Characteristics of the animal kingdom, signs of animals, habitat. Signs and characteristics of all kingdoms of living nature Are all representatives of the animal kingdom multicellular?

PART 4. Animal Kingdom

Subkingdom Unicellular

OPTION 1

For each task, choose one correct answer from the four proposed.

A1. Almost all animals eat

1) autotrophic

2) heterotrophic

3) in the process of photosynthesis

4) in the process of chemosynthesis

A2. Representatives of the kingdom have a nervous system

2) bacteria

3) plants

4) animals

AZ. The body is made up of one cell

2) lichens

3) cap mushrooms

4) protozoa

A4. The pseudopods of protozoan animals are

1) plastids

2) nuclear matter

3) growth of cytoplasm

4) supply of nutrients

A5. The organelle for excreting undigested food debris in protozoa is

4) powder

A6. Reproduction of protozoa occurs mainly through

1) phagocytosis

2) pinocytosis

3) cell division

4) cyst formation

A7. There is no permanent body shape

1) foraminifera

2) ciliates-slippers

3) green euglena

4) common amoeba

A8. Only in the cells of the simplest animals that feed autotrophically, there is

1) chlorophyll

2) cytoplasm

A9. Two nuclei are found in animal cells

1) ciliates

2) euglena

3) Volvox

B1.

A. Many simple animals are part of plankton.

B. Phagocytosis of protozoa is associated with the formation of a contractile vacuole.

1) Only A is correct

2) Only B is correct

3) Both judgments are correct

4) Both judgments are incorrect

B2. Are the following statements true?

A. Amoeba captures food with pseudopods.

B. Among the representatives of the simplest animals, there are multicellular organisms.

1) Only A is correct

2) Only B is correct

3) Both judgments are correct

4) Both judgments are incorrect

BZ. Choose three true statements. Absent in animal cells

1) cell wall

2) chloroplast

3) cytoplasm

5) outer membrane

6) large vacuole

B4. Establish a correspondence between the structural feature of the animal and its species.

BUILDING FEATURES

A. Presence of cilia

B. photosensitive peephole

B. pseudopods

G. Chloroplast

D. Two cores

KIND OF ANIMAL

2) Euglena

3) Ciliate slipper

OPTION 2

A1. Unlike plants, most animals have

1) autotrophic nutrition

2) limited growth

3) unlimited growth

4) immobility

A2. Body symmetry is characteristic of

1) algae

2) animals

3) bacteria rotting

4) moldy mushrooms

A3. Organ of locomotion of ciliates

2) eyelashes

3) limbs

4) muscle fiber

A4. Captures food with pseudopods

2) euglena

3) amoeba

4) ciliates

A5. In unfavorable conditions, protozoa form

1) cyst

3) powder

4) contractile vacuole

A6. Excess water is removed from the body of a protozoan animal

2) pseudopod

3) contractile vacuole

4) photosensitive peephole

A7. There are no special nutritional organelles in

1) common amoeba

2) ciliates-slippers

3) green euglena

4) Volvox

A8. Organisms that are capable of photosynthesis and feed on ready-made substances are called

1) autotrophs

2) heterotrophs

3) mixotrophs

4) photosynthetic

A9. The digestive organ of ciliates is

1) pharynx

2) eyelash

3) small core

4) contractile vacuole

B1. Are the following statements true?

B. Protozoa are capable of reproducing sexually.

1) Only A is correct

2) Only B is correct

3) Both judgments are correct

4) Both judgments are incorrect

B2. Are the following statements true?

A. Euglena green moves to illuminated places.

1) Only A is correct

2) Only B is correct

3) Both judgments are correct

4) Both judgments are incorrect

BZ. Choose three true statements. Animals have characteristic features of life activity

1) limited growth

2) immobility

3) active movement

4) unlimited growth

5) nutrition with prepared substances

6) formation of substances in the light

B4. Establish a correspondence between the life process of an animal and its species.

