Looking at your house cactus, I involuntarily thought: "And how did plants generally begin their journey on land? And when did this happen?" About this very interesting topic I would like to tell.
How and when did the first sushi plants appear
As you know, all life on earth originated in water. And plants are no exception. Once they were all protozoan algae, but then came the stage when they began to germinate on land.
And they began their exit to the surface at the end Silura (near 4 05-440 million years ago), what in Paleozoic era. Then there were active powerful mining processes, leading to shrinkage and the drying up of many seas. This is what caused some algae to “come out” on 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 kept disputes.
Psilophytes preferred swampy and wet area, because they did not have a powerful root system for extracting water. Today it is believed that once such plants lined endless carpets on the bare surface of the Earth.
In addition, psilophytes could be both very high(much more than human growth), 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, such difficulties could be called:
- necessity water conservation from its evaporation in air;
- need for education hard protective cover;
- adaptation to constant changing conditions environment.
And many others. Such plants also needed to learn how to exercise more complex photosynthesis, anchor in the soil and receive from it the necessary minerals.
All these difficulties have been overcome by plant organisms. And the evidence for 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 favored the growth and wide distribution of algae. Over time, the surface of the earth and the bottom of the oceans changed. New continents rose, those that had arisen before went under water. The earth's crust shook. This led to the fact that land appeared in place of the seas.
Retreating, sea water lingered in the depressions. The depressions sometimes dried up, then again filled with water during high tides. Algae, which used to live at the bottom of the seas, ended up on the earth's surface. But since the desiccation occurred slowly and gradually, they managed during this time to adapt to living in terrestrial conditions. After all, this process also took millions of years.
The climate at this time was established on the globe humid and warm. He favored the transition of plants from an aquatic lifestyle to an existence on land. These living conditions on land caused the complexity of the structure of plants. The structure of ancient algae has changed. From them arose the first terrestrial plants PSILOPHYTES. Psilophytes looked like 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 the psilophytes, like algae, did not have a root itself.
Mosses and ferns originated from psilophytes. And the psilophytes themselves later completely died out. It happened 300 million years ago.
The humid climate and the abundance of water contributed to the rapid reproduction of fern-like plants on Earth - ferns, horsetails, club mosses. But at the end of the Carboniferous period, the climate of the Earth began to change everywhere, becoming drier and colder. The giant tree ferns began to die. Dead plants gradually rotted and turned into coal. This coal later people heated their homes.
When ferns reproduced, seeds were formed on the leaves and lay openly. Hence later arose scientific name Gymnosperms. Modern pines, spruces, and firs, which are considered gymnosperms, originated from giant ferns.
With the cooling of the climate, the ancient ferns finally died out. When germinating in cold soil, their tender sprouts froze. They were replaced by seed ferns, which are considered the first gymnosperms. These plants turned out to be more adapted to life in a dry and cool climate, which replaced the humid and warm Carboniferous period. The process of reproduction in them ceased to depend on the presence of water in the external environment.
130 million years ago, grasses and shrubs appeared on Earth, in which the seeds were well protected by fruits. Therefore, they were called angiosperms. Angiosperms have dominated the earth for 60 million years.
The organs of plants that were 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 fossils have been found. However, scientists, using fossilized prints left by ancient plants, nevertheless restored them. appearance, and also considered the structural features of plants that became the first
The science that studies the features of the structure and life of fossil plants is called "paleobotany". It is paleobotanists who are looking for answers to questions about the origin of the plant world.
Classification of spore plants
The first plants on Earth reproduced with the help of spores. Among the 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, Zosterophylophytes, Trimsrophytes, Psilotophytes, Bryophytes (Bryophytes), Lycopodiophytes (Lycopterous), Equisetophytes (Horsetails) and Polypodiophytes (Ferns). Among these divisions, the first three are completely extinct, while the others contain both extinct and now existing groups.
