Answer:
The first organisms that did photosynthesis used hydrogen to carry it out as plants do today, although at that time hydrogen sulfide gas was abundant, that is why it was supposed that they used that hydrogenated source as a requirement for photosynthesis In this way, the presence of gaseous and sulfur structures in these fossils could affirm that they were photosynthetic.
On the other hand, it is believed that the first photosynthetic organisms were not plants per se, but rather prokaryotic organisms. Photosynthetic life begins in water without a doubt and around 400 million years ago, plants conquered the air, at which time they developed a material known as a cuticle and which acts as a waterproof to prevent desiccation, but which in turn prevents gas exchange, which led to the next evolutionary step: the appearance of stomata.
Explanation:
According to Carrión, who was a «later, during the Carboniferous, the first trees and the first forests appear. Only the flower delays its appearance until 140 million years ago (Lower Cretaceous) although it arrives giving rise to plants (angiosperms) that will later have greater evolutionary success, since although the flowers lack greater adaptive advantages, they do allow more development fast from the seeds, which in the face of a catastrophe like the fall of a meteorite is an advantage, since it allows them to recover quickly ”.
Thus, "the great invention of angiosperms is the appearance of very rapid fertilization and the rapid formation of a seed, through a process of evolutionary alteration of embryonic development that is known as progenesis and leads to the passing of a individual with a late sexual development to another in which sexual maturation occurs much faster ”, Carrión details.
In short, a process of acceleration of embryonic development as a simple consequence of a mutation in a regulatory gene, and an organism competitively much higher from the ecological point of view emerges, capable of replacing a gymnosperm from its ecological niche. Not surprisingly, in the words of the UMU Professor, "the places where plants grow best today are places like the tropics, with lots of light and lots of water and where angiosperms predominate."...
