The emergence of plants in the process of evolution. Stages of the evolution of the plant world

As a result of prehistoric events such as the Permian and Cretaceous-Paleogene, many plant families and some ancestors of existing 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 classes Rhiniaceae ( Rhyniophyta), zosterophyll ( 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 terrestrial flora for most of the Mesozoic era up to 100 million years ago.
• The last fourth group, angiosperms, appeared about 130 million years ago. The fossil record also shows that this group of plants was abundant in most parts of the world ranging from 30 million to 40 million years ago. Thus, angiosperms have dominated the vegetation of the Earth for nearly 100 million years.

Palaeozoic

Lyciformes

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 lymphoids, terrestrial vegetation evolved rapidly during the Devonian period (407-360 million years ago).

The ancestors of true ferns may have evolved in the mid-Devonian. Horsetails and gymnosperms appeared during the Late Devonian period. By the end of the period, all the main divisions of vascular plants existed, except for angiosperms.

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

The ancestors of conifers and cycads appeared in the Carboniferous period (360-287 million years ago). During the Early Carboniferous in high and middle latitudes, vegetation demonstrates 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 real ferns and horsetails ( Archaeocalamites).

Late Carboniferous vegetation at high latitudes was severely affected 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 swept by shallow seas or marshes and, since they were close to the equator, experienced tropical and subtropical climates.

At this time, the first appeared, known as coal forests. The huge amount of peat was established as a result of favorable conditions for year-round growth and adaptation of giant lycopodiums to tropical wetland environments.

In the drier areas surrounding the lowlands, horsetail forests, 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 fossils 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 massive Permian extinction, tropical swamp forests disappeared, and with them the lycopodiums; Cordaites and Glossopteris became extinct at higher latitudes. About 96% of all species of plants and animals disappeared from the face of our planet at this time.

Mesozoic era

In the early Triassic period (248-208 million years ago), the scanty fossil record indicates declines in the Earth's flora. From the mid to late Triassic, modern families of ferns, conifers, and the now extinct group of plants, bennettite, inhabited most terrestrial ones. After the mass extinction, the Bennettites moved into vacant ecological niches.

Late Triassic flora in equatorial latitudes is represented by a wide range of ferns, horsetails, cycads, bennettites, ginkgo and conifers. Combinations of plants in low latitudes are similar, but not rich in species. This lack of plant variation at low and mid latitudes reflects a 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 the descendants of ferns of this geological period of time , such as Dipteridaceae, Matoniaceae, Gleicheniaceae, and Cyatheaceae.

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

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

Warm, humid conditions also existed in the northern mid-latitudes (Siberia and northwest Canada), supporting the 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 ones, but due to drier conditions, conifers were abundant, and ginkgo species were scarce. The southern flora has spread to very high latitudes, including Antarctica, due to the lack of polar ice.

Cheirolipidic

During the Cretaceous period (144-66.4 million years ago), dry, semi-desert natural conditions existed in South America, Central and North Africa, and Central Asia. Thus, the terrestrial vegetation was dominated by conifers of cheirolipidia and matonia ferns.

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

In the Late Cretaceous period, significant changes took place in the vegetation of the Earth, with the emergence 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 certain decline in Bennettite, Ginkgo and Cycads.

Notofagus or southern beech

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

Sequoia Hyperion

High-latitude areas were devoid of polar ice; due to warmer climate conditions, angiosperms were able to thrive. The most diverse flora was found in North America, where evergreens, angiosperms and conifers, especially redwoods and sequoias, were present.

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

The greatest shock to terrestrial vegetation occurred in the mid-latitudes of North America. Pollen and spore readings just above the K-T line in the fossil record show a predominance of ferns and evergreens. Subsequent plant colonization in North America demonstrates a 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 rain forests 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, birch, moonseed, elm, beech, magnolia; and gymnosperms such as taxodiaceae, cypress, pine and ginkgo. This flora has spread across North America and Europe.

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

The Quaternary Period (1.8 million years ago and to date) began with 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 widespread.

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 terrestrial flora. Some areas, such as mountain slopes or islands, have unusual species distribution as a result of their isolation from global plant migration.

The main stages and directions of the evolution of the plant world. Until the end of the Silurian period, plants were represented by multicellular algae that either floated in the water or led an attached lifestyle. Multicellular algae were the original branch for terrestrial leafy plants. At the end of the Silurian period of the Paleozoic era, due to intense mountain-building processes, a reduction in the area of ​​the seas, part of the algae, finding themselves in new environmental conditions (in shallow water bodies and on land), died. Another part, as a result of multidirectional variability and adaptation to the terrestrial environment, acquired features that contributed to survival in new conditions. In the first terrestrial plants - rhinophytes - such signs are the differentiation of tissues into integumentary, mechanical and conductive tissues and the presence of a shell in spores. The emergence of plants on land was prepared by the activity of bacteria and cyanobacteria, which, when interacting with minerals, formed a soil substrate on the land surface.

In the Devonian period, rhinophytes were replaced by ploons, horsetails and ferns, which also reproduce by spores and prefer a humid environment. Their appearance was accompanied by the emergence of vegetative organs, which increased the efficiency of the functioning of individual parts of plants and ensured their activity as an integral system.

In the Carboniferous period (Carboniferous), the first gymnosperms appear, arising from ancient seed ferns. The emergence of seed plants was of great importance for the further development of the plant world, since the sexual process became independent of the presence of a liquid droplet medium. The resulting seed plants could live in drier climates. In the Permian period, the climate in many regions of the Earth became drier and colder, tree-like spore plants, which flourished in the Carboniferous, are dying out. In the same period, the gymnosperms began to flourish, which prevailed in the Mesozoic era. The evolution of higher terrestrial plants followed the path of an ever greater reduction of the haploid generation (gametophyte) and the predominance of the diploid generation (sporophyte).

In the Cretaceous period, the next major step in the evolution of plants took place - angiosperms appeared. The first representatives of this group of plants were shrubs or low-growing trees with small leaves. Then, rather quickly, the angiosperms reached a huge variety of forms with significant sizes and large leaves.

