Functions and types of tissues (biology). Tissues of plants and animals All living organisms are formed by tissues

Which statements are true?

Topic 1. How living things differ from living things

Bacteria are single-celled organisms.

All living organisms have mobility.

Plants are the main source of oxygen on Earth.

Only plants can grow.

Plants are able to actively move from one place to another.

Excretion occurs in all living organisms.

Plants and fungi belong to the same kingdom.

Reproduction is the reproduction of one's own kind.

Answers: 1,4,5,8,10

Topic 2. Chemical composition of cells

Oxygen, carbon, nitrogen, hydrogen are the most common elements in living nature.

Oxygen, carbon, nitrogen, hydrogen are elements characteristic only of living nature.

Glucose, glycogen, sucrose, starch, fiber are types of carbohydrates.

Water is a good solvent.

Carbohydrates perform only a supporting function.

Fats serve as a reserve source of energy.

The similarity of the chemical composition and cellular structure of plants and animals indicate the unity of the organic world.

Answers: 1,2,6,7,9,10

Topic 3. Structure of plant and animal cells

All cells of living organisms have a nucleus.

Cytoplasm is a viscous semi-liquid substance, the internal environment of the cell.

Complex carbohydrates are formed in ribosomes.

The cellular center provides the cell with energy.

Some viruses have a cellular structure.

The outside of a cell of any organism is covered with a cytoplasmic membrane.

Pinocytosis is the process of absorption of solid particles of matter into the plasma membrane.

All cells of living organisms have plastids.

Chromosomes are found in the nucleus.

Lysosomes provide the process of intracellular digestion.

Proteins are made in mitochondria.

Answers: 2,6,8,10,11

Topic 4. Cell division

The ability to divide is an important property of cells.

During mitosis, a cell goes through six main phases.

As a result of mitosis, four cells are formed.

As a result of meiosis, two cells with a single set of chromosomes are formed.

A chromatid is half of a doubled chromosome.

Meiosis consists of two successive divisions.

During meiosis, chromosome duplication occurs twice, i.e. before each division.

Paired chromosomes are called homologous.

Sex cells have half the set of chromosomes.

Answer: 1,2,6,7,9,10

Topic 5. Plant and animal tissues

All living organisms are formed by tissues.

Tissue is a group of cells similar in size, structure and functions.

Cells in tissues are connected by intercellular substance.

The educational tissue of the plant is located only at the top of the shoot.

The educational tissue of a plant is found only in the embryo.

The role of the skeleton in the plant is performed by the main tissue.

Blood is connective tissue.

The integumentary tissue of plants forms the wood of trees.

The main properties of muscle tissue are excitability and contractility.

Nerve cells have numerous processes.

The main properties of a nerve cell are excitability and contractility.

Answer: 2,3,5,6,7,9,10,12

Topic 6. Organs of flowering plants.

All plants have flowers.

An organ is a part of an organism's body that performs specific functions.

The root holds the plant in the soil.

Dandelion has a fibrous root system.

Carrots and beans have a taproot system.

The shoot consists of a stem, leaves and buds.

A bud is an embryonic shoot.

The buds that contain the flower primordia are called leaf buds.

All leaves have a leaf blade.

The stem can perform a storage function.

The main part of the flower is the corolla, as it attracts insects for pollination.

The pericarp is the enlarged and modified walls of the ovary.

The embryo consists of a germinal root, a stalk and a bud.

Answer: 2,3,5,6,7,9,10,12

Topic 7. Organs and organ systems of animals

Organs united by common work make up an organ system.

Heart, kidneys, lungs - internal organs.

The excretory system ensures gas exchange in the body.

The musculoskeletal system is formed by the skeleton.

The circulatory system carries substances dissolved in the blood throughout the body.

Animals breathe only through their lungs.

The nervous system of vertebrates consists of the brain and nerves.

The coordinated functioning of organs is ensured by the activity of the nervous system.

Answer: 1,2,5,8

Topic 9. What have we learned about the structure of living organisms

All living organisms are made up of cells.

