Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.
Moss moss
Moss-moss- one of the most ancient divisions of higher spore plants. Currently, they are represented by a relatively small number of genera and species, the participation of which in the vegetation cover is usually insignificant. Perennial herbaceous plants, usually evergreen, resembling green mosses in appearance. They are found mainly in forests, especially coniferous ones.
There are about 400 species, but only 14 are common in Russia (club-shaped moss, ram-moss, double-edged moss, etc.).
The structure of mosses
Lycopods are characterized by the presence of shoots with spirally, less often oppositely and whorled leaves. The underground parts of the shoots of some lycophytes have the appearance of a typical rhizome with modified leaves and adventitious roots, while in others they form a peculiar organ bearing spirally arranged roots and called a rhizophore (rhizophore). Roots of lycophytes are adventitious.
Nutrition and reproduction of mosses
Sporophylls may be similar to ordinary vegetative leaves, sometimes different from them. Among the lycophytes there are equi- and heterosporous plants. Homosporous gametophytes are underground or semi-underground, fleshy, 2-20 mm long. They are bisexual, saprophytic or semi-saprophytic, and mature within 1-15 years. Gametophytes of heterosporous unisexuals, non-green, usually develop within several weeks due to the nutrients contained in the spore, and upon maturity do not protrude or protrude slightly outside the spore shell. The reproductive organs are represented by antheridia and archegonia: in the former, bi- or multiflagellate sperm develop, and in archegonia, eggs develop. Fertilization occurs in the presence of drip-liquid water, and a sporophyte grows from the zygote.
Sporophyte club moss is a perennial evergreen plant. The stem is creeping, branched, produces vertical branched shoots about 25 cm high, densely covered with leaves that look like elongated pointed scales. Vertical shoots end in spore-bearing spikelets or apical buds. On the shaft of the spore-bearing spikelet there are sporophylls with sporangia on the upper side. The spores are identical, contain up to 50% non-drying oil, and germinate very slowly. The gametophyte develops in the soil in symbiosis with a fungus (mycorrhiza), which, receiving carbohydrates, amino acids and phytohormones from the vascular plant, makes water and minerals, especially phosphorus compounds, available for absorption and absorption by the plant. In addition, the fungus provides the plant with a larger absorption surface, which is especially important when it grows in poor soil. The gametophyte develops over 12-20 years, has rhizoids, and does not have chloroplasts. However, in some species it develops on the soil surface, then chloroplasts appear in its cells.
Gametophyte bisexual, shaped like an onion, acquires a saucer-shaped shape as it develops, and bears numerous antheridia and archegonia. Mature antheridia are almost completely immersed in the gametophyte tissue or slightly protrude above its surface. The archegonium consists of a narrow abdomen immersed in the tissue of the gametophyte and a long or short neck protruding above its surface. Antheridia usually mature before archegonia. The zygote germinates without a dormant period and gives rise to an embryo. Vegetatively propagated by parts of the stem and rhizome. Some club mosses also have specialized organs for vegetative reproduction: brood nodules on the roots, brood bulbs or buds on the tops of shoots.
Development cycle of clubmoss: A - sporophyte; B - gametophyte; 1 - creeping shoot with adventitious roots; 2 - ascending shoots; 3 - stalk of spore-bearing spikelets; 4 - leaves: ascending shoot (a) and stalks of spore-bearing spikelets (b); 5 - spore-bearing spikelets; 6 - sporolists: view from the ventral (c) and dorsal (d) sides; 7 - sporangia; 8 - disputes; 9 - germinating spore; 10 - archegonium; 11 - antheridium; 12 - fertilization; 13 - fertilized egg; 14 - development of a new sporophyte on the gametophyte.
Equisetaceae (Horsetails)
The living species are exclusively herbaceous plants ranging in height from a few centimeters to several meters.
In all types of horsetail, the stems have a regular alternation of nodes and internodes.
The leaves are reduced to scales and arranged in whorls at the nodes. Lateral branches are also formed here.
The underground part of horsetails is represented by a highly developed rhizome, in the nodes of which adventitious roots are formed. In some species (horsetail), the lateral branches of the rhizome turn into tubers, which serve as a place for the deposition of reserve products, as well as organs of vegetative propagation.