LIFE PROCESS

A. Phagocytosis - food capture by pseudopods

B. Undigested residues are removed through powder

B, Photosynthesis

D. Movement using cilia

KIND OF ANIMAL

2) Euglena

3) Ciliates-slipper

Write down the corresponding numbers in the table.

The basis of the structure of animals is the cell. Cells are bounded by a membrane, their internal contents are represented by cytoplasm. The cytoplasm contains: a) one or more nuclei, b) organelles, c) inclusions. In unicellular animals, the cell is an integral organism; in multicellular animals, cell specialization occurs, tissues, organs, and organ systems appear.

Animals are characterized by a heterotrophic type of nutrition (use of ready-made organic substances). Among unicellular animals there are organisms with a mixed (mixotrophic) type of nutrition.

The vast majority of animals are aerobic organisms (oxygen is required for oxidation processes), but there are also anaerobic organisms.

Unlike plants, most animals actively move; multicellular animals have a nervous system.

Reproduction is sexual and asexual.

About 1.5 million species of animals are known.

The Animal Kingdom is divided into subkingdoms:

Protozoa, or Unicellular;
Multicellular.

Animal taxonomy is a subject of debate. Recently, animals of the subkingdom Protozoa are divided into 7 types, and the subkingdom Multicellular - into 17 types (Sharova, 1999):

Animal Kingdom (Zoa)

Sub-kingdom Protozoa, or Unicellular organisms (Protozoa)
- - - - Type Sarcomastigophora
      - Type Apicomplexa
      - Type Myxosporidium (Myxozoa)
      - Type Microsporidia (Microspora)
      - Type Ciliates (Ciliophora)
      - Type Labyrinthulas (Labirinthomorpha)
      - Type Ascetospora
Sub-kingdom Multicellular (Metazoa)
- Supersection Phagocytella-like (Phagocytellozoa)
  - - - Type Lamellar (Placozoa)
- Supersection Parazoa
  - - - Type Sponges (Porifera, or Spongia)
- Supersection Eumetazoa
  - Chapter Radiant (Radiata)
    - - Type Coelenterata
      - Type Ctenophora
  - Chapter Bilaterally symmetrical (Bilateria)
    - Subsection Cavityless (Acoelomata)
      - Type Flatworms (Plathelminthes)
      - Type Round, or Primary cavity worms (Nemathelminthes)
      - Type Nemertina
    - Subsection Secondary cavities (Coelomata)
      - Type Annelida (Annelida)
      - Type Mollusks
      - Type Onychophora
      - Type Arthropods (Arthropoda)
      - Type Pogonophora
      - Type Tentacled (Tentaculata)
      - Type Chaetognata (Chaetognata)
      - Type Echinodermata (Echinodermata)
      - Type Hemichordata
      - Type Chordata

The classification is based on “species”, related species are combined into “genus”, related genera into “family”, families into “order”, orders into “class”, classes into “type”, types into “subkingdom”, subkingdoms into "kingdom".

The first living prokaryotic organisms appeared on Earth 3.5-4 billion years ago, eukaryotic organisms - about 1.5 billion years ago. Further, eukaryotic organisms evolved into three branches: plants, fungi, and animals. It should be emphasized that the appearance of animals is associated with the appearance of eukaryotic cells in general. According to modern concepts, organelles appear not only from specialized parts of the cell, but also as a result of several intracellular symbioses (symbiogenesis hypothesis).

The main stages of animal evolution can be represented as follows (see figure). First, unicellular animals appear, then lower multicellular animals (lamellae and sponges). Colonial flagellates are considered a transitional form between unicellular and lower multicellular animals. From lower multicellular animals come higher multicellular animals. In the process of evolution of multicellular organisms, the two-layer body structure is replaced by a three-layer one, the parenchyma between the internal organs is replaced by a primary and then a secondary body cavity. Deuterostomes develop in several directions, the main of which lead to the appearance of trochophore animals with a primary mouth and deuterostome animals - echinoderms, hemichordates and chordates. Among chordates, the most complex organization is achieved by warm-blooded vertebrates - birds and mammals.