Plants feed on ready-made organic substances.

The chemical composition of all living organisms is similar.

Proteins are the main source of energy.

Water is a good solvent.

Carbohydrates are carriers of hereditary information.

All cells have nuclei.

Proteins are made in ribosomes.

Viruses have a cellular structure.

The nucleus contains one or more nucleoli.

The ability to divide is an important property of every cell.

Cell division underlies the reproduction and development of organisms.

A chromatid is half of a doubled chromosome.

Tissue is a group of cells that are similar in structure and functions.

Chloroplasts are found in the cells of the main tissue.

The main organs of plants are the flower and the root.

Beans have a taproot system.

A bud is an embryonic shoot.

The shoot consists of a stem and leaves.

The main parts of a flower are the stamens and pistil.

The fruit develops from the ovary.

The embryo of a monocot plant contains one cotyledon.

Rice, rye, and wheat are dicotyledonous plants.

Animals breathe only through their lungs

Topic 10. Nutrition and digestion

Only plants can directly absorb solar energy.

Digestion makes complex nutrients available for absorption.

Animals consume ready-made organic substances.

The process of roots absorbing water and mineral salts from the soil is called soil nutrition.

Coelenterates do not have a digestive system.

All animals are omnivores.

Hydras have only a mouth opening.

Enzymes are special chemicals that aid digestion.

Photosynthesis produces carbon dioxide as a by-product.

Answers:1,2,3,4,8,9

Topic 11. Breathing

All living organisms breathe.

Gas exchange in the leaves occurs through the lentils.

Single-celled organisms breathe over the entire surface of the body.

Stomata are the respiratory organs of an earthworm.

Tracheal breathing is characteristic of insects.

Algae breathe through lentils.

Only fish can breathe through their gills.

Only mammals have lungs.

There is no cutaneous respiration in terrestrial vertebrates.

A person breathes through the lungs and skin.

Answers:1,3,5,10

Topic 12. Transport of substances in the body

All multicellular animals have red blood.

The earthworm has a closed circulatory system.

Blood consists of plasma and blood cells.

The blood of all animals carries only oxygen.

The circulatory system of vertebrates is closed and consists of a heart and blood vessels.

Fish have a three-chambered heart.

Plant organic matter moves through sieve tubes.

As water evaporates, the leaves of the plant cool.

Answers: 2,3,5,7,8

Topic 13. Selection

Plants and fungi do not have excretory systems.

The contractile vacuole is an excretory organelle of freshwater protozoa.

Flatworms do not have excretory organs.

The kidneys are the excretory organs of the worm.

The excretory system of fish consists of kidneys, ureters, bladder and a special opening.

Answers:1,2,5

Topic 14. Metabolism and energy

Metabolism occurs in all living organisms.

Only leaves take part in the metabolism of plants.

Plants receive oxygen, carbon dioxide, water, and mineral salts from the environment.

As a result of photosynthesis, organic substances and oxygen are formed.

Metabolism consists of two opposing processes.

Only the respiratory and circulatory systems take part in the metabolism of animals.

Fish are warm-blooded animals.

Warm-blooded animals have a constant body temperature.

Snakes and frogs are warm-blooded animals.

With the cessation of metabolism, the death of a living organism occurs.

Answers:1,3,4,5,8,10

Topic 15. The skeleton is the support of the body

All living organisms have an internal skeleton.

Some protozoa have an exoskeleton.

The skeleton performs supporting and protective functions, and also serves as an attachment point for internal organs.

Arthropods have an internal skeleton.

Mollusk shells are the exoskeleton.

Molting is typical for amphibians.

Vertebrates have an internal skeleton.

The vertebrate skeleton consists of the skeleton of the head, torso, and limbs.

