All living things are divided into 2 empires - cellular and non-cellular life forms. 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 cellular 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), curled 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.
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
Manifold 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
are missing.
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
(V 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 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
(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 cytoplasmic 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 modern organic world of our planet has about 2 million animal species, 500 thousand plant species and more than 10 million microorganisms. Therefore, the study of such a variety of organic individuals without their systematization and general classification causes certain difficulties. Modern science offers us the following systematization into 9 main categories - empire, supra-kingdom, kingdom, type, class, detachment, family, genus and species.
Major Overkingdoms— prokaryotes and eukaryotes
The empire of non-cellular and cellular organisms is also multifaceted. It is divided into viruses, bacteria and fungi, plants and animals. Viruses and bacteria belong to the superkingdom of prokaryotes, while the rest are classified by scientists as eukaryotes. Their main difference from each other is that the former are nuclear-free organisms. They are also called primitive, lacking a nucleus and many organelles. In these cells, it is customary to distinguish only the nuclear zone. It contains the DNA molecule, the outer cell membrane and ribosomes. As already noted, prokaryotes include viruses, bacteria and fungi. Plants and animals can be safely classified as belonging to the superkingdom of eukaryotes, which have a clearly defined nucleus and other basic structural components of the cell.
animal kingdom— multicellular cups and coelenterates
In the existing systematization of the animal kingdom, it is customary to distinguish lower and higher multicellular organisms. The former got their name due to the absence of tissues and organs, despite the fact that their body consists of different types of cells. These include sponges and coelenterates.
Sponges are considered the lowest multicellular sessile organisms, often forming colonies. They usually live in salt water (sea and oceans), attached to the substrate. The shape of their body, formed by two layers of cells, can vary, but usually it looks like a bag that has many holes. Between these layers is the mesoglea, in which the silicon or calcareous skeleton of the sponge is formed. IN environment sponges can act as a filter, but dirty water they die.
Just like sponges coelenterates They are usually classified as simple multicellular organisms. In nature there are about 20 thousand species. Many of them are characterized by an attached form, which is called a polyp. As a rule, these are hydras, sea anemones, etc., but there are also free-swimming organisms - jellyfish. They all have a single structure plan - two layers with a cavity inside. A long-term study of coelenterates showed that the differentiation of their cells is higher than that of sponges, and there are also nerve cells that form nervous system diffuse type.
Thus, systematization and general classification of the entire organic world on our planet allows us to better study its types. This makes it possible to characterize the mutual relationships between diverse organisms and give them common names, which in turn facilitates the exchange of scientific information between scientists from different countries.
Taxonomy methods
Comparative morphological method ( the main method of taxonomy) - is based on comparative morphology data and provides the most information about the relationship of taxa at the species and genus level; by using this method study the macrostructure of organisms; the method does not require complex equipment.
Comparative anatomical, embryological and ontogenetic methods (variants of the comparative anatomical method) - with their help, they study the microscopic structures of tissues, embryo sacs, features of gametogenesis, fertilization and development of the embryo, as well as the nature of the subsequent development and formation of individual plant organs; These methods require advanced technology (electron and scanning microscopy).
Comparative cytological and karyological methods - allow you to analyze the characteristics of organisms at the cellular level , helping to establish the hybrid nature of forms and study population variability of species.
Palynological method - uses data from palynology (the science that studies the structure of the shells of spores and pollen grains of plants) and allows, based on well-preserved shells of spores and pollen, to determine the age of extinct plants.
Ecological-genetic method - associated with experiments on plant culture; makes it possible regardless of factors natural environment study the variability, mobility of characters and establish the boundaries of the phenotypic response of the taxon.
Hybridological method - based on the study of taxon hybridization; important in solving questions of phylogeny and systematics.
Geographical method - makes it possible to analyze the distribution of taxa and the possible dynamics of their habitats (area of geographical distribution), as well as the variability of organisms, which is associated with geographically changing natural factors.
In addition to the above methods, taxonomy uses immunochemical and physiological methods, as well as data from entomology, archeology and linguistics, which provide information about insect pests and places where the most important agricultural plants are introduced into cultivation.
Rice. 7.2.1. Tobacco mosaic virus(A – electron micrograph, B – model).
Virus particle ( virion) consists of a nucleic acid (DNA or RNA) surrounded by a protein shell - capsid, consisting of capsomeres. The sizes of the virion of various viruses range from 15 to 400 nm (most are visible only in electron microscope).
Viruses have the following characteristic features:
· do not have a cellular structure;
· incapable of growth and binary fission;
· do not have their own metabolic systems;
· for their reproduction only nucleic acid is needed;
· use host cell ribosomes to form their own proteins;
· do not reproduce on artificial nutrient media and can exist only in the host’s body;
· are not retained by bacteriological filters.
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. 7.2.2.).
Rice. 7.2.2. Phage model.
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. Through the extension, DNA from the phage head passes into the cell of the affected microorganism. 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. Only active phage can lyse bacteria. An insufficiently active phage can exist in the cell of a microorganism without causing lysis. When the affected bacterium multiplies, the infected origin can pass into daughter cells. Phages are found in water, soil and other natural objects. Some phages are used in genetic engineering and in medicine for disease prevention.
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. That's why the 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 a cage of representatives of the most ancient of modern types In organisms, the cytoplasm and nuclear material with DNA are not yet separated from each other; 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). This ancient organisms on the ground. 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 minerals and organic matter. 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 are devoid of dense outer shell, retaining only the inner cytoplasmic membrane shell. 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.
- Describe viruses as non-cellular forms.
- Name the characteristics characteristic of all cellular organisms.
- Compare the structure and functions of prokaryotic and eukaryotic cells. Draw conclusions.
- What do you think is the practical significance of taxonomy? What problems does it help solve?