The acquisition of various adaptations for pollination of flowers and the spread of fruits and seeds allowed the angiosperms to occupy a dominant position in the plant kingdom in the Cenozoic.

Thus, the main features of the evolution of the plant kingdom were:

gradual transition to the dominant position of the sporophyte over the gametophyte in the development cycle;

landfall, differentiation of the body into organs (root, stem, leaf) and differentiation of tissues (conductive, mechanical, integumentary);

transition from external fertilization to internal fertilization; the emergence of a flower and double fertilization;

the emergence of seeds that contain the smell of nutrients and are protected from the effects of adverse environmental conditions by the seed covers (and by the walls of the pericarp in angiosperms);

improvement of reproductive organs and cross fertilization in angiosperms in parallel with the evolution of insects;

the emergence of various ways of spreading fruits and seeds.

The main stages and directions of the evolution of the animal world. The history of the evolution of animals has been studied most fully due to the fact that many of them have a skeleton and therefore are better preserved in fossils.

Multicellular animals descend from unicellular organisms through colonial forms. The first animals were probably intestinal cavities. Ancient coelenterates gave rise to flatworms, which are three-layered animals with bilateral symmetry.

From the ancient ciliary worms, the first secondary cavity animals, annelids, originated. The ancient marine polychaetes probably served as the basis for the emergence of types of arthropods, molluscs, and chordates.

The oldest animal tracks date back to the Precambrian (about 700 million years ago). In the Cambrian and Ordovician periods, sponges, coelenterates, worms, echinoderms, trilobites predominate, molluscs appear.

In the Late Cambrian, jawless armored fish appear, and in the Devonian, jaw fishes. Most of these animals are characterized by the presence of bilateral symmetry, the third embryonic layer, body cavity, external (arthropod) or internal (walking) rigid skeleton, progressive ability for active movement, isolation of the anterior end of the body with the mouth opening and sensory organs, gradual improvement of the central nervous system. systems.

Ray-finned and cross-finned fishes arose from the first jaw-finned fishes. Cystepenes had supporting elements in their fins, from which the limbs of terrestrial vertebrates later developed. The most important aromorphoses in this line of evolution are the development of mobile jaws from the gill arches (they ensured active capture of prey), the development of fins from the skin folds, and then the formation of belts of paired pectoral and abdominal limbs (increased the maneuverability of movements in water). Lungs and cross-finned fishes could breathe atmospheric oxygen through their swim bladders connected to the esophagus and supplied with a system of blood vessels.

From cross-finned fish originate the first land animals - stegocephals. Stegocephals split into several groups of amphibians, which flourished in the Carboniferous. The emergence of the first vertebrates on land was ensured by the transformation of fins into terrestrial limbs, air bubbles into lungs.

Truly terrestrial animals originate from amphibians - reptiles, which conquered the land by the end of the Permian period. The development of land by reptiles provided the presence of dry keratinized integuments, internal fertilization, a large amount of yolk in the egg, protective egg shells that protect embryos from drying out and other environmental influences. Among the reptiles, a group of dinosaurs stood out, giving rise to mammals. The first mammals appeared in the Triassic period of the Mesozoic era. Later, also from one of the branches of reptiles, toothed birds (Archeopteryx) originated, and then modern birds. Birds and mammals are characterized by such features as warm-bloodedness, a four-chambered heart, one aortic arch (creates a complete separation of the large and pulmonary circulation), intensive metabolism - features that ensured the flourishing of these groups of organisms.

At the end of the Mesozoic, placental mammals appear, for which the main progressive features were the appearance of the placenta and intrauterine development of the fetus, feeding the young with milk, and a developed cerebral cortex. At the beginning of the Cenozoic era, a detachment of primates separated from insectivores, the evolution of one of the branches of which led to the emergence of man.

In parallel with the evolution of vertebrates, the development of invertebrates proceeded. The transition from aquatic to terrestrial habitat took place in arachnids and insects with the development of a perfect hard external skeleton, articulated limbs, excretory organs, nervous system, sensory organs and behavioral reactions, the appearance of tracheal and pulmonary respiration. Among mollusks, landfall was observed much less frequently and did not lead to such a diversity of species as is observed in insects.

The main features of the evolution of the animal world:

progressive development of multicellularity and, as a consequence, specialization of tissues and all organ systems;

a free lifestyle, which determined the development of various mechanisms of behavior, as well as the relative independence of ontogenesis from fluctuations in environmental factors;

the emergence of a hard skeleton: external in some invertebrates (arthropods) and internal in chordates;

progressive development of the nervous system, which was the basis for the emergence of conditioned reflex activity.

Among the main stages in the evolution of the plant world, one can single out landfall, the transition from external fertilization to internal fertilization, the emergence of seeds and the improvement of the methods of their distribution; in the evolution of the animal world - the specialization of tissues and organ systems, the emergence of a rigid skeleton, the progressive development of the nervous system and the ability to lead a free lifestyle

Definition of the concept of "evolution".

There is a huge variety of primitive and highly developed plants on Earth. All this diversity of the plant kingdom appeared on Earth historically, that is, it developed from simple to complex gradually, over a long period of the existence of our planet and was associated with changing environmental conditions. From the first organisms on the basis of progressive (from Latin progressus - "moving forward", "progressive") more complex forms of plants arose. This process was accompanied by the extinction of organisms that were not adapted to exist in the changed conditions, and the emergence of new, more adapted forms. Extinct and all currently existing plants arose in the process of constant changes in the qualities of species, that is, they arose in the process evolution (from Lat. Evolutiono - "deployment").

Evolution it is an irreversible process of historical (proceeding in time) development of the living world in the direction of greater adaptation to living conditions.

The evolution of the plant world began on Earth a very long time ago, from the moment the first living organisms appeared, and continues at the present time.

The history of the development of the plant world.

