When Did Animals First Colonize Continental Interiors?

Animals were born in the water, stayed in the water for a long time, and did not land on land until more than 300 million years ago. Landing is another major event in animal history, opening a new chapter in the great prosperity of terrestrial animals. Waters and land are two distinct ecological environments. Land animals have evolved from aquatic animals. For aquatic animals to land, they must have a series of characteristics adapted to life on the land: animals on the land cannot use gills to breathe as they do in the water, but must use the lungs; unlike fish with water buoyancy, the land Animals are greatly affected by the attraction of the earth's center of gravity, so the limbs that support and move become important organs; there is a certain amount of water in the animal, and fish are not afraid of the loss of water in the water, but they must live on land. As the water evaporates, the threat of dry death is encountered. During the evolution of animals, only with this series of adaptive structures can they survive on land. The total fin fishes differentiated from primitive osteochondral fishes have lung-like air sacs. As auxiliary respiratory organs, they have stronger spines and even fins. Due to environmental changes more than 300 million years ago, the internal structure of the total finfish was differentiated. After a long and arduous journey, the characteristics of adapting to terrestrial life have been continuously produced and strengthened. The lungs replaced the gills, the even fins turned into limbs, gradually climbed onto the land, and evolved into amphibians. Amphibians landed on the land and opened up a new world of vertebrate land life. This has played a role in the evolution of vertebrates. ^[1]

45 million years ago, in

The earliest tetrapods appeared late at about 370 to 350 million years ago.

Koala's Tetrapod Features

Koalas like tetrapods are very suitable for arboreal life. Although unlike other arboreal marsupials such as tree kangaroos, koalas do not have obvious tails, but this does not affect its excellent sense of balance; koalas are muscular, with long, slender limbs and are suitable for Climb between branches and support its weight. The forelimbs are almost the same length as the legs, and the climbing strength mainly comes from the developed thigh muscles.

Koala's claws are particularly suitable for gripping objects and climbing. Rough palm and toe pads can help koalas cling to branches, with sharp long claws on all four limbs. The forefoot has five fingers, two of which are opposite to the other three, just like human thumbs, so they can be held against other fingers, which can make koalas hold objects more securely and confidently. On the soles of the feet, except for the big toe, which has no long claws, the other toes have sharp long claws, and the second toe is connected to the third toe.

When approaching the tree and ready to climb, Koala jumped from the ground, grasped the bark with its forepaws, and then jumped up to climb. Therefore, when a tree is often climbed as a Koala's home tree, the scratches left by Koala's claws on the bark are very obvious. Another mark used to prove that a tree is koala is that there will be koala pellets at the base of the tree.

No matter day or night, when sitting on a tree in a safe home, the koala will naturally present a variety of sitting and sleeping positions, and will keep on the tree because of avoiding the sun or enjoying the breeze. moving position. When the weather is hot, the koala will spread out its limbs and swing slightly to keep it cool, and when it gets cold, it will shrink the body to keep the body warm.

Koala's posture under the tree is to move his butt downwards. Koalas often descend to the ground and climb into another tree. At this time, they are often attacked by domestic dogs, foxes, and Australian wild dogs, or killed by passing vehicles. Koalas can swim, but only occasionally.

Koalas have thick fur on their bodies, which is very beneficial for them to keep the temperature constant. Moreover, they can also be used as raincoats when it rains to prevent the body from being affected by moisture and rain. Koala's fur appears in a variety of colors ranging from light gray to brown, with white patches on the chest, neck, limbs, and inner ears. Adult male koalas have a particularly striking brown scent gland in the center of their white breasts.

Koala's tail is particularly rich in fur. This is because koalas often use it as a cushion, and it is often contaminated, so that when koalas are lowered to the ground and their butts are facing you, it will be difficult to find them.

Adult male koalas generally weigh between 8-14 kilograms, while females weigh 6-11 kilograms, and are distributed in the southern koala. They need to adapt to colder climates and have a larger body weight and thicker fur.

Koalas generally belong to nocturnal animals, and are active at night and morning and dusk, because this can save more water and energy consumption than when the temperature is high during the day. Koalas spend an average of 18-22 hours a day sleeping and resting, with only 4 hours remaining for food intake, activities, personal hygiene and communication with other koalas. In the past, because koalas were sleeping almost all day, people thought that koalas were poisoned by eating eucalyptus leaves. Koalas are drowsy almost all day, in fact, they are an effective low metabolism adaptation mechanism that adapts to low-nutrition foods and saves energy consumption during long-term evolution.

The most obvious feature of a koala is that it has a particularly developed nose. It gives koala a highly developed olfactory ability, which can easily distinguish different types of eucalyptus leaves, and find out which can be eaten and which are poisonous and cannot be eaten. Of course, it can also smell the warning odors left by other koalas.

Koalas make a variety of sounds to communicate and communicate with other koalas. Male koalas mainly use roar to indicate their dominance and dominance, so as to avoid fighting to consume energy as much as possible, and to show other animals its location.

Female koalas do not roar as often as males, but they are not necessarily. For example, during mating, females will make rapid screams, giving the impression that they are fighting each other. There will also be a soft ticking, howling, gentle buzzing and grunting sound between the mother koala and the little koala, while the mild purring sounds dissatisfaction with the other. However, when Koala was afraid, she would make a sound like a baby crying, accompanied by trembling and shaking. Koalas also mark trees with the smell of their glands.