The body of many living organisms consists of tissues. Exceptions are all unicellular organisms, as well as some multicellular organisms, for example, which include algae and lichens. In this article we will look at the types of fabrics. Biology studies this topic, namely its section - histology. The name of this industry comes from the Greek words "fabric" and "knowledge". There are many types of fabrics. Biology studies both plants and animals. They have significant differences. Biology has been studied for quite some time. For the first time they were described even by such ancient scientists as Aristotle and Avicenna. Biology continues to study tissues and types of tissues - in the 19th century they were studied by such famous scientists as Moldenhauer, Mirbel, Hartig and others. With their participation, new types of cell aggregates were discovered and their functions were studied.

Types of tissues - biology

First of all, it should be noted that the tissues that are characteristic of plants are not characteristic of animals. Therefore, biology can divide tissue types into two large groups: plant and animal. Both combine a large number of varieties. We will consider them further.

Types of animal tissues

Let's start with what is closer to us. Since we belong to the animal kingdom, our body consists precisely of tissues, the varieties of which will now be described. Types of animal tissues can be grouped into four large groups: epithelial, muscle, connective and nervous. The first three are divided into many varieties. Only the last group is represented by only one type. Next, we will consider all types of tissues, the structure and functions that are characteristic of them, in order.

Nervous tissue

Since it only comes in one variety, let's start with that one. The cells of this tissue are called neurons. Each of them consists of a body, an axon and dendrites. The latter are processes through which an electrical impulse is transmitted from cell to cell. A neuron has one axon - it is a long process, there are several dendrites, they are smaller than the first one. The cell body contains the nucleus. In addition, the cytoplasm contains the so-called Nissl bodies - an analogue of the endoplasmic reticullum, mitochondria, which produce energy, as well as neurotubules, which are involved in conducting impulses from one cell to another.

Depending on their functions, neurons are divided into several types. The first type is sensory, or afferent. They conduct impulses from the sense organs to the brain. The second type of neurons is associative, or switching. They analyze the information received from the senses and develop a response impulse. These types of neurons are found in the brain and spinal cord. The last type is motor, or afferent. They conduct impulses from associative neurons to organs. Nervous tissue also contains intercellular substance. It performs very important functions, namely, it ensures a fixed location of neurons in space, and participates in the removal of unnecessary substances from the cell.

Epithelial

These are types of tissues whose cells are tightly adjacent to each other. They can have a variety of shapes, but are always located close. All the different types of tissues in this group are similar in that they have little intercellular substance. It is mainly presented in the form of a liquid, in some cases it may not be present. These are types of body tissues that provide its protection and also perform a secretory function.

This group includes several varieties. These are flat, cylindrical, cubic, sensory, ciliated and glandular epithelium. From the name of each one you can understand what form of cells they are made of. Different types of epithelial tissues also differ in their location in the body. Thus, the flat one lines the cavities of the upper organs of the digestive tract - the oral cavity and esophagus. Columnar epithelium is found in the stomach and intestines. Cubic can be found in the renal tubules. The sensory one lines the nasal cavity; it contains special villi that provide the perception of odors. Ciliated epithelial cells, as its name implies, have cytoplasmic cilia. This type of tissue lines the airways, which are located below the nasal cavity. The cilia that each cell has perform a cleansing function - they to some extent filter the air that passes through the organs covered by this type of epithelium. And the last type of this group of tissues is glandular epithelium. Its cells perform a secretory function. They are found in the glands, as well as in the cavities of some organs, such as the stomach. Cells of this type of epithelium produce hormones, gastric juice, milk, sebum and many other substances.

Muscle tissue

This group is divided into three types. The muscle is smooth, striated and cardiac. All muscle tissues are similar in that they consist of long cells - fibers; they contain a very large number of mitochondria, since they need a lot of energy to carry out movements. lines the cavities of internal organs. We cannot control the contraction of such muscles ourselves, since they are innervated by the autonomic nervous system.

Cells of striated muscle tissue are distinguished by the fact that they contain more mitochondria than the first. This is because they require more energy. Striated muscles can contract much faster than smooth muscles. Skeletal muscles are made of it. They are innervated by the somatic nervous system, so we can consciously control them. Cardiac muscle tissue combines some of the characteristics of the first two. It is capable of contracting as actively and quickly as the striated one, but is innervated by the autonomic nervous system, just like the smooth one.