More than 3.5 billion years ago, the first living inhabitants appeared on Earth in the ancient warm ocean. They were primitive (i.e. undeveloped, simple) unicellular organisms, similar to modern bacteria. They ate what was in the surrounding ocean water: dissolved mineral and organic substances (i.e. heterotrophic).
Many thousands of years later, organisms with chlorophyll in their cells appeared in ocean waters. Such organisms began to use sunlight as a source of energy to create the organic substances they needed. This is how autotrophs appeared, which were able to feed by carrying out photosynthesis.
The advent of photosynthesis is the largest event in the history of the development of life on our planet. Photosynthesis gave rise to a new way of existence of organisms associated with autotrophic nutrition.
Although the first autotrophs used the energy of solar radiation, they did not yet release a lot of free oxygen into the atmosphere. Only with the adventcyanobacteria , more vigorously carrying out photosynthesis, began a gradual accumulation of oxygen in the Earth's atmosphere. This created the opportunity for the development of organisms that need oxygen for the respiration process.
Cyanobacteria are the oldest group of living organisms that arose about 2.6 billion years ago. Cyanobacteria still exist. These are unicellular and multicellular filamentous organisms, the cells of which do not have a formed nucleus. According to this feature, as well as by cells, they are referred to the super-kingdom of prenuclear, or Prokaryotes (from Latin pro - "before", "earlier" and Greek karyo - "nucleus"), and to the kingdom of Bacteria.
Cyanobacterial cells contain chlorophyll, but they can feed heterotrophically. These organisms are found at the bottom of the oceans, in the water column, caves, hot springs, on ice, on snow, tree bark, on rocks, etc.
For a long period of time, only bacteria and cyanobacteria dominated our planet. Over time, they mastered the land and formed a layer of fertile soil on it, created the biosphere.
About 1.3 billion years ago, organisms more complex than cyanobacteria appeared -green and golden algae... They inhabited fresh and brackish water bodies. In these groups of algae, for the first time on Earth, the nucleus was well isolated in the cell, many intracellular organelles appeared and a sexual mode of reproduction arose - the fusion of two cells and the formation of a zygote, which gives rise to a new organism.
All organisms in whose cells there is a nucleus are referred to as a super-kingdom.Nuclear, or Eukaryotes(from Greek eu - "good", "completely"). Plants, fungi, animals (including humans) are representatives of eukaryotes.
In the course of the evolution of green algae, photosynthetic higher terrestrial plants arose.
Single-celled green algae became the ancestors of all modern plant groups. From them, 600-700 million years ago, multicellular algae originated - the inhabitants of the aquatic environment. Representatives of another kingdom, mushrooms, appeared in the soil environment. The emergence of multicellularity led to the development of different types of tissues.
The emergence of sexual reproduction and the emergence of multicellular organisms among primitive green algae is the greatest event in the development of life on our planet.
Although then, 600 million years ago, there was little oxygen in the atmosphere (100 times less than it is now), but it has already formed an ozone screen around the Earth. After another 200 million years, the ozone screen became so powerful that it protected living inhabitants from the destructive part of the solar radiation. Thanks to this, life began to actively develop not only in water, but also on land.

The emergence of plants on land.

The first plants (now extinct), about 450 million years ago, settled on the wet shores of fresh water bodies were rhinophytes... They originated from green algae attached to the bottom of the reservoir. The water level changed, the plants periodically found themselves in the water, then on land. Rhinophytes, reaching a height of 20-25 cm, did not yet have true roots and leaves, but stems and tissues had already appeared (Fig. 1). The covering tissue with stomata protected it from drying out, the mechanical one strengthened it in the air, root-like formations attached the plant to the soil and absorbed water with dissolved minerals, there was a primitive conducting system.

Rice. 1. First land plants: rhinia ( 1) and Kuksonium (2)

Since then, the evolution of plants has followed the path of increasing adaptation to the conditions of terrestrial existence.

After 100 million years, rhinophytes became extinct, but by this time mosses, moss, horsetails and ferns had already appeared. They already had shoots with green leaves and roots. The stem served as a nutrient-carrying organ.

About 250 million years ago, the climate became drier and colder. Giant tree ferns, horsetails, and lymphoids, which multiplied by spores, could not survive, but some of them gave rise to the first gymnosperms. In the changed climatic conditions, gymnosperms had an advantage over spore plants: they had a new way of reproduction that did not depend on the presence of water in the external environment - reproduction by seeds. Further cooling, increased dryness of the air and solar radiation led to the appearance of angiosperms.

Angiosperms better than other plants were able to adapt to environmental conditions. Their diverse forms spread widely, and over time the angiosperms became the dominant group of plants on Earth.

Paleontology is the science of fossil remains of plants and animals.

Paleobotany is a branch of paleontology that studies the fossil remains of plants that occur in geological strata.

The dead plants sometimes ended up in an oxygen-free environment (swamps, collapsed layers of the earth), where they did not rot, but were saturated with mineral substances and formed fossils (see Fig. 1).

Rice. 1. Fossilized plants

Hardened rocks may have imprints that reflect the appearance of extinct organisms well (see Fig. 2).

Rice. 2. Plant prints

Using special methods, the age of fossil plants is determined.

In ancient times, the plant world of the Earth was different from the present. In the most ancient deposits there are no signs of life, in the later ones the remains of primitive organisms are found (see Fig. 3).

The era of the emergence of life is considered the Archean era, in which the conditions for the origin of life (normal temperature, water) arose.

Rice. 3. Stromatolite (fossilized bacterial community)

The younger the layer, the more complex organisms are found there. In the process of historical development, many plants have died out, others have changed a lot.

The oldest geological rocks on earth were formed about 4 billion years ago. But it is not clear how many years it took to form them.

The first living organisms appeared in water about 3.5 - 4 billion years ago. The simplest organisms were bacteria (see Fig. 4), they did not have their own nucleus, but possessed the ability to metabolize and reproduce.

Rice. 4. Bacterial cell

For food, they used organic and mineral substances dissolved in the ocean. Gradually, the amount of organic matter in the ocean decreased, and photosynthesis appeared.

