Lichens

Lichens are a peculiar group of living organisms that grow on all continents, including Antarctica. In nature, there are more than 26,000 species of them.

For a long time, lichens have been a mystery to researchers. However, until now they have not come to a consensus regarding their position in the systematics of living nature: some attribute them to the kingdom of plants, others to the kingdom of fungi.

The body of the lichen is represented by a thallus. It is very diverse in color, size, shape and structure. The thallus can have the shape of a body in the form of a crust, a leaf-shaped plate, tubules, a bush and a small rounded lump. Some lichens reach a length of more than a meter, but most have a thallus 3-7 cm in size. They grow slowly - they increase by a few millimeters in a year, and some by fractions of a millimeter. Their thallus is often hundreds or thousands of years old.

Lichens do not have the typical green color. The color of lichens is grayish, greenish-gray, light or dark brown, less often yellow, orange, white, black. The color is due to pigments that are in the shells of the hyphae of the fungus. There are five groups of pigments: green, blue, purple, red, brown. The color of lichens may also depend on the color of lichen acids, which are deposited in the form of crystals or grains on the surface of the hyphae.

Living and dead lichens, dust and sand grains accumulated on them create a thin layer of soil in the non-exposed soil, in which mosses and other terrestrial plants can gain a foothold. Growing, mosses and grasses shade ground lichens, cover them with dead parts of their bodies, and lichens eventually disappear from this place. Falling asleep does not threaten lichens of vertical surfaces - they grow and grow, absorbing moisture from rains, dews and fogs.

Depending on the external appearance of the thallus, lichens are divided into three types: scale, leafy and bushy.

Lichen types. Morphological features

Lichens are the first settlers on bare ground. On bare stones scorched by the sun, on sand, on logs and tree trunks.

Name of the lichen	The form	Morphology	Habitat
Scale (about 80% of all lichens)	Type of crust, thin film, of different colors closely fused with the substrate	Depending on the substrate on which scale lichens grow, there are: epilithic epiphleoid epigean epixial	on the surface of rocks; on the bark of trees and shrubs; on the surface of the soil; on decaying wood
	The lichen thallus can develop inside the substrate (stone, bark, tree). There are scale lichens with a spherical shape of the thallus (nomadic lichens)
foliose	The thallus looks like scales or rather large plates. Monofilament- view of one large rounded leaf-shaped plate (10-20 cm in diameter). polyphilic- thallus of several leaf-shaped plates	They are attached to the substrate in several places using bundles of fungal hyphae.	On stones, soil, sand, tree bark. They are firmly attached to the substrate with a thick short leg. There are loose, nomadic forms
	A characteristic feature of leaf-shaped lichens is that its upper surface differs in structure and color from the lower one.
bushy. The height of small ones is a few millimeters, large ones are 30-50 cm	In the form of tubules, funnels, branching tubules. Type of bush, upright or hanging, strongly branched or unbranched. "Bearded" lichens	Thalluses come with flat and rounded lobes. Sometimes large bushy lichens in tundra and high mountains develop additional attachment organs (hapters), with the help of which they grow to the leaves of sedges, grasses, and shrubs. Thus, lichens protect themselves from separation by strong winds and storms.	Epiphytes- on tree branches or rocks. They are attached to the substrate in small sections of the thallus. Ground- filamentous rhizoids Usnea long- 7-8 meters, hanging in the form of a beard from the branches of larches and cedars in taiga forests
	This is the highest stage of development of the thallus

In extremely harsh conditions, lichens grow on stones and rocks in Antarctica. Living organisms have to live here at very low temperatures, especially in winter, and with little or no water. Due to the low temperature, precipitation there always falls in the form of snow. Lichen cannot absorb water in this form. But the black color of the thallus rescues him. Due to high solar radiation, the dark surface of the lichen body quickly heats up even at low temperatures. The snow falling on the heated thallus melts. The lichen immediately absorbs the moisture that has appeared, providing itself with the water it needs for respiration and photosynthesis.

Structure

The thallus consists of two different organisms - a fungus and an algae. They interact so closely with each other that their symbiosis seems to be a single organism.

The thallus is a set of intertwined mushroom threads (hyphae).

Between them, in groups or singly, there are cells of green algae, and in some - of cyanobacteria. Interestingly, the species of fungi that make up a lichen do not exist in nature without algae at all, while most of the algae that make up the lichen thallus are found in a free-living state, separately from the fungus.

The lichen is fed by both symbionts. The hyphae of the fungus absorb water and minerals dissolved in it, and the algae (or cyanobacteria), which contains chlorophyll, forms organic matter(due to photosynthesis).

Hyphae play the role of roots: they absorb water and mineral salts dissolved in it. Algae cells form organic substances, perform the function of leaves. Lichens absorb water with the entire surface of the body (they use rainwater, fog moisture). An important component in the nutrition of lichens is nitrogen. Those lichens that have green algae as a phycobiont receive nitrogen compounds from aqueous solutions when their thallus is saturated with water, partly directly from the substrate. Lichens that have blue-green algae as a phycobiont (especially nostocs) are able to fix atmospheric nitrogen.

Internal structure

This is a peculiar group of lower plants, which consist of two different organisms - a fungus (representatives of ascomycetes, basidiomycetes, phycomycetes) and algae (green - cystococcus, chlorococcus, chlorella, cladophora, palmella is found; blue-green - nostoc, gleokapsa, chroococcus), forming symbiotic cohabitation, characterized by special morphological types and special physiological and biochemical processes.

According to the anatomical structure, lichens are of two types. In one of them, the algae are scattered throughout the thickness of the thallus and are immersed in the mucus that the alga secretes (homeomeric type). This is the most primitive type. Such a structure is typical for those lichens whose phycobiont is blue-green algae. They form a group of slimy lichens. In others (heteromeric type), several layers can be distinguished under a microscope on a cross section.

