Looking at your home cactus, I couldn’t help but think: “How did plants even begin their journey on land? And when did this happen?” About this very interesting topic I would like to tell you.
How and when did the first sushi plants appear?
As is known, all earthly life originated in water. And plants are no exception. Once upon a time they were all protozoan algae, but then a stage came when they began to germinate on land.
And they began their emergence to the surface at the end Silura (near 4 05-440 million years ago), what in Paleozoic era. Then powerful events were actively taking place mining processes, leading to shallowing and drying up of many seas. This is what caused some algae to “come out” onto land.
The very first plants on the surface are psilophytes. They had only a bare stem, which was attached to the ground with the help of special outgrowths - rhizoids. The psilophytes themselves had a very simple structure, but they had branching stems with outgrowths that stored disputes.
Psilophytes preferred marshy and wet area, because they did not have a powerful root system to extract water. Today it is believed that such plants once lined endless carpets on the bare surface of the Earth.
In addition, psilophytes could be like very high(much larger than human height), and very low and tiny.
How did the first land plants adapt?
Worth a special mention fixture system, which plants have mastered for life on land. After all, they are very different from life under water. So, these difficulties could be called:
- necessity water conservation from its evaporation in air;
- need for education hard protective cover;
- adaptation to constantly changing conditions environment.
And many others. Such plants also needed to learn to carry out more complex photosynthesis, anchor in the soil and get from it the necessary minerals.
All these difficulties were overcome by plant organisms. And the evidence of this is our life on Earth.
How did the first plants appear on Earth?
400 million years ago most The surface of the Earth was occupied by seas and oceans. The first living organisms appeared in water. They looked like microscopic lumps of mucus. After several million years, some living organisms developed a green color. They became like algae.
Climatic conditions contributed to the growth and widespread distribution of algae. Over time, the surface of the earth and the bottom of the oceans changed. New continents rose, and those that arose earlier sank. The earth's crust was shaking. This led to the emergence of land in place of the seas.
Retreating, sea water lingered in the depressions. The depressions either dried up or were filled with water again during high tides. Algae that previously lived at the bottom of the seas ended up on the earth's surface. But since the desiccation occurred slowly and gradually, during this time they managed to adapt to living in terrestrial conditions. After all, this process also took millions of years.
The climate at this time was humid and warm on the globe. It favored the transition of plants from an aquatic lifestyle to existence on land. These living conditions on land caused the structure of plants to become more complex. The structure of ancient algae has changed. From them the first terrestrial plants PSILOPHYTES arose. Psilophytes resembled small herbaceous plants that grew along the banks of rivers and lakes. They had a stem that was covered with bristles. The underground part of the stem resembled a rhizome. But psilophytes, like algae, did not have a root.
Mosses and ferns originated from psilophytes. And the psilophytes themselves later became completely extinct. This happened 300 million years ago.
The humid climate and abundance of water contributed to the rapid proliferation of fern-like plants on Earth - ferns, horsetails, mosses. But at the end of the Carboniferous period, the Earth's climate began to change everywhere, becoming drier and colder. The giant tree ferns began to die. The dead plants gradually rotted and turned into coal. People later used this coal to heat their homes.
When ferns reproduced, seeds formed on the leaves and lay open. From here it later arose scientific name Gynosperms. From giant ferns came modern pines, spruces, and firs, which are considered gymnosperms.
With the climate cooling, the ancient ferns finally died out. When germinated in cold soil, their tender shoots froze. They were replaced by seed ferns, which are considered the first gymnosperms. These plants turned out to be more adapted to life in the dry and cool climate that replaced the wet and warm Carboniferous period. Their reproduction process no longer depends on the availability of water in the external environment.
130 million years ago, grasses and shrubs appeared on Earth, the seeds of which were well protected by fruits. That's why they were called angiosperms. Angiosperms have dominated the Earth for 60 million years.
The plant organs that formed during these times have not changed significantly to this day.
We, contemporaries, know very little about the first representatives of the plant world. Unfortunately, few of their fossil remains have been found. However, scientists, using fossilized imprints left by ancient plants, still restored them appearance, and also examined the structural features of the plants that became the first
The science that studies the structural features and vital functions of fossil plants is called “paleobotany”. It is paleobotanists who search for answers to questions about the origin of the plant world.