This period is called the first crisis in life, which arose due to a lack of organic matter. The second life crisis is associated with the saturation of the atmosphere with oxygen, as a result of which most of the oxygen-free bacteria died, and the surviving cells began to use oxygen for their metabolic processes.

Photosynthesis is the process of forming organic substances from carbon dioxide and water using the energy of light. With its appearance, oxygen began to accumulate in the atmosphere. Gradually, the composition of the air began to approach the modern one. This atmosphere contributed to the development of more advanced life forms.

The first eukaryotes appeared (see Fig. 5). Their cells had a real nucleus and mitochondria, plastids.

Rice. 5. Eukaryotic cell

Unicellular algae appeared. One of the most ancient - cyanobacteria (blue-green algae) - prokaryotic organisms.

There are many groups of eukaryotic algae. Single-celled algae are the ancestors of the green plant kingdom. Among multicellular algae, along with floating algae, bottom forms (fucus, kelp) have also appeared. This way of life led to the division of the plant into parts: some serve to attach to the substrate, others for photosynthesis.

The algae developed sexual reproduction, which led to increased variability and the emergence of new properties that sometimes helped to adapt to changing environmental conditions.

Over time, the surface of the continents and the ocean floor have changed. Due to vibrations of the earth's crust, land could arise in place of the sea.

The transition of plants to a terrestrial way of life was associated with the existence of land areas periodically flooded with water and freed from it. The areas were drained gradually, and some algae began to develop adaptations to the terrestrial lifestyle. And ancient multicellular algae gave rise to higher plants.

Adaptation of plants to life on land:

• The emergence of mechanical tissue
• The emergence of conductive tissue
• The appearance of stomata on the leaves
• Ability to store water
• Reproduction gradually ceases to be associated with water (in gymnosperms and angiosperms)

Bibliography

1. Biology. Bacteria, fungi, plants. 6th grade: textbook. for general education. institutions / V.V. Beekeeper. - 14th ed., Stereotype. - M .: Bustard, 2011 .-- 304 p .: ill.
2. Tikhonova E.T., Romanova N.I. Biology, 6. - M .: Russian word.
3. Isaeva T.A., Romanova N.I. Biology, 6. - M .: Russian word.

1. O-planete.ru ().
2. Beaplanet.ru ().
3. Bio.fizteh.ru ().

Homework

1. Biology. Bacteria, fungi, plants. 6th grade: textbook. for general education. institutions / V.V. Beekeeper. - 14th ed., Stereotype. - M .: Bustard, 2011 .-- 304 p .: ill. - with. 288, tasks and questions 1, 2 ().
2. How did the appearance of photosynthesis affect the development of the plant?
3. Describe the process of getting plants to land.
4. * What do you think, could life not come out on land, but remain in the aquatic environment? What would she look like then? Justify the answer.

"Biology. Bacteria, fungi, plants. Grade 6". V.V. Beekeeper

Theory of the origin of plants. Stages of development of the plant world

Question 1. On the basis of what data can we say that the plant world developed and became more complex gradually?
It can be argued that the plant world developed and became more complex gradually, based on the data of paleontology - the science of extinct organisms, about their change in time and space. Fossil remains (fossils, prints) of plants indicate that in ancient times the flora of our planet was completely different from what it is now. It has been proven that over the centuries the climatic conditions on the planet have changed, plants were forced to adapt to them. As a result, the species composition of plant communities changed. Some plant species died out, others came to replace them.
The first living organisms appeared in the Archean era. They were heterotrophs who consumed organic compounds of the "primordial broth" as food. The most important stage in the evolution of life on Earth is associated with the emergence of photosynthesis, which led to the division of the organic world into plant and animal. The first photosynthetic organisms were blue-green algae - cyanea. Cyanei and the subsequent green algae released free oxygen from the ocean into the atmosphere. In the Proterozoic era, many different algae already lived in the seas, including forms attached to the bottom. At the beginning of the Paleozoic era, plants inhabit mainly the seas, but the first terrestrial plants, psilophytes, appear in the Ordovician-Silurian. Further evolution of plants on land was aimed at differentiating the body into vegetative organs and tissues, improving the vascular system (ensuring the rapid rise of water to a great height). Already in the arid Devonian, horsetails, moss, and ferns are widespread. In the Carboniferous period (Carboniferous), characterized by a humid and warm climate throughout the year. Gymnosperms appear, descended from seed ferns. The transition to seed reproduction gave many advantages: the embryo in the seeds is protected from unfavorable conditions by membranes and is provided with food, has a diploid number of chromosomes. In some gymnosperms (conifers), the process of sexual reproduction is no longer associated with water. Pollination in gymnosperms is carried out by the wind, and the seeds have adaptations for distribution by animals. Flowering plants appear that conquered the entire land, due to the fact that during fertilization they could already completely do without water (double fertilization, fetal development, pollination with the help of animals and humans). These and other benefits have contributed to the widespread adoption of seed plants. Large spore plants die out in the Permian period due to the drying out of the climate. At the beginning of the Cenozoic era, thermophilic vegetation retreats to the south or dies out, cold-resistant herbal and shrub vegetation appears, in large areas forests are replaced by steppe, semi-desert and desert. Modern plant communities are being formed.

Question 2. Where did the first living organisms appear?
The first living organisms appeared in the primordial ocean.

Question 3. What was the significance of the appearance of photosynthesis?
The most important stage in the evolution of life on Earth is associated with the emergence of photosynthesis, which led to the division of the organic world into plant and animal. The first photosynthetic organisms were blue-green algae - cyanea. Cyanei and the subsequent green algae released free oxygen from the ocean into the atmosphere. The composition of the air began to gradually approach the modern one, which includes mainly nitrogen, oxygen and a small amount of carbon dioxide. This contributed to the emergence of bacteria capable of living in an aerobic environment. This atmosphere contributed to the development of more advanced life forms. In addition, photosynthesis has become a new source of organic matter necessary for the life of all living organisms.