Connective tissue types and their functions

All tissues of this group are characterized by a large amount of intercellular substance. In some cases it appears in a liquid aggregate state, in some - in a liquid state, sometimes - in the form of an amorphous mass. Seven types belong to this group. These are dense and loose fibrous, bone, cartilage, reticular, fatty, blood. The first type is dominated by fibers. It is located around the internal organs. Its functions are to give them elasticity and protect them. In loose fibrous tissue, the amorphous mass predominates over the fibers themselves. It completely fills the gaps between the internal organs, while dense fibrous forms only peculiar shells around the latter. She also plays a protective role.

Bone and form the skeleton. It performs a supporting and partly protective function in the body. In the cells and intercellular substance of bone tissue, phosphates and calcium compounds predominate. The exchange of these substances between the skeleton and blood is regulated by hormones such as calcitonin and parathyrotropin. The first maintains the normal condition of bones by participating in the conversion of phosphorus and calcium ions into organic compounds stored in the skeleton. And the second, on the contrary, with a lack of these ions in the blood provokes their production from skeletal tissues.

Blood contains a lot of liquid intercellular substance, it is called plasma. Its cells are quite peculiar. They are divided into three types: platelets, erythrocytes and leukocytes. The former are responsible for blood clotting. During this process, a small blood clot is formed, which prevents further blood loss. Red blood cells are responsible for transporting oxygen throughout the body and providing it to all tissues and organs. They may contain aglutinogens, which exist in two types - A and B. Blood plasma may contain alpha or beta aglutinins. They are antibodies to aglutinogens. These substances are used to determine the blood type. In the first group, no aglutinogens are observed on the erythrocytes, and in the plasma there are two types of aglutinins at once. The second group has aglutinogen A and aglutinin beta. The third is B and alpha. There are no aglutinins in the plasma of the fourth, but aglutinogens A and B are present on the red blood cells. If A meets alpha or B meets beta, the so-called aglutination reaction occurs, as a result of which the red blood cells die and blood clots form. This can happen if you transfuse blood of the wrong type. Considering that only red blood cells are used during transfusion (plasma is screened out at one of the stages of processing donor blood), then a person with the first group can only be transfused with blood of his own group, with the second - blood of the first and second groups, with the third - with the first and third groups, from the fourth - any group.

Also, D antigens may be present on red blood cells, which determines the Rh factor; if present, the latter is positive; if absent, it is negative. Lymphocytes are responsible for immunity. They are divided into two main groups: B lymphocytes and T lymphocytes. The former are produced in the bone marrow, the latter - in the thymus (gland located behind the sternum). T lymphocytes are divided into T-inducers, T-helpers and T-suppressors. Reticular connective tissue consists of a large amount of intercellular substance and stem cells. Blood cells are formed from them. This tissue forms the basis of the bone marrow and other hematopoietic organs. There are also cells that contain lipids. It performs a reserve, thermal insulation and sometimes protective function.

How do plants work?

These organisms, like animals, consist of aggregates of cells and intercellular substance. We will describe the types of plant tissues further. All of them are divided into several large groups. These are educational, integumentary, conductive, mechanical and basic. The types of plant tissues are numerous, as several belong to each group.

Educational

These include apical, lateral, insertional and wound. Their main function is to ensure plant growth. They consist of small cells that actively divide and then differentiate to form any other type of tissue. The apical ones are located at the tips of the stems and roots, the lateral ones - inside the stem, under the integumentary ones, the intercalary ones - at the bases of the internodes, the wound ones - at the site of damage.

Integumentary

They are characterized by thick cell walls composed of cellulose. They play a protective role. There are three types: epidermis, crust, plug. The first covers all parts of the plant. It may have a protective waxy coating; it also contains hairs, stomata, cuticle, and pores. The crust is distinguished by the fact that it does not have pores; in all other characteristics it is similar to the epidermis. Cork is the dead tissue that forms the bark of trees.