Classification of spore plants
The first plants on Earth reproduced using spores. Among modern representatives of the flora there are also spore plants. According to the classification, they are all combined into one group - “higher spore plants”. They are represented by Rhiniophytes, Zosterophilophytes, Trimsrophytes, Psilotophytes, Bryophytes (Bryophytes), Lycopodiophytes (Mocophytes), Equisetophytes (Equisetaceae) and Polypodiophytes (Ferns). Among these divisions, the first three are completely extinct, while the others contain both extinct and extant groups.
Rhiniophytes - the first land plants
The first land plants were representatives of the flora that colonized the Earth approximately 450 million years ago. They grew near various bodies of water or in shallow water areas, which were characterized by periodic flooding and drying out.
All plants that have mastered land have a common feature. This is the division of the body into two parts - aboveground and underground. This structure was also typical for Rhiniophytes.
The remains of ancient plants were first discovered in the second half of the 19th century in what is now Canada. But for unknown reasons, this find did not interest botanists. And in 1912, near the Scottish village of Rhynie, a local rural doctor found several more fossilized plants. He did not know that he was holding in his hands the remains of the first land inhabitants, but, being very inquisitive, he decided to thoroughly study the interesting find. Having made a cut, he discovered well-preserved plant remains. The stem was very thin, bare, and oblong-shaped processes (similar to elongated balls) with very thick walls were attached to it. Information about the find quickly reached paleobotanists, who found out that the remains found were the first land plants. There were doubts about the name of these ancient remains. But as a result, they decided to take the simplest route and named them Rhiniophytes after the name of the village near which they were discovered.
Structural features
The external structure of Rhiniophytes is very primitive. The body branched according to a dichotomous type, that is, into two parts. They did not yet have leaves or real roots. Attachment to the soil was carried out using rhizoids. As for the internal structure, on the contrary, it was quite complex, especially compared to algae. Thus, it had a stomatal apparatus, with the help of which the processes of gas exchange and evaporation of water were carried out. Due to their lack, the first plants on Earth were relatively small in height (no more than 50 cm) and stem diameter (about 0.5 cm).
Paleobotanists believe that all modern land plants descended from Rhiniophytes.
Psilophytes are the first land plants. Is this true?
More likely no than yes. The name "psilophytes" actually appeared as early as 1859. It was the American paleobotanist Dawson who named one of the plants found. He chose this particular option, since in translation this word means “naked plant.” Until the beginning of the 20th century, the genus Psilophytes was called ancient plants. But according to the results of subsequent revisions, this genus ceased to exist, and the use of this name became unauthorized. On this moment the most fully described genus Rinia gives the name to the entire department of the most ancient representatives of terrestrial flora. Consequently, the first land plants were Rhiniophytes.
Typical representatives of the first land plants
Presumably, the first land plants were cuxonia and rhinia.
One of the most ancient representatives of the flora was cooksonia, which looked like a small bush no more than 7 cm high. Swamp lowlands were a favorable growing environment for it. Fossilized remains of Cooksonia and related species have been found in the Czech Republic, the United States of America and in some areas of Western Siberia.
Closely related, rhinia has been much better studied than cooksonia. Its body was more massive: the plant could reach 50 cm in height, and the stem diameter could be 5 mm. At the end of the rhinium stem there was a dome in which there were spores.
Ancient representatives of the genus Rinia gave rise to many plants of the tropics and subtropics. According to modern classification, they are combined into the Psilophytes department. It is very few in number, as it includes about 20 species. In some ways they are very similar to their ancient ancestors. In particular, both of them have dichotomous branching. The approximate height of Psilophytes is from 25 to 40 cm.
Modern finds
Until recently, paleontologists found in sediments older than 425 million years only the remains of primitive trilete spores with a smooth shell. Such finds were found in Turkey. They are classified as Upper Ordovician. The specimens found could not shed light on information about the time of the emergence of vascular plants, since they were single and it was completely unclear from them which specific representatives of the plant species the smooth spores belonged to.
But not so long ago, reliable remains of triletic spores with an ornamented shell were discovered in Saudi Arabia. It was determined that the age of the found samples varies from 444 to 450 million years.
