Post the historical development of the plant world. The main stages of the evolution of flora and fauna

Planet Earth was formed over 4.5 billion years ago. The first single-celled life forms appeared, possibly about 3 billion years ago. First it was bacteria. They are classified as prokaryotes because they do not have a cell nucleus. Eukaryotic (with nuclei in the cells) organisms appeared later.

Plants are eukaryotes capable of photosynthesis. In the process of evolution, photosynthesis appeared earlier than eukaryotes. At that time it existed in some bacteria. These were blue-green bacteria (cyanobacteria). Some of them have survived to this day.

According to the most common hypothesis of evolution, the plant cell was formed by entering a heterotrophic eukaryotic cell of a photosynthetic bacterium that was not digested. Further, the process of evolution led to the emergence of a single-celled eukaryotic photosynthetic organism with chloroplasts (their precursors). This is how unicellular algae appeared.

The next stage in the evolution of plants was the emergence of multicellular algae. They reached a great diversity and lived exclusively in the water.

The surface of the earth did not remain unchanged. Where the earth's crust was rising, land gradually arose. Living organisms had to adapt to new conditions. Some ancient algae were gradually able to adapt to the terrestrial way of life. In the process of evolution, their structure became more complicated, tissues appeared, primarily integumentary and conductive.

The psilophytes, which appeared about 400 million years ago, are considered the first land plants. They have not survived to this day.

Further evolution of plants, associated with the complication of their structure, was already on land.

During the time of the psilophytes, the climate was warm and humid. Psilophytes grew near water bodies. They had rhizoids (like roots), with which they were fixed in the soil and absorbed water. However, they did not have true vegetative organs (roots, stems, and leaves). The movement of water and organic substances through the plant was ensured by the emerging conductive tissue.

Later, ferns and mosses originated from psilophytes. These plants have a more complex structure, they have stems and leaves, they are better adapted to living on land. However, just like the psilophytes, they remained dependent on water. During sexual reproduction, in order for the sperm to reach the egg, they need water. Therefore, they could not "go" far from wet habitats.

In the Carboniferous period (about 300 million years ago), when the climate was humid, ferns reached their dawn, many of their woody forms grew on the planet. Later, dying off, it was they who formed deposits of coal.

When the climate on Earth began to become colder and drier, ferns began to die out en masse. But some of their species before that gave rise to the so-called seed ferns, which, in fact, were already gymnosperms. In the subsequent evolution of plants, seed ferns died out, giving rise to other gymnosperms before this. Later, more advanced gymnosperms appeared - conifers.

The reproduction of gymnosperms no longer depended on the presence of liquid water. Pollination took place with the help of wind. Instead of spermatozoa (mobile forms), they formed sperm (immobile forms), which were delivered to the egg by special formations of pollen grains. In addition, gymnosperms did not form spores, but seeds containing a supply of nutrients.

The further evolution of plants was marked by the appearance of angiosperms (flowering). This happened about 130 million years ago. And about 60 million years ago they began to dominate the Earth. Compared to gymnosperms, flowering plants are better adapted to life on land. It can be said that they began to use the possibilities of the environment more. So their pollination began to occur not only with the help of wind, but also through insects. This increased the efficiency of pollination. Seeds of angiosperms are found in fruits, which provide more efficient distribution. In addition, flowering plants have a more complex tissue structure, for example, in the conducting system.

Currently, angiosperms are the most numerous group of plants in terms of the number of species.

plant evolution

The first living organisms arose about 3.5 billion years ago. They, apparently, fed on products of abiogenic origin and were heterotrophs. The high rate of reproduction has led: to the emergence of competition for food, and consequently, to divergence. The advantage was given to organisms capable of autotrophic nutrition - first to chemosynthesis, and then to photosynthesis. About 1 billion years ago, eukaryotes divided into several branches, from some of which multicellular photosynthetic organisms (green, brown and red algae), as well as fungi, arose.