Above is the upper bark, which looks like intertwined, tightly closed fungal hyphae. Under it, the hyphae lie more loosely, algae are located between them - this is the gonidial layer. Below, the fungal hyphae are located even more loosely, large gaps between them are filled with air - this is the core. The core is followed by the lower crust, which is similar in structure to the upper. Bundles of hyphae pass through the lower cortex from the core, which attach the lichen to the substrate. Crustose lichens do not have a lower bark, and the fungal hyphae of the core grow together directly with the substrate.

Bushy radially built lichens have a bark on the periphery of the transverse section, a gonidial layer under it, and a core inside. The bark performs protective and strengthening functions. Attachment organs usually form on the lower crustal layer of lichens. Sometimes they look like thin threads, consisting of one row of cells. They are called rhizoids. Rhizoids can join to form rhizoidal bands.

In some foliose lichens, the thallus is attached with a short stalk (gomfa) located in the central part of the thallus.

The algae zone performs the function of photosynthesis and accumulation of organic substances. The main function of the core is to conduct air to algae cells containing chlorophyll. In some bushy lichens, the core also performs a strengthening function.

The organs of gas exchange are pseudocyphellae (ruptures of the cortex, visible to the naked eye as irregularly shaped white spots). On the lower surface of leaf lichens there are round, regular white depressions - these are cyphella, also gas exchange organs. Gas exchange is also carried out through perforations (dead areas of the crustal layer), cracks and breaks in the crustal layer.

reproduction

Lichens reproduce mainly by pieces of the thallus, as well as by special groups of fungal and algae cells, which are formed in large numbers inside its body. Under the pressure of their overgrown mass, the body of the lichen is torn, groups of cells are carried by wind and rain streams. In addition, fungi and algae have retained their own methods of reproduction. Mushrooms form spores, algae reproduce vegetatively.

Lichens reproduce either by spores that form a mycobiont sexually or asexually, or vegetatively - by fragments of the thallus, soredia and isidia.

During sexual reproduction, sexual sporulation in the form of fruiting bodies is formed on the thalli of lichens. Among the fruit bodies in lichens, apothecia are distinguished (open fruit bodies in the form of disc-shaped formations); perithecia (closed fruiting bodies that look like a small jug with a hole at the top); gasterothecia (narrow elongated fruiting bodies). Most lichens (over 250 genera) form apothecia. In these fruiting bodies, spores develop inside the bags (sac-like formations) or exogenously, on top of elongated club-shaped hyphae - basidium. The development and maturation of the fruiting body lasts 4-10 years, and then for a number of years the fruiting body is able to produce spores. A lot of spores are formed: for example, one apothecia can produce 124,000 spores. They don't all grow. For germination, conditions are needed, primarily certain temperature and humidity.

Asexual sporulation of lichens - conidia, pycnoconidia and stylospores that occur exogenously on the surface of conidiophores. Conidia are formed on conidiophores that develop directly on the surface of the thallus, and pycnoconidia and stylospores - in special receptacles - pycnidia.

Vegetative reproduction is carried out by thallus bushes, as well as special vegetative formations - soredia (dust particles - microscopic glomeruli, consisting of one or more algae cells surrounded by fungal hyphae, form a fine-grained or powdery whitish, yellowish mass) and isidia (small, variously shaped outgrowths of the upper surface of the thallus , the same color as it, they look like warts, grains, club-shaped outgrowths, sometimes small leaves).

Lichens are the pioneers of vegetation. Settling in places where other plants cannot grow (for example, on rocks), after a while, partially dying, they form a small amount of humus, on which other plants can settle. Lichens destroy rocks by releasing lichen acid. it destructive action finish water and wind. Lichens are capable of accumulating radioactive substances.

Lichens - structure, reproduction and feeding methods

Lichens are a very interesting and peculiar group of lower plants. Lichens (lat. Lichenes) - symbiotic associations of fungi (mycobiont) and microscopic green algae and / or cyanobacteria (photobiont, or phycobiont); the mycobiont forms a thallus (thallus), inside which the photobiont cells are located. The group includes from 17,000 to 26,000 species in about 400 genera. And every year, scientists discover and describe dozens and hundreds of new unknown species.

Fig.1. Lichen Cladonia stellate Cladonia stellaris

The lichen combines two organisms with opposite properties: an algae (usually green), which creates organic matter during photosynthesis, and a fungus that consumes this substance.

As organisms, lichens were known to scientists and the people long before the discovery of their essence. Even the great Theophrastus (371 - 286 BC), "the father of botany", gave a description of two lichens - usnea (Usnea) and rocella (Rocce11a). The latter was already used to obtain dyes. The beginning of lichenology (the science of lichens) is considered to be 1803, when a student of Carl Linnaeus, Eric Acharius, published his work “Methodus, qua omnes detectos lichenes ad genera redigere tentavit” (“Methods by which everyone can identify lichens”). He identified them as an independent group and created a system based on the structure of the fruiting bodies, which included 906 species described at that time. The first to point out the symbiotic nature in 1866, using the example of one of the species, was the physician and mycologist Anton de Bari. In 1869, the botanist Simon Schwendener extended these ideas to all species. In the same year, Russian botanists Andrei Sergeevich Famintsyn and Osip Vasilievich Baranetsky discovered that the green cells in lichen are unicellular algae. These discoveries were perceived by contemporaries as "amazing".

Lichens are divided into three unequal groups:

1. It includes a greater number of lichens, a class of marsupial lichens, since they are formed by marsupial fungi

2. A small group, a class of basidial lichens, since they are formed by basidial fungi (less resistant fungi)

3. “Imperfect lichens” got their name due to the fact that fruiting bodies with spores were not found in them.

Interior design is a very inspiring process. Each person wants to make his apartment unique and cozy, give it an original look, highlight his home among the gray monotony of the "concrete jungle". All these tasks will be successfully solved by artificial moss: eco-style is now becoming more popular. It allows you to visually bring a typical city apartment closer to nature, without reducing its comfort. So designers are actively fantasizing in the direction of using this material.

wall ideas

Artists from Norway were the first to decide to use vegetation in the interior. True, they used live, not artificial moss. A few years ago, at an exhibition in London, they offered to the attention of an intrigued public a fragment of a room where the wall above the head of the bed was lined with reindeer moss. The audience liked the idea so much that it began to be actively exploited throughout the civilized world.

