Major kingdoms of living organisms
Science deals with the classification of living organisms.taxonomy . Usually in scientific literature all living organisms are divided into two empires -empire non-cellular , orviruses , Andempire cellular .
Viruses
Cellular organisms
superkingdom eukaryotes , ornuclear having a formed nucleus, separated from the cytoplasm by a nuclear envelope;
superkingdom of prokaryotes , orpre-nuclear , which do not have a nuclear membrane (see Fig. 1).
Rice. 1. Classification of living organisms
Prokaryotes are very small, single-celled organisms without a nucleus. Among them we can distinguish the kingdom of bacteria and the kingdom of archaea, or archaebacteria.
Eukaryotes includethree major kingdoms of multicellular organisms -- animal kingdoms , plants Andmushrooms , - as well as unicellular ones (for example, amoebas, ciliates, etc.), which are combined intokingdom protists , orprotozoa . The kingdom of protozoa, that is, single-celled eukaryotes, is currently recognized as a collective (that is, heterogeneous in origin) group and is divided into many kingdoms of organisms based on the structural features of intracellular structures and DNA sequences. Plants, animals, and fungi appear to have independently evolved from different groups of single-celled eukaryotes.
MODERN SYSTEMATICS. WILDLIFE DOMAINS
INCurrently, based on the structural features of cells and DNA sequences, scientists distinguish threedomain living nature (Fig. 2) are large groups that have diverged evolutionarily for a very long time and differ from each other in a whole set of characteristics. The structural features of their cells are different. Domains:
1. Archaea (formerly called archaebacteria).
2. Eubacteria (that is, true bacteria, as opposed to archaea). This group also includes cyanobacteria (formerly called blue-green algae) - photosynthetic prokaryotic organisms.
3. Eukaryotes - protozoa, plants, animals and fungi.
PROKARYOTES
Some prokaryotes are capable of photo- or chemosynthesis. For example, cyanobacteria, which were previously sometimes called blue-green algae, photosynthesize. Other prokaryotes feed by absorbing low molecular weight organic substances through the cell surface. Such bacteria can settle in food products, causing them to spoil or, conversely, contributing to the production of fermented milk products and the fermentation of vegetables (lactobacteria). Also, when settling in the human body, bacteria can cause diseases, for example, tetanus, cholera, diphtheria.
Archaea - a special, extremely peculiar group of prokaryotes that lives in extreme habitats - in hot springs, in the salty Dead Sea, etc., as well as in soil, animal intestines, sea water. Due to the presence of many unique characteristics, as well as genetic and molecular differences, archaea are currently classified as a separatedomain cellular organisms - a large independent group, along with true bacteria (eubacteria) and eukaryotes.
Plants
Plants are characterized by the presence of plastids - organelles, which include chloroplasts, due to which the vast majority of them are capable of photosynthesis. Plastids, apparently, were formed from cyanobacteria - symbionts of an ancient eukaryotic cell. Photosynthesis is the process of formation of organic substances from inorganic substances (carbon dioxide and water) using the energy of sunlight. Therefore, plants do not need organic substances for their life activity, that is, in generaldo not require organic nutrition . Such organisms are calledautotrophic , they form all the necessary organic substances themselves. They absorb water and minerals (salts) from the environment in the form of a solution. Photosynthetic plant cells, for example in leaves, secrete sugars and other organic substances that are transported to other tissues along vascular bundles, and cells in non-photosynthetic tissues (not green) absorb these substances by feeding on them. This type of nutrition is calledosmotrophic - absorption of low molecular weight organic substances from the environment by cells.
Plant cells are surrounded by a strongcell wall , which is based on polysaccharide fiberscellulose . A strong cell wall prevents the cell membrane from stretching under the influence of osmotic pressure (the pressure of water entering the cell). Plant cells are also characterized by the presencelarge central vacuole, which regulates the osmotic pressure and acidity of the environment in the cell, accumulates metabolic products unnecessary for the cell, which cannot be removed outside its boundaries, and in some cases serves for the deposition of reserve nutrients (Fig. 3).
Rice. 3. Plant cell structure
Animals
Animals areheterotrophs , i.e. feed on ready-made organic matter. Animal cells do not have a cell wall. Therefore, some types of animal cells are capable of contraction -muscle cells . This allows the animals to actively move (or push the medium through themselves, like stationary filter feeders). Multicellular animals have one or another typemusculoskeletal system , and to control movement and respond to external factors, it is formednervous system .
Animals move in search of sources of organic substances, that is, food. The animal ingests food and it enters the cavitydigestive system , where it is digested, whilepolymers (high molecular weight substances) of food are broken down intomonomers (their low molecular weight units). These monomers move from the digestive system through its lining into the blood (if any) and tissue fluid. This type of nutrition is calledholozoic . Basically, animal cells absorb low molecular weight substances dissolved in the blood and tissue fluid. Some animal cells are capable of engulfing large food particles (phagocytosis), such as the phagocytes of the immune system that ingest bacteria.
Rice. 4. Animal cell structure
Mushrooms
Third kingdom -mushrooms - in some ways it is similar to plants, and in others - with animals. Just like plants, fungi have a cell wall, but it is formed on the basis of a different polysaccharide -chitin . Without plastids, fungi are not capable of photosynthesis and feed on ready-made organic compounds, i.e. they areheterotrophs like animals. They also break down complex nutrient polymers usingenzymes , but, unlike animals, they do not have a digestive system and do not swallow food, but release enzymes into the environment. The resulting monomers are absorbed by the fungal cells in the form of a solution from the environment, that is, they exhibitosmotrophic food type. Unlike plants, fungi usually lack a large central vacuole. In most cases, fungal cells do not diverge after division, and since division occurs in the same plane, long threads are formed - hyphae. Hyphae can branch and, intertwining, form a network - mycelium, sometimes quite dense.
Rice. 5. Structure of a fungal cell
Unicellular eukaryotes
There are different single-celled eukaryotes with different cell features and types of nutrition. Among them there areheterotrophic unicellular , such as amoebas and ciliates. They feed by phagocytosis, that is, the absorption of solid food particles, such as bacteria, by cells, and pinocytosis, the absorption of droplets of nutrient fluid. These organisms are capable of movement: ciliates move due to the beating of the cilia covering the cell, and amoebas move through amoeboid movement (changing the shape of the cell and its flow, “crawling” along the surface to which they are attached).
There are alsoautotrophic unicellular , capable of photosynthesis, in particular unicellular algae - Chlamydomonas (moves, has flagella), Chlorella (immobile). Some single-celled organisms, such as green euglena, -mixotrophs , that is, they are able to switch between photosynthesis (autotrophy) and heterotrophic nutrition depending on environmental conditions.
