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The history of the evolution of plants is practically that of complex life on our planet. They were responsible for the oxygen enrichment of the Earth's atmosphere and, therefore, for the large number of changes that occurred on Earth linked to this.
If you want to learn more about the evolutionary history of plants, join us in this interesting article by Green Ecologist in which we offer a summary of the origin and evolution of plants and we include images with the timeline of this evolution.
The origin of plants
Life on planet Earth began in the oceans and, therefore, we must also go back to them to find the origin of plant evolution. We are looking here for the appearance of the first plant cells, that is, the first algae. We can say that the first plants were single-celled microalgae that inhabited the oceans. Here you can learn more about what are unicellular algae, characteristics, types and examples.
Its origin is currently attributed to the fusion between a protozoan and a cyanobacterium, capable of photosynthesis. This gave rise to the first living eukaryotic and photosynthetic being endowed with chloroplast. It is estimated that these first algae appeared approximately 1.6 billion years ago.
How plants came to earth
To explain how the plants came to earth and the first land plants, several factors must be taken into account and the following important phases can more or less be established:
- When the first algae appeared in the oceans, complex terrestrial life was not viable. The incidence of UV rays on the dry territory made it impossible to survive outside the water, and it was necessary that for a long time the algae and cyanobacteria (of the Monera Kingdom) produced oxygen by performing photosynthesis, which accumulated in the atmosphere and ended up giving rise to the ozone layer.
- This oxygen was lethal to the organisms that survived through fermentation, a process that can only be carried out in oxygen-free (anaerobic) conditions, which had to be removed to non-oxygenated environments. Currently, they still survive in environments such as silt on the bottoms of seas, rivers and lakes.
- So, it wouldn't be until between 500 and 700 million years ago that plants were the first to colonize the emerged lands, along with fungi and bacteria. It is believed that the colonization of plants on land It began in coastal areas such as river mouths or estuaries, where fresh waters mixed with those of the oceans.
- Thus, plants first adapted to the sweet aquatic environment and, later, they adapted to the terrestrial environment. These first emerged lands offered very harsh conditions for life: in addition to an even more intense UV radiation than the current one, there was no plant cover on the planet, like the one now, that would stop the winds and the terrain was basically divided into rock. hard mother and unstable sediment of rivers and other waters. In addition, the planet already had climatic seasons and, therefore, with alternating periods of humidity and drought, to which these first plants had to adapt as well. Of these first plants, complete fossils are not preserved, since they were most likely soft, small parenchymal species with a prostrate bearing. Of them we have microfossils and fragments, like spores. These must have spread over the humid substrates of the Ordovician period.
Summary of plant evolution
We have seen how plant life originates in the oceans in the form of microalgae and how these developed to be able to colonize land areas.
- From these first parenchymal plants that reigned in the Ordovician period, later the vascular plants in the Silurian period. These already had vessels through which they transport nutrients and water throughout their structure, which made possible a great development in size and complexity. Vascular plants diversified at full speed.
- The ability to reinforce their conducting vessels with lignin appeared in some species and already in Silurian landscapes with pastures and reed beds, much more similar to those we know today. By now, the first terrestrial arthropods were already living on Earth.
- In the Middle Devonian they appeared fern and the ancestors of gymnosperms, the first plants with seeds. These were the first to develop deep taproots as well as wood-shaped xylem.
- By late Devonian they could already be observed on land highly complex forests, with tall trees, bushes and grasses, which would give home to a wide diversity of animal life.
- In the Carboniferous the first gymnosperms as such, which would lead to conifers in the Permian. At the end of the latter period, however, a crisis occurred that wiped out all Paleozoic vegetation and largely reduced the diversity of plant life. Learn more with these other Green Ecologist articles about Gymnosperm Plants: what they are, characteristics and examples and Coniferous Trees: types, names and characteristics.
- Finally, angiosperms or flowering plants, which are currently 90% of the terrestrial plants, appeared and diversified during the Cretaceous, already imposing itself in the Tertiary as the most important and dominant vegetation in the terrestrial environment. The first stage of the Cenozoic Era, which began 66 million years ago, was called Tertiary. If we take this into account, it means that plants such as conifers, which already existed for a long time, have been with us for a long time without hardly changing. In this sense, the Ginkgo biloba or Japanese walnut deserves special mention. This currently unique tree is such an ancient species that it does not retain any living relatives. Quite a living fossil.
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