1.b.4 – What the evolution of plants has been?

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December 15, 2009 — Riccardo Sabellotti - Giacinto Sabellotti


What the evolution of plants has been?

The progenitors of the plants looked like algae, that live in deep waters and were illuminated by the sun; their habitat sometimes dried and, at the end, some of they found ways to survive turning into plants living on the ground. Originally those plants were similar to mosses, had not either branches or leaves, but with the production of a new material in cell walls, called lignin, they develop the stems and branches, as well as the vascular systems to absorb water from roots. To resist drought, which was a constant threat in the new terrestrial environment, plants closed their embryos in seeds to protect them while they waited to find the appropriate moisture conditions to develop.
During a period  from 350 to 250 million years ago, while the first land animals, the amphibians, evolved into  reptiles and  dinosaurs, lush tropical forests of “Ferns with seeds” covered extended regions of the planet. When, about 200 million years ago, glaciers formed on many continents, the ferns with seeds were replaced by evergreen conifers that could withstand the cold. Approximately 125 million years ago appeared the first plants with flowers, whose seeds were encased in fruit. From the outset, these plants have coexisted and they have evolved together with animals that ate the fruit and that disseminated in return the seeds not digested.





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