Rhiniophytes - the first land plants
The first terrestrial plants were representatives of the flora that settled the Earth about 450 million years ago. They grew near various reservoirs or in places of shallow water, which were characterized by periodic flooding and drying.
All plants that have mastered the land have a common feature. This is the division of the body into two parts - aboveground and underground. Such a structure was also characteristic of Rhyniophytes.
The remains of ancient plants were first discovered in the second half of the 19th century on the territory of modern Canada. But for unknown reasons, this find did not interest botanists. And in 1912, near the Scottish village of Rainy, a local rural doctor found several more fossilized plants. He did not know that he was holding the remains of the first terrestrial inhabitants in his hands, but, being very inquisitive, he decided to thoroughly study an interesting find. Having made a cut, he found well-preserved remains of plants. The stalk was very thin, naked, and elongated 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 go the simplest way and called Riniophytes after the name of the village near which they were found.
Structural features
The external structure of Rhyniophytes is very primitive. The body branched according to the dichotomous type, that is, into two parts. They did not yet have leaves and true roots. Attachment to the soil was carried out with the help of rhizoids. As for the internal structure, on the contrary, it was quite complex, especially in comparison with algae. So, it had a stomatal apparatus, with the help of which the processes of gas exchange and water evaporation were carried out. Due to their absence, 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 are descended from Rhyniophytes.
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 so. He chose this option, since in translation this word means "naked plant." Until the beginning of the 20th century, the Psilophytes were called the genus 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 the terrestrial flora. Therefore, the first land plants were Rhyniophytes.
Typical representatives of the first land plants
Presumably, the first land plants were kuksonia and rhinia.
One of the most ancient representatives of the flora was kuksonia, which looked like a small bush no more than 7 cm high. The swamp lowlands were a favorable growing environment for it. Fossilized remains of kuksonia 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 is much better studied than cooksonia. Her body was more massive: the plant could reach a height of 50 cm, and a stem diameter of 5 mm. At the end of the stem of the rhinia was a dome in which there were spores.
The ancient representatives of the genus Rinia gave rise to many plants of the tropics and subtropics. According to modern classification, they are united in the Psilophytes department. It is very rare, because 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 have found in deposits older than 425 million years only the remains of primitive trilet spores with a smooth shell. Such finds were found in Turkey. They are attributed to the Upper Ordovician. The specimens found could not shed light on information about the time of occurrence of vascular plants, since they were single and it was completely unclear from them which particular representatives of the plant species belonged to smooth spores.
But not so long ago, reliable remains of triennial 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.
The flowering of vascular plants after the glaciation
During the second half of the Ordovician, what is now Saudi Arabia and Turkey constituted 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 settlement of vascular plants began after the great glaciation that occurred at the turn of the Ordovician and Silurian.
Telome theory
In the course of the study of Rhyniophytes, 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 terrestrial plants. Zimmerman also showed the alleged ways of becoming important vegetative and reproductive organs of higher plants.
According to the German scientist, the body of Rhyniophytes consisted of radially symmetrical axes, the terminal branches of which Zimmerman called telomes (from the Greek telos - "end").
Through the evolutionary path, telomes, having undergone numerous changes, became the main organs of higher plants: stems, leaves, roots, sporophylls.
So, now you can unequivocally answer the question "What were the first land plants called?". Today the answer is obvious. These were the Rhyniophytes. They were the first to get to the surface of the Earth and became the progenitors of the 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 creatures on the planet from harmful ultraviolet radiation, as well as fertile soil. There are many theories about how plants appeared and how they settled on the planet. The first land plants had no roots and settled at the edge of water bodies, these first plants were kuksonia 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, dying, formed the soil near water bodies and about 400 million years ago, the plants began to develop roots, which allowed the plants to receive water and nutrients from the soil. In addition, the roots of plants are able to penetrate the stone, destroying it, and allowing plants to grow taller and larger.
