All living things are divided into 2 empires - cellular and noncellular forms life. The main forms of life on Earth are organisms cellular structure. This type of organization is inherent in all types of living beings, with the exception of viruses, which are considered non-cellular life forms.

Non-cellular forms

Noncellular organisms include viruses and bacteriophages. Other living things are cellular life forms.

Non-cellular life forms are a transitional group between non-living and living nature. Their life activity depends on eukaryotic organisms; they can divide only by penetrating into living cell. Outside the cell, noncellular forms do not show signs of life.

Unlike cellular forms, noncellular species have only one type of nucleic acid - RNA or DNA. They are not capable of independent protein synthesis due to the lack of ribosomes. Also, in noncellular organisms there is no growth and no metabolic processes occur.

General characteristics of viruses

Viruses are so small that they are only several times larger than large protein molecules. The size of particles of different viruses is in the range of 10-275 nm. They are visible only under an electron microscope and pass through the pores of special filters that retain all bacteria and cells of multicellular organisms.

They were first discovered in 1892 by the Russian plant physiologist and microbiologist D.I. Ivanovsky while studying tobacco disease.

Viruses are the causative agents of many plant and animal diseases. Viral diseases humans are measles, influenza, hepatitis (Botkin's disease), polio ( infantile paralysis), rabies, yellow fever, etc.

Structure and reproduction of viruses

Under an electron microscope different types viruses have the form of sticks and balls. An individual viral particle consists of a nucleic acid molecule (DNA or RNA), folded into a ball, and protein molecules, which are located around it in the form of a kind of shell.

Viruses cannot independently synthesize the nucleic acids and proteins of which they are composed.

Reproduction of viruses is only possible using enzymatic cell systems. Having penetrated the host cell, viruses change and rearrange its metabolism, as a result of which the cell itself begins to synthesize molecules of new viral particles. Outside the cell, viruses can enter a crystalline state, which contributes to their preservation.

Viruses are specific - a certain type of virus infects not only a specific type of animal or plant, but also certain cells of its host. Thus, the polio virus only affects nerve cells human, and the tobacco mosaic virus - only cells of tobacco leaves.

Bacteriophages

Bacteriophages (or phages) are peculiar bacterial viruses. They were discovered in 1917 by the French scientist F. d'Herelle. Under an electron microscope, they have the shape of a comma or tennis racket and are about 5 nm in size. When a phage particle attaches with its thin appendage to a bacterial cell, the phage DNA enters the cell and causes the synthesis of new DNA molecules and bacteriophage protein. After 30-60 minutes, the bacterial cell is destroyed and hundreds of new phage particles emerge from it, ready to infect other bacterial cells.

Previously, it was believed that bacteriophages could be used to combat pathogenic bacteria. However, it turned out that phages, which quickly destroy bacteria in a test tube, are ineffective in a living organism. Therefore, nowadays they are mainly used for diagnosing diseases.

Cellular forms

Cellular organisms are divided into two superkingdoms: prokaryotes and eukaryotes. Structural unit The cellular form of life is the cell.

Prokaryotes have the simplest structure: there is no core and membrane organelles, division proceeds by amitosis, without the participation of the division spindle. Prokaryotes include bacteria and cyanobacteria.

Eukaryotes - These are cellular forms that have a formed nucleus, which consists of a double nuclear membrane, nuclear matrix, chromatin, and nucleoli. Also in the cell there are membrane (mitochondria, lamellar complex, vacuoles, endoplasmic reticulum) and non-membrane (ribosomes, cell center) organelles. DNA in representatives of cellular forms is located in the cell nucleus, as part of chromosomes, as well as in cellular organelles, such as mitochondria and plastids. Eukaryotes combine plant, animal world and the Kingdom of Mushrooms.

The similarity between cellular and non-cellular species lies in the presence of a specific genome, the ability to evolve and produce offspring.

The discovery and study of cells became possible thanks to the invention of the microscope and the improvement of microscopic research methods. The first description of a cell was made in 1665 by the Englishman R. Hooke. Later it became clear that he did not discover cells (in the modern sense of the term), but only the outer membranes of plant cells.

History of discovery

Progress in the study of cells is associated with the development of microscopy in the 19th century. By this time, ideas about the structure of cells had changed: the main thing in the organization of a cell began to be considered not the cell wall, but its actual contents, protoplasm. A permanent component of the cell, the nucleus, was discovered in protoplasm. Numerous observations have been accumulated the finest structure and the development of tissues and cells made it possible to approach generalizations that were first made in 1839 by the German biologist T. Schwann in the form of the cell theory he formulated. He showed that plant and animal cells are fundamentally similar to each other. Further development and these ideas were generalized in the works of the German pathologist R. Virchow.

