When it comes to the radiation resistance of animals, many people first think of water bears, but in fact, sponges are the king of radiation resistance among animals.
Sponges are one of the oldest animals. They can live for thousands of years, divide their cells throughout their lives, and lack an immune system, so they should be particularly susceptible to cancer, but they happen to be one of the few animals with no documented cancer (others include ctenophores and filarial worms). Wait).
Recently, researchers conducted an experiment. They exposed the young sponges to X-rays, increasing the dose of radiation. To their surprise, when the dose reached 600 gray (a physical unit for measuring absorbed dose of radiation. 1 gray means 1 joule of radiation energy absorbed per kilogram of matter), they still showed no signs of cell death until Doses up to 800 Gy kill most sponges. In comparison, the lethal dose of X-rays to a person is 8Gy, and we do a chest X-ray in the hospital, which absorbs only about 0.1 milliGy.
However, the researchers noticed that sponges lost their original shape and ability to filter food from water over the next 20 days or so after absorbing 600 gray of X-rays. They then slowly recover and return to normal after about 180 days.
The sponges, which received high-dose X-rays, did not show any signs of tumors. They appear to have very good mechanisms for both preventing DNA damage in the first place and repairing it after it has occurred.
This may have something to do with their aquatic lifestyle and their status as the oldest animals. We know that water dissolves DNA-damaging toxins more easily than air does, and in the early history of the Earth, due to frequent volcanic eruptions, large amounts of volcanic ash fell into the water and were dissolved, so the toxins (such as arsenic) in the water were lower than they are now. Much more. As the earliest animals to live in water, they must first learn to protect themselves. So, sponges have evolved super-resistant DNA damage, which at the same time gives them amazing resistance to radiation.
There are tens of thousands of species of sponges, and scientists are looking for anticancer drugs among them.
There is now a lot of evidence that birds are descendants of dinosaurs, but this is still a bit difficult to accept. Indeed, dinosaurs were the overlords of the land, with scales and mouths full of sharp teeth, and they really did not resemble those heavenly birds with colorful clothes and toothless beaks. How did dinosaurs grow into birds?
Flyable dinosaur skeleton
Dinosaurs have always been made to fly, and although many never left the ground, they still had a basic structural framework for flight.
Before and after dinosaurs, the center of gravity of most quadrupeds was in the thoracic area, and they needed a lot of energy to lift themselves up with their hind limbs, making it difficult for them to stand upright easily. While the center of gravity of dinosaurs is not far from the hips, the relatively short torso before the hips is balanced by a more solid lower body and a long tail, like a labor-saving lever. So using the hips as a fulcrum, the dinosaur could stand on its hind legs without much effort, and even the less robust hind legs could support most of the body’s weight. In this way, dinosaurs can free their forelimbs for other activities, which is a big advantage of dinosaurs over other animals.
After the forelimbs of dinosaurs are idle, they can carry out some activities such as collecting fruits and catching prey. As time goes by, the forelimbs become more and more flexible. The most obvious change is that the originally straight carpal bones gradually transform into rotatable carpal bones. The forelimbs stretched out to scratch the back. Birds have inherited this “half-moon-shaped carpal bone” that bends their forelimbs back to their wrists, allowing them to flap their wings more flexibly and help them fly high.
dinosaur and bird skulls are similar
Birds also inherited many skeletal structures from dinosaurs that aided in flight: oviraptorids and dromaeosaurs had rib-like processes that connect the muscles of the shoulder blades, the well-developed sternum that provided the muscles for birds. The attachment surface is the source of flight power; in the fossil bones of oviraptorosaurs and ornithosaurs, it has been found that they have pygosacral and coccygeal bones formed by the fusion of specific vertebrae, the former will make the back stiff, Aid in flight, the latter in turn provide a scaffold for the growth of tail feathers.
Double breathing comes from dinosaurs
The well-developed and prominent sternum not only facilitates the development of stronger pectoral muscles, but also provides space for a unique respiratory organ, the air sac. With air sacs, birds can use double breathing, an efficient form of breathing, which The method most likely came from dinosaurs.
Scientists have discovered that plain monitor lizards also have multiple air sacs in their lungs, just like birds, and they speculate that this feature may have been common to all archosaurs and their ancestors, including living birds, crocodiles and lizards, as well as extinct dinosaurs. (a skeleton of steppe monitor lizard; bd schematic diagram of air sac; e schematic diagram of gas exchange in air sac).
A UK research team studied the cavities of four modern crocodiles and 29 bird species and compared their structures to those of 16 dinosaur species. After comparing the scans, they found that dinosaur vertebrae were more bird-like than crocodile vertebrae. Many dinosaurs, including Velociraptors and Spinosaurus, had rib-vertebral joints and also had the same vertebrae and ribs as birds. More importantly, people have found evidence of the existence of air sacs in sauropod and theropod dinosaur fossils. In addition to the vertebrae, Aerosaurus also has air sacs on bones such as wishbone, intestinal bone and abdominal rib. Traces show that it has an air bag system very similar to that of a bird.