Artificial moss for decoration can cover the entire wall, for example, over a seating area. And it can be used fragmentarily, framing a plasma screen or shelving with books. The “islands” of it, artistically scattered over the surface, look very elegant. And vertical narrow strips of moss visually overestimate low ceilings. At the same time, the relief of such a coating will make the decoration of the room more convex and spectacular.

Artificial moss is combined with almost all finishing materials. He loses only with a frankly urban element - plastic panels. But it combines wonderfully with glass and chrome, thanks to which it can be used even in a high-tech room.

Moss as a material for decorative elements

Not everyone dares to use vegetation for wall decoration. But for the decoration of individual details, decorative artificial moss is a very valuable find. First of all, this applies to flower pots. In most home gardens, they are of various sizes and have a different style orientation. Or even on the windowsills there are boring plastic containers. This creates the impression of some slovenliness and reduces both the effectiveness of the design as a whole and the attractiveness. indoor plants. The “landscape” will look much more elegant if the pots are glued with artificial moss. This idea is especially good for large tubs.

The artificial moss used in the design of frames for mirrors, paintings and photographs is very effective. Such natural spots in the interior make it warmer and more comfortable. Moss paintings are very interesting. True, to create them, you either need to be able to draw yourself, or hire a professional artist. And, finally, lampshades decorated with moss give a completely unimaginable effect. And so you can finish and table lamps, and sconces, and chandeliers.

Furniture with moss inserts

Designers from the Verde Profilo company have advanced the furthest in the eco-direction. Their furniture, trimmed with moss, made a splash. Inserts (from a living plant, by the way) are found on headboards, coffee tables, doors and lids of nightstands. In our country, this furniture is inaccessible. And if you find where to order it, it will cost you almost more than a budget car.

However, with some ingenuity and growing hands from where it should be, you will be able to get the result no worse. So, moss rolls on the surface of your favorite table. It is better to choose a model with a glass top, so it will be clearer and more effective. Then the vegetation is covered with glass of the same size - and you get magnificent furniture in a naturalistic style.

country design

Moss in the landscape is a long and actively used material. If your site is limited by an old stone fence, it can be revived with patterns and drawings made from this plant. They can also decorate the sides of an artificial pond or the basement of your country estate - the building will take on an old and mysterious look.

Benefits of artificial moss

Initially, the interior was finished with natural moss. However, it has a number of disadvantages. First, the plant needs moisture. When it dries out, it loses much of its decorative effect. Secondly, live moss tends to grow: often not at all where it is needed. Thirdly, some of its species are poisonous. If there are small children and animals in the house, plant installations can be dangerous for them.

All these shortcomings are deprived of artificial moss. And most importantly - it does not need to be grown, cared for and waited until it occupies the territory intended for it. Artificial moss is sold in mats, large rolls, and clumps. So the decorator has the opportunity to purchase it in the form that best suits the idea.

How to make artificial moss?

It is clear that if you are going to trim an entire wall with moss, then it is better to buy it in a specialized store. But if you need a small piece, you can do without shopping trips. There are several ways to make artificial moss with your own hands:

1. Thick paper is taken - colored or white. In the latter case, paints will be needed to give it the desired color. The paper is processed with fine sandpaper until it starts to crumble. Then it is torn into fragments of the desired size and used in decor.
2. The foam rubber is cut or torn into small pieces and dyed in suitable colors. For a sample, you can take a photograph of natural moss. When the workpiece dries, the pieces are glued to the intended place.
3. Take a sponge to wash dishes. The hard part comes off from it and is painted in the desired tone.

All of the above options will be a wonderful imitation of natural moss!

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Attention! The slide preview is for informational purposes only and may not represent the full extent of the presentation. If you are interested in this work, please download the full version.

/slide number 1/

Goals:

• to acquaint students with the features of the structure and life of lichens as symbiotic organisms;
• to show the adaptability of lichens to a variety of habitat conditions, their role in nature and human life. /slide number 2/

Type of lesson: lesson - travel

Class: 7

Lesson time: 45 minutes

Equipment: tables, herbarium material, portraits of scientists, drawings of lichens, K. A. Timiryazev’s book “Plant Life”, geographical map.

EPIPGRAPH: /slide number 3/

THE MORE WE KNOW THE LAWS OF NATURE, THE MORE INCREDIBLE MIRACLES BECOME FOR US.
CHARLES DARWIN

During the classes

I.Organizing time:

(The topic of the lesson, the tasks of the lesson and the main stages of the lesson are reported)

II. New theme: "Department of lichens".

Teacher:

IN THE WORLD OF LICHEN
You pass by a small world like a stranger.
Sitting on a stone, look at the amazing micro-relief.
On a forest boulder - between the mosses - the quirks of a cladonia.
Know these forms, capturing their fantasy.
As if the image of another biosphere is revealed to us in the model!
Here is a lichen - like a glass, next to it - like faceted ice.
And the outgrowths of cetraria are like the wilds of Venus,
An all-terrain beetle hurries through this thicket.
Without lichens, the North would immediately lose all its charm,
Therefore, I study the palette of appeased rocks.
Y. Linnik/slide №4/

Guys, today we will take a trip through the lichen department. During the journey, we will stop at some stations in order to better understand and assimilate a new topic. Our journey takes place on the "School Train", which has already made a stop at the first station:

1 station: "HISTORICAL"/slide number 5/

* Lichens and their difference from other plants
Teacher: Lichens represent a peculiar group of complex organisms, the body of which always consists of two components - a fungus and an algae. Now every student knows that the biology of lichens is based on the phenomenon of symbiosis - the cohabitation of two different organisms. But just over a hundred years ago, lichens were a great mystery to scientists. Gradually, the number of known species of lichens increased. True, in those days they were often called either mosses, or algae, or even "the chaos of nature" and "wretched poverty of vegetation."

* History of research, systematic position.