Significance in science

The creation of cell theory became the most important event in biology, one of the decisive proofs of the unity of all living nature. Cell theory had a significant influence on the development of embryology, histology and physiology. It provided the basis for a materialistic understanding of life, for explaining the evolutionary relationship of organisms, for understanding individual development.

“The main fact that revolutionized all physiology and made comparative physiology possible for the first time was the discovery of cells,” this is how F. Engels characterized this event, comparing the discovery of the cell with the discovery of the law of conservation of energy and Darwin’s evolutionary theory.

The basic principles of cell theory have retained their significance to this day, although over more than 100 years new information has been obtained about the structure, vital activity and development of cells.

Basic provisions

Currently cell theory postulates:

• A cell is the elementary unit of living things;
• cells of different organisms are homologous in structure;
• cell reproduction occurs by dividing the original cell;
• multicellular organisms are complex ensembles of cells united into holistic, integrated systems of tissues and organs, subordinate and interconnected by intercellular, humoral and neural forms of regulation.

Empire non-cellular organisms(Noncellulata). Kingdom of Viruses (Virae)

Virus particle ( virion) consists of a nucleic acid (DNA or RNA) surrounded by a protein shell - capsid, consisting of capsomeres.

Viruses have the following characteristic features:

They do not have a cellular structure;

They have the smallest dimensions, the size of the virion of various viruses is from 15 to 400 nm (most are visible only in electron microscope);

They do not have their own metabolic systems;

Use host cell ribosomes to form their own proteins;

Incapable of growth and division;

They do not reproduce on artificial nutrient media.

Viruses of microorganisms are named phages. Thus, there are bacteriophages (bacterial viruses), mycophages (fungal viruses), cyanophages (cyanobacterial viruses). Phages usually have a multifaceted prismatic head and appendage (Fig. 3.1).

Rice. 3.1. Structure of bacteriophage T4:

1 - head; 2 - tail; 3 - nucleic acid; 4 - capsid; 5 - “collar”; 6 - protein cover of the tail; 7 - tail fibril; 8 - spikes; 9 - basal plate

The head is covered with a shell of capsomeres and contains DNA inside. The process is a protein rod covered with a sheath of helically arranged capsomeres. After the phage enters, the bacterium loses its ability to divide and begins to produce not the substances of its own cell, but particles of the bacteriophage.

As a result, the bacterial cell wall dissolves (lyses), and mature bacteriophages emerge from it. An insufficiently active phage can exist in the cell of a microorganism without causing lysis. Phages are found in water, soil and other natural objects.

Diversity of living organisms.

Cellular and

non-cellular life forms

Teacher

Z. M. Smirnova

Modern system organisms

Empire

Cellular organisms

Pre-nuclear

Overkingdoms

Kingdoms

(prokaryotes)

Drobyanki

Nuclear (eukaryotes)

Mushrooms

Non-cellular organisms

Sub-kingdoms

Grow

Animals

Viruses

Vira

Cyanobacteria or (blue-green algae)

Eubacteria

viruses

Diversity of the organic world

Empire Cellular

Empire Noncellular

Plant Kingdom

Kingdom Mushrooms

Animal Kingdom

Kingdom Viruses

Multicellular

Eukaryotes

Subkingdom Protozoa

Unicellular

Prokaryotes

Kingdom of Drobyanka

Types of Cellular Organization

Eukaryotic

includes the superkingdom Eukaryotes.

Have a formed core

and a well-developed internal membrane system. The genetic apparatus is represented by molecules DNA in complex with proteins - histones that package DNA into nucleosomes.

Prokaryotic

includes the superkingdom of Prokaryotes.

Do not have a formal core

and membrane organelles. Genetic material - circular DNA molecule (nucleoid).

DNA is not blocked by proteins, therefore all genes in it are active.

Overkingdom Prokaryotes

Structural and functional parts of a prokaryotic cell:

• Cytoplasm

• Surface

• Genetic

material:

apparatus:

• nucleoid - zone

• plasmatic

cytoplasm with large

membrane;

molecule

Supramembrane

DNA, closed

complex:

in the ring

• mureic

cell wall (complex carbohydrate);

• plasmids –

• mucous capsule

short

ring

(performs

protective function)

DNA molecules

• flagella

Cytoplasmic structures:

Hyaloplasm:

• mesosomes

• sol (in favorable

conditions)

(invaginations

• gel (with

plasmatic

bad

membranes)

conditions,

• membrane

When

organoids

increases

are missing, their

perform the function

density

hyaloplasma)

mesosomes.