Organisms without air sacs use the same channel for inhaling and exhaling air, which means it is difficult to fully utilize the oxygen inhaled or completely empty the exhaust during a single breath. With the air bag, it is equivalent to an additional transfer station. The air inhaled into the body will be temporarily stored in the air bag and transported to the lungs in batches until it is fully utilized, and the exhaust gas can also be completely discharged from the body in batches.
In addition to helping gas exchange, the airbag also has an important function of dissipating heat. Dinosaurs have air sacs all over the body, which can absorb heat directly from the internal organs and then take it out of the body through exhalation. The air sacs in the bones are also beneficial for weight loss. The air sacs share part of the weight-bearing task of the bones. The bones can be simplified into a series of hollow structures, and unnecessary excess bones are minimized.
Efficient breathing, efficient heat dissipation and lightweight skeletal structure, all of these characteristics that are conducive to flight, birds have inherited from dinosaurs.
Dinosaurs actually had feathers
Bird feathers are essential to flight, and almost all birds have feathers, and now, more and more discoveries have upended our previous impression of dinosaurs: most dinosaurs actually had feathers.
A few decades ago, people regarded dinosaur feathers as a rare thing. Whenever a dinosaur with feathers was excavated, it would be widely reported, such as Archaeopteryx discovered in 1861 and Sinosauropteryx discovered in 1996. As you can see from the name, people think that these feathered animals are not so much dinosaurs as birds, and people still can’t believe that dinosaurs also had feathers. But now, we know that dinosaur feathers are not a special case, but a common phenomenon. Such as Psittacosaurus, which is a small horned dinosaur, paleontologists have found that its tail grows with filaments like goose feathers; Kurindabensaurus from Russia, which is almost covered by feather-like structures; The large carnivorous dinosaur Featherosaurus had gorgeous feathers; and so on.
These poor flyers are covered in feathers, so it can be speculated that perhaps all dinosaurs had feathers to some extent. At first, dinosaurs used feathers to store heat, which allowed dinosaurs, which were originally ectothermic, to maintain a constant body temperature. Over time, dinosaur feathers branched into new shapes and became more ornate, and they served one more function—socializing and courtship. There are also studies that have found that feathers may have more functions. For example, when running, feathers can help maintain balance and increase running speed; feathers also help in hunting. Dinosaurs with feathers on their arms may be like modern raptors – suppressing small prey At times, it confuses its prey by waving its feathers and increases its grip. Of course, when feathers come to birds, the role becomes more diverse.
“Slimming” success can go to heaven
However, even if dinosaurs have all the above-mentioned characteristics, this group of “fat people” with dozens or hundreds of tons still cannot fly high in the sky, and it is imperative to “slim down”!
In fact, for God’s sake, the crazy degree of dinosaurs’ “slimming” is not inferior to that of beauty-loving humans. In 2014, researchers in Australia, the United Kingdom and Italy and other countries based on more than 1,500 anatomical features of 120 species of dinosaurs, built a complex mathematical model to analyze the changes in the size of dinosaurs during the evolution process. The results of the analysis show that one of the theropod dinosaurs, their body size shrank from generation to generation, and finally evolved into a bird after 50 million years of “slimming” – 210 million years ago, its average weight was 163 kilograms. It has been reduced to 0.8 kg when it evolved to Archaeopteryx.
How did theropod dinosaurs succeed in “slimming”? Researchers have found that in theropod dinosaurs, a wonderful evolutionary process occurred – the continuation of the juvenile state. Juvenile continuation refers to the phenomenon that a species retains juvenile, even fetal characteristics, into later juvenile or even adulthood. For example, human newborns have sparse body hair, large heads, and strong brain learning ability. After reaching adulthood, these characteristics are still retained, which is a phenomenon of juvenile continuation. The study found that theropod dinosaurs also experienced juvenile continuation. After they were born, from infancy to adulthood, their body size did not grow much, and some parts even shrunk. During the growth process, the faces and bones of the theropod dinosaurs shrank and became smaller, and the leg bones continued to become slender, but the eyes and brains continued to develop. It is through this process that theropod dinosaurs retained their small body size in childhood, thus successfully losing weight and creating an evolutionary miracle.
The bodies of some dinosaurs gradually became smaller and became more and more bird-like: the bones were hollow and the body was light; the forelimbs were more flexible and could flap like bird wings; air sacs were all over the body, which was good for both breathing and heat dissipation; the body surface Grow beautiful feathers and no longer wear scales or scales. To better hide themselves, the covered-feathered dinosaurs would hide themselves in trees. These arboreal dinosaurs jumped and landed between trees, and over time, the dinosaurs learned how to use their feathered wings to stay in the air for longer — thus becoming birds.
Dinosaurs and their immediate relatives spent millions of years preparing for flight: minimalist skeletal structures, edgy airbag structures, stylish feathers, and insane thinning speeds, all of which eventually led to today’s soaring Birds of the sky.