Conductive

These tissues come in two varieties: xylem and phloem. Their functions are the transport of substances dissolved in water from the root to other organs and vice versa. Xylem is formed from vessels formed by dead cells with hard shells; there are no transverse membranes. They transport liquid upward.

Phloem - sieve tubes - living cells that do not have nuclei. The transverse membranes have large pores. With the help of this type of plant tissue, substances dissolved in water are transported downward.

Mechanical

They also come in two types: and sclerenchyma. Their main task is to ensure the strength of all organs. Collenchyma is represented by living cells with lignified membranes that fit tightly to each other. Sclerenchyma consists of elongated dead cells with hard membranes.

Basic

As their name implies, they form the basis of all plant organs. They are assimilation and spare. The first are found in the leaves and green part of the stem. Their cells contain chloroplasts, which are responsible for photosynthesis. Organic substances accumulate in the storage tissue, in most cases it is starch.

Any tissue is a group of cells that are similar in structure and origin, and also perform a common function. All fabrics are divided into 2 large groups:

• simple - consisting of one type of cell;
• complex - consisting of different types of cells, which, in addition to their main ones, also perform additional functions.

The morphological characteristics of tissues (i.e., structural features) depend on the functions they perform. The following types of tissues are distinguished in plants:

• educational,
• integumentary,
• mechanical,
• conductive,
• basic.

Let's look at a brief description of each of them.

Educational

Educational tissues are also called meristems, which is translated from Greek. "meristos" means "divisible". It is easy to guess that their main function is to ensure plant growth through the almost constant division of cells entering the tissue.

The cells themselves are quite small, because they simply do not have time to grow. Among the main features of their structure are thin shells, close adherence of cells to each other, large nuclei, an abundance of mitochondria, vacuoles and ribosomes. Mitochondria act as energy suppliers for various cellular processes, and ribosomes synthesize protein molecules necessary for the formation of new cells.

There are 2 subtypes of meristems:

• Primary - providing primary growth in length. It makes up the embryo of the seed, and in an adult plant this tissue is stored in the tips of the shoots and the tips of the roots.
• Secondary - ensuring the growth of the stem in diameter. This group is divided into apical, lateral, intercalary and wound secondary meristems. They consist of cambium and phellogen.

Integumentary

Integumentary tissues form the surface of the plant body and are found on all organs. Their main function is to ensure the body’s resistance to mechanical stress and sudden temperature fluctuations, as well as protection against excessive evaporation of moisture and the penetration of pathogenic microorganisms.

These fabrics are divided into 3 main types:

• Epidermis (also called epidermis or skin) is a primary tissue made up of a single layer of small transparent cells that fit tightly together. It covers the leaves and young shoots. The surface of this tissue has special formations called stomata, which regulate the processes of gas exchange and water movement throughout the plant body. It is also usually covered with a special cuticle or wax coating, which provides additional protection.
• Periderm is a secondary tissue covering stems and roots. It replaces the epidermis in perennial plants, less often in annual plants. It consists of cork cambium (otherwise called phellogen) - a dead layer of cells, the walls of which are impregnated with a waterproof substance. It is formed by division and differentiation of phellogen inward and outward, resulting in the formation of 2 layers - phelloderm and phellem, respectively. Thus, the periderm has 3 layers: phellem (cork), phellogen, phelloderm. Since the cells of the cork are saturated with suberin - a fat-like substance that does not allow air and water to pass through, as a result the contents of the cells die and they are filled with air. The dense cork layer is a reliable protection of plants from adverse external factors.
• Cork is a tertiary fabric that replaces cork. As a rule, it makes up the bark of trees and some shrubs. It is formed as a result of the fact that new areas of phellogen are laid down in the deep tissues of the cortex, from which, accordingly, new layers of cork are formed. Because of this, the outer tissues are isolated from the central part of the stem, deformed and die, and the surface of the stem is covered with dead tissue from several layers of cork and dead areas of bark. Of course, a thick crust provides greater protection than cork.