• ribosomes (small)
• cytoplasm

motionless, because

microtubules

none.

Overkingdom Eukaryotes

Structural and functional parts of a eukaryotic cell:

Surface

apparatus

Cytoplasm

Core

• nucleoli
• chromosomes
• karyoplasm

hyaloplasm

plasmalemma

(proteins,

lipids)

submembrane complex

(accumulation of microtubules and microfilaments of the cytoskeleton under the plasmalemma)

cytoplasmic

logical structures

(organelles and

inclusions)

supramembrane complex

(in an animal cell – glycocalyx,

V plant cell – cell wall (cellulose),

mushrooms - chitin)

Comparison of pro- and eukaryotic organisms

PROKARYOTES

Cell size

EUKARYOTES

1-10 µm

Metabolism

10-100 microns

Anaerobic or aerobic

Aerobic

Organelles

Not numerous (membrane invaginations - mesosomes and small ribosomes).

Cytoplasm

Nucleus, mitochondria, chloroplasts, endoplasmic reticulum, etc.

Circular DNA in the cytoplasm (nucleoid)

DNA – organized into chromosomes and surrounded by a nuclear membrane

Absence of cytoskeleton, cytoplasmic movement, endo- and exocytosis

Cell division, cellular organization

There is a cytoskeleton, cytoplasmic movement, endocytosis and exocytosis

Binary fission, predominantly unicellular and colonial

Mitosis (or meiosis), predominantly multicellular

Non-cellular life forms

Viruses were discovered by D.I. Ivanovsky (1892) while studying tobacco mosaic disease.

I. D. Ivanovsky

Tobacco mosaic virus

The place of viruses in the system of living nature

Empire Non-cellular life forms

Kingdom of Vir

Size comparison

1/10 part of a red blood cell

Bacteriophage

(eukaryote-

cheskaya

cell)

Adenovirus 90 nm

Tobacco mosaic virus

250 x 18 nm

Rhinovirus

Prion

200 x 20 nm

E. Coli (bacterium - Escherichia coli)

3000 x 1000 nm

Routes of entry into the human body:

- by airborne droplets from a sick person (flu, measles, smallpox);

- with food (foot-and-mouth disease virus);

- through damaged skin surface (rabies, herpes, smallpox);

- sexually (HIV, herpes);

- through blood-sucking (mosquitoes – yellow fever, ticks – encephalitis, Crimean fever);

- during blood transfusions and operations, the AIDS and hepatitis B viruses are transmitted.

Plant cells are affected as a result of violation integrity of the integument

Life forms of the virus

There are two life forms of viruses

Intracellular

– inside infected cell with viruses manifest themselves in the form of nucleic acid (DNA or RNA) and form a “virus-cell” complex capable of living and “producing” new

virions.

Extracellular (resting) – viral particles, or virions, consisting of nucleic acid and

capsid (shell made of protein and, less commonly, lipids).

The virion is essentially conglomerate of organic crystals.

Virion structure:

Core - genetic material

(DNA or RNA)

Shell

Complex viruses

Simple viruses have a shell

• capsid, consisting only of protein subunits - capsomeres

(flu, herpes, etc.)

have supercapsid :

• capsid,
• outside two layers

lipids (Part

plasmatic

membranes

host cells

• viral

glycoproteins

• non-structural

proteins - enzymes

Virus

tobacco mosaic

Features of the life activity of viruses:

Variety of shapes and sizes of viruses

(from 10 to 300 nm)

Plant viruses

(usually contain RNA);

Animal viruses;

• Precipitation;
• Penetration of the virus into the cell:

fusion of the virus membrane and the outer membrane occurs cyto plasma membrane- the virus ends up in cytoplasm of the cell.

Stages of the life of the virus

3. Destruction of viral protein shells.

Lysosome enzymes destroy the capsid virus and its nucleic acid freed up.

4. Synthesis of DNA with RNA virus.

5. Incorporation of viral DNA into cell DNA.

Functioning is suppressed genetic apparatus of the cell.

Stages of the life of the virus

6. Nucleic acid replication

acids of the virus.

7. Synthesis of capsid proteins. After replication, the biosynthesis of viral capsid proteins begins, using the ribosomes of the host cell.

8. Virion assembly

Begins with the accumulation of viral proteins and RNA

9. Exit of viruses from the cell

Complex viruses leaving the cell capture part of the cell membrane host cells and form a supercapsid.

