Why are stingrays stingrays? Detailed answer

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Why are stingrays stingrays? Detailed answer

Big encyclopedia for children and adults

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Why are stingrays stingrays?

Stingrays are cartilaginous fish. They have a flat body with wide fin-wings on the sides. They also have a long thin tail. Some stingrays have a venomous spike on their tails, and they are called stingrays. Stingrays never use this spike for offense, only for defense. But that doesn't make them any less dangerous.

Stingrays have many interesting features. For example, their mouth is on the underside of their body and they never see what they are eating. Female stingrays carry their eggs inside their body and give birth to small stingrays - this is called ovoviviparity.

The top of the body of the stingrays is dark, and the bottom is light. Guess why. To do this, imagine that you are looking at a stingray from under the water, from the bottom, and you see it against the background of a light sky, and then from above, and then it is already visible against the background of a dark bottom.

Author: Cellarius E.Yu.

Random interesting fact from the Great Encyclopedia:

Are the modern Olympics similar to the ancient Olympics?

Although the modern Olympic Games are modeled after the Games of ancient Greece, there are many significant differences. As in ancient times, the Games are held every four years. In those days, wars stopped so that the Games could take place, but in 1916, 1940 and 1944 the Olympics were not held, due to World Wars I and II. In ancient times, the Olympic Games were always held in Greece, in the mountains of Olympia. Each modern Olympics is held in various major cities around the world.

Previously, the games were only open to Greek citizens and athletes from Mediterranean countries. Athletes of all nations are invited to the modern Games. Another big difference is that the women's competition has become an important part of the modern Games. The female winners receive the same honors as the male winners. The ancient Games had awards for cultural achievement, while modern competitions are purely athletic.

Many of the competitions held at the modern Olympics were previously unknown. These include: cycling, yacht and canoe racing, football, basketball, judo, rifle shooting and water polo. One of the most popular events of the modern Olympics is the marathon. This grueling forty-two-kilometer run is the ultimate test of endurance for runners. The marathon was not included in the competition program of the ancient Olympics, despite the fact that it originated in Greece.

And finally, a relatively recent innovation in the history of the Olympics is the Winter Olympics, which were first held in 1924. They are held separately from the summer ones, but in the same year. The Winter Olympics include competitions in skiing, speed skating, figure skating, ice hockey, luge, bobsleigh, and biathlon. Such sports, which require cold weather, could never have appeared in the warm climate of Greece.

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Random news from the Archive

Childhood for testosterone 10.07.2018

Testosterone for men is, without exaggeration, one of the key hormones: puberty and the ability to have children depend on it, it also largely determines the behavior and appearance of a man (testosterone, for example, affects the development of bones and muscles, and therefore growth and body weight) .

In different people, its level can differ markedly, although remaining within the normal range. What affects testosterone levels? From genes, from lifestyle, from nutrition and from other factors.

Among these other factors, researchers from Durham University, Northwestern University and the University of Chittagong highlight childhood in particular - testosterone levels in an adult male are very dependent on the conditions in which he grew up.

Kesson Magid and colleagues compared the hormone levels of men with different biographies living in Bangladesh and the UK: some grew up in Bangladesh and stayed there; others moved to the UK as children; still others moved to the UK as adults; the fourth were born in Britain, but their parents were from Bangladesh; finally, in the fifth group there were men living in Britain and whose ancestors were Europeans.

All testosterone levels were within normal limits. However, for example, those who grew up in the UK (regardless of who their parents were and where they were born, here or in Bangladesh), the level of the hormone was about the same. Moreover, these men were about the same height, and they also began puberty at about the same age. And in general, they had more testosterone than those who grew up in Bangladesh. In turn, those who grew up in Bangladesh not only had less testosterone, they were also shorter on average and had a later onset of puberty.

Doctors have long been saying that childhood greatly affects testosterone levels, and this influence lasts almost a lifetime. For example, infertility in men can develop due to problems with testosterone, and infertility has been known to occur due to childhood mumps.

But the speech in this case is not only about childhood diseases - although they, it is worth repeating once again, quite strongly affect the level of testosterone. Obviously, children in different parts of the world eat differently and generally lead different lifestyles, which probably cannot but affect the development of the hormonal system.

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