The main conditions and stages of plant evolution:

• in the Proterozoic era, unicellular aerobic organisms (cyanobacteria and green algae) were widespread;
• formation of soil substrate on land at the end of the Silurian;
• the emergence of multicellularity, which makes possible the specialization of cells within one organism;
• development of land by psilophytes;
• from psilophytes in the Devonian period, a whole group of terrestrial plants arose - mosses, club mosses, horsetails, ferns that reproduce by spores;
• gymnosperms originated from seed ferns in the Devonian. The structures necessary for seed reproduction (for example, the pollen tube) that arose have freed the sexual process in plants from dependence on the aquatic environment. Evolution followed the path of reduction of the haploid gametophyte and the predominance of the diploid sporophyte;
• the Carboniferous period of the Paleozoic era is distinguished by a large variety of terrestrial vegetation. Arborescent ferns spread, forming coal forests;
• in the Permian period, the ancient gymnosperms became the dominant group of plants. In connection with the appearance of an arid climate, giant ferns and tree clubs are disappearing;
• in the Cretaceous period, the flowering of angiosperms begins, continuing to this day.

The main features of the evolution of the plant world:

1. transition to the predominance of the diploid generation over the haploid one;
2. development of female growth on the mother plant;
3. the transition from spermatozoa to the injection of the male nucleus through the pollen tube;
4. dismemberment of the body of plants into organs, the development of a conducting vascular system, supporting and protective tissues;
5. improvement of organs of reproduction and cross-pollination in flowering plants in connection with the evolution of insects;
6. seed development to protect the embryo from adverse environmental influences;
7. the emergence of various ways of dispersal of seeds and fruits.

Animal evolution

The most ancient traces of animals belong to the Precambrian (over 800 million years). It is assumed that they originated either from a common stem of eukaryotes or from unicellular algae, which is confirmed by the existence of Euglena green and Volvox, capable of both autotrophic and heterotrophic nutrition.

In the Cambrian and Ordovician periods, sponges, coelenterates, worms, echinoderms, trilobites predominate, and mollusks appear.

In the Ordovician, jawless fish-like organisms appear, and in the Silurian, fish with jaws appear. Ray-finned and lobe-finned fish arose from the first jawed-stomes. The crossopterans had supporting elements in their fins, from which the limbs of terrestrial vertebrates later developed. From this group of fish arose amphibians and then other classes of vertebrates.

The most ancient amphibians are the Ichthyostegs who lived in the Devonian. Amphibians flourished in the Carboniferous.

Reptiles, which conquered land in the Permian period, originate from amphibians, thanks to the emergence of a mechanism for sucking air into the lungs, the rejection of skin respiration, the appearance of horny scales and egg shells covering the body, protecting embryos from drying out and other environmental influences. Among the reptiles, a group of dinosaurs presumably stood out, which gave rise to birds.

The first mammals appeared in the Triassic period of the Mesozoic era. The main progressive biological features of mammals are the feeding of young with milk, warm-bloodedness, and a developed cerebral cortex.

Features of the evolution of the animal world:

1. progressive development of multicellularity and, as a result, specialization of tissues and all organ systems;
2. a free-moving way of life, which determined the development of various behavioral mechanisms, as well as the relative independence of ontogeny from fluctuations in environmental factors. The mechanisms of internal self-regulation of the organism developed and improved;
3. the emergence of a solid skeleton: external in a number of invertebrates - echinoderms, arthropods; internal in vertebrates. The advantage of the internal skeleton is that it does not limit the increase in body size.

The progressive development of the nervous system became the basis for the emergence of a system of conditioned reflexes and the improvement of behavior.

1. Which plants are the lowest? What is their difference from the higher ones?
2. What group of plants currently occupies a dominant position on our planet?

Methods for studying ancient plants. The world of modern plants is diverse (Fig. 83). But in the past, the plant world of the Earth was completely different. The picture of the historical development of life from its beginning to the present day is helped by paleontology (from the Greek words "palaios" - ancient, "he/ontos" - being and "logos") - the science of extinct organisms, of their change in time and space .

Rice. 83. Approximate number of species of modern plants

One of the divisions of paleontology - paleobotany - studies the fossil remains of ancient plants preserved in layers of geological deposits. It is proved that over the centuries the species composition of plant communities has changed. Many species of plants died out, others came to replace them. Sometimes plants fell into such conditions (in a swamp, under a layer of collapsed rock) that, without access to oxygen, they did not rot, but were saturated with minerals. There was a petrification. Petrified trees are often found in coal mines. They are so well preserved that you can study their internal structure. Sometimes imprints remain on solid rocks, by which one can judge the appearance of ancient fossil organisms (Fig. 84). Spores and pollen found in sedimentary rocks can tell scientists a lot. Using special methods, it is possible to determine the age of fossil plants and their species composition.

