Biology and Geology 4th compulsory secondary education
Paleozoic era (541 to 245 ma)
The main events that took place during the Paleozoic were:
The Phanerozoic began with the explosion of life of the Cambrian Period. Phanerozoic means "visible life". Large areas of coastline appeared with favorable climates that favored the appearance of almost all groups of Cambrian animals and plants.
The climate started out cold but alternated with warmer periods, there were even times of ice ages.
In the Paleozoic, Rodinia (Pangea I) fragmented and reunited, forming the supercontinent Pangea.
There was the same amount of oxygen in the atmosphere as there is today.
Graptolites. Colonial planktonic animals that lived between the Cambrian and Carboniferous. Many graptolite fossils resemble written hieroglyphs, which is why they are called that. They are also used as guide fossils.
At the end of the Paleozoic, most of the animal and plant species disappeared. The great Permian extinction is the largest known extinction. It was caused by the increase in the greenhouse effect produced by the great volcanic activity and by the disappearance of a large part of the coasts when Pangea formed in the macrocontinent.
Cambrian (541 to 505 ma)
During the Cambrian Period the fragmentation of Rodinia (Pangea I) occurred. In this period, invertebrates diversify, with the first animals with shells appearing, the first crustaceans and corals.
It began with a great extinction at the end of the Cambrian and ended with another great extinction, before the Silurian.
Although less famous than the Cambrian explosion, the Ordovician Period was also characterized by great adaptive radiation, especially marine fauna.
Trilobites, graptolites, brachiopods, bivalves, etc. abounded , all marine, since there was not much oxygen in the atmosphere. It is believed that some were able to reach the shores, but still unable to become independent from the sea.
The only plants that colonized the earth were non-vascular plants, such as bryophytes.