HIV infection

HIV infection is a slowly progressive disease characterized by cell damage immune system(lymphocytes, etc.) with the development of immunodeficiency (AIDS) - the body is not able to resist pathogens of various infections and malignant neoplasms.

IN – virus

AND – immunodeficiency

H – person

WITH – syndrome (complex of symptoms)

P – acquired (not congenital condition)

AND – immuno-

D – deficiency (the body loses the ability

resist various infections)

AIDS is the ultimate terminal stage HIV infection

Viruses and diseases they cause

Virus conjunctivitis,

pharyngitis

Adenoviruses

Rubella

Rubella virus

Human papillomavirus

Warts, genital papillomas

Flu

Orthomyxoviruses

Poliomyelitis, meningitis, ARVI

Picornavirus

Hepatotropic viruses

Viral hepatitis

HIV – infection, T-cell leukemia – adult lymphoma

Retroviruses

Herpes simplex, chicken pox, herpes zoster

Herpesviruses

Poxviruses

Smallpox

Herpes virus

Influenza virus

• Structure:

• head containing nucleic acid acid,

capsid covering the head;

• hollow rod (tail) with

protein cover;

• tail filaments

Reproduction of bacteriophages

• Play a big role

in medicine and widely

are used when

treatment of purulent

diseases,

caused by

staphylococci, etc.

• Used in gene

engineering as

vectors carrying

DNA sections

Viroids

Viroids– pathogens of plant diseases, which consist of a short fragment of circular, single-stranded RNA, not covered with a protein shell characteristic of viruses.

The first viroid identified was a potato tuber viroid

Prions

– "infectious proteins" that do not contain nucleic acids and cause serious illnesses central nervous system in humans and animals.

Mad cow disease

Prions

A prion protein, which has an abnormal three-dimensional structure, is capable of directly catalyzing the structural transformation of a normal cellular protein homologous to it into a similar one (prion)

β-sheets

α-helix

Prions form insoluble deposits in brain tissue

The bulk of living beings are organisms that have cellular structure. In progress evolution In the organic world, the cell turned out to be the only elementary system in which the manifestation of all the laws that characterize life is possible.

Organisms that have cellular structure, in turn, are divided into two categories: not having a typical nucleus - pre-nuclear, or prokaryotes, and having a typical nucleus - nuclear, or eukaryotes. Prokaryotes include bacteria and blue-green algae, eukaryotes include all other plants and all animals. It has now been established that the differences between prokaryotes and eukaryotes are much more significant than between higher plants and animals.

Prenuclear organisms

Prokaryotes – prenuclear organisms, which do not have a typical nucleus enclosed in a nuclear membrane. Their genetic material is in nucleoid and is represented by a single strand of DNA forming a closed ring. This thread has not yet acquired the complex structure characteristic of chromosomes and is called a gonophore.

Cell division is only amitotic. Prokaryotic cells lack mitochondria, centrioles and plastids.

Mycoplasmas

Unlike viruses, which carry out vital processes only after penetration into the cell, mycoplasma is capable of exhibiting vital functions characteristic of organisms that have cellular structure. These bacteria-like forms can grow and multiply on synthetic media. Their cell is built from a relatively small number of molecules (about 1200), but has a full set of macromolecules characteristic of any cell (proteins, DNA and RNA). A mycoplasma cell contains about 300 different enzymes.

According to some characteristics, mycoplasma cells are closer to the cells animals, than plants. They do not have a hard shell, but are surrounded by a flexible membrane; the composition of lipids is close to that in animal cells.

As has already been said, to prokaryotes include bacteria and blue-green algae, united by the general term “grinders”. The cell of a typical crusher is covered with a cellulose shell. Grinders play a significant role in the cycle of substances in nature: blue-green algae - as synthesizers of organic matter, bacteria - as its mineralizers. Many bacteria are of medical and veterinary importance as causative agents of infectious diseases.

Nuclear organisms

Eukaryotes are nuclear organisms that have a nucleus surrounded by a nuclear membrane. The genetic material is concentrated mainly in chromosomes, which have a complex structure and consist of strands of DNA and protein molecules. Cell division is mitotic. There are centrioles, mitochondria, plastids. Among eukaryotes, there are both unicellular and multicellular organisms.

Eukaryotes are usually divided into two kingdoms- plants and animals. Plants differ from animals in a number of ways. Most plants have an autotrophic type of nutrition, while animals have a heterotrophic type of nutrition. However, it is not possible to draw a clear line between all plants and all animals.

Currently, more and more biologists are coming to the conclusion that it is necessary to divide eukaryotes into three kingdoms– animals, mushrooms and plants. These new provisions are not universally accepted, but they are not without reason.