Mechanical

These tissues consist of cells with thick membranes. They provide a kind of “framework”, i.e., they maintain the shape of the plant and make it more resistant to mechanical stress. Among the features of these tissues, one can highlight the powerful thickening and lignification of the membranes, the close adjacency of cells to each other and the absence of perforations in their walls. They are most strongly developed in the stems, where they are represented by wood and bast fibers, but they are also present in the central part of the roots. There are 2 types of mechanical fabric:

• Callenchyma - consists of living cells with unevenly thickened membranes, which can significantly strengthen young growing organs. In addition, the cells of this tissue stretch very easily, so they do not interfere with the elongation of the plant.
• Sclerenchyma - consists of elongated cells with evenly thickened membranes, which, moreover, are often lignified, their contents die off in the early stages. The membranes of these cells have very high strength, so they form the tissues of the vegetative organs of land plants, constituting their axial support.

Conductive

Conductive tissues ensure the transport and distribution of water and minerals throughout the plant body. There are 2 main types of such fabrics:

• Xylem (wood) is the main water-conducting tissue. It consists of special vessels - tracheas and tracheids. The first are hollow tubes with through holes. The second are narrow, elongated dead cells with pointed ends and lignified membranes. Xylem is responsible for transporting liquid with minerals dissolved in it by an ascending current - from the roots to the above-ground part of the plant. Also performs a supporting function.
• Phloem (phloem) - represented by sieve tubes, provides a reverse, downward current: it carries nutrients synthesized in the leaves to other parts of the plant, including the roots. It is in close relationship with xylem, forming together with it certain complex groups in plant organs - the so-called vascular bundles.

Basic

Basic tissues (parenchyma), as the name suggests, form the basis of plant organs. They are formed by living thin-walled cells and perform several functions, so they are divided into several varieties. In particular, these are:

• Assimilation - contain a large number of chloroplasts, respectively, are responsible for the processes of photosynthesis and the formation of organic substances. Basically, plant leaves are formed from these tissues; a little less of them are found in young green stems.
• Storage - accumulate useful substances, including proteins and carbohydrates. These are the tissues of roots, fruits, seeds, bulbs, tubers and stems of woody plants.
• Aquifers - accumulate and store water. As a rule, these tissues form the organs of plants growing in dry and hot climates. They can be contained both in leaves (for example, in aloe) and in stems (in cacti).
• Airborne - due to the large number of intercellular spaces filled with air, they transport it to those parts of the body whose communication with the atmosphere is difficult. They are characteristic of aquatic and marsh plants.

As we see, plant tissues are no less diverse and complex than animal tissues. They achieved the greatest specialization in angiosperms: they have up to 80 types of tissues.

According to biology, tissue is a special structure that ensures the functioning of any organism as a whole. What structural features do you need to have to perform such an important function?

What is tissue: biology will answer

According to the definition of the concept, tissue is a group of cells that are similar in structure and function. Not all living organisms are formed by similar structures. Thus, viruses are non-cellular life forms, and all bacteria are unicellular.

Groups of specialized cells allow all physiological processes to be carried out more efficiently. That is why highly organized living objects consist of organs. This fact is proven by biology. Tissue is just a structure consisting of cells and forming organs.

Plant tissues

What is the fabric made of? Plant biology shows that not only from cells. Between them there is an intercellular substance that acts as a connecting link. Plant tissues are practically devoid of it.

They are presented in the following types:

1. Cover:

The skin is a living tissue with special structures - stomata, which serve for gas exchange;

Cork is a dead tissue in which lentils carry out metabolism.

2. Main - stores nutrients, carries out the process of photosynthesis, and forms the basis of organs.

3. Mechanical - performs a supporting function.

4. Conductive - provides upward (water from the root) and downward (organic substances from the leaves) flow of substances.

5. Educational - when dividing, it restores cells of any affected tissue, carrying out regeneration.

Animal tissue

A distinctive feature of this group of cells is the presence of a large amount of intercellular substance.