Rice. 84. Imprints of ancient plants

Change and development of the plant world. Fossil remains of plants indicate that in ancient times the flora of our planet was completely different than it is now.

In the most ancient layers of the earth's crust, it is not possible to find signs of living organisms. Remains of primitive organisms are found in later deposits. The younger the layer, the more complex organisms are found, which are becoming more and more similar to modern ones.

Many millions of years ago there was no life on Earth. Then the first primitive organisms appeared, which gradually changed, transformed, giving way to new, more complex ones.

In the process of long development, many plants on Earth have disappeared without a trace, others have changed beyond recognition. Therefore, it is very difficult to completely restore the history of the development of the plant world. But scientists have already proven that all modern plant species are descended from more ancient forms.

The initial stages of the development of the plant world. The study of the most ancient layers of the earth's crust, prints and fossils of previously living plants and animals, and many other studies have made it possible to establish that the Earth was formed more than 5 billion years ago.

The first living organisms appeared in water about 3.5-4 billion years ago. The simplest unicellular organisms were structurally similar to bacteria. They did not yet have a separate nucleus, but they had a metabolic system and the ability to reproduce. For food, they used organic and mineral substances dissolved in the water of the primary ocean. Gradually, the reserves of nutrients in the primary ocean began to deplete. Between the cells began the struggle for food. Under these conditions, some cells developed a green pigment - chlorophyll, and they adapted to use the energy of sunlight to turn water and carbon dioxide into food. This is how photosynthesis arose, that is, the process of formation of organic substances from inorganic substances using light energy. With the advent of photosynthesis, oxygen began to accumulate in the atmosphere. The composition of the air began to gradually approach the modern one, that is, it mainly includes nitrogen, oxygen and a small amount of carbon dioxide. Such an atmosphere contributed to the development of more advanced forms of life.

The appearance of algae. From the ancient simplest unicellular organisms capable of photosynthesis, unicellular algae originated. Unicellular algae are the ancestors of the plant kingdom. Along with floating forms among the algae, there appeared also those attached to the bottom. This lifestyle led to the dismemberment of the body into parts: some of them serve to attach to the substrate, others carry out photosynthesis. In some green algae, this was achieved thanks to a giant multinucleated cell, divided into leaf-shaped and root-shaped parts. However, it turned out to be more promising to divide the multicellular body into parts that perform various functions.

The emergence of sexual reproduction in algae was of great importance for the further development of plants. Sexual reproduction contributed to the variability of organisms and the acquisition of new properties by them, which helped them adapt to new living conditions.

Exit of plants to land. The surface of the continents and the bottom of the ocean have changed over time. New continents rose, the old ones went under water. Due to the fluctuations of the earth's crust, dry land appeared in place of the seas. The study of fossil remains shows that the flora of the Earth also changed.

The transition of plants to a terrestrial way of life, apparently, was associated with the existence of land areas periodically flooded and freed from water. The drying of these areas occurred gradually. Some algae began to develop adaptations for living out of water.

At that time, the world had a humid and warm climate. The transition of some plants from aquatic to terrestrial lifestyle has begun. In ancient multicellular algae, the structure gradually became more complicated, and they gave rise to the first land plants (Fig. 85).

Rice. 85. The first sushi plants

One of the first land plants were rhinophytes growing along the banks of reservoirs, for example, rhinia (Fig. 86). They existed 420-400 million years ago, and then died out.

Figure 86. Rhiniophytes

The structure of rhinophytes still resembled the structure of multicellular algae: there were no true stems, leaves, roots, they reached a height of about 25 cm. Rhizoids, with the help of which they attached to the soil, absorbed water and mineral salts from it. Along with the similarity of roots, stem and primitive conducting system, rhinophytes had an integumentary tissue that protected them from drying out. They reproduced by spores.

Origin of higher spore plants. Ancient club mosses, horsetails and ferns, and, apparently, mosses, which already had stems, leaves, and roots, originated from rhinophyte-like plants (Fig. 87). These were typical spore plants, they reached their heyday about 300 million years ago, when the climate was warm and humid, which favored the growth and reproduction of ferns, horsetails and club mosses. However, their exit to land and separation from the aquatic environment were not yet final. During sexual reproduction, spore plants require an aquatic environment for fertilization.