Animals are primarily heterotrophic organisms. Their cells are devoid of dense outer shell. These are usually mobile organisms, but can also be attached. Spare carbohydrates are stored in the form of glycogen.

Mushrooms are also primary heterotrophic organisms. Their cells have a well-defined shell consisting of chitin, less often cellulose. They are usually attached organisms. Spare carbohydrates are stored in the form of glycogen.

Plants- This autotrophic organisms, sometimes secondary heterotrophs. Their cells have a dense wall, usually consisting of cellulose, less often of chitin. Reserve substances are deposited in the form of starch.

Existence biosphere, the cycle of substances in nature is connected by primitive eukaryotes - unicellular ones. But in the process of evolution, multicellular plants, fungi and animals developed. Among autotrophic organisms, evolution reached its highest degree in the phylum angiosperms. The pinnacle of the evolution of heterotrophic organisms is the chordate type.

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Distinctive characteristics of living organisms. 1. Living organisms are an important component of the biosphere. Cellular structure - characteristic feature all organisms, with the exception of viruses. The presence of a plasma membrane, cytoplasm, and nucleus in cells. Feature of bacteria: lack of a formed nucleus, mitochondria, chloroplasts.

Features of plants: the presence of a cell wall, chloroplasts, vacuoles with cell sap in the cell, an autotrophic method of nutrition. Features of animals: absence of chloroplasts, vacuoles with cell sap, cell membranes in cells, heterotrophic mode of nutrition. 2. The presence of organic substances in living organisms: sugar, starch, fat, protein, nucleic acids and inorganic substances: water and mineral salts. The similarity of the chemical composition of representatives of different kingdoms of living nature.

3. Metabolism - main feature living things, including nutrition, respiration, transport of substances, their transformation and the creation of substances and structures of one’s own body from them, the release of energy in some processes and use in others, the release of final products of vital activity. Exchange of substances and energy with the environment.

4. Reproduction, reproduction of offspring is a sign of living organisms. The development of a daughter organism from one cell (zygote in sexual reproduction) or a group of cells (in vegetative reproduction) of the mother organism. The importance of reproduction is in increasing the number of individuals of a species, their settlement and development of new territories, maintaining similarity and continuity between parents and offspring over many generations.

5. Heredity and variability - properties of organisms.

Cellular and noncellular life forms: viruses, bacteriophages, eukaryotes and cell theory

Heredity is the property of organisms to transmit their inherent structural and developmental features to their offspring. Examples of heredity: birch plants grow from birch seeds, a cat gives birth to kittens similar to their parents. Variability is the emergence of new characteristics in the offspring. Examples of variability: birch plants grown from the seeds of a mother plant of one generation differ in the length and color of the trunk, the number of leaves, etc.

6. Irritability is a property of living organisms. The ability of organisms to perceive stimuli from environment and in accordance with them, coordinate their activities and behavior - a complex of adaptive motor reactions that arise in response to various irritations from the environment. Features of animal behavior. Reflexes and elements of rational activity of animals. Behavior of plants, bacteria, fungi: different shapes movements - tropisms, nasties, taxis.

You can choose the most basic.

Life on planet Earth is known only in two forms: extracellular and cellular.

Extracellular life form is special shape, represented by viruses and bacteriophages (phages), which occupy an intermediate position between living and inanimate nature.

3. Precellular and cellular forms of life.

Cellular life form (organisms), depending on the type of cell organization, is divided into prokaryotes and eukaryotes.

Prokaryotes are single-celled organisms that do not have a formed nucleus.

These include bacteria, cyanides (cyanobacteria or blue-green algae) and mycoplasmas, which form the kingdom of Drobyanka.

Eukaryotes are unicellular and multicellular organisms.

Their cells always have a clearly defined nucleus. Copyright of the materialCopying of materials is allowed only with an active link to the article!InformationVisitors in the group Guests, cannot leave comments on this publication.

Precellular life forms - viruses and phages

The precellular empire consists of a single kingdom - viruses. These are the smallest organisms, their sizes range from ‘2 to 500 microns. Only the largest viruses (for example, smallpox virus) can be seen with very high magnification (1800-2200 times) of an optical microscope. Small viruses are equal in size to large protein molecules. Most viruses are so small that they can pass through the pores of special bacterial filters.

Viruses are fundamentally different from all other organisms.

Let's name their most important features:

3. They have a very limited number of enzymes; they use the host’s metabolism, its enzymes, and the energy obtained during metabolism in the host’s cells.

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The vast majority of living organisms are made up of cells. Only a few of the most primitive organisms - viruses and phages - do not have a cellular structure.