Thus,The kingdoms of eukaryotes differ from each other in the structure of their cells and methods of nutrition .
Taxonomy of eukaryotes
The modern classification is based on new molecular data, as well as differences in the structure of cells of different groups of eukaryotes. The most important features for classification are the structure of flagella, chloroplasts and mitochondria.
The Unikonta group (uniflagellates) includes:
Amoebozoe
Tubular cristae of mitochondria
No plastids
Flagella are usually lost (present at some stages of development or non-functional), locomotion is usually due to pseudopodia.
Representatives: amoebas, myxomycetes, etc.
Opisthokonta (Postoflagellates)
No plastids
Flagellum one, posterior
Representatives: fungi (except for oomycetes and myxomycetes), choanoflagellates, animals (Metazoa), etc.
The Bikonta group (biflagellates) includes:
Archaeplastida
Lamellar cristae of mitochondria
Chloroplasts have double membranes, chlorophyll pigments, a and b
Representatives: red, green, charophyte algae, plants (from mosses to angiosperms), etc.
Excavates
Mitochondrial cristae shaped like tennis rackets
Chloroplasts with three membranes, chlorophyll pigments, a and b
Representatives: euglena algae, kinetoplastids (trypanosomes, leishmania), etc.
SAR (unites three clusters, mitochondrial cristae are tubular)
Rhizaria
Most lack plastids
There are rhizopodia
Representatives: foraminifera, sunfish, radiolarians, etc.
Alveolates
Apicoplast (remnant of a 4-membrane plastid) or 3(4)-membrane chloroplasts of dinoflagellate algae
There are alveoli under the cell membrane - membrane vesicles (empty, with protein or carbohydrate filler)
Representatives: dinoflagellate algae, ciliates, sporozoans, etc.
Stramenopiles
Plastids are 4-membrane, pigments are chlorophylls, a and c
Tripartite mastigonemes on flagella
Representatives: ochrophyte algae (including brown, golden, diatoms...), opalines, etc.
Features of the structure of an animal cell
Cytology - a science that studies the structure, development and functioning of cells.
Cell - the basic structural and functional unit of the body.
Organelles (organelles) - permanent parts of the cell that perform specific functions. Depending on their structure, organelles can be double-membrane, single-membrane or non-membrane.
Inclusions - temporary formations that are part of the cell: starch grains, salt crystals, drops of fat, etc.
contains chromosomes (chromatin)
storage and transmission of hereditary information
cell (cytoplasmic) membrane
two layers of fats (lipids) and protein molecules
separates the internal contents of the cell;
selective transport of substances;
protective function;
receptor function
cytoplasm
internal environment of the cell;
consists of cytosol (hyaloplasm), organelles and inclusions
environment for all cellular processes: chemical reactions and transport of substances
Endoplasmic reticulum (reticulum) - ER
a network of membranes connecting the cell membrane to the nuclear membrane;
two kinds:
smooth EPS
rough ER (with ribosomes)
membrane synthesis;
smooth ER: synthesis and transport of fats and carbohydrates;
rough ER: protein synthesis and transport
Golgi apparatus (Golgi complex)
"stack" of single-membrane tubes, vesicles and cisterns near the nucleus
protein transport
enzyme synthesis
lysosome formation
lysosomes
small bubbles covered with a single-layer membrane;
maintains an acidic environment inside and contains digestive enzymes
intracellular digestion
vacuoles
single-membrane small bubbles
digestive vacuole: digestion;
contractile vacuole: release of excess water and undigested food debris from the cell
mitochondria
oval body surrounded by a two-layer membrane:
The outer membrane is smooth, the inner membrane forms folds (cristae)
energy metabolism (cellular respiration)
ribosomes
the smallest organelles (visible only with an electron microscope);
consist of two parts: large and small subunits
protein synthesis
cell center
two centrioles (cylinders of microtubules) located perpendicular to each other
cell division
COMPARISON OF THE STRUCTURE OF ANIMAL AND PLANT CELLS
General principles of cell structure. Cell theory. Pro- and eukaryotesThe universal structural and functional unit of living things iscell . Cells are fairly small formations, usually visible only through a microscope, so the discovery and study of cells is closely related to the development of microscopic technology. Characteristic cell sizes: 1–5 μm for bacteria and 10–100 μm for animal and plant cells (micrometer, μm = 10−6 m, that is, a thousandth of a millimeter). The resolution limit of the human eye is about 100 microns (1/10 mm), but it must be taken into account that the object must be contrasty. Individual cells, even large ones, are often impossible to see within a tissue due to low contrast, and, as a rule, staining of the preparation is required to increase it. The case when a single cell with a size of the order of 100–200 microns can be seen with the naked eye is observation against a dark background in lateral light. Just as dust particles can be seen in an oblique beam of sunlight due to the scattering of light, in this case a cell can also be seen.
However, in most cases, optical instruments and preparation techniques are required to detect cells. Apparently, the first microscope was constructed by father and son Janssen at the end of the 16th century, but it was very imperfect.
The term “cell” was introduced by the English naturalist Robert Hooke (Fig. 1). He constructed a microscope and, using it to study various objects, in 1665 he discovered that a section of an ordinary wine cork was formed by regularly arranged rectangular cells (cells), which he called cells (Fig. 2 - illustration from his book “Micrography”) . He saw not living cells, but cell walls, since the cork is dead tissue. Subsequently, similar formations were discovered in other biological objects, and the term “cell” became generally accepted.
Rice. 1 Fig. 2
The Dutch scientist Antonie van Leeuwenhoek made a great contribution to the study of cells. At the end of the 17th century. He built a microscope and discovered various microorganisms in dental plaque, puddle water, and plant infusions. Leeuwenhoek's microscope was significantly improved by him and provided much more capabilities than the more primitive microscopes of his predecessors. Thus, the invisible world of microbes, which Leeuwenhoek called “animals,” was discovered. He also observed and sketched animal cells for the first time - sperm and erythrocytes (red blood cells). Leeuwenhoek described his observations in the book “Secrets of Nature Discovered by Anthony Leeuwenhoek Using Microscopes.”
After this, a period of rapid development of microscopy began, which led to the accumulation of information about the cellular structure of plant and animal tissues. As microscopic technology developed, it became clear that cells are universal components of living things.
Based on numerous observations of animal and plant cells in 1838, the botanist Matthias Schleiden and the histologist, physiologist, and cytologist Theodor Schwann formulatedcell theory . As further developmentcytology - cell science - this theory was developed and supplemented.
BASIC PROVISIONS OF CELL THEORY
The cell is the minimal structural and functional unit of living things.