Flowering of vascular plants after glaciation
In the second half of the Ordovician, present-day Saudi Arabia and Turkey formed the northern part of the supercontinent, apparently, and was the original habitat of vascular plants. For a long historical period, they lived only in their “evolutionary cradle,” while the planet was inhabited by representatives of primitive bryophytes with their cryptospores. Most likely, the mass expansion of vascular plants began after the great glaciation that occurred at the Ordovician-Silurian boundary.
Telome theory
During the study of Rhiniophytes, the so-called telome theory appeared, which was created by the German botanist Zimmermann. It revealed the structural features of Rhiniophytes, which by that time were recognized as the first land plants. Zimmerman also showed the supposed paths of formation of important vegetative and reproductive organs of higher plants.
According to the German scientist, the body of Rhiniophytes consisted of radially symmetrical axes, the terminal branches of which Zimmerman called teloms (from the Greek telos - “end”).
Through evolution, telomes, having undergone numerous changes, became the main organs of higher plants: stems, leaves, roots, sporophylls.
So, now we can unambiguously answer the question “What were the names of the first land plants?” Today the answer is obvious. These were Rhiniophytes. They were the first to reach the surface of the Earth and became the progenitors of representatives of modern flora, despite the fact that their external and internal structure was primitive.
How did plants appear on earth? Plants are the most ancient creatures that were the first to successfully colonize the sea and land, giving impetus to the development of animals and their distribution in water and on land. It was plants that shaped the current appearance of the planet, creating an atmosphere that protects all living beings on the planet from harmful ultraviolet radiation, as well as fertile soil. There are many theories about how plants appeared and how they inhabited the planet. The first land plants did not have roots and settled at the edge of reservoirs, these first plants were cooksonia and aglophytons, which were stems with bulbs at the top, these first land plants reached only 5-6 cm in length. It was these first plants that, when they died, formed the soil near bodies of water and about 400 million years ago, roots began to appear on the plants, which allowed the plants to obtain water and nutrients from the soil. In addition, plant roots are able to penetrate the stone, destroying it, and giving the plants the opportunity to grow taller and larger.
On land, plants grew and formed the fertile soil layer and the entire ecosystem. We can give a lot of examples of how people use plants for their own purposes, but the real potential of plants is still not fully revealed. Plants colonized land because they needed sunlight, and, of course, carbon dioxide for the production of sucrose, which the plant uses for nutrition. Surprisingly, oxygen is practically a waste product of the plant's production of the sucrose it needs. As plants developed, they became more and more complex, developed leaves and strong wood, growing into huge forests of lepidodendrons, fighting for a place in the sun. Plants have always influenced the formation and development of animal species. For example, the amount of oxygen released by plants affects the size of insects, which have spiracles scattered throughout the body, saturating internal organs insects with oxygen, and if there is little oxygen, insects cannot reach large sizes.
Animals came to land precisely because of the sucrose produced by plants, and in the process of evolution a lot of animal forms arose. If you know how animals influence plants, you can understand that plants have a powerful adaptation mechanism. Plants, in the process of evolution, have acquired a lot of ways to protect their leaves from herbivores. For example, the appearance of dinosaurs - sauropods - led to the fact that plants began to acquire thorns and even began to produce toxins, for example, capsicum, so that they could not be eaten. Considering how plants adapt to life in those different conditions, it immediately becomes clear that plants are the most adapted organisms on earth. During the process of evolution, most plants became flowering plants and began to use insects as pollinators. Plants grow in all areas where there is water and light necessary for the growth and development of plants, of which there are currently about 320 species.
The first representatives of the flora appeared on the planet more than 2 billion years ago, in the era that researchers call the Archean. Let's look at the most ancient plants on Earth - what they looked like and what role they played in the evolutionary process.
Archean era
This period is separated from us by billions of years, so the data on what living organisms existed at that time are very conditional and often have the nature of hypotheses. Scientists have little material for research, since the representatives of this ancient time did not leave any traces behind them. In this geological era, there was no oxygen in the atmosphere yet, so only those organisms that did not need it could survive. Features of the plant world of the Archean era are as follows:
- The most ancient plants on Earth are considered to be blue-green algae; the fact that they already existed is evidenced by organic substances - marble, limestone.
