Author: Huang Jie
<h1 style="text-align: center;" > the evolutionary history of precambrian organisms and the rise of mollusks</h1>
After its birth, microorganisms survived tenaciously in the extreme environment of the early Earth for a long time, until 500 million to 600 million years ago, the most primitive algae and animals appeared in the pristine oceans. At that time, the land was still a dead and silent scene, there was no sign of life at all, there were no large green trees, there were no flocks or solitary animals, not even the simplest grass of life, and there was desolate land and steep rocky cliffs everywhere.
In the primitive period of the ocean 600 million years ago, also known as the "Precambrian", in addition to the small to almost invisible seaweed green plants floating in the seawater, there were many low-level animals in the whole sea, but the ocean in the primitive period was dominated by a mollusk named · Trilobite". The appearance of this creature is very similar to today's shrimp, when the "trilobite" was one of the most adaptable creatures to the harsh environment of the earth, and the "trilobite" ruled the earth for hundreds of millions of years, but they still could not escape the judgment of fate, and thus became extinct on a large scale.
Illustration: "Trilobite"
However, in the process of life trial, some lucky "trilobites" escaped this fate and evolved into a water scorpion that can capture other aquatic animals. The Ability to Adapt to the Environment is known as the Trilobite Phase, but the Obalbin Sea Scorpion, like the Trilobite, is unable to adapt to the environment and is eliminated by nature.
Illustration: "Obabin Sea Scorpion"
<h1 style="text-align: center;" > new species of vertebrates</h1>
After the "Obabin Sea Scorpion" and "Trilobite" were eliminated by nature, new species sprouted in the mud of freshwater streams, this animal's body is small and flat, extremely slow, but the ability to adapt to the environment is very strong, they are the most primitive vertebrates on the earth, this vertebrate is covered with thick scales, the front part of the body grows flaky bones, and develops a symbol of wisdom • brain, this animal is called "unicorn fish", but "unicorn fish" is not really "fish".
Illustration: Schematic diagram of the evolution of the membranous jaw in vertebrates
After 75 million years of evolution, one of the unicorns evolved into a real fish." Long-snout unicorn", at this time the "long-snout unicorn" has a backbone and support the bones of the whole body muscles, a powerful jaw and a mouth that can open and close freely, the fish has fins on the body, the tail can swing back and forth in the water, the volume is many times larger than 75 million years ago, the body shape has developed into a streamlined type that plays a better role in the flow of water, these new features help the "long-snout unicorn" to freely travel in the water and resist the attacks of other predators.
"Long-snouted unicorns" continue to multiply and evolve, their offspring traces can be seen everywhere in fresh water, until some of their descendants migrated to the ocean in groups and groups, and settled in the ocean for a long time, this period is the peak of fish development, they are very diverse, the appearance is also strange, every water on the earth is the range of fish activities, for the next 50 million years, paleontologists call this time period - the century of fish.
Illustration: "Long-snouted unicorn"
<h1 style="text-align: center;" > species of new era gills and lungs</h1>
During the century of fish, two extremely important species lived:
First: the shark and its close relatives.
The biggest difference between this fish and other bony fish is that the body skeleton is cartilage, and the bones are very soft.
The second type: fish with lungs.
Fish that breathe with their lungs, their bones are very hard.
Cartilaginous fish are compared to bony fish, the latter accounting for a large proportion, and the total fin fish belongs to the latter type. The lungs, an organ, can absorb oxygen from the air, and droughts often occur in the fish world, and when drought occurs, thousands of fish that breathe with gills will die due to lack of oxygen, so that fish without long lungs will gradually be eliminated by nature again, and fish with long lungs can breathe fresh air without water, and are fortunate to survive.
Illustration: Lungfish in ancient times
The harsh life quietly left in a few short years, the earth's climate changed again, the arid earth was moistened, the oxygen dissolved in the water was back to a rich state, enough to supply the fish that relied on the gills to breathe, so the role and function of the fish lung gradually deteriorated, and some of the fish evolved the lung into a fish sac that could store air, that is, the fish fat, at the end of the fish domination of the world, the land had become a green forest dominated by a large area of sheeptooth plants. Some of the plants in the forest have grown to more than ten meters high, and these plants have become the necessary food for vertebrate life.
About 365 million years ago, the total fin fish with lungs began to migrate from the water to the land, gradually surviving on land, and the skeleton of the total fin fish at this time was very similar to the skeleton of the amphibian frog. The chest and abdomen still retain "fins". The total fin fish with lungs gradually evolved into terrestrial animals because of their ability to live on land.
Primitive amphibians originally evolved from the total fin fish, but primitive amphibians lived very unfamiliar land, and these ancient amphibians gradually became extinct over tens of millions of years of hardship. Today, only small frogs, toads, salamanders and other amphibians live in temperate areas.
Illustration: Living fossil and coelacanth in the ocean (still exists)
< h1 style="text-align: center;" > primitive reptile</h1>
Resilient primitive reptiles were born from reptiles, and the surface of the eggs born of this species was protected by a hard shell, which was characterized by the ability to hatch directly on land instead of laying eggs in the water. The limb structure of the reptile plays a key role in supporting the weight of the body, and the movement of the pectoral muscles and ribs helps the reptile breathe more effectively, while also having a significant effect on the blood circulation system.
Because of these advantages, reptiles became a new ruler on land, ushering in the era of reptiles, which were divided into many species. Dinosaurs are the most prominent of these.
<h1 style="text-align: center;" > reptile evolution and mammals</h1>
About 70 million years ago, the Earth's environment changed dramatically again, and the dinosaurs that once dominated the Earth could not escape the fate of extinction, and only some of these small reptiles survived and evolved into today's snakes, lizards and birds. Small dinosaurs also evolved into birds, and small animals that originally evolved from reptiles became very common, and small animals were almost as large as modern mice, compared to their ancestors 70 million years ago.
First: The blood is warm.
Second: Covered in hair.
The blood of many vertebrates cannot be maintained at a certain temperature, and if the temperature of the surrounding environment changes, their blood temperature will also change, and these long-haired warm-blooded animals are thermostatic animals. After the extinction of the dinosaurs, thermostatic animals made great progress and eventually became the oldest mammals. For a long time afterwards, more advanced mammals appeared on Earth, one of which gradually dominated the New World and they were primates.
<h1 style="text-align: center;" > recommended reading</h1>
The essence of "quantum mechanics", an article allows you to easily understand what "quantum mechanics" is
Proxima Centauri's Oort cloud creates stellar-level tidal forces that affect the Solar System
Maybe the solar system will become a "multi-planetary joint life system"
#Rumor Zero Plan ##周末开大课 #