The structure of horsetails
Horsetails are herbaceous plants with annual above-ground shoots. A small number of species are evergreen. The size of horsetail stems varies greatly: there are dwarf plants with a stem 5-15 cm high and a diameter of 0.5-1 mm and plants with a stem several meters long (in the polychaete horsetail the stem reaches a length of 9 m). Tropical forest horsetails reach a height of 12 m. The underground part is a rhizome, creeping, branched, in which nutrients can be deposited (tubers are formed) and which serves as an organ of vegetative propagation. Aboveground shoots grow at the top. Summer shoots are vegetative, branched, assimilating, consist of segments, with well-developed internodes. Whorled and also dissected branches branch off from the nodes. The leaves are inconspicuous and grow together into toothed sheaths that cover the lower part of the internode. Silica is often deposited in the epidermal cells of the stem, so horsetails are a poor food.
Spring shoots are spore-bearing, non-assimilating, unbranched, and spore-bearing spikelets are formed at their apex. After the spores mature, the shoots die. The spores are spherical, with four springy ribbons, greenish, germinate into shoots, unisexual - male or female. There are cases when antheridia and archegonia appear on the same prothallus. From the fertilized egg, a pre-adult grows, and then an adult horsetail.
Horsetails often make up a significant percentage of grasslands and wetlands; common in acidic soil. Most often, we have horsetail, meadow horsetail, marsh horsetail, marsh horsetail and forest horsetail.
Horsetails reproduce sexually. The sexual generation is the gametophyte (prothallus). Antheridia and archegonia are formed on gametophytes. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of drip-liquid water, and a sporophyte grows from the zygote without a rest period.
Ferns are found virtually all over the globe, from deserts to swamps, rice fields and brackish ponds. They are most diverse in tropical rainforests. There they are represented by both tree-like forms (up to 25m in height) and herbaceous and epiphytic forms (growing on tree trunks and branches). There are species of ferns only a few millimeters long.
The structure of ferns
The common fern plant we see is the asexual generation, or sporophyte. In almost all ferns it is perennial, although there are a few species that have an annual sporophyte. Ferns have adventitious roots (only in some species they are reduced).
Ferns - photo
The foliage, as a rule, prevails in weight and size over the stem. Stems can be erect (trunks), creeping or climbing (rhizomes); often branch. Our forest ferns (ostrich, bracken, male shield) have a well-developed rhizome with numerous adventitious roots extending from it. Only large pinnately dissected leaves - fronds - are located above the ground.
The young leaf is curled in a snail-like manner; as it grows, it straightens out. In some species, leaf development occurs within three years. The leaves of ferns grow from their apex like stems, indicating their origin from the stem. In other groups of plants, leaves grow from the base.
In size, they can range from several millimeters to three or more meters in length and in most species they perform two functions - photosynthesis and sporulation.
Fern propagation
On the underside of the leaf there are usually brown tubercles - sori with sporangia located in them, covered on top with a thin film. In sporangia, as a result of meiosis, haploid spores are formed, with the help of which fern reproduction occurs.
From a forest fern spore that finds itself in favorable conditions, a haploid prothallus develops, a gametophyte, a small green heart-shaped plate, up to 1 cm in diameter. The shoot grows in shaded, moist places and is attached to the soil with the help of rhizoids. Antheridia and archegonia develop on the underside of the gametophyte.
The “conquest” of land by ferns turned out to be incomplete, since the gametophyte generation can only exist with an abundance of moisture and shade, and an aquatic environment is necessary for the fusion of gametes.
Horsetails - structure
Horsetail - photo Horsetails are represented mainly by fossil forms. They arose during the Devonian and flourished in the Carboniferous period, reaching a wide variety of forms - up to giants 13 m high.
Modern horsetails number about 32 species and are represented by small forms - no more than 40 cm in height. They are found from the tropics to the polar regions, with the exception of Australia, and can live in both wet and dry areas. Some species have silicon deposits in the epidermis, which gives them a rough appearance.
Reproduction and development of horsetails
The sporophyte of horsetails consists of a horizontally branched underground stem - a rhizome, from which thin, branching roots and articulated aboveground stems extend. Some lateral branches of the rhizome are capable of forming small tubers with a supply of nutrients.
The stem contains numerous vascular bundles arranged in a ring around the central cavity. On the stems, as well as on the rhizome, nodes are clearly visible, giving them a segmented structure.
A whorl of secondary branches extends from each node. The leaves are small, wedge-shaped, also arranged in whorls, covering the stem in the form of a tube. Photosynthesis occurs in the stem.
In addition to assimilating stems, horsetail also has unbranched, spore-bearing shoots of brown color, at the ends of which sporangia develop, collected in spikelets. Spores form in them. After the spores spill out, the shoots die off and are replaced by green branching (vegetative, summer) shoots.