(“there is no life outside the cell”). Viruses do not have a cellular structure, but they exhibit all the properties of a living thing (such as metabolism, self-reproduction) only inside the living cell of the host they have infected.
All living organisms consist of cells and the extracellular substance formed by them. A multicellular organism is a system of cells and the intercellular substance secreted by them, formed as a result of the division of 1 original cell (fertilized egg - zygote).
Despite significant differences in the size and shape of cells, they all havegeneral plan of the building . Schwann and Schleiden believed that all cells have a membrane, cytoplasm and a nucleus, which is typical for plant and animal cells, but further development of microscopy made it possible to find out that there are also cells without a nucleus (that is, without a nuclear membrane), for example, bacterial cells. They are much smaller than plant and animal cells. However, the chemical foundations and general principles of the structure and functioning of cells are common to all living organisms. This is one of the proofs of the unity of origin of living nature and the kinship of all life on Earth.
Cells do not arise anew from non-cellular matter, but are formed by division of pre-existing cells (the so-called Virchow addition, made by Rudolf Virchow in 1858). It is assumed that billions of years ago cells arose abiogenically in the process of the origin of life from non-living matter, but it is believed that this is currently impossible because suitable conditions are not available. Even the great French scientist Louis Pasteur (1822–1895), in his experiments with boiling nutrient media in special flasks with curved spouts, where microorganisms and their spores did not fall, proved the impossibility of the spontaneous generation of life from inanimate matter.
pro- and eukaryotes
All cellular organisms are divided into two groups:
prokaryotes , orpre-nuclear , without a nuclear membrane;
eukaryotes , ornuclear , in which the genetic material (DNA) is located in the nucleus and is separated from the cytoplasmnuclear membrane.
Prokaryotes are very small, single-celled organisms without a nucleus. Among them we can highlightkingdom bacteria and kingdom archaea (formerly archaebacteria).
Eukaryotes include three main kingdoms of multicellular organisms -kingdoms of animals, plants and fungi, - as well as unicellular eukaryotes (for example, amoebas, ciliates, etc.), which are combined intokingdom protists, orprotozoa (currently recognized as a collective, that is, a group of heterogeneous origin and divided into many kingdoms of unicellular organisms).
FEATURES OF PRO- AND EUKARYOTIC CELLS
Pro- and eukaryotic cells are very different. Prokaryotes are more ancient and simply structured organisms (Fig. 3). Their cells are very small, on the order of several micrometers (1–5 µm). They do not have a nucleus and practically no internal membrane structures - organelles characteristic of eukaryotic cells. They usually have a cell wall on top of the membrane and sometimes an additional mucous capsule. DNA is found in the cytoplasm, this structure is callednucleoid (“nucleus” - core, “oides” - similar). DNA in prokaryotes is circular. In addition to the main chromosome, there may be additional small rings of DNA -plasmids . There is a lot in the cytoplasmribosomes - organelles like granules that carry out protein biosynthesis. Prokaryotic cells may have flagella.
Some prokaryotes are capable of photo- or chemosynthesis. For example, they photosynthesizecyanobacteria , which used to be sometimes called blue-green algae. Other prokaryotes feed by absorbing low molecular weight organic substances through the cell surface. Such bacteria can settle in food products, causing them to spoil or, conversely, contributing to the production of fermented milk products and the fermentation of vegetables (lactobacteria). Also, when settling in the human body, bacteria can cause diseases, such as tetanus, cholera, and diphtheria.
Archaea - a special, extremely peculiar group of prokaryotes that lives in extreme habitats - in hot springs, in the salty Dead Sea, etc., as well as in soil, in the intestines of animals.
Rice. 3. Structure of a prokaryotic cell
Eukaryotic cells are many times larger (10–100 µm) and much more complex in structure (Fig. 4) than prokaryotic cells. In the cytoplasm they have many complex structuresorganelles , including membrane ones, for example, the endoplasmic reticulum (ER), OR (its other name) the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, mitochondria, and sometimes plastids.
The nucleus of eukaryotes hasdouble membrane nuclear envelope . Inside the nucleus there are DNA molecules; they are not circular, but linear, and there are usually several or many of them (at least two). They are complexed with proteins in chromosomes. The structure of a large and complex eukaryotic cell is supported by a system of protein fibers -cytoskeleton , which is practically not developed in prokaryotes. Cytoskeletal threads are also involved in the distribution of chromosomes to daughter cells during eukaryotic division.
Eukaryotic cells, as a rule, are able to absorb particles from the environment by invaginating the membrane, which is not typical for prokaryotes. This process is calledendocytosis . The reverse process is also characteristic of eukaryotes -exocytosis - secretion of substances by the cell by fusion of vesicles with the outer membrane. The cytoskeleton and a large number of membrane organelles, apparently, allowed eukaryotic cells to acquire large sizes during evolution. Found only in eukaryotestrue multicellularity .
Detailed information about the organelles of eukaryotic cells can be found in separate topics dedicated to them.
Rice. 4. Structure of a eukaryotic cell
The main (though not all) differences between pro- and eukaryotic cells are shown in the table.
ER, Golgi apparatus,lysosomes, vacuoles
No
There is
mitochondria, plastids
No
There is
ribosomes
smaller
more
DNA
1 ring
many linear chromosomes
cytoskeleton
not developed
developed
nitrogen fixation
It happens
can not be
endocytosis
No
There is
flagella
external
(not covered with membrane)
internal
(covered with membrane)
The structure of prokaryotic cells. Bacteria
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Cellsprokaryote do not have a nuclear membrane (Greek “pro” - before, “karyon” - core), they are small in size (usually 1 - 5 microns) and simple in structure.
SURFACE APPARATUS
All cells, including prokaryotic cells, are surrounded bycytoplasmic membrane . It isolates the contents of the cell from the environment, transports substances from and into the cell, and receives signals from the environment. Thus, the membrane ensures the maintenance of a constant intracellular environment.
Based on the structure of the surface apparatus, bacteria are divided into two large groups -gram-positive (gram+) andgram-negative (gram–). These names are given because of the varying ability of these cells to be Gram stained (a specific staining method).
In gram-positive bacteria, the murein layer is quite thick. Their cell walls also contain special compounds -teichoic acids .
In gram-negative bacteria, a thin murein layer is covered on top by a second membrane. Between the membranes there isperiplasmic space .
Rice. 1. Surface structure of gram+ and gram– bacteria
Some types of bacteria have an additional outer layer on top of the cell wall calledcapsule . Unlike the wall, it is loose and transparent. It consists of loosely bound polysaccharides and protects the cell from mechanical damage, and in the case of pathogenic bacteria, from the defense systems of the host organism.
