If two active tentacles are disturbed by the outside world, they will wake up immediately.
Manatees like to sleep at the bottom of the sea, but unlike dolphins and whales, they can hold their breath underwater for a long time. Manatees have to surface for breath in about 10 minutes, so their "good dreams" are difficult to connect.
Seals are much smarter. They either sleep on land, or stretch their nose out of the ice cave to breathe while sleeping, and their bodies float vertically in the water, looking like upright sculptures, which is convenient for ventilation and does not delay deep sleep.
Marine animals have different sleeping styles.
Why do some plants "walk"
A botanist made a scientific investigation in a deserted place in the western United States. When he left, in order to find the place next time, he chose a special plant and marked it. However, after a few months, when he returned there, he found that the plant was missing! Careful scientists carefully observed the surrounding situation and found a shallow trace on the ground. Following this trace, he walked a long way and finally found the marked plant by a small lake. Plants can walk by themselves?
It turns out that this plant can grow in a fixed place where there is sufficient water. Once it is dry and short of water, its roots will leave the soil and the plant body will roll into a sphere. When the wind blows, it will move with the wind. When it encounters water, it will stop, insert its roots into the soil, obtain water and nutrients, and start its new life. Because this plant seems to be able to sense its surroundings and wake up from a deep sleep, it is called a wake-up tree.
There is also a plant called Tumbleweed in the desert. It can also roll its roots into a ball and roll with the wind when it is dry. From a distance, it looks like a small ball rolling rapidly. Where there is water, it will take root and grow again.
Why is there no three legged animal
It is recorded in the book of mountains and seas, the eastern classic of the great wilderness: "there is Liubo mountain in the East China Sea, seven thousand miles into the sea. There are animals on it, which look like cattle. The Cang body has no horns. If one foot goes in and out of the water, there will be wind and rain. Its light is like the sun and moon, and its sound is like thunder. Its name is Kui. The Yellow Emperor took it, took its skin as a drum, pegged it with the bones of thunder animals, and heard it for five hundred miles to threaten the world." This legendary ancient mythical beast is actually an animal with only one leg.
Legs are the moving organs of animals. In reality, snails crawl on one "leg". Frogs, lizards, leopards and elephants jump, crawl and walk on four legs. Humans, bats, birds and extinct pterosaurs have two legs. However, if you rack your brains, you may not be able to list which animal has three legs. The reason is likely to be related to the evolutionary process of organisms.
At the beginning of life, a cell is a life. After that, life composed of multiple cells began to appear on the earth, such as the most primitive and lowest multicellular animal sponge. Although some sponges have certain shape and symmetry, most of them grow irregularly like plants, forming flat, round, dendritic and other asymmetric body structures. Then, coelenterates such as jellyfish began to appear. There are many sections of the central axis (from the mouth surface to the opposite mouth surface) in their bodies, which can divide their bodies into two equal parts. Biologically, organisms with this form are called "radially symmetric organisms". They can only be divided into top and bottom, not front, back, left and right. They can only be fixed in the water or float with the current, and passively absorb food from the surrounding environment.
Later, in order to gain the right to take the initiative, a kind of animals suitable for swimming and crawling appeared. To do this, their bodies must be clearly divided into front and back, left and right, back and abdomen. In morphology, through the central axis of the animal body, only one symmetry plane (or section) can divide the animal body into two equal parts. This kind of animal is called "bilateral symmetrical animal" or "left-right symmetrical animal". This change from non directional movement to directional movement makes animals adapt to a wider range, which is a higher evolutionary form than radial symmetry.
There are many animals with bilateral symmetry, such as mollusks such as snails and snails, mammals such as humans, leopards and elephants, birds, amphibians and reptiles such as frogs and lizards, and insects such as dragonflies and locusts. As the name suggests, when they are reflected in the number of legs, they are either 1 (can be divided into two), or even numbers such as 2, 4 and 6, otherwise they cannot be symmetrical in shape. Therefore, it is impossible for three legged animals to exist in bilateral symmetrical rows and columns.
So, is it possible to appear in radially symmetric organisms? In an animal known as pentaradiosymmetry, there are indeed five wrist starfish that can move slowly. According to this inference, you may propose "some kind of starfish" that should also have three legs. Unfortunately, it has not been found so far. And fundamentally, these creatures that are fixed or floating for passive movement actually have no real "leg" structure.
Perhaps, in the long history of life evolution, there have been three legged animals. It's just a pity that neither living nor related fossils have found such animals. As for the animals with three legs occasionally seen in news reports, it is because of the deformity caused by environmental and genetic mutations, and there is no way to stably inherit them to the next generation.