Moss mosses - structure
Moss mosses were widespread during the late Devonian and Carboniferous periods. Many of them were tall tree-like plants. At present, a small number of species (about 400) have been preserved compared to the past - all of these are small plants - up to 30 cm in height. In our latitudes they are found in coniferous forests, less often in swampy meadows. The bulk of club mosses are inhabitants of the tropics.
Our common species is the club moss. It has a stem creeping along the ground, from which needle-branched side shoots extend vertically upward. Its leaves are thin, flat, arranged in a spiral, densely covering the stem and side branches. The growth of clubmosses occurs only at the growing point, since there is no cambium in the stem.
Annual moss - photo Reproduction of club mosses
At the top of the stem there are special leaves - sporophylls, collected in a strobile. Outwardly, it resembles a pine cone.
A germinating spore produces a germ (gametophyte), which lives and develops in the ground for 12-20 years. It has no chlorophyll and feeds on fungi (mycorrhiza). The change of sexual and asexual generations in horsetails and mosses occurs in exactly the same way as in ferns.
Fossil ferns formed thick layers of coal. Hard coal is used as fuel and raw material in various industries. Gasoline, kerosene, flammable gas, various dyes, varnishes, plastics, aromatics, medicinal substances, etc. are obtained from it.
The meaning of ferns, horsetails and mosses
Modern pteridophytes play a significant role in the formation of plant landscapes on Earth. In addition, people use horsetails as a diuretic and as an indicator of soil acidity. Due to the rigidity of the stems, associated with silicon deposits in the cell walls, horsetails were used for polishing furniture and cleaning dishes.
Moss moss spores are used in medicine as a powder, and male shield spores are used as an anthelmintic. They are used to treat tobacco addiction, alcoholism and eye diseases. Some species of fern-like plants are bred as ornamental plants (adiantum, asplenium, nephrolepis).
Since the gametophyte of club mosses develops very slowly (12-20 years), these plants should be protected.
Equisetophyta (sphenophyta).
Equisetophyta - from the Latin horse bristles. Sphenophyte - the name articulate reflects the structural features of the shoots. The nodes contain an intercalary meristem.
Horsetails, like lycophytes, appeared in the Upper Devonian. Paleozoic era, most widespread in the late Paleozoic (Carboniferous period) were part of vast forests, were large, tree-like, tall. Today, the last few remnants of a once extensive group that went extinct at the beginning of the Mesozoic are observed.
Modern representatives are perennial plants, rhizomatous, herbaceous, all belong to the same genus horsetail, the predominant generation in the cycle is the sporophyte, the body of the sporophyte is divided into a well-developed above-ground shoot. Its height ranges from several centimeters to several meters. There is also a well-developed rhizome, with adventitious roots extending from it.
All horsetails are characterized by a clear division of the stem, lateral branches and rhizomes into nodes and hollow internodes. The branching is whorled.
Horsetail produces two types of stems
1. Non-chlorophyllous, bearing spores, quickly dying.
2.Green, vegetative.
(Both are longitudinally grooved.)
In other horsetails, such as Horsetail, the strobile develops on a vegetative shoot.
The leaves of modern horsetails are very small, have the appearance of scales or teeth, but their origin is different from the leaves of club mosses. Macrophilic lineage of evolution leaf.
The extinct horsetails from the cuneate-leaved class had relatively large leaves. They had dichotomous venation, their evolutionary development consisted of thickening, convergence, fusion, and reduction.
Due to the fact that the leaves of modern horsetails are small, the function of the leaves is taken over by the stem.
The roots are only adventitious, extending from the rhizome.
Sporiferous spikelet (strobilus)
In extinct horsetails, the strobili had a rather complex structure, in modern ones they are simpler: on the axis of the spikelet sporangiophores (sporophylls, leaves bearing sporangia) are located in a whorled pattern; they are sharply different from leaves, lack chlorophyll and bear sporangia. Horsetails are homosporous.
Among living plants there are no heterosporous plants; extinct horsetails were heterosporous. In clinolists, in calomites. Spores in horsetails differ from other spores in higher plants: they have 3 shells, 2 of which are exine and intine. There is a 3rd feather bed (external). Which is divided into 2 ribbon-like elotera springs (with the ability to move). Depending on the humidity of the environment, they curl up around the spore body, or in humid weather, on the contrary, they unwind, loosen and form a loose spore mass that can fly out of the sporangium. These spores fall out of the sporangium and germinate in close proximity to the sporangium. The gametophytes of modern horsetails have the appearance of a lobed or rugged upper part of a green plate several millimeters thick. Multilayered, attached to the soil using rhizoids. For a long time, gametophytes were considered dioecious, although all modern horsetails are homosporous. As a result of artificial cultivation and observation, it was determined that gametophytes are potentially bisexual, but development begins as male and female. On females, antheridia can form with age, but on males, archegonia are never formed, thus horsetails exhibit morphological homosporous and physical heterosporous.