Traditionally, all living organisms are divided into three domains (superkingdoms) and six kingdoms, but some sources may indicate a different classification system.

Organisms are placed into kingdoms based on similarities or shared characteristics. Some of the traits that are used to define a kingdom include: cell type, nutrient acquisition, and reproduction. The two main types of cells are and cells.

Common methods of obtaining nutrients include absorption and ingestion. Types of reproduction include and.

Below is a list of the six kingdoms of life and a brief description of the organisms that comprise them.

Kingdom of Archaea

Archaea growing in Morning Glory Lake in Yellowstone National Park produce vibrant color

Initially, these prokaryotes with one were considered bacteria. They are found in and have a unique type of ribosomal RNA. The composition of these organisms allows them to live in very challenging environments, including hot springs and hydrothermal vents.

Domain: Archaea;
Organisms: methanogens, halophiles, thermophiles, psychrophiles;
Cell type: prokaryotic;
Metabolism: depending on the type - metabolism may require oxygen, hydrogen, carbon dioxide, sulfur, sulfide;
Method of nutrition: depending on the species - food consumption can be carried out by absorption, non-photosynthetic photophosphorylation or chemosynthesis;
Reproduction: Asexual reproduction by binary fission, budding or fragmentation.

Note: in some cases, archaea are classified as belonging to the Kingdom of Bacteria, but most scientists classify them as a separate Kingdom. In fact, DNA and RNA data show that archaea and bacteria are so different that they cannot be combined into one Kingdom.

Kingdom Bacteria

Escherichia coli

These organisms are considered true bacteria and are classified under the domain of bacteria. Although most bacteria do not cause illness, some can cause serious illness. Under optimal conditions, they reproduce at an alarming rate. Most bacteria reproduce by binary fission.

Domain: ;
Organisms: bacteria, cyanobacteria (blue-green algae), actinobacteria;
Cell type: prokaryotic;
Metabolism: depending on the species - oxygen may be toxic, transportable or necessary for metabolism;
Method of nutrition: depending on the type - food consumption can be carried out by absorption, photosynthesis or chemosynthesis;
Reproduction: asexual.

Kingdom Protista

Domain: Eukaryotes;
Organisms: amoebas, green algae, brown algae, diatoms, euglena, slimy forms;
Cell type: eukaryotic;
Feeding mode: depending on the species - food consumption includes absorption, photosynthesis or ingestion;
Reproduction: predominantly asexual. occurs in some species.

Kingdom Mushrooms

Includes both single-celled (yeast and mold) and multicellular (fungi) organisms. They are decomposers and obtain nutrients through absorption.

Domain: Eukaryotes;
Organisms: fungi, yeast, mold;
Cell type: eukaryotic;
Metabolism: Oxygen is necessary for metabolism;
Nutrition method: absorption;
Reproduction: sexual or asexual.

Plant Kingdom

They are extremely important for all life on Earth, since they release oxygen and provide other living organisms with shelter, food, etc. This diverse group contains vascular or avascular plants, flowering or non-flowering plants, and others.

Domain: Eukaryotes;
Organisms: mosses, angiosperms (flowering plants), gymnosperms, liverworts, ferns;
Cell type: eukaryotic;
Metabolism: Oxygen is necessary for metabolism;
Nutrition method: photosynthesis;
Reproduction: Organisms undergo alternating generations. The sexual phase (gametophyte) is replaced by the asexual phase (sporophyte).

Animal Kingdom

This Kingdom includes everyone. These multicellular eukaryotes depend on plants and other organisms for sustenance. Most animals live in aquatic environments and range from tiny tardigrades to extremely large blue whales.