That's why the most important feature all living things are divided into two empires - precellular (viruses and phages) and cellular (this includes all other organisms: bacteria and related groups; fungi; green plants; animals).

The idea that all living things are divided into two kingdoms - animals and plants - is now outdated. Modern biology recognizes the division into five kingdoms: prokaryotes, or crushed plants, green plants, fungi, animals; The kingdom of viruses - precellular life forms - is distinguished separately.

Precellular life forms - viruses and phages

The precellular empire consists of a single kingdom - viruses.

These are the smallest organisms, their sizes range from ‘2 to 500 microns. Only the largest viruses (for example, smallpox virus) can be seen with very high magnification (1800-2200 times) of an optical microscope. Small viruses are equal in size to large protein molecules. Most viruses are so small that they can pass through the pores of special bacterial filters.

Viruses are fundamentally different from all other organisms. Let's name their most important features:

They have a very limited number of enzymes; they use the host’s metabolism, its enzymes, and the energy obtained from metabolism in the host’s cells.

4. Mature virospores (“spores” of viruses) can exist outside the host cell; during this period they do not show any signs of life.

Viruses were first discovered in 1892.

the outstanding Russian biologist D.I. Ivanovsky, who became the founder of a new biological discipline - virology.

Origin of viruses

Loss of many biologically important properties, according to this point of view, is considered as a secondary phenomenon.

There is a third point of view - Viruses are considered as “stray” or “run wild” genes.

Firstly, it was discovered that viruses are a powerful mutagenic factor.

After viral diseases(infectious jaundice, measles, influenza, encephalitis, etc.) in humans and animals the number of damaged chromosomes increases sharply. Thus, viruses are suppliers of new mutations for natural selection. Secondly, the genome of a virus can be included in the genome of the host and viruses can transfer genetic information not only from one individual of a given species to another, but also from one species to another. It has been experimentally shown that with the help of viruses, sections of DNA from one species can be transferred to another mind.

Cellular organisms

Organisms with a cellular structure are united into an empire of cells, or karyotes (from the Greek.

karion - core). The typical cell structure characteristic of most organisms did not arise immediately. In a cage of representatives of the most ancient of modern types In organisms (blue-greens and bacteria), the cytoplasm and nuclear material with DNA are not yet separated from each other.

Based on the presence or absence of a nucleus, cellular organisms are divided into two superstars: non-nuclear (prokaryotes) and nuclear (eukaryotes) (from the Greek.

protos - the first and eu - actually, the real one). The first group includes blue-greens and bacteria, the second group includes all animals, green plants and fungi.

Overkingdom of prokaryotes

Prokaryotes include the most simply organized forms of cellular organisms. Prokaryotic DNA forms one double helix strand, which is closed in a ring.

This ring-shaped strand of DNA consists of a significant number of genes, but it is not yet a real chromosome, which appears only in eukaryotes. Due to the fact that DNA is represented by a single strand, there is only one gene linkage group.

Here are the main characteristics of prokaryotes:

Circular DNA is concentrated in the central part of the cell, not separated by the nuclear envelope from the rest of the cell;

Missing mitochondria;

They lack plastids;

Prokaryotic cells do not undergo mitosis;

No centrioles;

Chromosomes are missing;

The spindles are not formed;

No digestive vacuoles; no true flagella; the actual sexual process is unknown; gametes are not formed.

The superkingdom of prokaryotes consists of a single kingdom, which includes two half-kingdoms: blue-green and bacteria.

Prokaryotes: superkingdom and blue-green type

There are 1,400 modern species of blue-green.

In blue-green cells there is not only a nucleus, but also no chromatophores - cellular formations containing pigments and taking part in photosynthesis; there are no vacuoles. In the central dense part of blue-green cells, nucleoproteins are concentrated - compounds of nucleic acids with protein.

Blue-greens are remarkable in that they are able to use nitrogen from the air and convert it into organic forms nitrogen.

During photosynthesis, they can use carbon dioxide as the only carbon source. Unlike photosynthetic bacteria, blue-green bacteria release molecular oxygen during photosynthesis.

In the peripheral part of the cells, blue and brown pigments are diffusely distributed, which, in combination with chlorophyll, determine the blue-green color of these organisms.

Some blue-greens may have additional pigments that change their characteristic color to black, brown, or red. The color of the Red Sea is determined by its wide distribution of purple-pigmented blue-greens.

Blue-greens can use both solar energy (autotrophy) and energy released during the breakdown of finished organic substances (heterotrophy).

Blue-greens reproduce only asexually.