Besides the fact that lichens are pioneers, developing habitats free from other plants, they are also recognized as one of the oldest plant organisms on land, which arose at the time when stable links were formed between the first terrestrial algae (or cyanobacteria) and fungi. The first more or less reliably documented finds of fossil thalli, with a high degree of probability belonging to lichens, are of Early Devonian (about 480 million years ago) and even Precambrian age (almost 600 million years).

The first descriptions of lichens are known from "History of Plants" by Theophrastus who indicated two lichens - Usnea and Rocella, / slide No. 6 / which was already used to obtain dyes. Theophrastus assumed that they were growths of trees or algae. In the 17th century, only 28 species were known.

French physician and botanist Joseph Pitton de Tournefort/slide number 7/ in his system singled out lichens as a separate group as part of mosses. Although over 170 species were known by 1753, Carl Linnaeus described only 80, describing them as "a meager peasantry of vegetation", and included them, along with liverworts, in the "terrestrial algae".

Lichens are very ancient history: they appeared on Earth more than a hundred million years ago, when the Cretaceous thickness of our planet was formed.

But only at the end of the 18th - beginning of the 19th century did the science of lichens arise - LICHENOLOGY.

the beginning lichenology(lichen science) is considered to be 1803 when the student Carl Linnaeus - Eric Acharius/slide number 8/ published his work “Methodus, qua omnes detectos lichenes ad genera redigere tentavit” (“Methods by which everyone can identify lichens”). He identified them as an independent group and created a system based on the structure of the fruiting bodies, which included 906 species described at that time. Russian scientists A. N. Beketov in 1860 year, the term “lichen” was proposed to refer to these organisms. / slide No. 9 / In 1860-1868. German botanist S. Shwedener/slide number 10/ in a series of works described the biology of lichens as “double organisms” (close cohabitation of fungi and algae). The first to symbiotic nature in 1866 year, using the example of one of the species, the doctor and mycologist indicated Anton de Bari. AT 1867 year Russian botanists Andrey Sergeevich Famintsyn and Osip Vasilyevich Baranetsky/slide number 11/ found that the green cells in the lichen are unicellular algae. These discoveries were perceived by contemporaries as "amazing".

Lichens received the Russian name for visual similarity with the manifestations of some skin diseases, which received the general name "lichen". /slide №12/

Today, lichenology is an independent discipline, adjacent to mycology and botany.

The lichen itself as a single organism is a unique natural phenomenon. Several completely different organisms coexist in it, mutually providing for each other's living. Most often, this partnership is formed by two organisms - a fungus and an algae (usually green or rarely blue-green bacteria - cyanobacteria), but sometimes 3 or even 4 components can occur. But in the body of one species of lichen, only one mycobiont (mushroom) is always present, the rest are photobionts(algae and/or cyanobacteria). Therefore, for a long time scientists could not determine the nature of these organisms. modern science taxonomy still places lichens in the kingdom of fungi, since the main function - reproduction - remains with the fungal component - mycobiont. In this regard, one of the modern names for lichens used in the scientific literature is lichenized fungi. Binominal nomenclature is used to designate lichens.

Teacher: Guys, our train has arrived at the next station -

2. Station "GEOGRAPHICAL"/slide №13/

(A map "Natural zones of Russia" is posted on the board)./slide №14/

Lichens can be found everywhere. In the spruce forests, shaggy, gray "beards" hang from the branches. In dry pine forests they form a continuous carpet of branched white or pink bushes. On the bark of trees you can see lichens in the form of plates. In the mountains, lichens cover stones and rocks. Lichens appeared on Earth more than 100 million years ago. /slide №15/

They are distributed throughout the land from polar deserts to tropical forests. At the same time, lichens are so unpretentious that they grow where other plants simply cannot survive - in the extremely harsh polar and alpine deserts, in which there are eternal snows, there is no summer, and only stones and rocks exposed by the winds can remain open. Three-quarters of all lichen species are rather microscopic organisms, the study of which is impossible without special optical instruments. Most lichen species in northern latitudes are extremely slow growing, capable of growing by only 0.1–2 mm per year, rarely by 3 mm. Therefore, it is difficult for them to compete with fast-growing mosses and other higher plants. For example, the alpine lichen umbilicaria in 200 years grows by only 1 mm. They live for a very long time. In the Arctic, specimens of Rhizokarpon geographical were found, whose age is 4.5 thousand years. / slide No. 16 / In 1981, it was found that the age of some Arctic lichens is at least 10 thousand years old.

Lichens settle on bare stone, on icy rocks, on the sands of the desert burned by the sun, grow on clean paper, glass, and iron.

K. A. Timiryazev in his famous book “The Life of Plants” wrote: “Will a water cliff come out of the waves of the ocean, will a piece of rock come off, revealing a fresh, not weathered fracture, will a boulder break, which has lain underground for centuries, everywhere on a bare barren surface lichen appears first, decomposing the rock, turning it into fertile soil. He climbs further than all plants to the north, above all in the mountains, he does not care about the winter cold, the summer heat; slowly but stubbornly he conquers every inch of the earth, and only in his footsteps, along the beaten path, more complex forms of life appear. /slide №17/

Teacher: Our next stop is

3.Station "RESEARCH"/slide №18/

* The structure of the lichen:

Lichens are very diverse in form - these are all kinds of spots and crusts on stones, openwork bushes that form extensive carpets and mats on the soil, or clusters of miniature "glasses" that stick around old stumps and deadwood; many lichens in the form of thin pale green or dark brown strands hang from the branches of trees, or in the form of various lobes, scales and warts settle on the branches of spruces and pines; often large graceful blades cover moss tussocks or mossy boulders and the bases of tree trunks.

The color scheme is also diverse - lichens can often be gray inconspicuous, but often they are bright yellow or orange, from rusty to bright red, green or dark brown, sometimes white with all sorts of shades or dark - almost black.