Domain: Eukaryotes;
Organisms: mammals, amphibians, sponges, insects, worms;
Cell type: eukaryotic;
Metabolism: Oxygen is necessary for metabolism;
Method of feeding: ingestion;
Reproduction: Most animals reproduce sexually, but some animals reproduce asexually.

In our article we will look at the characteristics of the animal kingdom. Representatives of this systematic unit are highly diverse and widely distributed in nature. These include more than 5 million species, including humans.

Animal kingdom: general characteristics and diversity

What signs can be used to determine whether an organism is an animal? First of all, this is a heterotrophic method of nutrition, active movement in space, a developed nervous system, and a pronounced reaction to a stimulus. These are the main characteristics of the Animal Kingdom.

The number of species of these representatives of the organic world is several times greater than plants and fungi combined. Among animals there are both microscopic single-celled organisms and real giants. For example, the humpback whale, whose body length approaches 15 meters.

Habitat

In nature, animals can be found absolutely everywhere. Their main habitat is ground-air. They run on the ground, fly, crawl in a wide variety of conditions: from hot deserts to cold tundra. A large number of animals live in water bodies. These are dolphins. In some species, life with water is only partially connected: walruses, seals, elephant seals, seals. Many species of worms are traditionally considered to be soil dwellers. But mole rats and moles also live here. Their visual organs are underdeveloped due to their adaptation to the lack of sunlight.

Nutrition

Consumption of prepared organic substances is a basic characteristic of the animal kingdom. This feature is decisive in matters of classification. For example, the single-celled organism Chlamydomonas actively moves with the help of flagella and a light-sensitive eye. But it is a representative of the plant world, since it is capable of photosynthesis.

Active movement of the body in space is another important characteristic of the animal kingdom. Unicellular species carry it out using special structures. They are called movement organelles. In ciliates these are numerous cilia, in green euglena it is a flagellum. But it does not have a constant body shape. Its cytoplasm constantly forms temporary protrusions - pseudopods, or pseudopodia.

Movement is carried out by more complex structures. Thus, coelenterates have skin-muscle cells. By contracting, they change the shape and position of the body in space. The integument of worms is represented by a skin-muscular sac. It consists of the integumentary epithelium, as well as one or more layers of muscle. Highly organized animals have a musculoskeletal system. This is a combination of skeleton and muscles. Differentiation of the latter allows animals to carry out the most complex movements.

Height

The increase in body size of most animals occurs only during a certain period of their life. This type of growth is called limited. For example, human development stops at about 25 years of age. Unlimited growth is also a characteristic of some members of the animal kingdom. It is characteristic of crocodiles, turtles, and some types of fish.

In insects, crustaceans and reptiles, growth is accompanied by molting. The fact is that their covers are not capable of stretching. And only shedding the cuticle and chitin allows the body to increase in size.

Reproduction methods and development

Most animals are characterized by sexual reproduction. It occurs with the participation of germ cells - eggs and sperm. The process of their fusion is called fertilization. Depending on the place in which it occurs, fertilization can be external or internal.

In the first case, the sex cells fuse outside the female’s body. This feature is typical for amphibians and fish. Since fertilized eggs are not protected from unfavorable environmental conditions, females lay thousands of eggs into the water. In the second case, both fertilization and subsequent development take place inside the female body. Therefore, such individuals have a greater chance of survival, and their number is smaller.

In rare cases, animals can reproduce by budding. For example, freshwater hydra. First, a small protrusion forms on her body, it increases in size, acquires the features of an adult organism, after which it begins to exist independently. Some species of crustaceans reproduce parthenogenetically. This is the development of an organism from an unfertilized egg.

The mode of individual development is another characteristic of the animal kingdom. These are qualitative changes in organisms. With direct development, an animal is born that is a copy of the adult organism. It is typical for birds, reptiles, and mammals.