Question 4. Under the influence of what conditions did ancient plants move from aquatic life to terrestrial?
The transition of plants to a terrestrial mode of life was associated with the existence of periodically flooded and freed from water areas of land. The drainage of these areas occurred gradually, and some algae began to develop adaptations for living outside the water.

Question 5. What ancient plants gave rise to ferns, which - gymnosperms?
Ancient lyes, horsetails and ferns originated from rhinophyte-like plants. The ancestors of gymnosperms were tree-like, liana-like and herbaceous seed ferns.

Question 6. What is the advantage of seed plants over spore plants?
Seed-propagating plants are better adapted to life on land than spore-propagating plants. Fertilization in seed plants does not depend on the presence of water in the environment. Seeds (multicellular formations) have a much larger supply of nutrients than spores (they are unicellular). Embryo: the future plant, located inside the seed, is better protected from adverse conditions.

Question 7. Compare gymnosperms and angiosperms. What structural features provided an advantage for angiosperms?
Angiosperms turned out to be the most adapted plants for life on land. Angiosperms have a highly developed conducting system, the flower attracts pollinating insects, which ensures the reliability of cross-pollination, the embryo is supplied with food reserves (thanks to double fertilization, the triploid endosperm develops) and is protected by membranes, etc.

Goals:

• to generalize the knowledge of students about the main divisions of plants, to identify the stages of complication of the structure of plants and the factors of evolution of the plant world;
• bring schoolchildren to the conclusion about the kinship and unity of all life on Earth, continue to develop students' skills to analyze, draw conclusions, reason logically using problematic situations;
• to test the knowledge of students of previously studied material.

Equipment:

1. Flat plant models (chlamydomonas, kelp, cuckoo flax, pine)
2. Colored cards - 6 pcs. for the Bruner test.
3. Magnetic model of the development of the plant world from color flat pictures.
4. Magnetic board.
5. Multimedia equipment.
6. Interactive board.

During the classes

Today I want to start the lesson with the words of S.Ya. Marshak written on the board:

A man - even if he were three times a genius -
Remains a thinking plant.
Trees and grass are related to him,
Do not be ashamed of this relationship!

Read these lines again and tell me what thoughts came to you while reading.

Students' answers (approximate):

1. All living organisms have a cellular structure ...
2. Man is part of nature ...
3. No matter how smart a person is, he should not consider himself the king of nature ...
4. Man, trees, grass are all living organisms ...
5. Unity of origin of animals and plants ...

So, life has existed on our planet for billions of years. It fills all its corners: lakes, rivers, mountains, deserts, and even the air is inhabited by living beings. It is assumed that over the entire history of life on Earth, there were 4.5 billion species of plants and animals. But since ancient times, the best minds of mankind have been interested in the questions: how did life arise and develop on our Earth? Have plants and animals always been the same as they are now? Who was the first on Earth - plants or animals? ..

Do you care about these questions?

Which ones?

(I ask the children what interests them the most.)

So let's try today in the lesson to find answers to at least some of them ...

What can you tell by looking at this plate?

And the table has no name - what would you call it? (Evolution of the plant world.)

What is “evolution”? Who found the definition of this term at home? (Referring to the dictionary).

Children read out the answers from the dictionary of V. I. Dal, from the TSB, from the explanatory dictionary of Ozhegov. - The word “evolution” is Latin and in translation means “deployment”, and in a broad sense - any change, development, transformation. In biology, the word “evolution” was first used in 1762 by the Swiss naturalist and philosopher Charles Bonnet.

Where have you heard this word?

Can we use it in class today?

That's right, because the topic of our lesson "The main stages of the development of the plant world" we can write down the same way - "Evolution of the plant world".

IV. New material.

Approximate student answer:

3.5 billion years ago, the ancient Earth very little resembled the planet on which we live. Its atmosphere consisted of water vapor, carbon dioxide and, according to some sources, from nitrogen, according to others, from methane and ammonia. There was no oxygen in the air of the lifeless planet. And, I must say, the absence of oxygen was necessary for the emergence of life.

The land is covered with water. For centuries, torrential rains have been raging on the planet, accompanied by lightning strikes. And in this “warm diluted broth” the first living organisms (coacervates) are already found. This hypothesis of the origin of life on Earth was first expressed in 1922 by the Soviet biologist Alexander Oparin. The formed gelatinous lumps are difficult to call organisms, these are complex organic protein compounds. The structure of coacervates gradually became more complicated - this is how the first protozoan unicellular organisms appeared.

Teacher: Right! According to Oparin, the distance from these "clots" to the most primitive bacteria is no less than from amoeba to humans.

But, let's assume who they are - these first living organisms:

• Prokaryotes or eukaryotes
• What was the way they were fed (autotrophs or heterotrophs)
• Are they animals or plants? (There is a discussion).

Conclusion: The first living organisms that appeared on Earth were nuclear-free cells that fed on ready-made organic substances, and they can not be attributed to either the plant kingdom or the animal kingdom.

We will write down our knowledge in table No. 2. And on a magnetic board from flat models we will construct a dynamic picture of the development of the plant world on Earth. ( Slide № 8.)

The development of the plant world on Earth.

About 1 billion years have passed ...

The land is still a bare desert. But a new oxygen gas appears in the water. What does this indicate? Who do you think of their ancient organisms could be the culprit? the appearance of oxygen?

Student's answer: These were the first protozoa organisms that did not have enough nutrients that were on Earth and some cells adapted to using sunlight to convert water and carbon dioxide into organic matter, i.e. a process arose photosynthesis... And as a result of photosynthesis, oxygen began to accumulate. - What way of feeding organisms has appeared? Student response: These cells containing chloroplasts are autotrophs, i.e. themselves synthesize organic substances necessary for vital activity due to the energy of light. This is how the first plants.- Other living things have retained the same way of feeding - heterotrophic, primary plants began to serve them as food. These were the first animals. This happened in the Precambrian period. It lasted over 3 billion years.

Who else has additions for this period?