The color of the lichen thallus depends on the presence of pigments that are deposited in the hyphae membranes, less often in the protoplasm. The hyphae of the crustal layer of lichens and various parts of their fruiting bodies are the richest in pigments. Lichens have five groups of pigments: green, blue, purple, red, brown. The mechanism of their formation has not yet been elucidated, but it is quite obvious that the most important factor influencing this process is light.
Sometimes the color of the thallus depends on the color of lichen acids, which
deposited in the form of crystals or grains on the surface of the hyphae.
The brighter the lighting in the place where the lichen grows, the brighter it is colored. As a rule, lichens of the highlands and polar regions of the Arctic and Antarctic are very brightly colored. This is also related to lighting conditions. For alpine and polar
areas of the globe are characterized by a high transparency of the atmosphere and a high intensity of direct solar radiation, providing here
significant brightness.

* The internal structure of the lichen:

The thallus (lichen body) is formed by an interlacing of fungal filaments, which are clearly visible under a microscope in a cross section / slide No. 19 / Closer to the surface of the thallus, the fungal filaments form a dense interlacing, playing the role of an integumentary tissue. Closer to the center, it becomes loose. And in the cavities between the threads, groups of green algae cells (blue-green or cyanobacteria) are noticeable. Spherical cells of algae accumulate on the side of the thallus that faces the sun. Like all green plants, algae uses the energy of the sun to form organic substances necessary for its life from carbon dioxide, water and mineral salts. Moreover, the algae gives part of the organic substances to the fungus.

It can be clarified that the body of the lichen that we see (scientifically called “thallus” or “thallus”) is an outer shell formed by a fungal partner, inside which algae are covered (thereby protected from excessive drying and aggressive environmental factors) . /slide №20/

Unlike plants, the lichen body, which is called the thallus or thallus, is not divided into root, stem and leaves. Without roots, lichens are quite firmly attached to the substrate with special outgrowths located on the underside of the thallus.

By external structure lichens are divided into three groups. If the thalli are tightly attached to the substrate in the form of a granular or dusty coating or in the form of scales and crusts of various shapes, then such lichens are called scale./slide №21/

If the thallus of lichens look like more or less dissected plates (lobes), they are called leafy. /slide №22/

Finally, lichens that have a bushy thallus, consisting of erect columns branched to varying degrees, are called bushy./slide №23/

According to their habitat, lichens are divided into the following types:

• Ground (epigean) lichens - can grow both in open places and in forests; /slide №24/
• Epiphytic lichens - settle on trees and shrubs; /slide №25/
• Epilithic lichens - settle on stones and rocks, tiled roofs, brick walls; /slide №26/
• Aquatic lichens grow on rocks near water. /slide №27/

* Lichen feeding methods:

It is known that fungi are heterotrophic organisms, that is, they are only able to consume organic matter (due to which they live). But the lichen, as an organism as a whole, nevertheless, is autotrophic, as it lives off organic substances produced independently. This is due to the fact that, in addition to the fungal partner, the lichen also includes an algae - a photobiont, which is capable of photosynthesizing in the light and producing organic substances that are used for the life support of both the photobiont itself and the mycobiont. This union of fungus and algae allows the whole organism to exist autotrophically. Quite a lot is known to modern scientists about the nature and mechanisms of mutually supporting or mutually beneficial partnerships.

One of the most important factors in the survival of lichens is, apparently, their ability to dry out very quickly. Their moisture content in this case is from 2 to 10% of the dry mass. Photosynthesis stops, and the body plunges into deep suspended animation (temporary cessation of life). Lichens, even when dried to the point that it can be ground into powder, come to life after the first rain. Wetting by rain, lichens absorb water like a sponge - in an amount 3-3.5 times their own weight. The entire surface of the body, they absorb the moisture of rain, dew and fog. In many habitats, the humidity of lichens fluctuates during the day, and photosynthesis is possible only for a few hours, usually early in the morning, after wetting with fog or dew.

*Reproduction of lichens (teacher's explanation, table).

Lichens reproduce vegetatively, asexually and sexually. /slide №28/

Individuals of the mycobiont reproduce by all means at a time when the photobiont does not reproduce or reproduces vegetatively. Lichens reproduce mainly in a vegetative way: fragments of the thallus or special organs - groups of fungal and algae cells that form inside its body or in the form of outgrowths on the surface of the body. Under the pressure of overgrown cells, the body of the lichen is torn, groups of cells are carried by wind and rain streams. /slide №29/

The lichen thallus grows very slowly, due to the division of the algae and the fungus itself, since each of the lichen components reproduces independently. A lichen is formed only when the hyphae (threads) of the fungus meet the corresponding algae on their way.

4. Station "INDUSTRIAL". value in nature./slide №30-32/

Lichens take a special part in the process of soil formation (they prepare the soil for colonization by more highly organized organisms), that is, lichens play the role of pioneers in nature. Settling in the most barren places, they secrete special acids that slowly destroy rocks. When they die, they form soil on which other plants can live.

The importance of lichens in human and animal life is great.

In the north, they serve as the main food for animals. Vitamin C is obtained from them and decoctions are prepared that protect against suppuration.

Some lichens are used as dyes in weaving, medicine, perfumes, perfumes, and in the manufacture of glucose.

By the way, lichen substances (previously they were not quite accurately called lichen acids) are one of the notable features of lichens. These substances help them, in particular, to corrode solid rocks. The bearded lichen, or usnea (Usnea barbata), gives a fabulous look to the taiga. His "beard" sometimes grows up to 7-8 m in length. The usnic acid obtained from it kills bacteria, helps to heal wounds. Decoctions of various lichens are known in folk medicine as an aphrodisiac and anti-inflammatory agent. Lichens are used in the manufacture of powder, perfumes, fragrant soaps. Litmus is obtained from them, without which not a single chemical laboratory can do.
But highest value for humans, lichens of the tundra have. Here they cover vast areas. Carl Linnaeus said that the well-being of all Lapland (the north of the Scandinavian Peninsula) is based on lichen. He meant moss, or "deer moss" (Cladonia rangiferina), and centraria, or "Icelandic moss" (Centraria islandica). During the long winter months, these lichens are the only food for reindeer (they also make up 70% of their annual diet). And the deer gives everything to the inhabitants of the tundra - food, clothes, shelter, and a means of transportation. Deer extract lichens from under the snow, tearing it with their hooves.