Rice. 2. Bacterial capsule. Colorized electron micrograph
Rice. 3. Structure of a bacterial cell
INTERNAL STRUCTURE
In an electron micrograph of the inside of a bacterial cell, an electron microscope shows areas of varying density.
Rice. 4
The part that is more transparent to electrons (light) contains DNA and is callednucleoid (Greek “nucleus” - core, “oides” - similar). It is not separated from the rest of the cell, called the cytoplasm, and has approximately the same composition. DNA in prokaryotes is usually represented by one circular molecule, attached to the cytoplasmic membrane at a certain point.
Ribosomes are scattered throughout the internal space of a bacterial cell, the number of which can reach 10,000 per cell. Because of this, the cytoplasm appears darker and more granular in electron micrographs. In addition, inside the cell there are a few invaginations of the cytoplasmic membrane, calledmesosomes . Previously it was believed that they are the site of ATP synthesis; According to new data, these are most likely fixation artifacts, and respiration occurs in other areas of the membrane.
Sometimes granules of some substances are observed in the cells of some bacteria. They may contain reserve nutrients (polysaccharides, fat drops, polyphosphates) or metabolic waste that cells cannot excrete (sulfur, iron oxides, etc.). Such granules are calledinclusions (see Fig. 5).
Rice. 5
Outside the bacterial cell membrane, long filamentous structures of two types can be located. The first of them areflagella - are protein helices capable of rotating relative to the bacterial cell membrane and ensuring the movement of bacteria by “screwing” the bacteria into the medium. Not all bacteria have flagella. The second group of threads -drank - not capable of movement, but ensures the attachment of bacteria to other cells.
SPORE FORMATION
Some bacteria are capable of formingdisputes . Spores in bacteria do not serve to reproduce, but to endure unfavorable conditions. The spore is formed inside the cell (one in each cell). It necessarily contains the genetic material of the bacterium. The spore covers itself with a dense shell, after which all remaining external parts of the cell die.
Rice. 7. Spores in the cells of the anthrax pathogen
Bacterial spores generally survive boiling. They can only be destroyed by autoclaving (pressure steam treatment, usually at a temperature of 120 OC), calcination. The destruction of all bacteria and their spores is calledsterilization .
ECOLOGY OF BACTERIA
Bacteria are able to exist in a wide variety of conditions. They are found in the atmosphere at an altitude of several kilometers and on the bottom of the oceans. Some types of bacteria live even several kilometers underground in oil and coal formations.
Bacteria, despite their small size, carry out large-scale processes in the biosphere.
1. Bacteria are one of the most important groupsdecomposers - organisms that decompose dead organic matter.
2. Many bacteria are capable of producing organic substances from inorganic ones, that is, they areautotrophs . They can do this at the expensephotosynthesis using light energy (photoautotrophs, primarilycyanobacteria - green, contain chlorophyll, are the ancestors of chloroplasts) orchemosynthesis - oxidation of inorganic substances (chemoautotrophs).
Rice. 8. Cyanobacteria (photosynthetics)
Thus, prokaryotes can be producers of biomass -producers , in some biocenoses the most important or the only ones. Thus, chemosynthetic bacteria, primarily those that oxidize hydrogen sulfide, are the only producers in deep-sea ecosystemsblack and white smokers - oceanic geothermal sources.
Rice. 9
3. Only bacteria are capable of converting molecular nitrogen from the atmosphere into nitrogen from organic compounds, i.e., carrying outnitrogen fixation . Nitrogen is fixed, for example, by nodule bacteria - symbionts of leguminous plants, as well as cyanobacteria.
BACTERIA AND HUMANS
Bacteria play an important role in human life.
First of all, we must say aboutpathogenic bacteria , causing various diseases of humans, domestic animals and cultivated plants (see the topic “Bacterial and viral diseases of humans”).
In addition, bacteria cause food spoilage and destruction of various materials.
A number of bacteria are used by humans in their economic activities. Bacteria are used in the food industry to produce yoghurts, curdled milk, cheeses and a number of other lactic acid products. Thanks to bacteria, the processes of pickling cabbage, pickling cucumbers, and ensiling feed are carried out.
Fermentation processes carried out by bacteria are an industrial source of a number of substances, such as acetone, lactic and butyric acid.
Some bacteria and related actinomycetes produceantibiotics , used in medicine. Bacteria are a source for obtaining a numberenzymes , used in the food industry, medicine and other industries.
ARCHAEA
Nuclear-free, that is, prokaryotic cells, are also found in a completely special group of living organisms, different from bacteria and eukaryotes -archaea (See the topic “The main kingdoms of living organisms”). In size and structure, archaeal cells are very similar to bacterial cells, but they differ greatly in biochemical and molecular biological characteristics. For example, some archaea have a membrane that is completely different from the membranes of all other organisms - it does not consist of phospholipids, but of ethers of polyisoprenoid alcohols (that is, alcohols formed by isoprene units, such as natural rubber). The archaeal cell wall consists of eitherpseudomureina , resembling murein, or from proteins, which is also not found in other organisms. Archaea, unlike other bacteria, never form spores.
Rice. 10. Cells of methanogenic archaea (colorized electron micrograph)
Rice. 11. Redwood City, California. Aerial view. Purple archaea live in salty ponds
Viruses are non-cellular life forms
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Virus (from Lat. virus - poison) - the simplest form of life, a microscopic particle, which is a nucleic acid molecule (DNA or RNA) enclosed in a protein shell (capsid ) and capable of infecting living organisms.
Viruses, with rare exceptions, contain only one type of nucleic acid: either DNA or RNA (some, such as mimiviruses, have both types of molecules).
Currently, viruses are known that reproduce in the cells of plants, animals, fungi and bacteria (the latter are usually calledbacteriophages ). Viruses that infect other viruses have also been discovered (satellite viruses ).
Rice. 1 Bacteriophage
Structure of viruses
Simply organized viruses consist of a nucleic acid and several proteins that form a shell around it -capsid. Examples of such viruses are the tobacco mosaic virus. Its capsid contains one type of protein with a small molecular weight.
Rice. 2 Tobacco mosaic virus
Complexly organized viruses have an additional shell - protein or lipoprotein; sometimes the outer shells of complex viruses contain carbohydrates in addition to proteins. Examples of complexly organized viruses are the pathogens of influenza and herpes. Their outer shell is a fragment of the nuclear or cytoplasmic membrane of the host cell, from which the virus exits into the extracellular environment.
