- Sep 26, 2017
- Dec 27, 2018
- Oct 24, 2018
actively thanks to emergence of very informative research techniques of isotope geochronology.
The Precambrian period is the greatest piece of geological history of the planet Earth. Its duration — about 4 billion years. The period was marked by emergence of life — at first vegetable, and then and animal organisms.
The Cambrian is characterized by blossoming of diverse arthropods and cancroid types. Studying of sedimentary rocks of this era more informatively as in them mineral skeletons of the organisms inhabiting the planet remained.
Scientists have the data confirming that they on Earth already lived in this period both monocelled, and metaphytes.
The analysis of the sedimentary rocks which are dated this period showed that, except blue-green seaweed , the planet during a Precambrian era was inhabited:
About 540 million years ago on Earth there were organisms having the body framework consisting of mineral salts.
This period of time was marked by emergence of a large number of arthropods and cancroid organisms; then there were also cephalopod mollusks, rifostroyashchy organisms, coral polyps.
Generally animals of that time lived in reservoirs. However are available data that at this particular time the first soil invertebrate types appeared:
The Cambrian Period was marked by so-called cambrian explosion — emergence of a large number of various types and formation in them of the new structures leading to further progress (a chord, a skeleton, an organ of vision).
Bright feature of a cambrian era is emergence in animal chords — primitive structure which for millions of years will gradually turn into a backbone.
The most characteristic representatives of cambrian fauna:
The period of time finishing the Cambrian is characterized by mass disappearance of a set of the animal types created during this era. One of the possible reasons of this phenomenon researchers call decrease in content of oxygen in water, the vast majority of life forms, necessary for breath.