Rice. 87. Origin of higher plants

Development of seed plants. At the end of the Carboniferous, the Earth's climate became drier and colder almost everywhere. Tree ferns, horsetails and club mosses gradually died out. Primitive gymnosperms appeared - descendants of some ancient ferns.

Living conditions continued to change. Where the climate became more severe, the ancient gymnosperms gradually died out (Fig. 88). They were replaced by more advanced plants - pine, spruce, fir.

Plants propagated by seeds are better adapted to life on land than plants propagated by spores. This is due to the fact that the possibility of fertilization in them does not depend on the presence of water in the external environment. The superiority of seed plants over spore plants became especially clear when the climate became less humid.

Angiosperms appeared on Earth about 130 million years ago.

Angiosperms proved to be the most adapted to life on land plants. Only angiosperms have flowers; their seeds develop inside the fruit and are protected by the pericarp. Angiosperms quickly spread throughout the Earth and occupied all possible habitats. For more than 60 million years, angiosperms have dominated the Earth.

Having adapted to various conditions of existence, angiosperms created a diverse vegetation cover of the Earth from trees, shrubs and grasses.

New concepts

Paleontology. Paleobotany. Rhyniophytes

Questions

1. On the basis of what data can it be argued that the plant world developed and became more complex gradually?
2. Where did the first living organisms appear?
3. What was the significance of photosynthesis?
4. Under the influence of what conditions did ancient plants switch from an aquatic lifestyle to a terrestrial one?
5. Which ancient plants gave rise to ferns, and which to gymnosperms?
6. What are the advantages of seed plants over spore plants?
7. Compare gymnosperms and angiosperms. What structural features provided an advantage to angiosperms?

Quests for the curious

In summer, explore steep river banks, slopes of deep ravines, quarries, pieces of coal, limestone. Find fossilized ancient organisms or their footprints.

Sketch them. Try to determine which ancient organisms they belong to.

Do you know that...

The oldest imprint of the flowers of the plant was found in the state of Colorado (USA) in 1953. The plant looked like a palm tree. The age of the imprint is 65 million years.

Some forms of ancient angiosperms: poplars, oaks, willows, eucalyptus, palm trees - have survived to this day.

The plant kingdom is remarkably diverse. It includes algae, mosses, club mosses, horsetails, ferns, gymnosperms and angiosperms (flowering) plants.

Lower plants - algae - have a relatively simple structure. They can be unicellular or multicellular, but their body (thallus) is not divided into organs. There are green, brown and red algae. They produce a huge amount of oxygen, which is not only dissolved in water, but also released into the atmosphere.

Man uses seaweed in the chemical industry. Iodine, potassium salts, cellulose, alcohol, acetic acid and other products are obtained from them. In many countries, algae is used to prepare a variety of dishes. They are very useful, as they contain a lot of carbohydrates, vitamins, and are rich in iodine.

Lichens consist of two organisms - a fungus and an algae, which are in a complex interaction. Lichens play an important role in nature, being the first to settle in the most barren places. When they die, they form soil on which other plants can live.

Higher plants are called mosses, club mosses, horsetails, ferns, gymnosperms and angiosperms. Their body is divided into organs, each of which performs certain functions.

Mosses, club mosses, horsetails, ferns reproduce by spores. They are classified as higher spore plants. Gymnosperms and angiosperms are higher seed plants.

Angiosperms have the highest organization. They are widely distributed in nature and are the dominant group of plants on our planet.

Almost all agricultural plants grown by man are angiosperms. They provide a person with food, raw materials for various industries, and are used in medicine.

The study of fossil remains proves the historical development of the plant world over many millions of years. From plants, algae first appeared, which descended from simpler organisms. They lived in the water of the seas and oceans. Ancient algae gave rise to the first land plants - rhinophytes, from which mosses, horsetails, club mosses and ferns originated. Ferns reached their heyday in the Carboniferous period. With climate change, they were replaced first by gymnosperms, and then by angiosperms. Angiosperms are the most numerous and highly organized group of plants. She became dominant on earth.