If an individual is born that is significantly different from an adult, then this method of development is called indirect. For example, frog larvae resemble fish fry in appearance and actively swim in the water. The same can be said about butterflies. Their larvae, called caterpillars, eat plant leaves, and adults eat flower nectar.

The best

A brief description of the animal kingdom would be incomplete without getting acquainted with the most unusual of them. The record holder for size is the blue whale, reaching a length of more than 30 meters. The weight of this giant is also impressive - 190 tons. And Even a schoolchild will answer that this is a giraffe. The most amazing fact is that with a height of about 6 meters, there are only 7 vertebrae in his cervical region. The same amount is found in both the field mouse and the chinchilla.

The title of the fastest on the planet is rightfully occupied by the cheetah, antelope, killer whale, and sailfish. In their habitat, no one can keep up with them. Among the strongmen, the leader is the rhinoceros beetle, which is able to lift 850 times its own weight.

So, the main characteristics of representatives of the animal kingdom are:

distribution in all habitats;
heterotrophic nutrition;
active movement in space;
development of the musculoskeletal and nervous systems;
limited growth.

Characteristics of animals Heterotrophic type of nutrition Active movement Limited (closed growth). In animal cells there is a cell center, a glycocalyx, a storage substance - glycogen.

Structure In the cytoplasm of protozoa there are special organelles (digestive and contractile vacuoles) that perform the functions of digestion, osmoregulation, and excretion. Almost all protozoa are capable of active movement. Movement is carried out with the help of pseudopods (amoeba and other rhizomes), flagella (euglena green) or cilia (ciliates).

Structure Protozoa are capable of capturing solid particles (amoeba), which is called phagocytosis. Most protozoa feed on bacteria and decaying organic matter. After ingestion, food is digested in the digestive vacuoles. The secretion function in protozoa is performed by contractile vacuoles, or special openings - powder (in ciliates).

Habitat Protozoa live in fresh water bodies, seas and soil. The vast majority of protozoa have the ability to encyst, that is, to form, upon the onset of unfavorable conditions (lower temperatures, drying out of the reservoir), a resting stage - a cyst covered with a dense protective shell. The formation of a cyst is not only an adaptation to survival under unfavorable conditions, but also to the spread of protozoa. Once in favorable conditions, the animal leaves the cyst shell and begins to feed and reproduce.

Amoeba A representative of the rhizopod class is the common amoeba. Unlike many protozoa, it does not have a constant body shape. It moves with the help of pseudopods, which also serve to capture food - bacteria, unicellular algae, and some protozoa.

Amoeba Having surrounded the prey with pseudopods, the food ends up in the cytoplasm, where a digestive vacuole forms around it. In it, under the influence of digestive juice coming from the cytoplasm, digestion occurs, as a result of which digestive substances are formed. They penetrate the cytoplasm, and undigested food remains are thrown out.

The amoeba breathes through the entire surface of the body: oxygen dissolved in water directly penetrates into its body through diffusion, and carbon dioxide formed in the cell during respiration is released outside.

Amoeba The concentration of dissolved substances in the body of the amoeba is greater than in water, so water continuously accumulates and its excess is excreted through a contractile vacuole. This vacuole is also involved in removing decay products from the body. Amoeba reproduces by division. The nucleus divides in two, both halves diverge, a constriction forms between them, and then two independent daughter cells arise from one mother cell.

Euglena green Another widespread species of protozoa lives in fresh water bodies - green euglena. It has a spindle-shaped shape, the outer layer of cytoplasm is compacted and forms a shell that helps maintain this shape

Euglena green A long thin flagellum extends from the front end of the body of the green euglena, rotating which the euglena moves in the water. In the cytoplasm of euglena there is a nucleus and several colored oval bodies - chromatophores containing chlorophyll. Therefore, in the light, euglena feeds like a green plant (autotrophic). A light-sensitive eye helps euglena find illuminated places.

