Why were most prehistoric plants and animals much larger than modern ones?

High oxygen levels In prehistoric times, the oxygen content of the atmosphere reached more than 30% (Carboniferous), which is much higher than the oxygen content in the air today (21%), so the individual animals were larger than they are now. The reason why the oxygen content is so high is that there were many plants and few animals at that time, and there were giant dragonflies, giant centipedes, etc. in the Carboniferous period, and some of the arthorax genera were even 3 meters long. Gravity used to be smaller and farther from the sun.

At that time, the earth was less gravitationally attracted by the sun, the material structure was loosely dense, and the gravitational force of the bones of animals was relatively small, so they could be larger. Temperature In many prehistoric periods, temperatures were lower than they are today, and it took a large individual to preserve body temperature. Food In ancient times, because the biological food chain was not yet perfect, and the climatic conditions were better than now, there would be a certain type of species that were particularly abundant, so that for the animals that fed on them, on the one hand, there was abundant food**, and on the other hand, there was no natural predator trouble, and their size would become very large.

Dinosaurs are a prime example of this. Evolution is small, so you don't need much food. In addition, due to species extinction, ice ages, etc., the food chain was disrupted, and most of the large animals became extinct.

In order to adapt to changes in the environment, large animals can only slowly evolve to adapt to the environment. In the case of insects, it is because there is a period of high oxygen content in the atmosphere, and during that time, plants have just evolved lignin, which grows tall and violent, and fungi have not evolved the ability to degrade and quality, causing carbon dioxide to be fixed by plant photosynthesis and release oxygen, and there is no decomposer to release the carbon fixed as lignin back into the atmosphere (the carbon sink is greater than the carbon source). As a result, the concentration of oxygen in the atmosphere rises, and insects grow larger.

At the same time, plants that cannot be degraded form a large amount of mineral energy, hence the name of the Carboniferous. Later, fungi evolved to degrade lignin (about 200,000 years?). The numbers are forgotten), and the world becomes like our current world again.

On the one hand, the ancient environment was different from today, for example, the high oxygen content of the atmosphere could support the growth of larger bodies of animals and plants with low metabolic efficiency, such as insects. On the other hand, after the survival of a species is guaranteed (on a time scale of 100,000 or millions of years), individuals tend to become larger, because larger bodies usually have an advantage in reproductive and survival competitions (in general), so that after reproduction from generation to generation, they are usually larger than their ancestors. However, the consequence of the large-scale body is the deepening of the degree of dependence on the environment, or the degree of adaptation, when the living environment changes dramatically, the ability to adapt will appear low and quickly die.

All mammals in the world today are made up of the same ancestor, the Cretaceous, a small insect-eating animal that looks like a rat. Sixty-five million years ago, at the end of the age of the dinosaurs, these animals had the opportunity to evolve and differentiate into the mammals of the world today. Carnivores appeared about 60 million years ago in the Paleocene.

The oldest carnivore is the little archaic cat, which, although called cats, is the common ancestor of all animals of the family of cats, canines, bears, mustelidae, hyenas, civets, and pinnipeds (a class of seals and sea lions). About 48 million years ago, two groups of cat suborders and canine suborders were divided into small ancient cats. Originating in the late Eocene, about 40 million years ago, the canines were the oldest group of carnivores, first differentiated from the little archaic cats.

The evolution of canines has three main lines, namely the three subfamilies of the canidae: the modern canine subfamily, the ancient canine subfamily, and the borophaginae subfamily (hyena-like canids). <

Because the air at that time had a higher level of oxygen, the way of breathing was different from that of today's animals, and the stress caused by humans to animals, animals became smaller and smaller.

This is because the level of oxygen in the air has decreased, and the evolution of species has been to become smaller and smaller, and human activities have also affected the places where animals live.

This is the case because prehistoric environments are more suitable for large animals to survive, while modern environments are not suitable for large animals.

Probably because of the natural environment, in prehistoric times there was little food, and creatures needed to become very large in order to grab food and survive.

Nowadays, oxygen is scarce, and it is difficult for large organisms to grow, but in prehistoric times, oxygen was abundant and vegetation was abundant, which could give birth to many large animals.