- Colonial algae appeared later.
- The next stage in the development of flora is the appearance of photosynthetic organisms. They absorbed carbon dioxide from the atmosphere and released oxygen.
We can conclude that algae are the most ancient plants on Earth; their role was more than significant: it was these tiny representatives of the flora that managed to fill the atmosphere with the oxygen necessary for life and made it possible for further evolution. Living organisms were able to leave the sea and move to land.
Proterozoic
The next stage in the development of the most ancient plants on Earth is the Proterozoic era, it was then that many varieties of algae originated:
- red;
- brown;
- green.
It was during this era that a clear division of organisms into plants and animals occurred. The former could synthesize oxygen, but the latter did not have this ability.
Paleozoic
The most ancient plants on Earth are seaweeds, it is to them that we owe the appearance of the atmosphere, oxygenated. They made our world habitable. In the first two periods of the Paleozoic, the flora was represented exclusively by algae, but other plants gradually appeared:
- During the Silurian period, spore plants formed. Soil appeared, so they were able to grow on land.
- Rhyniophytes, the simplest representatives of the fauna, arose in Delur.
- Next, mosses and primordial ferns and gymnosperms appear.
- During the Carboniferous period, horsetail-like ferns appear.
The first forests of huge horsetails, ferns and mosses appear on the planet. During the Carboniferous period, club mosses and calamites reached their peak, often rising 30-40 meters above the surface of the earth. Gradually dying off, these plants formed reserves of coal, which humanity uses to this day. The most ancient plants on Earth played vital role, giving us a valuable mineral resource. Without coal, industrial development would be impossible.
During the Permian period, some coniferous species are formed.
Plants coming to land: features of the process
The most ancient plants on Earth that left the water element and moved to land, as researchers believe, were algae and lichens. They did not leave behind any traces and conclusions about their existence are made only based on indirect signs:
- Rock formation. This process is possible only with the participation of living organisms.
- The process of soil formation could not take place in water - this indicates that the plants had already reached the surface of the earth.
- Nowadays, fossil-like algae are found on land as plaque on rocks and tree bark, under conditions of increased importance. Therefore, researchers suggest that in ancient periods they could also adapt to life outside the sea.
In later periods of the Paleozoic, land plants appeared that have not survived to this day. Only their petrified spores have survived. They are very similar to the spores of liverworts, modern plants related to mosses. We can conclude that the most ancient plants on Earth are mosses, while horsetails “emerged” from the sea and settled on land during the late Paleozoic period.
First forests
The first representatives of the flora preferred to settle in damp places, so fern forests were often buried in water. The most ancient forests were shallow bodies of water, similar to swamps, but lacking a peat layer. It was here that giant ferns grew. Such an ecosystem is often called a forest-reservoir.
First gymnosperms
The most ancient plants on Earth reproduced by spores, which were very vulnerable and could die in unfavorable environmental conditions. Therefore, the appearance of gymnosperms was the most important step on the path of evolution. The seeds had a number of advantages over disputes:
- they had a supply of nutrients;
- could survive adverse conditions;
- were not afraid of exposure to UV rays and drying out;
Mesozoic
At this time, the most important processes occur:
- formation of continents;
- the birth of lakes and seas;
- climate change.
The flora is also undergoing significant changes: giant ferns and club mosses are dying out, and gymnosperm coniferous trees are becoming widespread. Imprints of plants with characteristics characteristic of angiosperms were discovered in layers of the Early Cretaceous and Jurassic periods. These were primitive and few in number. Angiosperms became widespread in the Middle Cretaceous, about one hundred million years ago. However, by the end of the period they became the dominant form of plant life on Earth. The plant world became more and more similar to what we are used to.
Features of the flora of the Mesozoic era are as follows:
- The appearance of vessels in plants, the functions of which were to conduct water and nutrients.
- A reproductive organ is formed - a flower. Thanks to insect pollination flowering plants quickly spread across the continents.
- The predecessors of modern cypresses and pines appear.
We looked at which plants are the most ancient on Earth, and traced the main paths of the evolutionary development of flora across geological eras. Despite the fact that the first algae did not leave any traces behind, their role was enormous: they were able to fill the planet’s atmosphere with oxygen and made possible exit living organisms on land.