Blue-greens are represented not only by unicellular, but also by colonial, filamentous and multicellular forms. However, green pigments - chlorophylls exist in four forms, slightly different from each other. chemical composition: Multicellular nuclear organisms did not evolve from multicellular blue-greens, but from unicellular nuclear forms. Thus, for the first time, the blue-greens are experiencing an attempt to break through to the next stage - to the level of multicellularity.

However, this attempt did not have any special consequences for evolution. Blue-green- ancient organisms Earth. However, to this day they play a large role in the cycles of matter and energy.

Prokaryotes: bacteria

Currently, about 3,000 species of bacteria are known. Some bacteria are able to directly utilize solar energy (autotrophs), others (heterotrophs) obtain energy using organic matter. Autotrophic bacteria include photosynthetic and chemosynthetic bacteria.

Green and purple bacteria can use and accumulate solar energy. In green bacteria, the color is determined by a special substance - bacteriochlorophyll, and not chlorophyll a, as in blue-green bacteria. No blue or brown pigments are released during photosynthesis.

Chemosynthesis, etc.

e. the use of energy from the oxidative processes of inorganic substances is common only among some bacteria. Sulfur bacteria are capable of oxidizing hydrogen sulfide to sulfur. Nitrifying bacteria convert ammonia into nitrogen and nitric acid. The predominance of nitrogen in the modern atmosphere is a consequence of the activity of nitrifying bacteria.

Iron bacteria convert ferrous iron into oxide iron.

Among heterotrophic bacteria, one part uses the energy of fermentation processes. The end product of the fermentation process is organic acids. The best known are lactic acid, butyric acid and acetic acid bacteria. Another part of heterotrophic bacteria - putrefactive bacteria - use the energy released during the breakdown of proteins.

Life forms: non-cellular and cellular.

The final product of decomposition during such putrefactive processes is nitrogen compounds, in the subsequent oxidation of which nitrifying bacteria take part.

Bacteria, like blue-green bacteria, have existed for about 3 billion years.

years ago and played a huge role in the creation modern composition atmosphere, in changing the face of the Earth.

The question of the origin of bacteria is not entirely clear. There is no doubt that a number of bacteria arose directly from blue-green bacteria. Bacteria are known that are very close to blue-green, differing from the latter only in the absence of pigment.

Two empires of nature. The vast majority of living organisms are made up of cells. Only a few are the most simple organized organisms- viruses and phages - do not have a cellular structure. According to this most important feature, all living things are divided into two empires - non-cellular (viruses and phages) and cellular, or karyotes (from the Greek “karyon” - nucleus) (Fig. 84).

Non-cellular life forms - viruses and phages. The non-cellular empire consists of a single kingdom - viruses.

Rice. 84. Scheme of classification of cellular organisms

Cellular forms of life, their division into non-nuclear and nuclear. The typical cell structure characteristic of most organisms did not arise immediately. In the cell of representatives of the oldest modern types of organisms, the cytoplasm and nuclear material with DNA are not yet separated from each other, and there are no membrane organelles. Based on the presence or absence of a nucleus, cellular organisms are divided into two superkingdoms: non-nuclear (prokaryotes) and nuclear (eukaryotes) (from the Greek “protos” - first and “eu” - completely, completely).

Prokaryotes. Prokaryotes include the most simply organized forms of cellular organisms.

The superkingdom of prokaryotes is divided into two kingdoms - archaea and bacteria.

Archaea. Archaea are nuclear-free organisms, similar in size and shape of cells to bacteria, to which they were previously classified. However, according to the structure of the genome, the protein synthesis apparatus, cell membranes they are very different from bacteria. Most archaea are extremophiles, living in conditions in which other living organisms cannot exist - with very high temperatures and pressures near deep-sea thermal springs, in saturated salt solutions, in very acidic or very alkaline bodies of water. Some archaea, using various organic compounds, produce methane, which is not characteristic of any other organisms. Methane-producing archaea, which are part of the intestinal microflora of some animals and humans, provide their hosts with vital vitamin B12.

Bacteria. The kingdom Bacteria includes the subkingdoms cyanobacteria and bacteria. Cyanobacteria were previously classified as plants and are still sometimes called blue-green algae (Fig. 85). These are the oldest organisms on Earth. Cyanobacteria played a huge role in the formation of soil and the modern atmosphere of the Earth. These included those ancient photosynthetic unicellular organisms that, having entered into symbiosis with other prokaryotes, became the ancestors of the chloroplasts of all green plants that exist today.

Among the bacteria, there is a group of purple proteobacteria, which include the prokaryotic ancestors of mitochondria.