It had to do with the environment, the oxygen concentration was very high, and spiders and dragonflies were the size of a human head, which was terrifying.

Because many organisms adapt to the development of the environment in the process of evolution, they will make themselves smaller and smaller, so that they can protect their lives.

Caused by many factors.

From what I learned from the textbooks, one of the important factors is that the composition of atmospheric gases in geological history was different from the current content. The high oxygen concentration in it will make the animal significantly larger. At the current level of oxygen, it is not possible to maintain the huge size of paleontology.

There are two main reasons:

1.Air humidity, it has been shown that crustaceans of the same species grow larger in places with higher air humidity. The theory can also be deduced, because many lower creatures are still using ** or gills to assist breathing.

In the case of larger leaves or taller leaves, the less humidity in the air, the more difficult it is for the plant to supply water to the upper end of the morphology, and in the hot summer months, the leaves of the plant can be seen curling the leaves furthest from the main trunk first, starting to dry up from the edges.

2.The oxygen concentration, which has basically been explained upstairs, is that large organisms need to consume more oxygen. Just like a theory in mathematics, the ratio of the surface area of a ball to its volume, the smaller the ball, the larger the specific surface area.

Primitive tortoises don't shrink their heads, and paleontologists have found evidence that they looked weird 200 million years ago.

When I talk about ancient times, I am talking about the age of dinosaurs, when the size of animals and plants on the earth was indeed very large, not only dinosaurs, but also many ferns were much taller than now, and even small insects such as mosquitoes and flies were 2 to 3 times larger than today. But it's safe to say that they're not caused by the destruction of mutations by radioactive materials, and I think there are three main reasons why they've grown so big.

At the beginning of the dinosaur era, the animals and plants on the earth began to develop towards large-scale, not only dinosaurs, and radioactive element alteration genes could not change the genes of all species, and geologists did not find radioactive elements in the strata with dinosaur fossils, nor did they find strata with radioactive elements, so there should be little relationship between them.

The first reason is that the climate and ecological environment are good.

At that time, the animals and plants grew very big, the main reason is that the ecological environment of the earth is very good, it can be said that it is much better than now, in the nearly 200 million years from the appearance of the dinosaurs to extinction, the climate on the earth is relatively warm and humid, the plants grow lush and lush, good growth conditions, so that plants can grow very big, and the habitat of animals is much larger than now, because of the abundant food, animals have no risk of nutritional deficiency, so animals can also grow very big.

The second reason is that the oxygen content in the Earth's atmosphere was relatively high at that time.

Scientists believe that the oxygen content in the atmosphere should have exceeded 30% at that time, which is 1 3 more than now, and in the oxygen-rich ecological environment, the bodies of animals and plants grow and develop relatively quickly, so the volume is correspondingly large, especially for small animals such as insects, which are 2 to 3 times the volume of the same species now.

The third reason is that some animals do not have inhibition of growth genes.

This is mainly for large animals, such as dinosaurs, the main reason why they grow so big is because they do not form genes that inhibit the growth of the body, so they grow all their lives, which is why the older the dinosaurs tend to be.

The size of prehistoric animals is huge, which may be related to genes, or the genes of prehistoric animals, as well as genes that can make the body size continue to grow, or the prehistoric environment has a history, and the prehistoric animal size has become larger, but in modern times, in order to adapt to the current environment, the size of animals has been constantly decreasing.

In prehistoric times, the oxygen content on the surface of the earth was relatively high, so the size of living things was relatively large, but now the oxygen content has decreased, and the size of living things has shrunk.

It is because the oxygen content in the earth's atmosphere was very high in prehistoric times, and the high oxygen content led to the fact that organisms had enough energy to evolve greatly.

Scientific exploration: why are prehistoric creatures so big, and now animals can't compare to them at all, it's really a long insight!

There were many giant species in the age of dinosaurs, and even giant dinosaurs such as the fragile dinosaur were close to the size of the blue whale, which is quite remarkable on land, and there have been giant insects in the history of the earth, but they are not very common.

From the perspective of biological evolution, the best is the one that can adapt to the environment, and the diversity of species on the earth has created the difference in the size of the earth's organisms.

