After more than 4 billion years of long nights, 560 million years ago, the earth ushered in a new era - cambrian.
The cryptonic world dominated by microorganisms has since ceased to exist, macroscopic creatures have begun to appear on the stage of life on earth, the all-round radiation of complex organisms has made the oceans bustling, and the earth has completed the leap from the cryptozoic to the Phanerozoic.
When Darwin first saw the Cambrian fossil community, he also doubted himself!
Darwin's theory of evolution holds that all living things have only one common ancestor, and that organisms develop from simple to complex, from single-celled to multicellular. But cambrian creatures seem to have popped up out of nowhere, spewing out in large numbers that evolution cannot explain. Therefore, Darwin once believed that the Cambrian explosion of life was only an illusion of fossil eruptions, not a real biological evolutionary event.
However, in the period of about 560 million to 520 million years, the Earth did experience a magnificent Cambrian explosion of life, which was the beginning of a revolution and a mysterious era of waves and undercurrents, short and beautiful.
In less than 1% of the history of the earth, the earth gave birth to the ancestors of almost all animal phylums today, these creatures evolved rapidly in a short period of time, flourished in the almost barren marine world, and explored the possibilities of various morphological spaces and ecological strategies endlessly, producing a large number of physical configurations and ecological types in a relatively short period of time, turning the pre-cambrian and silent ocean into a lively zoo in an instant, and the animal-led marine ecosystem was formed for the first time.
While the mollusks of the late Ediacaran period were still cruising on the ocean floor, the earth's first overlord, the odd shrimp, quietly ascended to the throne of the top predators. The odd shrimp overtakes in unconventional curves, turning it directly from a centimeter-sized creature into a 1-meter-long giant beast, standing out from many tiny crustaceans or soft-bodied organisms, so that when paleontologists first discovered it, they treated different parts of it as different organisms.
The odd shrimp are 1 meter long and up to 2 meters long, and they have a pair of giant eyes with stalks, a pair of segmented giant forelimbs for rapid prey, and a pair of paddle-like appendages suitable for swimming on both sides, allowing them to travel quickly through the ocean. Their large and strong mouth structure allowed them to prey on any large creature at the time, which was a completely deadly top predator for other creatures that did not even have eyes and swimming ability at that time.
As a result, a large number of animals have evolved hard shells to defend, and trilobites are representatives!
As the most elementary consumer in the Cambrian ocean, trilobites can only inhabit the seabed and nibble on weak plankton. Although trilobites have also evolved the strongest organ, such as the eye, in the face of the giant claws of the odd shrimp, they can only hide in the thick armor, grow spikes on their backs, and evolve different forms of defense structures to steal life. But they are also considered to be the success of evolution, trilobites won in numbers, all over the Cambrian ocean, so that cambrian is also known as the "age of trilobites", until the Permian three hundred million years later diluted the stage of life on earth.
The Cambrian explosion gave birth to many strange creatures, and the explosive increase in species diversity made the ocean stage an imposing drama. This explosion of life was not simply a process of increasing biological species, it led to extensive biomineralization, the increase in the size of animals, the complexity of somatic structure, and the formation of most of the tissues, organs, and systems that make up animals. Over a period of 40 million years, the ancestors of animals had enough time to evolve traits and organs such as eyes, appendages, tentacles, muscles, intestines, blood vessels, gills, and mineralized bones, forming powerful digestive, circulatory and nervous systems, and diversifying and complexing morphology and ecology.
The Cambrian explosion of life is the only major explosion of animal phyla in the history of the earth, laying the foundation for the evolution of marine ecosystems since the Ezoozoic, but what is the reason for the "Cambrian explosion of life"? To this day, I'm afraid it's hard for scientists to say it clearly! You can only peek into what happened in that distant era through the signs that remain in the formation.
The dissolution of the Rhodinia supercontinent 600 million years ago may have contributed to the birth of the Precambrian Ediacaran biota. Similarly, 540 million years ago, the pannosian supercontinent in the southern hemisphere of the Earth disintegrated, splitting into the continent of Gondwana and three smaller continents: Lauren, The Baltic and Siberian.
A large number of cleavage events led to the extremely long coastline of the Earth at that time, and at the same time, the cleavage event was accompanied by a large number of volcanic eruptions, the temperature of the Earth further increased, the glaciers of the Snowball Earth era completely disappeared, and the earth's sea level rose, resulting in the expansion of the distribution area of the shallow sea and the recovery of the fungal algae mat. The growth of fungal mats has formed a stable structure on the surface of the seabed, providing a habitat base for entrenching benthic organisms and providing a hotbed for biological outbreaks.
Secondly, due to the end of the snowball earth, the retreat of glaciers, and the removal of a large amount of material from the earth's crust to the ocean, including important elements such as calcium, potassium, and phosphorus that make up life, fundamentally changed the chemical composition of the ocean, the concentration of phosphate in the seawater increased sharply, and the marine sediment also changed from dolomite to calcareous, providing the calcium ions needed for biological evolution, these new components help to promote biomineralization, providing life with the chemicals needed to produce shells and bones.
Therefore, the vast shallow seas, suitable temperatures, and rich nutrients provide sufficient environmental conditions and material basis for the outbreak of biodiversity, allowing top predators such as odd shrimp to climb to the position of hegemony.
According to the "harvest theory" proposed by American ecologist Steven, ecosystem complexity is also the basis for generating species diversity, and the emergence of large predators avoids the situation that one or a few organisms have an absolute advantage in the ecosystem, making room for the formation of other species.
For billions of years before the Cambrian, primary producers of marine ecosystems were mainly prokaryotic cyanobacteria, which were ecologically monoculture and homogeneous in their trophic grades. Because the living space on Earth is stubbornly occupied by small but large biological communities, the rate of biological evolution is very slow. The emergence of predators such as odd shrimp has changed the original ecosystem structure, created a living space for other organisms, and enhanced the biodiversity of the ecosystem.
As a result, the trophic pyramid of the Cambrian began to develop rapidly in two directions: lower-level producers added more new species, enriching species diversity, while new predators were added at the top, enriching the trophic-level diversity, thus gradually enriching the biomes of the entire ecosystem, and possibly promoting the Cambrian explosion of life.
The Cambrian explosion of life is the inevitable process of the evolution of life on earth, a natural process that occurs under the conditions of many factors checking and balancing, requiring many, different sizes and scales, internal and external necessary conditions, small to elements and molecules, large to the habitable earth. No matter which of the necessary conditions is not met, the Cambrian explosion will not occur.
However, just over 50 million years after the explosion of life, the earth ushered in the first great purge in geological history - the ordovician mass extinction, about 49% of the genus on the earth disappeared in this event, the pioneers of those lives disappeared on the journey of life evolution, and the vigorous Cambrian explosion was temporarily over.
Everything will be covered in dust, and everything will be rebuilt on top of the wasteland. Although the Cambrian explosion ended in extinction, the seeds of life are still there, the story of evolution continues, and the Ordovician will be a magnificent era!
Video link: One of the top 10 scientific puzzles! Cambrian life exploded, why did life suddenly appear?
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