Lichens are peculiar and amazing organisms. These plants are fabulous! They endure severe cold, get wet in the water for years, are not afraid of the fiery sun, fly over the desert with living and invincible dust. But as soon as they get into a humid place, they come to life.

- (Student's message: "Manna from Heaven") (Appendix 2)/slide №33/

Teacher: A huge number of mites, springtails, caterpillars, spiders, bedbugs, etc. live in the “lichen thickets”. In total, about 400 species of animals are registered, whose life is somehow connected with lichens. Some of them use the lichen thallus as a temporary shelter.

A number of animals feed on the thallus of lichens and the products of their destruction.

5. Station "ECOLOGICAL"/slide №34/

Lichens love thick fogs. However, neither in the heat nor in the cold can they live without crystal clear air. As soon as the atmosphere is slightly polluted, the lichens die to the last. This exceptionally hardy organism serves as the best "indicator" of the purity of the air. They are used as an indicator organism in the monitoring of atmospheric pollution. Lichens react most sharply to sulfur dioxide, which, perhaps, quickly destroys the already small amount of their chlorophyll. In addition, these organisms are able to bind heavy metals from environment and accumulate them in your thallus. Lichens are used to control fallout, especially in areas that are difficult to survey by other means.

Lichens growing near sources of atmospheric pollution, if they do not disappear completely, then most often lose their elegant, attractive appearance. A whitish coating appears on the edges of the blades, the size of the thalli decreases. Bacteria appear in abundance on mushroom vultures, algae cells decrease in size, and sometimes die completely; it happens that the entire algal layer of the thallus is destroyed. In a word, lichens look sick. / slide No. 35.36 /

Human life and planetary life
Concepts are inseparable.
You, man, loving nature,
Feel sorry for her sometimes.
On fun trips
Do not trample its fields.
Don't burn it down
And don't go to the bottom.
And remember the simple truth -
We are many, but she is one!
V. Shefner

III. Fixing:

• Find meaningful pairs. Match the words marked with numbers with the corresponding terms marked with letters. ./slide №37/

1. Lichens 2. Nutrition 3. Thallus 4. Thallus shape 5. Litmus 6. Lichen acids

A. lichen body

B. organic compounds, a characteristic feature of lichen

V. organisms consisting of fungi and algae.

G. hyphae of fungi absorb water and minerals dissolved in it, and algae, which contains chlorophyll, forms organic substances through photosynthesis.

D. special substance for the chemical industry.

E. scale (crustal), leafy (leaf-like), bushy.

Answers.

1)1V 2G 3A 4E 5D 6B

2) Complete the sentences. /slide №38/

Lichens are _________ organisms. They are made up of a fungus and _________. Green ____________ forms _____________ substances used by _______________, which supplies ________________ with water and _____________ salts dissolved in it.

Lichens reproduce mainly _____________________ - parts of ___________________.

IV. Homework:/slide №39/

1. Textbook pp. 28 -34, answer the questions at the end of the paragraph;
2. Creative task:

Write a syncwine about lichens;

Having solved the puzzle, you will read what K. Linnaeus said about reindeer moss and Icelandic moss. Why did he think so?

(Answer: The well-being of all Lapland is based on lichen.)

Thank you for the lesson! See you soon!

Internet resources:/slide №40/

1. Article on the topic "Lichens"
2. http://biouroki.ru/material/plants/lishainiki.html
3. Article on the topic "Manna from heaven"
4. http://fb.ru/article/73111/oleniy-moh---manna-nebesnaya
5. http://ru.wikipedia.org/wiki/%CB%E8%F8%E0%E9%ED%E8%EA%E8
6. http://biologiyavklasse.ru/otdel-lishajniki.html
7. Active links to used images:
8. Image of lichen cladonia deer:
9. http://kamfotos.ru/photo/rastitelnyj_mir_kamchatki/foto_4761/20-114
10. Scale lichens:

Lichens can be found almost everywhere, even in Antarctica. This group of living organisms has been a mystery to scientists for a long time, even now there is no consensus about their systematic position. Some believe that they should be attributed to the plant kingdom, while others - mushrooms. Next, we consider the types of lichens, the features of their structure, their significance in nature and for humans.

General characteristics of lichens

Lichens are the lowest group of organisms that consist of a fungus and algae that are in symbiosis with each other. The first are most often representatives of phycomycetes, ascomycetes or basidiomycetes, and the second organism is green or blue-green algae. Between these two representatives of the living world there is a mutually beneficial cohabitation.

Lichens, regardless of variety, do not have a green color, most often they can be gray, brown, yellow, orange or even black. It depends on the pigments and also on the color of the lichen acids.

Distinctive features of lichens

This interesting group organisms have the following characteristics:

• The cohabitation of two organisms in a lichen is not accidental, it is due to historical development.
• Unlike plants or animals, this organism has a specific external and internal structure.
• The physiological processes occurring in the fungus and algae differ significantly from those in free-living organisms.
• Biochemical processes also have their own distinctive features: as a result of vital activity, secondary metabolic products are formed that are not characteristic of any group of living organisms.
• Special way of reproduction.
• Attitude to environmental factors.

All these features baffle scientists and do not allow to determine the permanent systematic position.

Lichen varieties

This group of organisms is often called the "pioneers" of land, since they can settle in completely lifeless places. There are three types of lichens:

1. Scale lichens. They got their name for the shape, similar to scale.
2. Leafy lichens. They look like one large leaf blade, hence the name.
3. fruticose lichens resemble a small bush.

Consider the features of each type in more detail.

Description of scale lichens

Almost 80% of all lichens are scale. In their form, they look like a crust or a thin film, firmly fused with the substrate. Depending on the habitat, scale lichens are divided into:

Due to their distinctive appearance, this group of lichens can be completely invisible and blend in with their surroundings. The structure of scale lichens is peculiar, so they are easy to distinguish from other species. But the internal structure is almost the same for everyone, but more on that later.