Classification
Division Equisetae
1. Class wedge-leaved (possessed secondary growth, formed thickets, a meter long, ribbed surface, with the ribs moving from one internode to another without alternation, on the stems of whorls of leaves. The most ancient ones have split leaves, the later ones have a wedge-shaped plate, stems of a complex anatomical structure, in the center there is primary xylem (proto and metaxylem), between its rays there is phloem, between them there is cambium, in the outer layers phellogen forms a plug. 10 cm in length Most clinolists are homosporous, some heterosporous)
2.Class Horsetails
A) Order Calamite (extinct, appeared in the Devonian, the greatest development in the Carboniferous and disappears in the Jurassic period. These trees are horsetails. They lived in swamp soil from which shoots grew up to 30 meters high, the stems had crevices and internodes, the ribs of neighboring nodes alternated. From rhizomes with numerous adventitious roots. Leaves are linear with one vein. Among them there were both homosporous and heterosporous).
B) The order Horsetails (represented by one family, one genus, in Africa as alien plants, despite the primitive structure and ancient origin, successfully competes with terrestrial plants. Development cycles
Equisetaceae are characterized by the presence of shoots consisting of clearly defined segments (internodes) and nodes with whorled leaves. Equisetaceae include herbaceous plants with stems ranging from several centimeters to several meters in length. Tree-like forms that reached a height of 15 m and a diameter of more than 0.5 m became extinct.
Higher spore plants are the first terrestrial plants that live in moist places, often under the forest canopy, or in swamps, or in fields with acidic soils. The tree ferns, horsetails and club mosses that dominated the Paleozoic are now represented by herbs, with the exception of tropical tree ferns. Mosses have changed little during this period, since they occupy only their characteristic wet habitats. These plants require water to reproduce, since their gametes - sperm - are transferred to the eggs only in dripping liquid water, and the shoots can only grow in moist soil. Life in difficult land conditions led to selection for such adaptive characters as the formation of vegetative organs (root, stem, leaf), reproductive organs (archegonia, antheridia, sporangia), as well as tissues. In the food chains of past geological eras, higher spore plants occupied a leading place: they served as food for herbivorous amphibians and reptiles. Currently, their role as forage plants has noticeably decreased, but their importance in nature remains: they retain water in the soil, create conditions for the preservation and germination of seeds of gymnosperms and angiosperms, and provide a habitat for animals. In the human economy, the role of ancient tree-like forms is great, providing deposits of coal, which, like peat, serves not only as fuel, but also as a valuable chemical raw material. Among this group of plants, only horsetail is a difficult-to-eradicate weed in fields with high soil acidity. Higher spores are living fossils that have survived to this day, so they must be preserved and protected. The Red Book of the USSR includes 32 species of mosses and 6 species of ferns; The Red Book of the RSFSR contains 22 species of mosses, 10 species of ferns and 4 species of mosses. |
A characteristic feature of horsetails is the presence of peculiar sporangium-bearing structures - sporangiophores. The vast majority of horsetails are homosporous plants.
Reproduction
The sexual generation is the gametophyte (prothallus). Antheridia and archegonia are formed on gametophytes. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of drip-liquid water, and a sporophyte grows from the zygote without a rest period.
Classification
Of the horsetails, there is now one class of horsetails (or equisetopsids). Of the horsetail family, the most common genus is horsetail. Horsetails often make up a significant percentage of grasslands and wetlands; common in acidic soil. The genus includes about 30 species; In our country, 4 are common, in Ukraine - 9. Most often, we have horsetail, meadow horsetail, marsh horsetail, marsh horsetail and forest horsetail.
Horsetail
A herbaceous plant with annual above-ground shoots. A small number of species are evergreen. The size of horsetail stems varies greatly: there are dwarf plants with a stem 5-15 cm high and a diameter of 0.5-1 mm and plants with a stem several meters long (in the polychaete horsetail the stem reaches a length of 9 m). Tropical forest horsetails reach a height of 12 m. The underground part is a rhizome, creeping, branched, in which nutrients can be deposited (tubers are formed) and which serves as an organ of vegetative propagation. Aboveground shoots grow at the top. Summer shoots are vegetative, branched, assimilating, consist of segments, with well-developed internodes. Whorled and also dissected branches branch off from the nodes. The leaves are inconspicuous and grow together into toothed sheaths that cover the lower part of the internode. Silica is often deposited in the epidermal cells of the stem, so horsetails are a poor food.