Real bacteria, or eubacteria, play a huge role in the biological cycle of substances in nature and human economic life. The production of curdled milk, acidophilus, cottage cheese, sour cream, cheeses, and vinegar is unthinkable without the action of bacteria.

Rice. 85. Cyanobacteria

Currently, many microorganisms are used for industrial production needed by a person substances, such as drugs. The microbiological industry has become an important industrial sector.

Eukaryotes. All other organisms are classified as nuclear, or eukaryotes. The main features of eukaryotes are shown in table § 10.

Eukaryotes are divided into three kingdoms: green plants, fungi and animals.

The plant kingdom is divided into three subkingdoms: true algae, red algae (purple algae) and higher plants.

True algae are lower plants. Among the several types of this subkingdom there are unicellular and multicellular, the cells of which are different in structure and function (Fig. 86).

Rice. 86. Real algae.
1 - unicellular; 2 - colonial; 3 - caulerpa - a multinucleated alga, the body of which is not divided into cells; 4 - filamentous algae; 5 - multicellular chara algae

It is remarkable that in different types of algae there are trends in the transition from unicellularity to multicellularity, to specialization and the division of germ cells into male and female.

Thus, different types algae seem to be trying to break through to the next floor - to the level of a multicellular organism, where different cells perform various functions. The transition from unicellularity to multicellularity is an example of aromorphosis in the evolution of green plants.

Red algae are multicellular organisms. The color of red algae is determined by the presence in their cells, in addition to chlorophyll, of red and blue pigments (Fig. 87). Scarlet algae differ sharply from real algae in that even male gametes - sperm - lack flagella and are immobile.

Rice. 87. Purple algae

Higher plants include a group of plants that have a special vascular system through which mineral and organic substances are transported. Purchasing such a conductive vascular system was the most important aromorphosis in the evolution of plants. Higher plants include spore-bearing plants - bryophytes, ferns (Fig. 88) and seed plants - gymnosperms, angiosperms (flowering plants).

Spore plants are the first of the green plants to reach land. However, their mobile gametes equipped with flagella are capable of moving only in water. Therefore, such a landfall cannot be considered complete.

Rice. 88. Higher spore plants (ferns).
From left to right - horsetail, clubmoss, fern

The transition to seed reproduction allowed plants to move away from the shores inland, which is considered another important aromorphosis in the evolution of plants.

Mushrooms. Among the mushrooms, there are various forms: bread mold, penicillium mold, rust mushrooms, cap mushrooms, tinder fungi. Common feature for such diverse forms is the formation of the vegetative body of the fungus from thin branching filaments that form the mycelium.

Lichens belong to the group of lower eukaryotes. This is a peculiar group of organisms that arose as a result of symbiosis. The body of the lichen is formed by a fungus in which cyanobacteria and green algae can live.

Animals. If you ask how animals differ from plants, you can usually hear the answer: “Animals are mobile, but plants are immobile.” This is basically the correct answer, although movement in plants (mimosa leaves) and immobile animals (coral polyps) are known. But why are most animals mobile?

All animals are heterotrophic organisms. They actively extract organic substances, eating certain, usually living, organisms. Obtaining such food requires mobility. The development of various organs of movement is associated with this (for example, amoeba pseudopods, ciliate cilia, insect wings, fish fins, etc., Fig. 89). Fast movements are impossible without the presence of a movable skeleton to which the muscles are attached. This is how the external chitinous skeleton of arthropods and the internal bone skeleton of vertebrates arise.

Rice. 89. Representatives of arthropods.
1 - cancer; 2 - spider; 3 - tick; 4 - centipede; 5 - butterfly; 6 - fly; 7 - beetle; 8 - grasshopper

Another thing is related to mobility. important feature animals: animal cells lack a dense outer membrane, retaining only the inner cytoplasmic membrane membrane. The presence of water-insoluble solid storage substances (for example, starch) in an animal cell would impede cell motility. That is why the main storage substance in animals is a readily soluble polysaccharide - glycogen.

The animal kingdom is divided into two subkingdoms: protozoa (or single-celled animals) and multicellular animals. Morphologically the simplest is a cell, functionally it is an organism. Hence the duality of his nature follows. The functions of organs and tissues in protozoa are carried out by individual sections of cells. True multicellular organisms are characterized by a union of cells various types in fabric.

1. Describe viruses as non-cellular forms.
2. Name the characteristics characteristic of all cellular organisms.
3. Compare the structure and functions of prokaryotic and eukaryotic cells. Draw conclusions.
4. What do you think is the practical significance of taxonomy? What problems does it help solve?