Territories of scale lichens

We have already considered why scale lichens got their name, but the question arises: are the habitats different? The answer can be given in the negative, because they can be found in almost every latitude. These organisms are amazingly able to adapt to absolutely any conditions.

Scale types of lichens are distributed throughout the planet. Depending on the substrate, one or another species predominates. For example, in the Arctic it is impossible to meet species that are common in the taiga, and vice versa. There is a binding to a certain type of soil: some lichens prefer clay, while others feel calm on bare rocks.

But among the wide variety of this group of organisms, you can find species that live almost everywhere.

Features of leafy lichens

The thallus of this species has the form of scales or plates of medium size, attached to the substrate with a bundle of fungal hyphae. The simplest thallus resembles a rounded leaf blade, which can reach a size of 10-20 cm in diameter. With this structure, the thallus is called monophilic. If there are several plates, then polyphilic.

A distinctive feature of this type of lichen is the difference in the structure and color of the lower and upper parts. There are nomadic forms.

"Bearded" lichens

This name was given to fruticose lichens for their thallus, consisting of branched filaments that grow together with the substrate and grow in different directions. The thallus resembles a hanging bush, there are also upright forms.

The sizes of the smallest representatives do not exceed a few millimeters, and the largest specimens reach 30-50 cm. In tundra conditions, lichens can develop attachment organs, with the help of which organisms protect themselves from separation from the substrate in strong winds.

The internal structure of lichens

Almost all types of lichens have the same internal structure. Anatomically, there are two types:

It should be noted that those lichens that belong to scale do not have a lower layer, and the hyphae of the core directly grow together with the substrate.

Nutritional features of lichens

In the process of nutrition, both organisms living in symbiosis take part. Fungal hyphae actively absorb water and minerals dissolved in it, and algae cells have chloroplasts, which means they synthesize organic substances as a result of photosynthesis.

We can say that hyphae play the role of the root system, extracting moisture, and algae act as leaves. Since for the most part lichens settle on lifeless substrates, they absorb moisture with their entire surface, not only rainwater but also fog, dew.

For normal growth and vital activity, lichens, like plants, need nitrogen. If green algae are present as a phycobiont, then nitrogen compounds are extracted from solutions when the thallus is saturated with moisture. It is easier for lichens, which have blue-green algae, they are able to extract nitrogen from the air.

Lichen reproduction

Regardless of the variety, all lichens reproduce in the following ways:

Considering that these organisms grow very slowly, we can conclude that the process of reproduction is also quite long.

Ecological role of lichens

The significance of this group of organisms on the planet is quite large. They are directly involved in the process of soil formation. They are the very first to settle in lifeless places and enrich them for the growth of other species.

Lichens do not require a special substrate for life, they can cover a barren area, preparing it for plant life. This is due to the fact that in the process of life, lichens secrete special acids that contribute to the weathering of rocks, oxygen enrichment.

Settling on bare rocks, they feel absolutely comfortable there, gradually creating favorable conditions for other species. Some small animals are able to change their color to match the color of lichens, thus disguise themselves and use them to protect themselves from predators.

The value of lichens in the biosphere

Currently, more than 26 thousand species of lichens are known. They are distributed almost everywhere, but it is surprising that they can serve as an indicator of the purity of the air.

These organisms are quite sensitive to pollution, therefore, in large cities near roads, lichen plants are practically not found. They simply do not survive there and die. It should be noted that scale lichens are the most resistant to poor environmental conditions.

Lichens are also directly involved in the circulation of substances in the biosphere. Since they belong to autoheterotrophic organisms, they easily accumulate the energy of sunlight and create organic substances. Participate in the process of decomposition of organic matter.

Together with bacteria, fungi and algae, lichens create favorable conditions for higher plants and animals. Settling on trees, these symbiotic organisms cause practically no harm, since they do not penetrate deep into living tissues. In some ways, they can even be called defenders, because a plant covered with lichens is less attacked by pathogenic fungi, lichen acids inhibit the growth of wood-destroying fungi.

But there is also back side: if the lichens grow too much and cover almost the entire tree, then they close the lenticels, disrupting gas exchange. And for insect pests, this is a great refuge. For this reason, it is better to control the growth of lichens on fruit trees and clean the wood.

The role of lichens for humans

The question of the role of lichens in human life cannot be omitted. There are several areas where they are widely used:

Lichens do not cause any harm to human economic activity.

Summing up all that has been said, we can say that such nondescript and amazing organisms exist next to us. Despite their small size, their benefits are enormous, and for all living organisms, including humans.

Lichens- a group of symbiotic organisms, the body of which consists of two components - heterotrophic - fungus (mycobiont) and autotrophic - algae (phycobiont).

Lichens are combined into a department attributable to the kingdom Mushrooms. Currently, more than 20,000 lichens are known, and scientists are constantly describing more and more new species. Lichenology- the science of lichens - deals with issues related to the occurrence, structure, systematics, distribution and ecology of lichens.
The fungi that make up lichens, in most cases, belong to ascomycetes, only in some tropical and subtropical species of lichens - to basidiomycetes. Phycobionts of most lichens belong to the department Green algae; less commonly, these are yellow-green algae and cyanobacteria. The biology of lichens is based on the phenomenon of symbiosis. Algae in the process of photosynthesis creates organic substances - carbohydrates that the fungus uses for its life. The fungus, on the other hand, provides the algae inside the lichen body with a habitat, protection from overheating and drying out, supplies the algae with water and mineral salts dissolved in it, which it itself absorbs from the environment - the substrate, atmospheric air.

Lichen body(thallus, thallus), as in other lower plants, not differentiated into leaves, stem and root. Its color can be different: gray, gray, greenish, brown-brown, yellow, orange, depending on which pigments are contained in the cells. Lichens easily tolerate complete drying; in a dehydrated state, their moisture content is 2-10% of the dry mass. Photosynthesis and nutrition cease at this time. Lichens are able to absorb water very quickly, and at the same time their mass increases tenfold.
Not every random accumulation of hyphae of fungi and algae forms a lichen. A real lichen is a single organism formed by fungi and algae that have gone through a long path of joint evolution, as a result of which special life forms of the thallus have developed, special organs of attachment to the substrate, specific features of biochemistry and physiology that distinguish them from free-living algae and fungi. So, for example, the secondary metabolic products of lichens - lichen substances - are not found in other groups of organisms.