Hello, friends! Today I would like to talk about prehistoric plants, how they evolved into modern plants.

The plant kingdom today is dominated by flowering plants, but club mosses and ferns covered the Earth in prehistoric times.

Over 400,000 species of flora are known today, all of which are descended from several ancient marine plants. Species that have disappeared from the face of the Earth are not included in this number, because they could not adapt to changing conditions on Earth, or could not withstand the competition from newly appeared plants that were better adapted to the new habitat.

Paleobotanists have established the distribution of vegetation cover over the Earth's surface in different geological periods, as well as the patterns of its change. The fact that plants do not have a hard skeleton that easily turns into a fossil is the difficulty of research.

Fortunately, early forms of flora can sometimes be found in ancient silt deposits, and some plant remains have been found in rocks, their age is about 3.1 billion years.

The fact that life on the planet should have begun with the appearance of plant-like organisms, which later became an important link in the animal food chain, is evidenced by fossils.

But the role of plants in the evolutionary history of the Earth is much more significant, since they actually transformed our planet and made it suitable for the existence of the animal world.

Probably, in the conditions of the initial content of a huge amount of carbon dioxide in the atmosphere, the animals would not be able to breathe. Plants convert carbon dioxide into oxygen in the process of photosynthesis, saturating the atmosphere with it.

The basis of the food chain was the ability of plants to use sunlight to produce complex organic substances. The evolution of carnivores and herbivores was provided by plants.

Evolution, however, is an extremely slow process, and natural selection favors individuals that adapt to changes in their environment, not just changes per se.

The oldest species of the plant world could not do without water, since they did not have the structures necessary for life on land.

The first plants that came out of the water probably settled in swamps, where their lower part could be constantly under water. Most likely, the first truly terrestrial plants remained moisture-loving and grew near water.

A moist breeding environment was still necessary for liverworts, mosses and ferns, which have evolved as plants since ancient times.

Precursors of flowering plants - gymnosperms, among them conifers - needed wind to disperse seeds and pollinate, since then there were no insects capable of doing this.

Simultaneously with insects and animals, flowering (angiosperms) plants that prevail today developed, therefore they are often pollinated by them.

The simplest algae were the oldest known plants.

These are unicellular organisms, all the functions of which were performed by a single cell without a nucleus. These blue-green algae were extremely primitive, and only about 1.5 billion years ago did they have a cell nucleus.

Multicellular organisms evolved over time. Perhaps they are similar to seaweeds and have reproductive organs in different parts of the plant.

About 590 million years ago, during the Cambrian period, many forms of life firmly settled on Earth. More than 900 species belong to this period - and these are the plants that survived and were discovered hundreds of millions of years later.

Land migration.

440 - 408 million years ago, during the Silurian period, plants came out of the water and began to populate the land. The habitat of plants and animals in ancient times was limited to the oceans, but algae have adapted to life in fresh water. Terrestrial species likely evolved from these freshwater algae.

Aquatic plants must have a completely different structure in order to survive on land. They should contain a more rigid organ supporting the plant, as well as a network of vessels.

A reproductive system that can function normally in the air must be created by terrestrial plants before moving to drier areas.

Traces of the most ancient plants were found in the rocks of the Silurian period. The body of one of them, Zosterophyllum, was a thallus, that is, it was not divided into a stem, root and leaves. Rhynia is a plant without leaves and roots, but at the ends of shoots with large sporangia.

It consisted of a functioning root, rhizome and above-ground shoots dotted with small scaly leaves. It is very likely that they were all marsh plants.

Roots that accumulate and absorb water appeared in plants for growing on land. Less dependent on moisture, methods of reproduction improved in them during a very long period of evolution.

Unlike later flowering plants, surviving relict species such as liverworts and mosses still need a moist environment and water to reproduce.

evolutionary progress.

The process of evolution does not have to be straightforward or continuous with a constant pace of development.

The following groups of plants almost certainly arose in the course of evolution, and in the order given. The fact that evolution is an ongoing and now continuous process should not be forgotten. It is only after a very long period of time that changes can be detected.

bacteria.

It is likely that the first cellular organisms lived in the "primary" broth and resembled. It is generally accepted that bacteria are closer to plants than to animals, although they have little in common with either one or the other. With astonishing speed, these microscopic unicellular organisms can reproduce under ideal conditions.