Spring shoots are spore-bearing, non-assimilating, unbranched, and spore-bearing spikelets are formed at their apex. After the spores mature, the shoots die. The spores are spherical, with four springy ribbons, greenish, germinate into shoots, unisexual - male or female. There are cases when antheridia and archegonia appear on the same prothallus. From the fertilized egg, a pre-adult grows, and then an adult horsetail.
Horsetails
Horsetails, or arthrostems, or segmented ones. or wedge-shaped (lat. Equisetóphytina) - a subdivision of higher spore plants of the fern division, previously placed in the now abolished department Equisetophyta.
Horsetails are characterized by the presence of shoots consisting of clearly defined segments (internodes) and nodes with whorled leaves. In this feature, modern and fossil horsetails differ sharply from all other higher spore plants and in appearance resemble some algae (Characeae), gymnosperms (Ephedra), or even flowering plants.
Horsetails are peculiar plants. Many vegetative characteristics make them similar to cereals. Apparently, horsetails are the most competitive among pteridophytes, which is explained by numerous improvements in vegetative organs: the stem of horsetails is articulated and grows in nodes (like cereals); the epidermis is reinforced with silica; the weight of the stem is lightened due to the presence of a central cavity; there are numerous strands of mechanical tissues that increase the strength of the stem; there are air-carrying cavities that make it possible to establish an oxygen supply to underground and underwater parts; true vessels develop (as in angiosperms); spores are equipped with special pushing processes (elaters), which help loosen the spore mass and, consequently, transport the spores by the wind. It is due to these structural features that horsetails, as in the distant Carboniferous period, continue to dominate in some biocenoses - mainly along the banks of reservoirs. Horsetails have another interesting feature: they have heterosexual growths, and the development of male or female growths is predetermined by environmental conditions. In general, the worse the conditions, the greater the percentage of male growths that are formed. Thus, horsetails demonstrate a transitional stage from typical homosporous to typical heterosporous
Appearance
Horsetails include both herbaceous extinct and living plants with a stem ranging from several centimeters to several meters in length, as well as tree-like extinct forms that reached 15 m in height and a trunk diameter of 50 cm.
Anatomy
The conductive system of the horsetail stem is represented by an actinostele or arthrostele, that is, a segmented stele consisting of sections of different structures alternating with each other along the stem. The conducting elements of the xylem are represented by tracheids of various types, and in horsetails also by vessels. Phloema consists of sieve elements and parenchyma cells.
Origin and evolution
Horsetails appeared in the Upper Devonian and descended from the now extinct rhiniales (Rhyniales) or some plants close to them, but they flourished in the Carboniferous period, when they were widely represented by a variety of woody and herbaceous forms. Together with lepidodendrons and tree ferns, horsetails took a large part in the formation of coal forests.
Fossil horsetails (for example, tree-like calamites) reached a height of 25 m, and secondary xylem was found in their trunks. However, in the Permian their extinction begins, and first of all the arboreal forms die out, so that only herbaceous horsetails are known from the Mesozoic. To date, only the genus Horsetail (Equisetum) has survived from this entire large group.
Both extinct and modern horsetails differ from all known plants by shoots composed of individual segments. The name “Articular” comes from this specific structure of their shoots, which are divided into clearly defined nodes and internodes, easily breaking up into segments. The segmentation is due to the whorled leaf arrangement and the presence in the lower parts of the internodes of an intercalary meristem, along which breaking into segments occurs.
Modern horsetails are characterized by peculiar leaves - their leaf blades are greatly reduced to small dark, sometimes green or colorless teeth, and well-defined sheaths have fused into a common membranous sheath. The reproductive organs of arthropods are characterized by the presence of strobili in the form of spikelets and only in some Paleozoic species - spore-bearing zones. In modern horsetails, sporangiophores have a shield shape, but in ancient extinct ones they had a wide variety of shapes, except leaf-shaped. The vast majority of horsetails are homosporous plants, and only a few extinct species were heterosporous.
Classification
The segmented subdivision, or horsetails, includes three classes, the evolution of which apparently followed independent, parallel paths - two extinct classes: Sphenophyllopsida, Cladoxylopsida and the now existing class Equisetopsida.