Approximate student answer:

During this period, the structure of living beings was more and more improved. The first unicellular plants, blue-green algae, learned to break down water. They accomplished a real feat - oxygen began to be released into the atmosphere. The composition of the air gradually approached the modern, i.e. consisted of nitrogen, oxygen, carbon dioxide. This atmosphere contributed to the development of more advanced life forms. Primary unicellular algae gave rise to multicellular algae.

Let's continue filling in Table 2.

Over time, the Earth's climate has changed. Due to vibrations of the earth's crust, dry land appeared in place of some seas and oceans. Primary seas began to grow shallow. And thanks to oxygen, a layer of ozone appeared in the upper layers of the atmosphere, softening ultraviolet radiation ... What then began to happen to some ancient algae under the influence of new living conditions?

Student response: some algae have become more sophisticated and adapted to live in humid places of land along the banks of water bodies. The transition of some plants from aquatic to terrestrial life began.

This happened ~ 350-400 million years ago.

What is the name of the oldest group of land plants? (psilophytes and rhinophytes)

What were they like?

Approximate student answer:

These plants covered the banks with a green carpet up to 25 cm high. They did not have roots, stems, leaves, but represented branching axes, on the underground parts of which rhizoids developed. In rhinophytes, tissue differentiation occurred: integumentary tissue (skin) and vascular bundles (wood and bast). Reproduction took place with the help of spores.

Let's enter this information into table number 2.

And where else can we use this meaning - rhinophytes?

Right. We will place this word in the empty frame of Table 1. These are the first higher plants that appeared on Earth.

Rhinophytes became the predecessors of which plants?

Student answer:

Ferns and mosses. The habitat is terrestrial, humid. Ferns developed a stem, leaves and roots.

In what period did ferns flourish?

Student answer:

In the Carboniferous period 300 million years ago.

Calamites spread like a continuous carpet, ferns branched out, giant horsetails rose in whole groves, lepidodendrons turned green ...

Let us write down the next stage of plant development in plate number 2.

At the end of the Carboniferous period, the climate on Earth became drier and colder, and tree ferns were replaced by the first primitive gymnosperms - seed ferns, the seeds developed on their leaves.

Living conditions continued to change. Where the climate became more severe, ancient spore plants died out and ancient gymnosperms appeared.

Student answer: Gymnosperms are seed plants. They reproduce by seeds that are not protected by the walls of the fruit (gymnosperms do not have flowers and fruits). The emergence of a seed is an important stage in the evolution of a plant. The supply of nutrients in the seed ensures the life of the embryo when it is especially vulnerable - in the initial period of its development. Strong seed covers protect the embryo from adverse environmental factors. These evolutionary acquisitions and the independence of fertilization from the availability of water (in contrast to spore plants) caused the widespread distribution of gymnosperms on land.

Let's enter this data into table number 2:

120 million years ago

What event happened during this time period?

Approximate student answer:

Angiosperms descend from gymnosperms, but which families are more ancient and closer to gymnosperms is not precisely determined by science. Some scientists believe that the most ancient angiosperms are catkins (birch, alder, willow), others are polycarpous: magnolias and buttercups.

Angiosperms differ from gymnosperms by the presence of a flower, fruit, sepals, petals, as well as the formation of a pistil through which the pollen tube grows to the ovule and ovum. The seeds of angiosperms develop inside the fruit and are well protected by the pericarp.

Angiosperms have been dominating the Earth for over 60 million years. This is the only plant group forming complex multi-tiered communities. This contributes to a more intensive use of the environment and the successful conquest of new territories.

Let's finish drawing up our plate number 2:

Summary table "Development of the flora on Earth".

Development stages	Habitat	Time of occurrence
The emergence of life on earth	Water	2-3 billion liters back
The emergence and dominance of algae	Water	1.5 - 2 billion years ago.
Plant emergence on land	Land-water	350-400 million years ago.
The emergence and dominance of ferns	Ground wet	300 million years ago
The emergence and dominance of gymnosperms	Land	Over 200 million years ago
The emergence and domination of port-seed	Land	About 120 million years ago

At home, you will consolidate the information received by reading pr. 58 + plate in the notebook.

What is the word written on the board? (Paleobotany.) What does it mean?

Student answer: Paleobotany is a science that studies plants from past eras.

From the fossil remains of plants, scientists have established that the older the organisms, the simpler they are. The closer to our time, the more complex organisms become and more and more similar to modern ones.

So, as a result of the development of the organic world, higher plants and highly organized animals appeared, as well as a thinking person who tries to get an answer to the question: "When and how did life arise on Earth?"

And an inquiring mind finds these answers ( Slide № 11.):

"The thinking mind does not feel happy until it succeeds in tying together the various facts it observes."

D. Hevelsey.

Did you feel happy? What is happiness? Why? (Lesson summary.)

I give an overall assessment of the work of students in the lesson.

The origin of plants. The main stages of the development of the plant world.

The diversity of the plant world. Methods for studying ancient plants.

task 190 in the workbook

Paleontology is the science of extinct organisms, their change in time and space.

Paleobotany- studies fossil remains of ancient plants.

Fossils

Prints

pollen in sedimentary rocks

The earth was formed- more than 5 billion years ago.

The stages of evolution of the plant world- five.

The first living organisms appeared- 3.5 - 4 billion years ago in water. They were similar in structure to bacteria. Organic and mineral substances dissolved in water were used for food, the supply of which was gradually depleted and chlorophyll appears in some cells, which led to the occurrence of the process of photosynthesis. From the ancient protozoa, unicellular algae originated. Among the algae, those attached to the bottom appear, which led to the dismemberment of the body into parts: some serve for attachment, others carry out the process of photosynthesis.

CAMBRIAN SYSTEM:

Presented by primitive algae .

Ordovician system:

There were various types of algae. In the late Ordovician, the first true terrestrial plants appeared.

The first ground organisms - rhinophytes, the appearance of which is associated with the existence of periodically freed from water areas of land. Their structure resembled the structure of multicellular algae. They had a tree-like shape.

Silurian:

Plants populated the shores of reservoirs. The predominance of primitive psilophid plants.

