The most fundamental reason is that it is much more difficult to evolve a fire than to discharge.
But imagine what evolutionary process it would be if fire-breathing creatures did exist.
Whether it is a protist such as paramecium, or the basic physiological activities of any animal, plant, or fungus, it depends on changes in potential. Even life after the Cnidarian phylum has a nervous system that itself is a conduction system of electrical signals.
In the process of evolution, the work done by electric eels is only to modify the neural circuit slightly, and they have the ability to discharge externally.
In the body of the electric eel, the generator connected by neurons is specialized from muscle cells and has the same sodium and potassium ion channels as neurons.
These generators are tightly arranged and then insulated with fat, which is equivalent to a small battery.
Such a small battery, there are about thousands of electric eels on each side of the body.
In general, the longer the body of an electric eel, the stronger its ability to generate electricity.
Some of the freshwater eels with the strongest power generation capacity can generate up to 800V.
Even electrocute crocodiles:
The principle of transformation from the nervous system to such a "biological battery" as an electric eel is not complicated.
There are actually many fish that can be discharged, in addition to electric eels, there are electric rays, electric catfish, electric catfish, etc., higher than fish and Amazon electric snakes.
However, the electricity environment of these organisms is all water environment.
In other words, some organisms in the aquatic environment have just the right survival pressure to evolve discharge ability.
Organisms that are mainly active on land, the advantage of electricity will be greatly weakened, needless to say, will not evolve the discharge ability, and even if the original discharge ability, may gradually "degenerate" in the long-term evolution.
The evolution of organisms is not what "skills" are the strongest, what they "evolve", but what organisms evolve into "skills" suitable for survival, so that they will not be eliminated and can continue to reproduce.
For example, all kinds of blind fish and shrimp living in caves have gradually degraded in the long-term evolution process because they do not use their eyes, but they are a burden that consumes energy.
The same is true for discharge, if the benefits brought by the discharge of terrestrial organisms are far lower than the cost of discharge, then this discharge "skill" cannot be "evolved" at all.
Next, let's explore what kind of evolutionary process it would be if animals really breathed fire.
First of all, aquatic animals do not have the conditions to really breathe fire, so I will not say much here.
The dark geranium bream that seems to breathe fire spews out only luminous mesomorphs.
So, there is a little possibility that fire-breathing animals can evolve, basically only terrestrial animals.
According to the physiological characteristics of all terrestrial animals, arthropods and vertebrates are the most likely.
Burning materials can be divided into gases, liquids, and solids.
When the flame burns, to minimize the damage to the body or even cause no damage, then the combustion must be ejected.
Solids usually need to be powdered to be suitable for spraying, and for living organisms, the production cost will be much higher than that of gases and liquids, so pass it first.
- Let's start with the spray liquid.
Many insects can fart, but in fact, those farts are not gas, but mainly liquid.
Let's take the artillery armor as an example:
Their injection device has three main structures:
They are used for storage, combustion, and spraying of liquids.
When the projectile armor is threatened, it mixes hydrogen peroxide and hydroquinone stored in the body, and through the catalyst to generate benzoquinone solutions up to 100°C, which are sprayed out at the same time.
Through the high temperature and high corrosiveness of benzoquinone, the artillery armor has achieved a survival advantage in its own habitat species.
So, in another plane, is there a creature similar to the cannon armor, but evolved the ability to breathe fire?
In principle, this is possible.
The ignition point of benzoquinone is 560 °C, and the flash point is as low as 38~93 °C, which is a typical flammable and explosive substance.
As long as you need to make the projectile armor of this plane and evolve the ignition device, you can achieve the Spitfire skill.
And by discharging for a short time, a very high temperature can be generated.
Therefore, it is only necessary to evolve another discharger at the same time to ignite.
The level is according to the spraying posture of the cannon armor, and if it really breathes fire, it is easy to play with fire and set itself on fire. And if the concentration of benzoquinone injected is in the range of 1.7~13.5%, an explosion will occur.
Therefore, the spraying posture of the cannon armor still needs to be adjusted.
However, compared to the cannon armor, which also needs to evolve the ignition device and optimize the jet device, the adjustment of posture is a small case.
In general, it is possible for the Spitfire Rifle Armor of another plane to evolve, but only if the Gungun Infantry of that plane reproduces particularly successfully, the internal competitive pressure is unprecedentedly high, and the difficulty of entering the hell level must be upgraded from the jet to survive, so there is a possibility of evolving into the Spitfire form.
In general, there is a certain possibility of evolving a truly fire-breathing insect, but the probability is extremely low.
Let's look at vertebrates.
Vertebrate poison is basically a protein component, so it is almost impossible to eject liquid flammables.
The main thing that can be relied on is gas.
For example, farts.
Farts contain about 30% combustible gas, mainly hydrogen, and the rest is mainly methane.
Next, let's assume that in another plane, there is a vertebrate that is evolving into a fire-breathing beast.
Since this fire-breathing beast is too dragon Aotian, we might as well name it Aotian Beast.
The Aotianbeast lives near the water, has the habit of fishing in the water, and has specialized discharge muscles similar to electric eels.
Later, because the climate became arid, the swamp turned into a grassland, and some of the Aotian beasts evolved into herbivores.
In order to digest plants, their intestines are inhabited by a large number of commensal bacteria, which produce a large number of farts every day.
Due to the discharge habit of courtship, although the firing ability of other muscles in the body of the Aotian Beast has deteriorated, the discharge device in the mouth is still retained, and it has even been strengthened by male competition.
Because of an accidental mutation, an individual's fart can overflow from the mouth and accidentally spew flames during the courtship performance. Although it burns itself at first, after a long period of training, it eventually masters the technique of flame courtship.
Due to its unprecedented courtship performance, it became the most popular male of this female, and it was able to produce more offspring.
After the N generation, the proportion of fire-breathing beasts in the Aotian Beast population is getting higher and higher.
The Aurora Beast is becoming more and more successful and developing more and more prosperously.
One day, the climate changed again, and some of the Aotian beasts were forced to change from plant-fed to omnivorous.
At first, they preyed on small animals such as insects through flames, and with a slight advantage, they survived.
Over time, their fire-breathing abilities have gradually increased, and they have begun to hunt some larger animals such as rodents.
After tens of millions of years of evolution, their fire breathing system has been gradually optimized, and even part of the intestine is specially used to make combustible gas, and a special sac has evolved in the throat to compress and store combustible gas, greatly improving the efficiency of fire and the energy of the flame.
In this way, the Aotian Beast became the most successful species in this plane, standing at the top of the food chain.
In short, purely from the logic of evolution, it is possible for vertebrates that breathe fire to "evolve".
It's just that the probability is extremely low and requires various harsh qualifications.
But just as the birth of life itself is an extremely low probability, there is no guarantee that there really are no fire-breathing creatures in the universe.
But in any case, for Earth creatures, discharging is always much easier than breathing fire.