Rice. 3 Influenza virus
Spread of viruses on Earth
Viruses are one of the most common forms of existence of organic matter on the planet in terms of numbers: the waters of the world's oceans contain a colossal number of bacteriophages (about 250 million particles per milliliter of water), their total number in the ocean is about 4 × 1030, and the number of viruses (bacteriophages) in bottom sediments of the ocean practically does not depend on depth and is very high everywhere. The ocean is home to hundreds of thousands of species (strains ) viruses, the vast majority of which have not been described, much less studied. Viruses play an important role in regulating the population size of some species of living organisms (for example, the feralization virus reduces the number of arctic foxes several times every few years).
Viral infection process
Conventionally, the process of viral infection on the scale of one cell can be divided into several overlapping stages:
cell penetration
cell reprogramming
persistence (transition to an inactive state)
creation of new viral components
maturation of new viral particles and their exit from the cell
PENETRATION INTO THE CELL
At this stage, the virus needs to deliver its genetic information inside the cell. Some viruses also carry their own proteins necessary for its implementation. Different viruses use different strategies to penetrate the cell: for example, picornaviruses inject their RNA through the plasma membrane, and orthomyxovirus virions are captured by the cell during endocytosis, enter the acidic environment of lysosomes, where their final maturation occurs (deproteinization of the viral particle), after which the RNA is in complexed with viral proteins overcomes the lysosomal membrane and enters the cytoplasm. Viruses also differ in the localization of their replication; some viruses (for example, the same picornaviruses) multiply in the cytoplasm of the cell, and some (for example, orthomyxoviruses) - in its nucleus.
CELL REPROGRAMMING
When a cell is infected with a virus, special antiviral defense mechanisms are activated. Infected cells begin to synthesize signaling molecules - interferons, which transfer surrounding healthy cells into an antiviral state and activate the immune system. Damage caused by the virus multiplying in a cell can be detected by internal cell control systems, and the cell will have to "commit suicide" in a process called apoptosis or programmed cell death. Its survival directly depends on the ability of the virus to overcome antiviral defense systems. It is not surprising that many viruses (for example, picornaviruses, flaviviruses) during evolution acquired the ability to suppress the synthesis of interferons, the apoptotic program, etc.
In addition to suppressing antiviral defenses, viruses strive to create the most favorable conditions in the cell for the development of their offspring.
PERSISTENCE
Some viruses can becomelatent state (the so-called persistence for eukaryotic viruses or lysogeny for bacteriophages - bacterial viruses), weakly interfering with the processes occurring in the cell, and are activated only under certain conditions. This is how, for example, the reproduction strategy of some bacteriophages is constructed - as long as the infected cell is in a favorable environment, the phage does not kill it, is inherited by daughter cells and is often integrated into the cellular genome. However, when a bacterium infected with a lysogenic phage enters an unfavorable environment, the pathogen seizes control of cellular processes, so that the cell begins to produce materials from which new phages are built (the so-called lytic stage). The cell turns into a factory capable of producing many thousands of phages. Mature particles leaving the cell rupture the cell membrane, thereby killing the cell. Some cancers are associated with the persistence of viruses (for example, papovaviruses).
CREATION OF NEW VIRUS COMPONENTS
In the most general case, virus replication involves three processes:
Transcription of the viral genome, that is, synthesis of viral mRNA.
Its translation, that is, the synthesis of viral proteins.
Many viruses have control systems that ensure optimal consumption of host cell biomaterials. For example, when enough viral mRNA has accumulated, transcription of the viral genome is suppressed, and replication, on the contrary, is activated.
MATURATION OF VIRIONS AND EXIT FROM THE CELL
Eventually, the newly synthesized genomic RNA or DNA is dressed with appropriate proteins and leaves the cell. It should be said that an actively replicating virus does not always kill the host cell. In some cases (for example, orthomyxoviruses), daughter viruses bud from the plasma membrane without causing its rupture. Thus, the cell can continue to live and produce the virus.
Kingdom is one of the divisions of classification of living organisms in nature from a scientific point of view. One of the five main kingdoms of living organisms is the kingdom of bacteria. Otherwise they are called crushers.
This level of classification unites such subkingdoms as:
- bacteria.
The subkingdom of bacteria of the latter unites representatives of archaebacteria and. Bacteria are the smallest prokaryotic organisms characterized by a cellular structure. are 0.1-30 microns, and it is impossible to see them visually. Today, about 2,500 have been studied in nature. Microbiology studies bacteria. She examines representatives of the kingdom of bacteria that are not visible without special equipment (microorganisms):
- bacteria,
- microscopic mushrooms,
- seaweed.
Microbiology systematizes them into kingdoms, analyzes morphology, biochemistry, physiology, evolution and role in ecological systems.
A distinctive feature of representatives of the kingdom of bacteria is the absence of a membrane-surrounded nucleus separated from the cytoplasm. Some of them have , which makes them resistant to phagocytosis. Representatives of this kingdom are capable of reproduction every 20-30 minutes. Possibly both sexually and by budding in some species. There are also varieties capable of sporulation (like mushrooms).
Classifications of microorganisms
Depending on the shape of the bacterial cell, they are distinguished:
- (balls);
- (sticks);
- vibrios (curved like a boomerang);
- spirilla (spirals);
- (chain-shaped);
- (bunch-shaped).
According to the method of assimilation of nutrients from the surrounding nature, representatives of this kingdom are divided into the following groups:
In terms of their feeding method, bacteria are similar to fungi (saprotrophs, symbionts). Bacteria live in nature wherever there is at least some organic matter: dust, water, soil, air, on animals, inside other living organisms. Their numbers grow every 20-30 minutes. In addition, there is another group of microscopic organisms that are. These are cyanobacteria. They are able to photosynthesize thanks to pigments similar in properties to those found in plants and algae. , thanks to the pigment, can be blue-green and green. They live colonially, in filamentous formations and alone. Due to their similarity to algae, they can be in symbiosis with fungi, forming a group of lichens. :
- obligate aerobes - live in conditions of free access to oxygen;
- obligate anaerobes - live in conditions of complete absence of oxygen;
- facultative anaerobes - can exist under any conditions of oxygen access.
Functions of microorganisms in human life
They play a huge role, which is explained by the following facts:
- by the process of their life activity they contribute to the formation of humus (an organic fertilizer necessary for plant life).
- Some microorganisms are capable of converting organic substances into inorganic ones in nature in a short time, which is especially important for.
- In the human and animal body there are microorganisms involved in the digestion of food consumed and the formation of vitamins.
- Bacteria capable of causing are widely used to produce alcohol, acetic acid, fermented milk products, and silage.
- Some bacteria can produce substances that can inhibit the vital activity of other living organisms, which has found its application in the production of antibiotics.
- Feed protein synthesis.
- Participation of some bacteria in the synthesis of insulin, organic acids, alcohols, and polymeric substances.