Why are animals getting smaller and smaller? According to scientists' research, this is related to the oxygen content in the air, and the oxygen content in the air today is 21%. In ancient times, the vegetation was lush and untouched, and the air contained 20% more oxygen than it does now.

So, at that time, centipedes were one meter long, dragonfly wings were also one meter wide, and dinosaurs could grow up to 25 meters long.

As far as giant dinosaurs are concerned, they live in a long era with a relatively stable environment, and the earth's land and marine plants are quite lush in a long period of time, so that the earth's organisms can produce a lot of organic matter and fix a large amount of sunlight energy, and the prosperity of the earth's organisms makes the creatures not lack food, and the number of species can produce more mutant genes.

At the same time, the weak eat the strong, and the small size means a greater survival risk, and it is easy to become the food of other predators, so natural selection, the size of the animal is getting bigger and bigger.

Later, the living environment of the earth deteriorated dramatically, and the large animals could not find food, and gradually became extinct, leaving only very small or low-level animals and plants, so that the size of the animals changed from large to small.

In recent millions of years, with the rise of apes, the emergence of more intelligent creatures has further crowded out the living space of other large animals, resulting in the extinction of animals such as thylacine and West African lion.

Like the rats in recent years, in order to adapt to today's high-rise buildings and the thin seams of each door, the rats have become smaller from fat to smaller, as small as one or two heavy!

Because the amount of oxygen in the air decreased, the surrounding environment in ancient times was a hyperaerobic environment, and the photosynthesis of plants would cause it to inhale more oxygen, thus evolving into a larger body size. The same is true for animals, where the nitrox environment increases oxygen consumption, making the musculoskeletal muscles bigger and stronger.

Because in ancient times, the oxygen content of the earth was very high, and the high oxygen content would cause plants to grow very large, and animals would evolve to be very large, but then experienced a mass extinction of life 65 million years ago, and only small animals and plants survived.

Because scientists have studied that the air composition of the surface in ancient times is different from that of today's air, the proportion of oxygen in the air in ancient times was the largest, which made ancient animals and plants grow fast and have large individuals, and now the proportion of oxygen is small and small.

When you look at some things like Godzilla and King Kong, have you ever thought about why prehistoric creatures are basically huge! Now the creatures on land are not as big and tall as they used to be?

The first is the difference in temperature!

Take dinosaurs as an example, dinosaurs are cold-blooded animals, and the size of cold-blooded is directly proportional to the temperature at that time, in prehistoric times, scientists have found that the atmosphere at that time was not as thick as it is now, and the sun is stronger than the energy that shines on the earth now, and the temperature is relatively high. At that time, the earth was all tropical rainforests, and food was abundant. You don't have to worry about food at all!

This is followed by a change in oxygen concentration!

In ancient times, the climate was warm and humid, the forest cover was much higher than it is now, the plants were abundant and lush, and the plants were the foundation of the ecosystem, so the oxygen content was also high! Nowadays, animals are generally smaller, which means that the oxygen content is lower.

Adequate oxygen is also necessary for the growth of large organisms, and if the dinosaurs were pulled to this environment, it is estimated that they would have suffocated to death due to low oxygen levels.

At present, the largest creature on the earth is the blue whale, in fact, the oxygen demand of aquatic organisms and terrestrial organisms is different, so some creatures in the sea are represented by blue whales, and their size is still relatively large compared to land organisms! However, the life in the sea has also been reduced from prehistoric times due to temperature and climate change, so the blue whale is the largest animal ever seen on the earth, and it is said that the blue whale can break the elephant's head with a flick of its tail!!

Finally, their own genes are different!

The genes of prehistoric dinosaurs were not as complete as they are now, and the animals of the dinosaur era lacked reproductive genes in their bodies that inhibit cell growth. Many creatures in ancient times did not have this gene, so their size increased uncontrollably, and the current blue whale does not have this gene.

Just like the current crocodiles and dinosaurs belong to the same era, as long as the crocodile does not die, the body cells have been growing, but because of various factors such as temperature, oxygen content, etc., the crocodile is not as big as prehistoric.

In recent centuries, human indiscriminate hunting and killing have also targeted more tall animals, most of the large animals have been subjected to varying degrees of distribution retreat and population decline, and now the speed of animal extinction is comparable to the speed of five prehistoric mass extinctions!