In animals, the following tissues are classified:

1. Epithelial - performs a protective function. It also forms glands and carries out metabolism. What is epithelial tissue made of? Its biology is simple: small, tightly adjacent cells of various shapes.

2. Connective - consists of large cells and a large amount of intercellular substance. It is the basis of the entire organism. Its varieties are blood, bone, cartilage and adipose tissue.

3. Muscle - represented by individual fibers capable of contraction - myofibrils. Thanks to them, it is possible to move the body in space and move individual organs.

4. Nervous - connects the body with the environment, determines the presence of conditioned and innate reflexes. It consists of cells called neurons and their processes - axons and dendrites. It is through them that information is transmitted from the receptors of the sensory systems to the brain, and from there to the working organs.

Relationship between structure and function

But most importantly, as the science of biology states, tissue is a group of cells whose functions are determined by their structure.

For example, small, closely spaced epithelial cells, practically devoid of intercellular substance, look like a shield. With such structural features, the function is obvious - protection. Connective tissue is structured completely differently. Since it creates the basis of all organs, there should be a lot of it. This explains the presence of large cells and a large amount of intercellular substance. There is especially a lot of it in the blood. This substance is known to everyone as plasma. It contains shaped elements. Erythrocytes - red blood cells - transport oxygen from the lungs to the organs and carbon dioxide in the opposite direction. Platelets are blood platelets that provide blood clotting. Leukocytes are colorless cells. They form immunity, helping the body resist infectious diseases.

Fabrics and evolution

Biology did not immediately find out what tissue is. After all, only with the invention of the light microscope was an amazing microscopic image of cells, and with it tissues, revealed to man.

Lower plants, which include algae, do not have tissues. And even their multicellular representatives consisted of individual unspecialized cells, functionally unrelated to each other. Further, with changes in climatic conditions, the first plant land-dwellers appeared on Earth. According to biology, tissue is a necessary condition for their survival in new conditions. Mosses and mosses first developed mechanical tissues necessary for their spatial arrangement. And then - conductive ones. This development led to the formation of real organs: roots and shoots.

The most primitive multicellular animals also do not have true tissues. We are talking about a representative of the type Coelenterate freshwater hydra. Its body is formed by specialized cells: epithelial, muscle, reproductive, skin-muscular, glandular, etc. But they do not form clusters, but are scattered throughout the body.

Thus, the appearance of tissues marked the beginning of the complication of the structure of living organisms, allowing them to better adapt to any conditions.

Definition 1

Organism is a biological system that consists of interconnected parts functioning as a whole.

Any organism is characterized by all the signs of a living thing: metabolism, reproduction, growth, development, irritability, heredity and variability.

Organisms with cellular structure

Organisms with a cellular structure are the basic and progressive form of life on Earth.

Being an elementary living system, the cell underlies the development and structure of animal and plant organisms on the planet. This is the smallest structure of an organism, which is the boundary of its divisibility and has all the basic characteristics of a whole living organism.

Definition 2

Cell is an elementary (simplest) living system capable of self-reproduction, self-renewal and self-regulation.

The cells that make up a living organism are not identical and not identical, but they all have a single structural principle and common characteristics. This indicates the unity of origin of all living organisms on Earth, the uniformity of the entire organic world of the planet.

Cells are characterized by the presence of two systems that ensure their vital functions:

• a system responsible for the reproduction, growth and development of a cell and including structures that carry out DNA replication, RNA and protein synthesis;
• a system that provides energy supply to the processes of synthesis of substances in the cell and other types of physiological activity.

These systems interact closely. Living cells absorb water and nutrients from the environment and respond to external stimuli by adaptively changing their structures and vital processes. In addition, the elements from which cells of different origin are built are also similar at different levels - atomic ($C$, $H$, $O$, $N$, etc.), molecular (proteins, nucleic acids and etc.), supramolecular (organelles, supramembrane structures).