Euglena green If a euglena is in the dark for a long time, then the chlorophyll disappears and it switches to a heterotrophic method of nutrition, that is, it feeds on ready-made organic substances, absorbing them from the water over the entire surface of the body. Respiration, reproduction, division in two, and cyst formation in green euglena are similar to those of amoeba.

Volvox Its shape is spherical, the body consists of a gelatinous substance in which individual cells - members of the colony - are immersed. They are small, pear-shaped, and have two flagella. Thanks to the coordinated movement of all flagella, the Volvox moves. In a Volvox colony there are few cells capable of reproduction; Daughter colonies are formed from them.

Slipper ciliates Another type of protozoan is often found in fresh water bodies - the slipper ciliate, which got its name due to the peculiarities of the shape of the cell (in the form of a slipper). Cilia serve as organelles for movement. The body has a constant shape, as it is covered with a dense shell. The ciliate slipper has two nuclei: large and small.

Ciliate-slipper The large nucleus regulates all life processes, the small one plays an important role in the reproduction of the slipper. Ciliates feed on bacteria, algae and some protozoa. With the help of vibrations of the cilia, food enters the mouth, then into the pharynx, at the bottom of which digestive vacuoles are formed, where food is digested and nutrients are absorbed. Undigested residues are removed through a special organ - powder. The secretion function is performed by the contractile vacuole.

The ciliate slipper reproduces, like the amoeba, asexually, but the ciliate slipper also has a sexual process. It consists in the fact that two individuals unite, an exchange of nuclear material occurs between them, after which they disperse (Fig. 73).

Slipper ciliates This type of sexual reproduction is called conjugation. Thus, among freshwater protozoa, the ciliate slipper has the most complex structure.

Irritability When characterizing the simplest organisms, special attention should be paid to one more of their properties - irritability. Protozoa do not have a nervous system; they perceive irritations of the entire cell and are able to respond to them with movement - taxis, moving towards or away from the stimulus.

Protozoa living in sea water and soil and others. Of the marine inhabitants, the most common are foraminifera and radiolarians (rayfish). Foraminifera have a shell consisting of calcium carbonate or grains of sand. Some foraminifera and radiolarians are part of plankton (organisms living in the upper layers of water) or benthos (organisms existing in the bottom and on the surface of water bodies). Dead foraminifera play an important role in the formation and deposition of chalk or lime. Dead radiolaria form deposits of minerals such as jasper, opal, etc. Soil protozoa are representatives of amoebas, flagellates and ciliates, which play an important role in the soil-forming process.

Functions In nature, protozoa participate in the cycle of substances and perform a sanitary role; in food chains they form one of the first links, providing food for many animals, in particular fish; take part in the formation of geological rocks, and their shells determine the age of individual geological rocks.

Subkingdom multicellular In representatives of this subkingdom, the body consists of many cells that perform various functions. Due to specialization, multicellular cells usually lose the ability to exist independently. The integrity of the body is ensured through intercellular interactions. Individual development, as a rule, begins with a zygote and is characterized by the fragmentation of the zygote into many blastomere cells, from which an organism with differentiated cells and organs is subsequently formed.

Phylogeny of multicellular organisms The origin of multicellular organisms from unicellular organisms is currently considered proven. The main proof of this is the almost complete identity of the structural components of the cell of multicellular animals with the structural components of the cell of protozoa. Hypotheses for the origin of multicellular organisms are divided into two groups: a) colonial, b) polyergid hypotheses.

Colonial hypotheses Supporters of the colonial hypotheses believe that colonial protozoa are a transitional form between unicellular and multicellular animals.

