The evolutionary ladder of plants. Stages of evolution of the plant world

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.

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

The surface of the continents and the bottom of the ocean 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 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 drying of these areas occurred gradually. Some algae have developed adaptations for living out of water.

The climate at that time on the globe was humid and warm. The transition of some plants from aquatic to terrestrial lifestyle has begun. The structure of these plants gradually became more complex. They gave rise to the first land plants. The most ancient group of known land plants are the psilophytes.

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

Psilophytes already existed 420-400 million years ago, and later died out. Psilophytes grew along the banks of water bodies and were small multicellular green plants. They had no roots, stems, leaves. The role of their roots was performed by rhizoids. Psilophytes, unlike algae, have a more complex internal structure - the presence of integumentary and conductive tissues. They reproduced by spores.

Bryophytes and ferns evolved from psilophytes, which already had stems, leaves and roots. The heyday of ferns was about 300 million years ago in the Carboniferous period. The climate at that time was warm and humid. At the end of the Carboniferous period, the Earth's climate became noticeably drier and colder. Tree ferns, horsetails and club mosses 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 subsequently became completely extinct. Their seeds developed on the leaves: these plants did not have cones. Seed ferns were tree-like, liana-like and herbaceous plants. Gymnosperms originated from them.

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 connected 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. Plants propagated by seeds are better adapted to life on land than plants propagated by spores. This became especially clear when the climate became less humid.

On the growths developing from spores (in mosses, club mosses, 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 groundwater is needed, in which the spermatozoa move to the eggs.

Gymnosperms do not need free water for fertilization, since fertilization occurs inside the ovules. They have male gametes (spermatozoa) approaching female gametes (eggs) along the pollen tubes growing inside the ovules. Thus, fertilization in spore-bearing plants is completely dependent on the availability of water; in plants propagating by seeds, this dependence is not present.

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 settled throughout the Earth and occupied a wide variety of habitats. For more than 60 million years, angiosperms have dominated the Earth. On fig. 67 shows not only the sequence of appearance of certain divisions of plants, but also their quantitative composition, where angiosperms are given a significant place.

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 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 plants (green, brown and red algae), as well as fungi, arose.

Basic conditions and stages of plant evolution

■ blue-green and green algae are widespread in the Proterozoic era;

■ formation of soil substrate on land at the end of the Silurian period;

■ Land development 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. Reproduction by seeds 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;

I the Carboniferous period of the Paleozoic era is distinguished by a large variety of terrestrial vegetation. Arborescent ferns spread, forming coal forests;

■ In the Cretaceous period, the flowering of angiosperms begins, continuing to this day.

The main features of the evolution of the plant world

i Transition to the predominance of the diploid generation over the haploid one.

■ Development of a female shoot on the mother plant.

■ Transition from spermatozoa to injection of the male nucleus through the pollen tube.

■ The dismemberment of the body of plants into organs, the development of a conductive vascular system, supporting and protective tissues.

■ Improvement of organs of reproduction and cross-pollination in flowering plants in connection with the evolution of insects.

■ Development of the embryo sac to protect the embryo from adverse environmental influences.

■ The emergence of a variety of ways to distribute seeds and fruits.

The most ancient traces of animals belong to the Precambrian (about 700 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.

Sponges, coelenterates, worms, echinoderms, and trilobites predominate in the Cambrian and Ordovician periods. Shellfish 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. Amphibians and then other classes of vertebrates arose from this group of fish.

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 appearance 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, presumably, a group of dinosaurs 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 were the feeding of young with milk, warm-bloodedness, and a developed cerebral cortex.

Progressive development of multicellularity and, as a result, specialization of tissues and all organ systems.

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 body developed and improved.

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.

The evolution of animals led to the development of group adaptive behavior, which became the basis for the appearance of man.

EXAMPLES OF TASKS №49

1. Tell us about the main stages in the development of the organic world, listing the main "acquisitions" of plants and animals.

2. What is the relationship between the conquest of land by vertebrates and the development of the nervous system?

3. What is the connection between the appearance of a flower and the flowering of insects.

4. What aromorphoses of mammals ensured their ubiquitous distribution?

ANTHROPOGENESIS. DRIVING FORCES. ROLE OF LAWS

PUBLIC LIFE IN SOCIAL BEHAVIOR

HUMAN

The most significant contribution to the solution of the problem of anthropogenesis was made by Charles Darwin in his work "The Origin of Man and Sexual Selection". He substantiated the evolutionary relationship of man with the higher apes. The evolution of man as a biological species took place within the family of hominids (humans).

Hominids are the second branch that separated from the higher narrow-nosed monkeys (hominoids). The first branch is pongids, or anthropomorphic monkeys: orangutan, gorilla, chimpanzee.

The main directions and results of human biological evolution were:

■ development of bipedalism;

■ release of the upper limb of the grasping type;

■ increase in brain volume and significant development of the cerebral cortex; complication of higher nervous activity.

Social factors in human evolution

■ use, and then the creation of tools;

■ the need for adaptive behavior in the process of establishing a social way of life;

■ the need to predict one's activities;

■ the need to educate and educate offspring, passing on the accumulated experience.

Driving Forces of Anthropogenesis

■ individual selection aimed at morphophysiological traits - upright posture, hand structure, brain development;

■ group, aimed at social organization;

■ biosocial selection, the result of the joint action of the first two forms of selection. He acted at the level of an individual, a family, a tribe.

V Proterozoic era(about 1 billion years ago), the trunk of the most ancient eukaryotes was divided into several branches, from which plants, fungi and animals arose. Most of the plants of that time floated freely in the water, some were attached to the bottom.

Multicellular algae were the original branch for terrestrial leafy plants. In the end Silurian period of the Paleozoic era due to intensive mountain-building processes and the 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. The other part, as a result of multidirectional variability and adaptation to the terrestrial environment, acquired features that contributed to survival in new conditions. Such signs in the first terrestrial plants - rhinophytes - are the differentiation of tissues into integumentary, mechanical and conductive 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 mineral substances, formed a soil substrate on the surface of the land.

V Devonian rhiniophytes were replaced by club mosses, 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.

V carboniferous period(Carbone) the first gymnosperms appear, which arose 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 drop-liquid medium. The resulting seed plants could have lived in drier climates. In the Permian period, the climate in many regions of the Earth became drier and colder, tree-like spore-bearing plants, which reached their peak in the Carboniferous, die out. In the same period, the flowering of gymnosperms began, which dominated the Mesozoic era. The evolution of higher land plants has taken the path of ever greater reduction of the haploid generation (gametophyte) and the predominance of the diploid generation (sporophyte).

V Cretaceous 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 devices for pollinating flowers and distributing fruits and seeds allowed angiosperms to occupy Cenozoic dominant position in the plant world.

The main features of the evolution of the plant world

1. gradual transition to the dominant position of the sporophyte over the gametophyte in the development cycle;
2. access to land, differentiation of the body into organs (root, stem, leaf) and differentiation of tissues (conductive, mechanical, integumentary);
3. transition from external fertilization to internal; occurrence of double fertilization;
4. the emergence of seeds containing a supply of nutrients and protected from the effects of adverse environmental conditions by seed coats (and the walls of the pericarp in angiosperms);
5. improvement of organs of reproduction and cross-fertilization in angiosperms in parallel with the evolution of insects;
6. the emergence of various ways of dispersal of fruits and seeds.

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

Warm, humid conditions also existed in the northern mid-latitudes (Siberia and Northwest 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, the terrestrial vegetation was dominated by conifers of Cheirolipidaceae and Matoniaceae ferns.

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 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 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.