The sizes of lichen thalli range from a few millimeters to tens of centimeters. Three main morphological types of lichen thalli are distinguished by shape: scale (crustal), leafy and bushy.

The simplest scale thallus, which looks like a thin powdery coating, consists of clusters of individual lumps - algae glomeruli surrounded by fungal hyphae. They can be found on the surface of rocks in narrow and dark mountain gorges, in forests on damp decaying stumps, at the base of tree trunks, on plant debris and mosses, on moist soil. Scale lichen graphic writing develops on the smooth bark of many tree species. In lichens growing on a stony substrate, the thallus is divided by small cracks into separate areas - areoles - identical in shape and size. Such areolated thalli are characteristic of lichens that live on the surface of rocks in high-mountainous regions, deserts, and are an adaptation to endure sharp temperature fluctuations, which can be up to 50-60 ° during the day. Scale lichens from the genera Placopsis, Verrucaria, Lecanora, Lecideus, Biatora, Rhizocarpon, etc. grow on a stony substrate.

foliose lichens have thalli in the form of scales, rosettes or rather large plates cut into lobes, spread over the substrate and fused with it with the help of bundles of fungal hyphae called rhizins. In some species, the thallus is attached to the substrate in one place with the help of an outgrowth - gomfa, formed by fungal hyphae. Leafy lichens are considered to be more highly organized forms compared to scale ones. Between the thallus and the substrate there is a layer of air, which contributes to better gas exchange of the inner layers of the lichen body; moisture and various organic and inorganic substances that can be used by lichens linger there longer. The separation of the thallus from the substrate led to the complication of the anatomical structure of the thallus. In contrast to crustaceous lichens, in foliose forms under a microscope on transverse sections one can see four clearly distinguishable layers: the upper crustal layer, the algae layer, the core and the lower crustal layer. Both cortical layers, the structure of which is very diverse, play not only a protective, but also a strengthening role. Leafy lichens include species of the genera Parmelia, Cetratia, Fiscia, etc.

fruticose lichens represent the most highly organized type of thallus. It has the form of branching ribbons or branched stems cut into lobes, growing together with the substrate only at the base. Fruticose lichens grow either vertically upwards, or sideways, or hanging down in the form of strands. The sizes of their thalli range from a few millimeters to 50 cm or more. Many forest and tundra ground lichens have thalli in the form of dense compact tufts. In the northern and high-mountain tundras, in pine forests, on the surface of the soil one can often observe large multi-colored carpets formed by tufts of fruticose lichens. Fruticose lichens include species of the genus Cladonia, known as "deer moss".

There are two types of anatomical structure of lichen thalli: homeomeric(from the Greek "gemoyos" - the same) and heteromeric(from the Greek "heteros" - another, different; "meros" - part, share).

In more primitive - homeomeric - cells are distributed evenly in the thickness of the thallus and in the mucus secreted by them, fungal hyphae pass in all directions. These are the species of the genus collema, often found on the rocks of the south of our country. In the dry state, they look like brittle crusts or pads, which, when moistened, increase in size from swelling of the mucus, inside which the mycobiont and phycobiont are evenly distributed.

In lichens with heteromeric thalli, several layers are distinguishable in cross section. From above, the thallus is covered with an upper bark consisting of tightly intertwined hyphae of the fungus. This is plectenchyma. Inside the thallus from the plectenchyma, the hyphae lie loosely and between them there are cells that form a zone of algae. Further inside is a core of loosely located fungal hyphae with large voids filled with air. From below, the thallus is covered with a lower bark, similar in structure to the upper one. Mushroom hyphae, rhizins, often pass from the core through the lower bark, with the help of which lichens attach to the substrate. Scale lichens do not have a lower bark, since they grow together with the substrate with a core.

Lichens have vegetative, asexual and sexual reproduction. Either the whole lichen or the mycobiont reproduces.Vegetative propagation is the most common. It is based on the ability of the lichen thallus to regenerate from its individual sections and is carried out by fragmentation (separation of sections) of the thallus, or with the help of special formations - soredia, isidium and lobules.

Fragmentation. In dry weather, lichens become brittle and break easily at the touch of passing animals and people; pieces of thalli, carried by them or by the wind to new places, develop into new lichens. Soredia - the smallest formations consisting of one or more algae cells surrounded by fungal hyphae. They form in the algal layer of the lichen. Isidia- typical for some lichens, tuberculate rod-shaped outgrowths on the upper surface of the thallus, consisting of a phycobiont and a mycobiont. They differ from sorals in that they are covered with bark. Lobules look like small scales located vertically on the surface of the thallus or along its edges.

Sexual reproduction of lichens in in general terms similar to that of free-living fungi.

Lichens are very widespread throughout the world. As autotrophic components of biogeocenoses, lichens accumulate solar energy and synthesize organic substances. In tundra, forest-tundra, forest biogeocenoses, they make up a significant part of the vegetation cover. As heterotrophic organisms, lichens decompose organic and mineral substances. As a result of the death of lichens, the organic substances that make up their thallus accumulate on the surface of the substrate and contribute to the formation of soil humus and the creation of conditions for the growth of higher plants.

Lichens are very sensitive to air pollution and can serve as indicators of its purity. With an increase in the degree of air pollution, fruticose lichens disappear first, then leafy and last - scale.

Tundra lichens serve as the main food for reindeer, which migrate across the tundra in search of better pastures. In addition to deer, domestic animals - pigs, sheep, cows - can also consume species of "deer moss" forest cladonia soft. In some countries, lichens are traditionally used for food. In Japan, one of the delicacies is the foliose lichen umbilicaria edible; in the deserts of the Middle East, they consume edible aspicilia; in Egypt, when baking bread, evernia flaky was added to flavor it. Many types of lichens are sources of gelling agents used in the confectionery industry.