However, some of them can live in organic substances, such as nitrogen and ammonia, which is possibly related to their appearance in ancient times, when the Earth's atmosphere contained a large amount of ammonia.

Blue-green algae.

These primitive plants bear little resemblance to real algae, despite their name. At 3.1 billion years old, individual fossils found in rocks closely resemble modern blue-green algae.

This proves their belonging to the most ancient species capable of photosynthesis. Microscopic unicellular non-nuclear organisms - this is the majority of blue-green algae.

But due to the fact that in the mucus of some algae there are whole colonies of these plants, some of them can be seen with the naked eye.

Seaweed.

This is another type of primitive plant that lacks flower structures and leaves. Almost all types of algae are capable of obtaining food through photosynthesis under the influence of natural sunlight.

Such primitive plants predominate, including plankton, mainly consisting of unicellular algae and multicellular algae.

Freshwater and terrestrial algae are widespread. It is they who lead to the “blooming” of water in reservoirs and the plaque that forms on the walls of aquariums, wet clay pots and other vessels.

Algae are multicellular and unicellular and can form colonies or filaments. Some of their species are considered to be the link between animals and plants.

Euglenophytes are flagellated, have a light-sensitive red eye, and can ingest solid food particles.

Lichens.

The result of the mutualism of fungi and algae is such complex plants. Only after these two independent plant species had formed could lichens appear.

From the point of view of evolution, they have occupied a free niche and are able to exist in adverse conditions in which only a few other plants can survive.

Mosses and liverworts.

Although the evolution of mosses and liverworts is still ongoing, they are similar to primitive plants. They have clearly defined stems and leaf-like structures, as well as signs of the beginning of the development of vascular conductive tissue. Mosses and liverworts reproduce by spores, and there are two stages of reproduction.

First, the sporophyte appears, the dominant form that carries spores), and then the gametophyte (sexual generation).

Generation alternation - the name of this complex process. It requires a very humid environment or water. This is another property that confirms the ancient origin of mosses and liverworts and prevents their spread over land.

Ferns and horsetails.

These plants reproduce more often by spores than by seeds, but they are also characterized by alternation of generations. Therefore, they need water or a high moisture content to reproduce successfully.

Sporophytes depend less on moisture. And although the spore generation for the development of gametophytes must grow near wet areas, this means that the habitat of ferns is more diverse than mosses and liverworts.

The more complex structure of ferns speaks of a later evolution. However, it is known that in the Devonian (480 - 360 million years ago) they were widespread. This structure allows ferns to adapt to life on land and gives them the rigidity necessary for further growth.

In kinship with ferns are mosses and horsetails, but are much less common than ferns. In the Carboniferous period (360 million years ago), horsetails dominated. And most of the coal was formed from their petrified remains. Then, they were gradually replaced by other species.

Pteridosperms.

The progenitors of modern flowering plants were pteridosperms or seed ferns. Now it is an extinct species. Outwardly, pteridosperms looked like ferns, but at the ends of special shoots they formed seeds. They lived in the period from the Devonian to the Triassic (248 million years ago).

Gymnosperms.

Almost one tree includes gymnosperms. Their evolutionary process began later than those of the groups listed above. They appeared in the Mesozoic era. They have ovules and cones, which, unlike angiosperms, lack carpels.

Coniferous trees such as larch and pine are the best known gymnosperms. As well as tropical species - ginkgo and cycads. In the Mesozoic era, cycads were most widespread.

Also coniferous trees include giant sequoia, which can reach very large sizes. Coniferous trees are of great economic importance. For the production of timber and pulp, they are grown in large quantities.

Angiosperms.

In the modern world, this is the predominant group of plants. It includes both flowers (daisy and dandelion) and trees (for example, horse chestnut, oak). Angiosperms include most of the vegetables we eat, orchids, ornamental grasses that we plant in lawns, and a variety of grains (including oats and wheat).

Angiosperms are flowering plants. Their seeds are enclosed in carpels. The evolution of these plants proceeded in different ways. Both insects and the wind play an important role in the pollination of these plants. Certain species of insects or birds pollinate some of them. Seed dispersal methods are also very diverse.