Spore plants(flowering) arose about 300 million years ago, from rhinophyte-like plants. These were ancient ploons, horsetails and ferns. During sexual reproduction, they needed water.

Devonian system:

Plants managed to move away from the water's edge and soon vast areas of land were overgrown with dense primeval forests.

The number of various vascular plants has increased.

Spore lycophytes (lycophytes) and horsetails appeared, some of them developed into true trees 38 m high.

Coal system:

The river deltas and the shores of vast bogs are overgrown with dense forests of giant ploons, horsetails, tree ferns and seed plants up to 45 m high.

The undecomposed remains of this vegetation have over time turned into coal.

Permian system:

Forests of large seed ferns-glossopteris have spread over the southern land masses.

The first conifers appeared, quickly populating inland areas and high mountains.

Among terrestrial plants, arthropod ferns and gymnosperms predominated.

Gymnosperms arose about 345 million years ago, when the Earth's climate became drier and colder. These were primitive gymnosperms that evolved from tree, liana and herbaceous seed ferns.

Angiosperms arose about 130 million years ago. The angiosperms turned out to be the most adapted to life on land and created a diverse vegetation cover on the Earth.

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Slide captions:

The origin of plants. The main stages of the development of the plant kingdom.

The diversity of the plant world. Methods for studying ancient plants. task 190 in the workbook Paleontology is the science of extinct organisms, their change in time and space. Paleobotany - studies the fossil remains of ancient plants. Fossils Imprints Spores of pollen in sedimentary rocks

The earth was formed - more than 5 billion years ago. There are five stages in the evolution of the plant world. The first living organisms appeared 3.5 - 4 billion years ago in water. They were similar in structure to bacteria. Organic and mineral substances dissolved in water were used for food, the supply of which was gradually depleted and chlorophyll appears in some cells, which led to the occurrence of the process of photosynthesis. From the ancient protozoa, unicellular algae originated. Among the algae, those attached to the bottom appear, which led to the dismemberment of the body into parts: some serve for attachment, others carry out the process of photosynthesis.

Represented by primitive algae. CAMBRIAN SYSTEM:

Ordovician System: There were various types of algae. In the late Ordovician, the first true terrestrial plants appeared.

The first terrestrial organisms are rhinophytes, the appearance of which is associated with the existence of land areas periodically freed from water. Their structure resembled the structure of multicellular algae. They had a tree-like shape.

Silurian period: Plants colonized the shores of water bodies. The predominance of primitive psilophid plants.

Spore plants (flowering) arose about 300 million years ago, from rhinophyte-like plants. These were ancient ploons, horsetails and ferns. During sexual reproduction, they needed water.

Devonian system: Plants managed to move away from the water's edge and soon vast areas of land were overgrown with dense primeval forests. The number of various vascular plants has increased. Spore lycophytes (lycophates) and horsetails appeared, some of them developed into true trees 38 m high.

Carboniferous system: Deltas of rivers and the banks of vast swamps are overgrown with dense forests of giant ploons, horsetails, tree ferns and seed plants up to 45 m high. The undecomposed remains of this vegetation have turned into coal over time.

Permian system: Forests of large seed ferns-glossopteris have spread over the southern land masses. The first conifers appeared, quickly populating inland areas and high mountains. Among terrestrial plants, arthropod ferns and gymnosperms predominated.

Gymnosperms originated about 345 million years ago, when the Earth's climate became drier and colder. These were primitive gymnosperms that evolved from tree-like, liana-like, and herbaceous seed ferns.

Angiosperms originated about 130 million years ago. The angiosperms turned out to be the most adapted to life on land and created a diverse vegetation cover on the Earth.

There are many hypotheses regarding the possible pathways of the origin of the main kingdoms of living nature. Let us consider the main paths of the historical development of the kingdoms of plants and animals, which are the most studied from this point of view.

The number of species of currently existing plants reaches 500 thousand, of which about 300 thousand are flowering species. The first autotrophs were cyane and partly green algae. Their remains are found in rocks even Archean age.

V proterozoic the seas were inhabited by many different representatives of green and golden algae. At the same time, algae attached to the bottom appear to have appeared. On the surface of a lifeless land, the first soil is created, resulting from the action of abiotic (climatic conditions) and biotic (presence of bacteria and cyanide) conditions.

V paleozoic a major evolutionary event is taking place in the plant kingdom - plants come out onto dry land. However, in the early periods of this era, plants still inhabit mainly the seas. There are green and brown algae attached to the bottom, and in the water column, diatoms, golden, euglena. At the end Ordovician and the beginning silurian and the appearance of the first terrestrial plants, psilophytes, was noted, which covered the coastal land areas with a continuous green carpet. Rearrangements take place in the vascular system and integumentary tissues of plants: a vascular system with poorly differentiated phloem and xylem, cuticle and stomata appear. Psilophytes were found to be more reliably attached to the substrate using dichotomously branched lower axes. Some have primitive leaves. Psilophytes occupied an intermediate position between terrestrial vascular plants and algae.

Further evolution of plants under terrestrial conditions led to an increase in the compactness of the body, the appearance of roots, the development of epidermal tissue with thick walls impregnated with wax-like substances, a change in the methods of reproduction, distribution, etc.

From the moment of reaching land, plants develop in two main directions: gametophytic and sporophytic. The gametophytic direction was represented by mosses, the sporophytic direction by the rest of the plants. The sporophyte branch turned out to be more adapted to the terrestrial way of life. In these plants, the root and vascular systems, integumentary and mechanical tissues gradually improved and became more complex. Already in devonian there are lushly overgrown forests of horsetails, lycopods, ferns and ancient gymnosperms (Kordaites).In carbon these forests are even more widespread, and the climate is humid and evenly warm throughout the year. Plants grow up to 40 m in height.

In the same period, the first seed woody plants from gymnosperms are found, the flowering of which occurs at the end carbon – Permian period. Their difference from ferns and buoyancy is the transformation of the megasporangium into an ovule. Complete release of water from a part of the plants of the process of sexual reproduction. So, pollination in gymnosperms is carried out by the wind and after fertilization the ovule turns into a seed, and the seeds have adaptations for spreading by wind and animals.

