Is the whale the only marine mammal? Detailed answer

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Is the whale the only marine mammal? Detailed answer

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Is the whale the only marine mammal?

A mammal is a warm-blooded animal, viviparous, feeding its young with milk. Oddly enough, among the inhabitants of the sea there are also several mammals. Zoologists call this group cetaceans. These include whales, dolphins and sperm whales.

By studying their skeletons and other body parts, we can tell that their predecessors once lived on land. When they began to live in the water, their body shape gradually began to resemble the body shape of a fish, as they had to lead the same way of life. The fur that once covered their bodies is gone and their skin is smooth. Instead of gradually disappearing hind legs, powerful flat tails appeared in cetaceans. The forelimbs became fins.

For breathing, fish have gills, and whales have lungs, and they breathe air. Therefore, they need to float to the surface every half an hour to breathe air. At the moment when they emerge from under the water, the trapped air escapes from their lungs. It exits through the nostrils at the top of the nose, not through the mouth. Whales can swim with their mouths open because their nostrils are directly connected to the windpipe.

Therefore, they do not choke when water enters their mouths. We all know that dinosaurs were huge creatures, but even the largest dinosaurs were smaller than some types of whales. So, the yellow-bellied minke whale is probably the largest of all animals that have ever existed on Earth. Some of them reach 30 meters in length, while the length of the largest dinosaur did not exceed 24 meters. The average weight of these giants is 68 tons.

A newborn whale is larger than an adult elephant! During the first year of life, while he is with his mother, he reaches 18 meters in length.

Author: Likum A.

Random interesting fact from the Great Encyclopedia:

How does silkworm spin silk?

Thousands of years ago, the Chinese learned the secret of making silk clothes from a beautiful linen spun by a special caterpillar in the manufacture of a cocoon. This secret was kept in the strictest confidence, and if someone exported a silkworm or its eggs from China, then he was sentenced to death.

Now, of course, silkworms are common not only in China, but also in Japan, India, France, Spain, Italy and many other countries. The best silk is produced by a caterpillar of a small greyish-white moth that feeds on white mulberry leaves.

In early summer, each female lays 500 or more eggs. They are perfectly preserved on a piece of paper or clothing until the next spring, when the mulberry leaves begin to bloom again. Tiny black worms emerge from the eggs placed in the incubator. They are placed on a tray with plucked mulberry leaves, and they constantly feed on them for six weeks.

When the worms begin to barely turn their heads, this indicates that they are ready to weave their cocoon. They put small branches on a tray. Worms twine themselves with an almost invisible thread that extends from a small opening in their jaws. The cocoon, which consists of 460-1100 meters of thread, is finally ready in about 72 hours.

Inside the cocoon is a shriveled caterpillar, which turns into a moth after 12 days. The cocoons are placed in troughs with warm water, which dissolves the silk glue that holds all the threads in a certain shape.

Threads from several cocoons are connected together into one thread, which is wound into a spool. Then comes the next stage - twisting raw silk into yarn. This thread, consisting of 10-12 fibers of individual cocoons, is called a single silk thread.

When we buy things made of silk, they are marked with what kind of thread they are made of - double or triple. In our time, nylon has become so popular and cheap that it has begun to replace silk. But still, silk will always be valued for its beauty, good quality and softness.

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Mining uranium from sea water 23.09.2012

At a recent meeting of the American Chemical Society in Philadelphia, a group of American scientists presented an original project to extract uranium from sea water. The scientists presented their calculations for mining uranium using a plastic adsorbent that can only capture 2 grams of uranium per kilogram of plastic.

Fossil and relatively easily accessible reserves of uranium on our planet are rapidly depleted. Therefore, scientists turned their attention to the oceans, which contain a huge amount of valuable material - 4,5 billion metric tons. However, this uranium is found in very low concentrations in sea water - 3,3 parts per billion. Therefore, the attractive idea of extracting uranium from sea water was just a beautiful theory for decades. Fortunately, modern technologies and materials for the first time can make this idea a commercially viable project.

The extraction of uranium using such material will look like this: an adsorbent is applied to the polymer substrate, after which the substrate is woven into a 60-meter "braid", which is taken out to the ocean by boat. "Spits" are attached to the bottom of the ocean, constructing a forest of artificial algae. After about 60 days, the boat returns, collects the adsorbent and takes it to the shore, where the uranium is eluted by traditional methods.

The adsorbent can be reused up to 6 times with a 5% drop in material efficiency with each reuse. These parameters have already been achieved by Japanese researchers and are real. In the future, the adsorbent can be used twice as many times, as well as reduce its cost. For example, dimethylformamide, which is used to wash polymers before being reshipped to the ocean, today accounts for 10% of the total cost of the entire offshore uranium mining system. So the prospects for reducing the cost of the process are great.

But even with today's advances, subsea mining can produce uranium at a cost of $1230 per kilogram—about 10 times more than conventional mining methods. So far this seems too high a price, but the cost of uranium is growing every year. At the same time, in the future, the cost of "marine" uranium can be reduced to $ 300. However, it should be borne in mind that millions of tons of plastic per year will need to be used to extract 5500 kilograms of uranium during the year.

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