On land, plants have grown and formed a fertile layer of soil and the entire ecosystem. There are many 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 from the production of the plant, the sucrose it needs. As the 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 at all times influenced the formation and development of animal species. For example, the amount of oxygen released by plants affects the size of insects that 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 forms of animals arose. If you know how animals affect plants, you can understand that plants have a powerful adaptability mechanism. Plants in the process of evolution have acquired a lot of ways to protect leaves from herbivores. For example, the advent of the sauropod dinosaurs caused plants such as saplings to develop spines and even began to produce toxins such as capsicum to make them impossible to eat. Considering how plants adapt to life in those other conditions, it immediately becomes clear that plants are the most adapted organisms on earth. In the process of evolution, most plants became flowering 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 an era that researchers call Archaea. Consider 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 character 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, 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.
- Later, colonial algae appeared.
- The next stage in the development of flora is the appearance of photosynthetic organisms. They took in carbon dioxide from the atmosphere and gave off oxygen.
It can be concluded that algae are the most ancient plants of the Earth, their role was more than significant: it was these tiny representatives of the flora that managed to fill the atmosphere with 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, while the latter did not possess 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 were formed. Soil appeared, so they could grow on land.
- Rhinophytes, the simplest representatives of the fauna, arose in Delour.
- Then there are club mosses and great-ferns, gymnosperms.
- During the Carboniferous, horsetail-like, ferns are born.
The first forests of huge horsetails, ferns and club mosses appear on the planet. In the Carboniferous period, club mosses and calamites reach their peak, which often towered 30-40 meters above the ground. Gradually dying off, these plants formed reserves of coal, which mankind uses to this day. The most ancient plants on Earth played essential role, giving us a valuable mineral. Without coal, the development of industry would not have been possible.
In the Permian period, some coniferous species are formed.
Exit of plants 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 any traces behind them, and conclusions about their existence are made only by indirect signs:
- The formation of rocks. This process is possible only with the participation of living organisms.
- The process of soil formation in water could not go on - this indicates that the plants have already climbed to the surface of the earth.
- Now fossil-like algae are found on land in the form of plaque on stones and tree bark, in conditions of increased importance. Therefore, the researchers suggest that in ancient periods they could also adapt to life outside the sea.
In the later periods of the Paleozoic, land plants appear 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. It can be concluded that the most ancient plants on Earth are mosses, while horsetails "came" out of the sea and settled on land during the Late Paleozoic.
First forests
The first representatives of the flora preferred to settle in damp places, so fern forests were often buried in water. The oldest forests were shallow water bodies, similar to swamps, but devoid of a peat layer. It was here that giant ferns grew. Such an ecosystem is often referred to as a forest-reservoir.
First gymnosperms
The most ancient plants on Earth reproduced by spores, which were very vulnerable and could die in adverse environmental conditions. Therefore, the appearance of gymnosperms was the most important step on the path of evolution. Seeds had a number of advantages over spores:
- they had a nutrient supply;
- could survive adverse conditions;
- not afraid of exposure to UV rays and drying;
Mesozoic
At this time, the most important processes take place:
- formation of continents;
- the birth of lakes and seas;
- climate change.
The plant world is also undergoing significant changes: giant ferns and club mosses are dying out, and gymnosperms of coniferous trees are spreading. Plant imprints with angiosperm-like features have been found in beds from the early Cretaceous and Jurassic. These were primitive and few forms. Angiosperms became widespread in the Middle Cretaceous, about a hundred million years ago. However, by the end of the period, they had become 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. Through pollination by insects flowering plants quickly spread across the continents.
- The predecessors of modern cypresses and pines appear.
We examined which plants are the most ancient on Earth, traced the main paths of the evolutionary development of flora over geological epochs. Despite the fact that the first algae did not leave any traces behind them, their role is enormous: they were able to fill the atmosphere of the planet with oxygen and made possible way out living organisms on land.
