Giant worm

Giant worm

Well do you know caterpillars? Sometimes you see a cute little insect with many legs ... (Of course, many may not find it cute). Suppose one day you are sitting in a chair on the lawn of your house drinking tea, when you see a caterpillar two meters (six feet) long and half a meter (one and a half feet) wide coming towards you ...

What, scared? And if I say this kind of caterpillar was real? Not only that, almost all the insects we know were once three or four times bigger. This time you must be surprised. Let's know a little detail.

This monster-shaped insect existed on Earth in the Pennsylvanian period 310 million years ago. Not only that, at that time almost all the animals of the Arthropoda period were several times bigger than our present age. A grasshopper was about the size of a hawk!

So why were the insects so huge then? And why or later they became so small?

The answer to both questions is basically the same ... that is because of oxygen! In the Mississippian and Pennsylvanian eras, the amount of oxygen in the Earth's atmosphere was much higher (at that time the oxygen in the atmosphere was 35 percent. Now the oxygen in the atmosphere is 21 percent). First of all, why was the level of oxygen so high at that time?

This is because at that time there was an abundance of forests. Forests began to form on Earth during the Devonian period (400 million years ago), and during the Pennsylvanian period, ferns appeared, lands were covered almost entirely by forests, and algae were abundant in the oceans. On the other hand, the number of animals was very low. As a result, the plant produced a lot of oxygen. Another reason for the high oxygen content was that some insects and bacteria now decompose dead plants and convert their body carbon into carbon-dioxide to maintain the balance of oxygen and carbon dioxide. But these bacteria and insects have not yet arrived in that era. As a result, the amount of oxygen gradually increased. Dead plants accumulated directly in nature as carbon and at one time collapsed to form coal and petroleum mines (hence the Mississippian period and the Pennsylvanian period together are called the Carboniferous era).

Now, what is the relationship between the shape of insects and more oxygen? To understand this, we need to look at how insects breathe. Insects have no lungs. As a result, if our body needs more oxygen, we can increase the amount of oxygen absorption in our body by breathing fast, or if there is an excess of oxygen, we can balance the oxygen in the body by breathing slowly, but they cannot do that. Insects basically have many spiral holes on both sides of the body, these holes are connected to a duct called trachea, trachea goes a little inside the body and divides into a few ducts called tracheol, these tracheols are filled with tissue juice. As a result, the air enters through the spiracle and passes through the trachea to the tracheol, then the gas is exchanged in a diffuse manner. Oxygen then reaches each cell through the tissues of the tracheol (details can be found in the Zoology class XI-XII book).

It should be noted here that insects have no means of 'pulling' air into their bodies, they get as much oxygen as the air normally enters, so they are confined to as many cells in their body as they can keep alive with that amount of oxygen. So now that the amount of oxygen in the environment is less, less oxygen enters their body, so the number of cells in their body is also comparatively less. And during the Pennsylvanian period, there was more oxygen in the atmosphere, so the number of cells in the body of insects was higher, so they were relatively large in size.

Now, if this is true, then if we keep an insect in an artificial environment and increase the oxygen level there, will the size of the insect also increase?

The answer is yes. Some researchers in the state of Arizona found that some arthropod insects were placed in an artificial biomass to increase oxygen levels, and that the insects were actually growing larger than normal.

However, scientists in Michigan State say a little differently. The spiral hole that insects use to breathe can be blocked by adult insects if they wish. As a result, if more oxygen is lost in the body, the saturation of oxygen in the body can be reduced by keeping the spiracle closed. But insect larvae do not have valves to keep the spiracle closed. So even if more oxygen is left in their body, they do not have the control system in their body. Therefore, according to Michigan State scientists, in the Pennsylvanian era, insect larvae that had smaller larvae needed less oxygen and had more oxygen saturation in their bodies due to more oxygen in the environment, or died due to more oxygen saturation problems. But as the larvae that grew as a result of mutations had more cells in their bodies, the oxygen they absorbed would spread to more and more cells and become balanced. As a result, larger larvae benefited, and larger larvae survived the evolutionary process. In this way the larvae of the insects continue to grow, and from the larger larvae larger insects begin to form. This is why the size of the insects gradually got bigger.

Let's come, how did these big insects become extinct?

Of course, the oxygen level in the atmosphere is also responsible here. By the end of the Permian Period (the next phase of the Pennsylvanian Period, 265 million years ago), the level of oxygen in the atmosphere decreases dramatically. At that time the level of oxygen came to 18 percent.

Scientists do not yet know the reason for the sudden decrease in oxygen in this age. At the same time, bacteria capable of digesting dead plants arrive, and their decomposition further reduces oxygen levels. As a result, it became increasingly difficult for giant insects to survive. Not only giant insects, but also a large number of organisms became extinct due to the depletion of this oxygen level, during which time about 98% of the world's marine species and 80% of terrestrial vertebrates became extinct. This extinction event is called the Permian-Triassic Extinction Event and is the most destructive extinction event in the history of the world. This phenomenon is largely responsible for the extinction of arthropods, hence the name extinction of Insects.

This time the arthropods are evolving in the opposite direction. This means that the larger larvae die and the smaller larvae that mutate survive. As a result, the size of the insects gradually became smaller and the larger ones became extinct.

Many scientists, however, think that although most of the giant insects are extinct at this time, not all of them have been washed away. It took more time for these insects to become extinct. So scientists attribute another reason for the eventual extinction of insects, the advent of modern birds.

Archeopteryx appeared about 150 million years ago at the end of the Jurassic period. Archeopteryx evolved from reptiles and is the ancestor of modern birds. Modern birds emerged from Archeopteryx. Birds were better than insects in all respects. As a result, these insects could not compete with the birds.

Birds compete with insects in two ways.

In some cases, birds catch and eat large insects directly. On the other hand, some carnivorous large insects ate small insects. But the birds also ate small insects, so they could not compete with the birds. And as a result of the previous extinction, their number had already decreased a lot, so they all became extinct.

No one has suffered more than arthropods to survive on this earth. Once from small to big, again from big to small. What a situation!

Of course, they also got the fruits of their labor, now the biggest phase of the animal kingdom is Arthropoda. Three-quarters of the world's animals belong to the arthropod episode.