Mesozoic the era is characterized by intensive mining processes: the Urals, Tien Shan, Altai and others appear. Climate drainage continues, the areas of oceans and seas are shrinking. V triassic the development of deserts, the extinction of giant ferns, treelike horsetails, and lyre are noted. V jurassic period, against the background of the flowering of gymnosperms, the first angiosperms appear and bennetite- the prototype of flowering plants.

Angiosperms are gradually spreading, conquering all continents, which is associated with the presence of a number of advantages in them. Angiosperms have a highly developed conducting system, a flower and a fruit (the embryo is supplied with a supply of nutrients). In the process of evolution, the flower undergoes significant changes. Plants with cross-pollination were given preference. Pollinators were attracted by the aroma of nectar, the bright color of the flower.

Cenozoic the era is considered the heyday of the angiosperms. At the beginning of the Cenozoic, the climate is still warm. In the Neogene and Paleogene, the Andes, Pyrenees, Himalayas are formed, the Mediterranean, Black, Caspian and Aral seas are isolated. Botanical and geographical areas close to modern ones are being formed. In the north, coniferous forests prevail, in the south - chestnut-beech forests with the participation of sequoias and ginkgo. All of Europe was covered with lush forests of trees such as oak, birch, pine, chestnut, beech, grape, walnut, etc. The climate is warm and temperate.

In the quaternary period of the Cenozoic era (2-3 million years ago), the amount of precipitation increased and a significant part of the Earth glaciated, which caused the extinction or retreat of thermophilic Tertiary vegetation to the south. Cold-resistant herbaceous and shrub plants have appeared. On vast territories, forests were replaced by steppe, semi-desert and desert. Vegetation appears with a pronounced seasonality in the development cycle, modern phytocenoses are formed.

Thus, the main features of the evolution of the plant kingdom are as follows:

1. Transition from haploid to diploid. In many algae and mosses, all cells (except for the zygote) are haploid. In ferns, an independent gametophyte is still present, but already in gymnosperms and angiosperms, a complete reduction of the gametophyte and a transition to the diploid phase are observed.

2. Liberation of the process of sexual reproduction from the presence of water.

3. Differentiation of the body with the transition to ground conditions: root, stem, leaf.

4. Specialization of pollination (insects).

The first plant organisms arose in the will at a very distant time. The first living things were microscopically small lumps of mucus. Much later, some of them developed a green coloration, and these living organisms became similar to unicellular algae. Single-celled creatures gave rise to multicellular organisms, which, like single-celled ones, arose in water. A variety of multicellular algae developed from unicellular algae.

The surface of the continents and the ocean floor have changed over time. New continents were rising, those that existed before were submerged. Due to vibrations of the earth's crust, dry land arose in place of the seas. The study of fossil remains shows that the flora of the Earth also gradually changed.

The transition of plants to a terrestrial way of life, according to scientists, was associated with the existence of periodically flooded and freed from water areas of land. The receding water lingered in the depressions. They then dried up, then again filled with water. The drainage of these areas took place gradually. Some algae have developed adaptations for living outside the water.

The climate at that time on the globe was humid and warm. The transition of some plants from aquatic to terrestrial life began. The structure of these plants gradually became more complex. They gave rise to the first land plants. The oldest known land plant group is psilophytes.

The development of the plant kingdom on Earth is a long-term process, which is based on the transition of plants from aquatic to terrestrial life.

Psilophytes already existed 420-400 million years ago, and later became extinct. Psilophytes grew along the banks of water bodies and were small, multicellular green plants. They did not have roots, stems, leaves. The role of roots was played by rhizoids. In psilophytes, in contrast to algae, a more complex internal structure is the presence of integumentary and conductive tissues. They multiplied by spores.

From psilophytes came bryophytes and ferns, which already had stems, leaves and roots. The flowering of ferns was about 300 million years ago in the Carboniferous period. The climate at this time was warm and humid. At the end of the Carboniferous period, the Earth's climate became noticeably drier and colder. Treelike ferns, horsetails and moss began to die out, but by this time primitive gymnosperms had appeared - the descendants of some ancient ferns. According to scientists, the first gymnosperms were seed ferns, which later became completely extinct. Their seeds developed on the leaves: these plants did not have cones. Seed ferns were treelike, liana-like and herbaceous plants. From them gymnosperms originated.

Living conditions continued to change. Where the climate was more severe, ancient gymnosperms gradually died out and were replaced by more perfect plants - ancient conifers, then they were replaced by modern conifers: pine, spruce, larch, etc.

The transition of plants to land is closely associated not only with the appearance of such organs as the stem, leaf, root, but, mainly, with the appearance of seeds, a special way of reproduction of these plants. Seed-propagated plants are better adapted to life on land than spore-propagated plants. This became especially clear when the climate became less humid.

On the outgrowths developing from spores (in mosses, moss, ferns), female and male gametes (sex cells) are formed - eggs and spermatozoa. In order for fertilization to occur (after the fusion of gametes), atmospheric or ground water is needed, in which sperm move to the eggs.

Gymnosperms do not need free water for fertilization, since it occurs inside the ovules. They have male gametes (sperm) approaching female (eggs) through pollen tubes growing inside the ovules. Thus, fertilization in spore plants is completely dependent on the availability of water; in plants that reproduce by seeds, this dependence is not.

Angiosperms - descendants of ancient gymnosperms - appeared on Earth over 130-120 million years ago. They turned out to be the most adapted to life on land, since only they have special reproductive organs - flowers, and their seeds develop inside the fruit and are well protected by the pericarp.

Thanks to this, angiosperms quickly spread throughout the Earth and occupied a wide variety of habitats. For more than 60 million years, angiosperms have dominated the Earth. In fig. 67 shows not only the sequence of the appearance of certain parts of plants, but also their quantitative composition, where a significant place is allocated to angiosperms.