Cells are also characterized by other general properties, where the unity of vital chemical processes comes to the fore: respiration, use and transformation of energy, synthesis of macromolecules (nucleic acids, proteins, ATP, enzymes, etc.).

All chemical reactions of the cell occur in an orderly and coordinated manner in inextricable connection with the molecular structures of the cell.

A typical cell includes a plasma membrane, cytoplasm with various organelles, and a nucleus. Plant cells also have a vacuole, a well-formed cellulose membrane and various types of plastids.

Life forms of cellular organisms

Organisms living on Earth are characterized by a very diverse structure. They happen unicellular, colonial and multicellular. Moreover, only among unicellular organisms there are prokaryotes, and all colonial and multicellular organisms are eukaryotes.

Unicellular - the simplest forms among organisms. Their representatives are found in all the main kingdoms of living nature: Drobyanki, Plants, Animals and Mushrooms.

A feature of unicellular organisms is their fairly simple structure. Their body consists of one cell, which has all the basic characteristics of the whole organism.

Organelles cells are similar to the organs of multicellular organisms and are capable of performing various functions.

Single-celled organisms are capable of multiplying quite quickly: under favorable conditions, they can produce two or even three generations within an hour. Under unfavorable conditions, they form densely coated spores, in which vital processes practically cease. When favorable conditions occur, the spores again turn into actively functioning cells.

Prokaryotic unicellular organisms are represented only in the kingdom of Drobyanka. Single-celled eukaryotes are found in other kingdoms of life. In the kingdom of Plants - these are unicellular algae, in the kingdom of Animals - protozoa, in the kingdom of Mushrooms - unicellular fungi.

Unicellular organisms consist of only one cell, which carries out all the necessary vital functions and processes.

Example 1

Single-celled organisms are bacteria, protozoa (amoeba, malarial plasmodium, ciliates), many algae (Chlamydomonas, Chlorella, Microcystis), primitive fungi (mucor, yeast). Many of them (bacteria, cyanobacteria) belong to non-nuclear forms (prokaryotes). Instead of a nucleus, the cells of such organisms contain its genetic analogue, diffusely dispersed in the cytoplasm.

According to many scientists colonial organisms are transitional forms of life from cellular to multicellular forms.

A primitive example of this phenomenon is observed in bacteria, which, during division, form colonies (each type of bacteria is characterized by its own form of colony. They are able to synthesize certain enzymes, thanks to which nutrients can be used more efficiently. Under unfavorable conditions, the cells of the colony form spores, allowing them to survive .

Green algae also form colonies.

Example 2

The colonial green algae Volvox resembles a multicellular organism. Thanks to the coordinated beating of the flagella, the directed movement of the colony is ensured. The reproductive cells responsible for reproduction are located on one side of the colony. They form daughter colonies inside the mother colony, which then separate and begin to exist independently.

Although representatives of unicellular organisms are numerous and widespread, in comparison with them multicellular organisms have a number of advantages. First of all, they are able to use environmental resources inaccessible to a single cell.

Example 3

The presence of many cells that form tissues and organs, allows the tree to reach large sizes, the roots provide water and mineral nutrition, and the green leaves form organic matter.

In multicellular organisms, the body is formed by a collection of many cells. Their groups are specialized in performing certain vital functions. These are fabrics. From tissue complexes, in turn, organs are formed, thanks to the joint and harmonious functional activity of which an organ system is formed. A complex of such organ systems, connected functionally, forms an organism.

Example 4

An example of the structural features and distribution of functions between the cells of a multicellular organism are tissues:

• in animals – nervous, epithelial, connective, muscular;
• in plants – integumentary, assimilating (photosynthetic), conducting, forming.

In plants, due to the formation of cellular communities, the efficiency of their immobile autotrophic existence increases. In animals, on the contrary, groups of cells are formed in such a way that the body, during active movement, is capable of obtaining food or performing other functions, i.e. they are interconnected and form effectively interacting systems.

Note 1

Multicellular organisms, due to the presence of tissues and organs, are capable of better obtaining food and developing new places of residence.