Such is the evolution of plants, it turns out that this is a rather complicated process. 🙂

Table covering the evolution of plants by geological period

As a result of prehistoric events such as the Permian and Cretaceous-Paleogene, many plant families and some ancestors of extant species became extinct before recorded history began.

The general trend of diversification includes four main groups of plants that dominate the planet, from the middle Silurian period to the present:

Zosterophyllum model

• The first main group, representing terrestrial vegetation, included seedless vascular plants, represented by the Rhynia classes ( Rhyniophyta), ozosterophyllic ( Zosterophyllopsida).

ferns

• The second main group, which appeared in the late Devonian period, consisted of ferns.
• The third group, seed plants, appeared at least 380 million years ago. It included gymnosperms ( Gymnospermae), which dominated the terrestrial flora during most of the Mesozoic era until 100 million years ago.
• The last fourth group, angiosperms, appeared about 130 million years ago. The fossil record also shows that this plant group was abundant in most parts of the world between 30 million and 40 million years ago. Thus, angiosperms dominated the earth's vegetation for nearly 100 million years.

Palaeozoic

Lycopsformes

The Proterozoic and Archean eons precede the appearance of terrestrial flora. Seedless, vascular, terrestrial plants appeared in the middle of the Silurian period (437-407 million years) and were represented by rhinophytes and, possibly, lycopods (including lycopodiums). From primitive rhinophytes and club mosses, ground vegetation rapidly evolved during the Devonian period (407-360 million years ago).

The ancestors of true ferns may have evolved in the middle Devonian. During the late Devonian, horsetails and gymnosperms appeared. By the end of the period, all the main divisions of vascular plants already existed, except for angiosperms.

The development of features of vascular plants, during the Devonian, made it possible to increase the geographical diversity of the flora. One of them was the occurrence of flattened leaves, which increased efficiency. The other is the emergence of recycled wood, allowing plants to grow significantly in shape and size, leading to trees and probably forests. The reproductive development of the seed was a gradual process; the earliest is found in Upper Devonian deposits.

The ancestors of conifers and cycads appeared in the Carboniferous period (360-287 million years ago). During the Early Carboniferous at high and middle latitudes, the vegetation shows the dominance of lycopodiums and Progymnospermophyta.

Progymnospermophyta

In the lower latitudes of North America and Europe, a wide variety of lycopodiums and Progymnospermophyta, as well as other vegetation. There are seed ferns (including calamopityales), along with true ferns and horsetails ( archaeocalamites).

Late Carboniferous vegetation at high latitudes was severely damaged by the onset of the Permian-Carboniferous Ice Age. In the northern mid-latitudes, the fossil record shows the dominance of horsetails and primitive seed ferns (pteridosperms) over few other plants.

In the northern low latitudes, the land masses of North America, Europe, and China were covered by shallow seas or swamps and, because they are close to the equator, they experienced tropical and subtropical climates.

At this time, the first, known as coal forests, appeared. Enormous amounts of peat have been established as a result of favorable year-round growth conditions and the adaptation of giant lycopodiums to tropical wetland environments.

In the drier regions surrounding the lowlands, forests of horsetails, seed ferns, cordaites, and other ferns existed in great abundance.

The Permian period (287-250 million years ago) indicates a significant transition of conifers, cycads, glossopteris, gigantopterids, and peltasperms from poor fossil record in the Carboniferous to significant abundant vegetation. Other plants such as tree ferns and giant lycopodiums were present in the Permian but not in abundance.

As a result of the Permian mass extinction, tropical swamp forests disappeared, and with them the lycopodiums; cordaites and glossopteris became extinct at higher latitudes. About 96% of all plant and animal species disappeared from the face of our planet at this time.

Mesozoic era

At the beginning of the Triassic period (248-208 million years ago), the scanty fossil record indicates a decline in the Earth's flora. From the middle to the late Triassic, modern families of ferns, conifers, and the now extinct group of plants, the bennettites, lived in most terrestrial. After the mass extinction, the bennettites moved into free ecological niches.

Late Triassic flora at equatorial latitudes is represented by a wide range of ferns, horsetails, cycads, bennettites, ginkgoes and conifers. Plant combinations in low latitudes are similar, but not rich in species. This lack of plant variation at low and mid-latitudes reflects the global frost-free climate.