1 theory “Gastrea” hypothesis by E. Haeckel (1874). The transitional form between unicellular and multicellular animals is a single-layered spherical colony of flagellates. Haeckel called it “blastea”, since the structure of this colony resembles the structure of a blastula. In the process of evolution, the first multicellular organisms, “gastrea” (similar in structure to the gastrula), arise from the “blastea” by invagination (invagination) of the colony wall. "Gastrea" is a swimming animal whose body consists of two layers of cells and has a mouth. The outer layer of flagellar cells is the ectoderm and performs a motor function, the inner layer is the endoderm and performs a digestive function. From “gastrea,” according to Haeckel, primarily coelenterate animals originate, from which other groups of multicellular organisms originate. E. Haeckel considered the presence of blastula and gastrula stages in the early stages of ontogenesis of modern multicellular organisms to be evidence of the correctness of his hypothesis.

2 theory The “placula” hypothesis of O. Büchli (1884) is a modified version of Haeckel’s gastrea hypothesis. Unlike E. Haeckel, this scientist accepts a lamellar single-layer colony of the gonium type as a transitional form between unicellular and multicellular animals. The first multicellular organism is Haeckel's "gastrea", but in the process of evolution it is formed by stratification of the colony and cup-shaped deflection of a two-layer plate. Evidence of the hypothesis is not only the presence of blastula and gastrula stages in the early stages of ontogenesis, but also the structure of Trichoplax, a primitive marine animal discovered in 1883.

3 theory “phagocytella” hypothesis by I. I. Mechnikov (1882). Firstly, I.I. Mechnikov discovered the phenomenon of phagocytosis and considered this method of digesting food to be more primitive than cavity digestion. Secondly, while studying the ontogeny of primitive multicellular sponges, he discovered that the gastrula in sponges is formed not by invagination of the blastula, but by the immigration of some cells of the outer layer into the cavity of the embryo. It was these two discoveries that formed the basis for this hypothesis. I. I. Mechnikov also takes “blastea” (a single-layer spherical colony of flagellates) as a transitional form between unicellular and multicellular animals. From the “blastea” come the first multicellular organisms – “phagocytella”. The “phagocytella” does not have a mouth, its body consists of two layers of cells, the flagellar cells of the outer layer perform a motor function, and the inner layer - the function of phagocytosis. “Phagocytella” is formed from “blastea” by immigration of part of the outer layer cells into the colony. The prototype, or living model of the hypothetical ancestor of multicellular organisms - the “phagocytella” - I. I. Mechnikov considered the larva of sponges - the parenchyma.

4 theory The “phagocytella” hypothesis of A. V. Ivanov (1967) is an expanded version of Mechnikov’s hypothesis. The evolution of lower multicellular organisms, according to A.V. Ivanov, occurs as follows. The transitional form between unicellular and multicellular animals is a colony of collarate flagella, which does not have a cavity. From colonies of collared flagellates of the Proterospongia type, “early phagocytella” are formed by immigration of part of the cells of the outer layer inward. The body of “early phagocytella” consists of two layers of cells, does not have a mouth, and its structure is intermediate between the structure of parenchymula and trichoplax, closer to trichoplax. From the “early phagocytella” lamellar, sponge and “late phagocytella” originate. The outer layer of “early” and “late phagocytella” is represented by flagellar cells, the inner layer – by amoeboid cells. Unlike “early phagocytella,” “late phagocytella” have a mouth. Coelenterate and ciliated worms originate from “late phagocytella”

Polyergid hypotheses Proponents of polyergid hypotheses believe that polyergid (multinucleate) protozoa are a transitional form between unicellular and multicellular animals. According to I. Hadji (1963), the ancestors of multicellular organisms were multinucleate ciliates, and the first multicellular organisms were flatworms such as planarians. The most well-reasoned is the “phagocytella” hypothesis of I. I. Mechnikov, modified by A. V. Ivanov. The subkingdom Multicellular is divided into three subdivisions: 1) Phagocytella, 2) Parazoa, 3) Eumetazoa.