- The ability of some microorganisms to cause the death of the host.
- Live bacteria are also used to make vaccines.
Negative effects of bacteria
In addition to all the positive properties of microorganisms listed, it should be mentioned that some bacteria can cause diseases. They are called
Test yourself by completing the suggested tasks (at the teacher's discretion - in class or at home).
1. Life on the modern planet is diverse and represented by several kingdoms.
Answer: plants, animals, fungi, bacteria.
2. The kingdom of bacteria unites living organisms that have common characteristics: they consist of
Answer: one cell
- in a cage
Answer: there is no clearly defined core
- very small organisms, visible
Answer: only through a microscope
- meet
Answer: in all habitats
3. Bacteria have all the signs of life. They breathe
Answer: they feed, excrete the products of their vital activity, i.e. carry out metabolism, reproduce, adapt to environmental conditions.
4. They are able to live in the presence of oxygen
Answer: bacteria - aerobes,
and in an oxygen-free environment
Answer: bacteria are anaerobes
5. Even in everyday life, it is important for a person to know about the existence of anaerobic bacteria, since
Answer: the absence of atmospheric oxygen is a favorable environment for their development. Anaerobe bacteria are dangerous to humans, so preserving a jar of mushrooms at home can result in poisoning.
6. In industry, bacteria are used to produce fermented milk products, for example
Answer: kefir, sour cream, cheeses.
7. Most bacteria are heterotrophs, i.e. used for nutrition
Answer: ready-made organic substances.
Among them there are saprotrophs that use
Answer: organic matter from dead bodies; Bacteria inhabit living organisms
8. In the process of metabolism, bacteria not only consume ready-made organic substances, but also release waste products into the environment. This feature of bacteria is used in biotechnology, producing
Answer: antibiotics, vitamins, proteins.
9. Bacteria multiply by
Answer: cell division into two parts. The high rate of bacterial reproduction is especially dangerous in the case of the proliferation of pathogenic bacteria, for example Answer: dysentery bacteria.
10. Knowing about the existence of “invisible bacteria”, it is important to follow the rules of hygiene
Answer: wash your hands and body, brush your teeth, keep your clothes clean, do not drink water from untested sources, fight flies, wear gloves when working in the garden, cover your coughs and sneezes with a tissue.
11. In case of simple injuries, it is necessary to know first aid techniques. Test yourself by naming these techniques.
Answer: the wound on the body must be treated with hydrogen peroxide and bandaged.
12. Having mastered all habitats, bacteria play a large role in the life of the modern planet.
Answer: They convert organic substances from fallen leaves, dying plants, and dead animals into minerals and return them to the soil solution, participating in the cycle of substances.
First question The kingdom of bacteria unites living organisms that have common characteristics: 1 Consist of... (one or many) cells 2 in the cell... (is present or absent) a clearly defined nucleus 3 Very small organisms, visible... (to the naked eye) eye or only with a microscope) 4 Found... (in all or only some) habitats Second question They are able to live both in the presence of oxygen (.... bacteria) and in an oxygen-free environment (.... .bacteria) Third question In industry, bacteria are used to produce fermented milk products, for example..... . Fourth question: Most bacteria are heterotrophs, that is, they are used for nutrition... . Among them there are saprotrophs that use... ; Bacteria settle in living organisms... Fifth question Bacteria multiply by... . The high rate of bacterial reproduction is especially dangerous in the case of the proliferation of pathogenic bacteria, for example... . Sixth question Knowing about the existence of (invisible bacteria), it is important to follow the rules of hygiene: ... . I give 60 points
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Part 1. Kingdom of Bacteria
Subkingdom Real bacteria
Subkingdom Archaebacteria
Subkingdom Oxyphotobacteria
To the kingdom bacteria (from the Greek “bacterion” - stick) unite the most ancient inhabitants of our planet, which in everyday life are often called microbes. These organisms have a cellular structure, but their hereditary material is not separated from the cytoplasm by a membrane - in other words, they lack a formed nucleus. Most of them are much larger in size than viruses. Based on important features of life activity, and above all metabolism, scientists divide the kingdom of bacteria into three subkingdoms: Archaebacteria, True bacteria And Oxyphotobacteria.
Science studies the structure and characteristics of the life activity of microorganisms microbiology.
Subkingdom Real bacteria
Let us consider the structural features of bacteria using the example of representatives of the subkingdom True bacteria.
These are very ancient organisms, apparently appearing more than 3 billion years ago. Bacteria are microscopically small, but their clusters (colonies) are often visible to the naked eye. Based on the shape and characteristics of the grouping of cells, several categories of true bacteria are distinguished. Cocci have a spherical shape; diplococci consist of pairwise close spherical cells; streptococci formed by cocci, close together in the form of a chain; sarcins – clusters of cocci, looking like dense packs; staphylococci – a complex of cocci in the form of a grape bunch. bacilli, or sticks, – elongated bacteria; vibrios – arched bacteria, and spirilla – bacteria with an elongated, corkscrew-shaped shape, etc.
On the surface of bacterial cells there are often flagella - organelles of movement, with the help of which they move in a liquid environment. In their organization they differ from the flagella and cilia of plants and animals. Some bacteria move in a “reactive” way, releasing a portion of mucus into the environment. The cell wall of bacteria is built in a very unique way and includes compounds not found in plants, fungi and animals. Usually it is quite strong, its basis is the substance murein, which is a mixture of polysaccharides and proteins. The cell wall of many bacteria is covered with a layer of mucus on top. The cytoplasm is surrounded by a membrane that separates it from the inside from the cell wall.
Bacteria shape
Location of flagella in bacteria
There are few membranes in the cytoplasm of bacteria, and they are not independent structures, but invaginations of the outer cytoplasmic membrane. There are no organelles surrounded by a membrane (mitochondria and plastids). Protein synthesis is carried out by ribosomes, which are smaller in size than those of eukaryotes. All enzymes that provide vital processes are scattered in the cytoplasm or attached to the inner surface of the cytoplasmic membrane.
Bacteria usually reproduce by dividing in two. First, the cell elongates, the ring chromosome is doubled, a transverse constriction is gradually formed, and then the daughter cells disperse or remain connected in characteristic groups - chains, packets, etc.
Under unfavorable conditions, such as increased temperature or drying, many bacteria form disputes. In this case, part of the cytoplasm containing hereditary material is isolated and covered with a thick multilayer capsule. The cell seems to dry out - the metabolic processes in it stop. Bacterial spores are very resistant; they can remain viable in a dry state for many years, and also survive in the body of a sick person, despite active treatment with antibiotics. Bacterial spores are spread by wind and other means. When exposed to favorable conditions, the spore transforms into an active bacterial cell.