In the Jurassic period (208-144 million years ago), terrestrial vegetation appeared, similar to modern flora, and modern families can be considered descendants of ferns of this geological period of time. , such as the Dipteridaceae, Matoniaceae, Gleicheniaceae, and Cyatheaceae.

Conifers of this age can also include modern families: podocarp, araucaria, pine and yew. These conifers, during the Mesozoic, created significant deposits such as coal.

During the early and middle Jurassic, in the equatorial latitudes of the western part of North America, Europe, Central Asia and the Far East, a variety of vegetation grew. It included: horsetails, cycads, bennettites, ginkgoes, ferns and conifers.

Warm, humid conditions also existed in the northern mid-latitudes (Siberia and northwestern Canada), supporting ginkgo forests. Deserts were found in the central and eastern parts of North America and North Africa, and the presence of bennettites, cycads, cheirolepidia and conifers testified to the adaptability of plants to arid conditions.

The southern latitudes had similar vegetation to the equatorial latitudes, but due to drier conditions, conifers were abundant and ginkgos were scarce. The southern flora has spread to very high latitudes, including Antarctica, due to the lack of polar ice.

Cheirolipidic

In the Cretaceous period (144-66.4 million years ago) in South America, Central and North Africa, and Central Asia, there were dry, semi-desert natural conditions. Thus, coniferous species of Cheirolipidaceae and Matoniaceae ferns predominated in the terrestrial vegetation.

The northern mid-latitudes of Europe and North America had more diverse vegetation, consisting of bennettites, cycads, ferns, and conifers, while the southern mid-latitudes were dominated by bennettites.

In the late Cretaceous, significant changes occurred in the vegetation of the Earth, with the appearance and spread of flowering seed plants, angiosperms. The presence of angiosperms meant the end of the typical Mesozoic flora with a predominance of gymnosperms and a definite decline in the bennettites, ginkgos and cycads.

Nothofagus or southern beech

During the Late Cretaceous, dry conditions prevailed in South America, Central Africa, and India, resulting in tropical vegetation dominated by palm trees. The mid-southern latitudes were also influenced by deserts, and the plants fringing these areas included: horsetails, ferns, conifers, and angiosperms, notably notophagus (southern beech).

Sequoia Hyperion

The high latitudes were devoid of polar ice; due to warmer climate conditions, angiosperms were able to flourish. The most diverse flora was found in North America, where evergreens, angiosperms and conifers were present, especially redwood, sequoia.

The Cretaceous-Paleogene mass extinction (K-T extinction) occurred about 66.4 million years ago. This is an event that suddenly caused global climate change and the extinction of many animal species, especially dinosaurs.

The greatest "shock" for terrestrial vegetation occurred in the middle latitudes of North America. Pollen and spore readings just above the K-T boundary in the fossil record show a predominance of ferns and evergreens. The subsequent colonization of plants in North America demonstrates the predominance of deciduous plants.

Cenozoic era

The increase in precipitation at the beginning of the Paleogene-Neogene (66.4-1.8 million years ago) contributed to the large-scale development of rainforests in the southern regions.

Notable during this period was the arcto polar forest flora found in northwestern Canada. Mild, humid summers alternated with continuous winter darkness with temperatures ranging from 0 to 25°C.

Birch Grove

These climatic conditions supported deciduous vegetation, which included sycamore walnut, birch, moonseed, elm, beech, magnolia; and gymnosperms such as taxodia, cypress, pine and ginkgo. This flora spread throughout North America and Europe.

Approximately eleven million years ago, during the Miocene epoch, there was a marked change in vegetation with the appearance of grasses and their subsequent spread to grassy plains and prairies. The appearance of this widespread flora contributed to the development and evolution of herbivorous mammals.

The Quaternary Period (1.8 million years ago to the present) began with a continental glaciation in northwestern Europe, Siberia, and North America. This glaciation affected terrestrial vegetation, with flora migrating north and south in response to glacial and interglacial fluctuations. In the interglacial periods, maple, birch and olive trees were common.

The final migrations of plant species at the end of the last ice age (about eleven thousand years ago) shaped the modern geographic distribution of land flora. Some areas, such as mountain slopes or islands, have unusual species distributions as a result of their isolation from global plant migration.