Invertebrate animals Coelenterates are a very ancient group of primitive bilayer animals, numbering about 9000 species. Their study is of great importance for understanding evolution; some species are of interest for medicine. Coelenterates lead an exclusively aquatic lifestyle. They live in marine and fresh water bodies. Most species are characterized by radial-axial symmetry of the body. This type of symmetry is characteristic of animals leading a sedentary or sedentary lifestyle. In the simplest case, the body of coelenterates has the form of a sac, the opening of which is surrounded by a corolla of tentacles. The cavity of the sac is called the gastric cavity. Sessile forms - polyps - have this structure. Free-living forms have a more flattened body and are called jellyfish.

Morphology The division into polyps and jellyfish is not systematic, but purely morphological. A common feature for all representatives of the type is two-layered. Their body consists of ectoderm and endoderm, between which is mesoglea. In hydra it has the form of a non-cellular supporting plate, in jellyfish it is more developed. It is rich in water and takes on a gelatinous form, making up most of the body.

Morphology Cells of the body of coelenterates are differentiated. The ectoderm contains epithelial-muscle cells, interstitial, or intermediate, stinging, reproductive and nervous cells. Interstitial cells are cells that play a critical role in controlling the spontaneous motility of the gastrointestinal tract (GIT), including being pacemakers (pacemakers) that set the frequency of slow waves of the electrical potential of the smooth muscle tissue of the gastrointestinal tract, which, in turn, determine the frequency of peristalsis of various parts of the gastrointestinal tract.

Structure Epithelial muscle cells perform motor and protective functions. Stinging devices are the apparatus of attack and defense. They have a capsule, inside of which there is a stinging thread in the form of a spiral, which is thrown out when irritated. Interstitial are small undifferentiated cells; subsequently, all types of ectoderm cells are formed from them. The endoderm is divided into epithelial-muscle cells and glandular cells. The latter secrete enzymes and perform the function of digestion. The endoderm also contains small numbers of nerve cells. With their processes they communicate with each other, forming a diffuse nervous system.

Structure Digestion of coelenterates occurs in the gastric cavity, therefore, it becomes cavitary. Undigested food remains are removed from the body through the mouth. However, intracellular digestion is also preserved, since endoderm cells are capable of phagocytosis - capturing food particles from the gastric cavity.

Reproduction Coelenterates are characterized by asexual and sexual reproduction. Asexuality occurs by budding. In the summer, a kidney-shaped protrusion forms on the body of the polyp. The bud then separates and falls to the bottom of the pond, growing into a new individual. Sexual reproduction is usually observed in the fall. There are dioecious and hermaphroditic species. The egg develops in the ectoderm closer to the sole, and the sperm develops near the mouth. Mature sperm enter the water and meet the egg. The fertilized egg is covered with a thick shell, the body of the hydra is destroyed, and the zygote sinks to the bottom and begins to divide again only in the presence of heat, in the spring, forming a new individual.

Reproduction Many coelenterates are characterized by alternating generations. Polyps reproduce by budding and give rise to both polyps and jellyfish. Jellyfish reproduce sexually. Fertilized eggs produce planula larvae covered with cilia. They attach to the substrate and give rise to a new generation of polyps. The phylum Coelenterata is divided into three classes: Hydroid, Scyphoid and Coral polyps.

Hydroids Hydroids - whose life cycle includes a jellyfish with a characteristic feature - velum, and a polyp, which, unlike other cnidarians, never has internal partitions (septa) and a pronounced pharynx. They are divided into 6 orders: hydroids (Hydrida), leptolids (Leptolida), limnomedusae (Limnomedusae), trachymedusae (Trachymedusae), narcomedusae (Narcomedusae), siphonophores (Siphonophorae). More than 2,500 species are known. (Representatives: freshwater hydra, Portuguese man-of-war, obelia, cross).

Coral polyps often live in colonies. They develop without a change of generations. They live in warm seas. Some representatives form reefs. Representatives: sea anemones, noble corals, sea pen.

The role of coelenterates in nature and human life. A link in the water supply chain. Biological water treatment. Calcium cycle in the biosphere. Formation of sedimentary rocks. Eating. Making jewelry and art objects. Biologically active substances.