Spore formation scheme
Reproduction of a bacterial cell by fission in two
Autotrophic bacteria (from the Greek “auto” - myself and “trophos” - I feed), which independently synthesize organic substances from inorganic ones, a little. Some of them are capable of chemosynthesis– synthesis of organic substances that form their body from inorganic ones using the energy of oxidation of inorganic compounds. Others form organic molecules from inorganic ones in the process photosynthesis, using the energy of sunlight.
In relation to oxygen, bacteria are divided into aerobes (existing only in an oxygen environment) and anaerobes (existing in an oxygen-free environment). In addition, groups of bacteria are known that live in both oxygen and oxygen-free environments.
Pathogenic bacteria
In nature, bacteria are extremely widespread. They inhabit the soil, playing role destroyers organic matter - the remains of dead animals and plants. By converting organic molecules into inorganic ones, bacteria thereby cleanse the surface of the planet from rotting residues and return chemical elements to the biological cycle.
And the role of bacteria in human life is enormous. Thus, the production of many food and technical products is impossible without the participation of various fermentation bacteria. As a result of the vital activity of bacteria, yogurt, kefir, cheese, koumiss, as well as enzymes, alcohols, and citric acid are obtained. The fermentation processes of food products are also associated with bacterial activity.
Bacteria are found symbionts (from the Latin “sim” - together, “bios” - life), which live in the organisms of plants and animals, bringing them certain benefits. For example, nodule bacteria, settling in the roots of some plants, they are able to absorb gaseous nitrogen from the soil air, convert it into soluble compounds and thus supply these plants with the nitrogen necessary for their life. As plants die, they enrich the soil with nitrogen compounds, which would be impossible without the participation of such bacteria.
Known predatory bacteria that eat representatives of other types of prokaryotes.
The negative role of bacteria is also great. Various types of bacteria cause food spoilage by releasing metabolic products that are toxic to humans. Most dangerous pathogenic (from the Greek “pathos” - disease and “genesis” - origin) bacteria are the source of various diseases in humans and animals, such as pneumonia, tuberculosis, tonsillitis, anthrax, salmonellosis, plague, cholera, etc. They affect bacteria and plants.
Symbiont bacteria form nodules on plant roots
The result of the activity of wood destroying bacteria
Subkingdom Archaebacteria*
Archaebacteria (from the Greek “archios” - the most ancient), perhaps the most ancient of living prokaryotes, and therefore of all other living organisms; they appeared on our planet more than 3.8 billion years ago.
In total, a little more than 40 species of archaebacteria have been described. Some of them are capable of living in extreme conditions.
Among the archaebacteria, the most famous methane-producing bacteria which, as a result of metabolism, emit flammable gas methane. A significant portion of methane on Earth (10–15 × 10 6 tons annually) is produced only by this group of prokaryotes. Methane-producing archaebacteria live in strictly anaerobic conditions: in flooded soils, swamps, sludge of reservoirs, wastewater treatment plants, and ruminant rumen.
Another group of archaebacteria - the so-called halobacteria– organisms capable of growth at very high salt concentrations. They live in salt lakes.
Among archaebacteria there are those that oxidize sulfur and its inorganic compounds to form sulfuric acid and therefore can cause the destruction of stone and concrete structures, corrosion of metals, etc.
Halobacteria
Halobacteria live in the salty sediments of the Dead Sea
Sulfur bacteria
Methane-producing archaebacteria live in swamps
Subkingdom Oxyphotobacteria*
The subkingdom includes several groups of bacteria, in particular the department cyanobacteria, often called blue-green algae. They are very widespread throughout the world. About 2 thousand species of cyanobacteria are known. These are ancient organisms that arose about 3 billion years ago. It is assumed that changes in the composition of the ancient atmosphere of the Earth and its enrichment with oxygen are associated with the photosynthetic activity of cyanobacteria.
Cyanobacterial cells, round, elliptical, cylindrical, barrel-shaped or other in shape, can remain solitary, unite in colonies, or form multicellular filaments. They often secrete mucus in the form of a thick sheath, surrounded in some forms by a dense shell. In some species, the threads branch and in some places form multi-row thalli. Filamentous forms of cyanobacteria, in addition to ordinary cells, have those that are capable of absorbing nitrogen from atmospheric air, converting it into various soluble inorganic substances. These cells supply nitrogen compounds to other cells of the thread. Cyanobacteria, unlike true bacteria, never have flagella. Cyanobacteria usually reproduce by dividing cells in two; they do not have a sexual process.
Different forms of cyanobacteria
Cyanobacteria and archaebacteria in a hot spring
Cyanobacteria often cause blooms in ponds
Cyanobacteria form green spots on rocks
Most cyanobacteria are autotrophic organisms and can synthesize all cell substances using light energy. However, they are also capable of a mixed type of nutrition.
Cyanobacteria often enter into symbiosis with other organisms. And in symbiosis with fungi they form organisms such as lichens.
Most species inhabit freshwater basins, a few live in the seas. When cyanobacteria multiply en masse, they often cause water “blooming” in ponds, which negatively affects the life of the inhabitants of the reservoir, since many cyanobacteria release toxic substances during their life processes. In addition, due to the massive death of cyanobacteria, the water begins to rot and an unpleasant odor appears. You cannot drink water from such reservoirs. On land, cyanobacteria live in the soil and form characteristic green deposits on rocks and tree bark.
Species of the genus Anabena are artificially bred in the tropics in rice fields to enrich the soil with nitrogen compounds. Thanks to the nitrogen-fixing properties of this bacterium, which lives in the cavities of the leaves of the azolla aquatic fern, rice can grow for a long time in the same place without applying fertilizers. Some cyanobacteria in Eastern countries are used as food.
Microphotographs of various cyanobacteria
Questions and tasks
1. What are the structural features of a bacterial cell? What chemicals make up the body of bacteria?
2. Name the main forms of bacterial cells.
3. How do bacteria travel?
4. Using the textbook material, make a table and enter into it groups of bacteria and how they obtain energy.
5. Are there predators among bacteria?
6. What systematic group do archaebacteria form?
7. What organisms are called aerobes? Why? How are they different from anaerobes?
8. List the structural features of cyanobacterial cells.
9. How do bacteria reproduce?
10. Why do you think bacteria are considered the most ancient organisms?
11. Discuss in class how you can prevent water bodies from blooming.
12. Make a detailed plan for the paragraph.
Work with computer
Refer to the electronic application. Study the material and complete the assigned tasks.
1. http://artsiz.ucoz.ua/publ/shkolnikam_na_zametku/prokarioty/2-1-0-1 (General characteristics of prokaryotes)
2. http://www.worldofnature.ru/dia/?act=viewcat&cid=578 (Prokaryotes: information and illustrations)
Part 2. Kingdom of Mushrooms
Division Chytridiomycota
Division Zygomycota
Division Basidiomycota
Group Imperfect fungi
Oomikota Department
Lichens group
Modern biologists classify fungi as an independent kingdom of organisms that differ significantly from plants and animals.
Science is studying the kingdom of mushrooms, which includes at least 100 thousand species. mycology (from the Greek “mikos” - mushroom, “logos” - teaching).
Scientists believe that fungi are a collective group of organisms with different origins. It is possible that fungi were among the first eukaryotes, but their early history is virtually unknown. The vast majority of modern fungi live on land. However, the oldest fungi were obviously freshwater or marine organisms.
Mushrooms lack the pigment that ensures photosynthesis, chlorophyll, and are heterotrophs. Some properties of mushrooms bring them closer to animals: they accumulate in cells as a reserve nutrient glycogen, and not starch, like plants; the cell membrane contains chitin, similar to arthropod chitin; as a product of nitrogen metabolism they form urea On the other hand, in terms of their feeding method (by absorption, not swallowing food), in terms of unlimited growth and immobility, they resemble plants.
A distinctive feature of mushrooms is the structure of their vegetative body. This mycelium, or mycelium, consisting of thin branching thread-like tubes - gif.
Cap mushrooms
Mushrooms are diverse in structure and widely distributed in various habitats. Their sizes vary widely: from microscopically small (unicellular forms - yeast) to large specimens, the body of which reaches half a meter or more in diameter (for example, large spherical puffballs, as well as edible mushrooms - porcini, boletus, etc.).
The mycelium, or mycelium, has a huge surface area through which it absorbs nutrients. The part of the mycelium located in the soil is called soil mycelium. The outer part - what we usually call a mushroom - also consists of hyphae, but very tightly intertwined. This - fruiting body mushroom. Reproductive organs are formed on it.
In most fungi, the mycelium is divided by partitions into individual cells. The septa have pores through which the cytoplasm of neighboring cells communicates. Uniting in bundles, the hyphae form large strands, sometimes reaching several meters in length. Such cords perform, in particular, a conductive function. In some cases, dense interlacing of hyphae form thickenings rich in reserve nutrients, ensuring the survival of the fungus in unfavorable conditions when the main part of the mycelium dies. From these, in conditions suitable for existence, mycelium develops again.
Mushroom structure
A fungal cell, as a rule, has a well-defined cell wall. The cytoplasm contains a significant number of ribosomes and mitochondria; the Golgi apparatus is poorly developed. Protein granules can often be found in vacuoles. A large number of inclusions are represented by glycogen granules and fat droplets. The hereditary, or genetic, apparatus of the cell is concentrated in the nuclei, the number of which ranges from one to several dozen.
Some unicellular fungi, such as yeast, have a body formed by a single budding cell. If the budding daughter cells do not separate from each other, a mycelium consisting of several cells is formed.
Fungi reproduce mainly asexually - disputes or vegetatively - parts of the mycelium. Spores develop on specialized hyphae - sporangiophores, rising above the soil or other substrates. There is also sexual reproduction.
Cloud of spores formed by fungi
Fungal hyphae in soil
Diagram of the structure of a fungal cell
A close connection is established between the roots of trees and the mycelium of some mushrooms, which is beneficial to both the mushroom and the plant - symbiosis occurs. The mycelium threads entwine the root and even penetrate inside it, forming mycorrhiza (from the Greek “mikos” - mushroom and “riza” - root). The mycelium absorbs water and dissolved minerals from the soil, which flow from it into the roots of trees. Thus, the mycelium can partially replace root hairs for trees. From the roots of the plant, the mycelium, in turn, receives the organic substances it needs for nutrition and the formation of fruiting bodies.
Mushrooms play both positive and negative roles in human economic activity. Yeast, which causes the fermentation process, is of great importance in the food industry. Many fungi produce biologically active substances, enzymes, and organic acids. They are used in the microbiological industry for the production of citric and other organic acids, as well as enzymes and vitamins. A number of species, such as ergot and chaga, are used as raw materials for the production of medicines.
Mushrooms are traditionally eaten. There are over 150 species of edible mushrooms found in our country, but only a few dozen are widely used.
Fungi are known to cause human diseases, such as mycosis of the feet, hands, and nails. Some fungi cause diseases in domestic animals, harming livestock production. An example of such a fungal disease is ringworm. Many fungi cause plant diseases - tinder fungi on trees, ergot in cereals, etc.
Sexual reproduction of basidiomycete fungi
Pathogens: Chytridiomycota fungi
Sporangia with spores
Mycologists include several divisions in the kingdom of mushrooms: Chytridiomycota, Zygomycota, Oomycota, Ascomycota And Basidiomycota. The largest of them are Ascomycota And Basidiomycota.
A separate group is formed imperfect mushrooms, which reproduce only asexually or vegetatively and never form fruiting bodies.
Division Chytridiomycota*
Division Zygomycota
Pilobolus on manure
Flour on bread
Mortirella
Division Ascomycota, or marsupial mushrooms
Ascomycota is one of the most extensive divisions (about 30 thousand species). They got their name due to the formation of closed structures - bags (ascas) containing spores. The Ascomycota department includes, in particular, yeast, represented by single budding cells, numerous multicellular fungi with large fruiting bodies, for example morels And lines.
Representatives of Ascomycota are widespread in all natural zones and regions. According to their feeding method, they are heterotrophs; they live in the soil, forest litter, on various plant substrates and feed on rotting remains. Some species of ascomycota develop on substrates of animal origin, while others participate in the decomposition of plant residues containing cellulose into inorganic molecules.
Many species of ascomycota form substances used in medicine for the treatment of infectious diseases (antibiotics), enzymes, organic acids and are used for their industrial production.
A group widely used by humans from the Ascomycota division is yeast. It is important to note that among yeast there are no species that form substances toxic to humans. When food spoilage caused by yeast, the taste and appearance change, but harmful substances do not accumulate, as is observed with poisonous mushrooms and bacteria. Baker's yeast exists only in culture. They are represented by hundreds of races: wine, bakery, beer and spirits.
Bag (asca) with spores
Ergot cells contain highly toxic (poisonous) substances that can cause poisoning if they get into flour or animal feed. Substances isolated from ergot are widely used in modern medicine to treat cardiovascular, nervous and other diseases. They are especially effective in obstetric and gynecological practice.
Some representatives of Ascomycota, such as morels and truffles, edible.
Ergot
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