The subkingdom of unicellular organisms or protozoa include the smallest creatures whose body consists of one cell. These cells represent an independent organism with all its characteristic functions (metabolism, irritability, movement, reproduction).
The body of unicellular organisms can have a permanent shape (slipper ciliates, flagellates) or a non-permanent shape (amoebas). The main components of the body of protozoa are − core And cytoplasm. In the cytoplasm of protozoa, along with general cellular organelles (mitochondria, ribosomes, Galgi apparatus, etc.), 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. The movement is carried out using pseudopods(in amoeba and other rhizomes), flagella(green euglena) or eyelashes(ciliates). Protozoa are capable of capturing solid particles (amoeba), which is called phagocytosis. Most protozoa feed on bacteria and decaying organic matter. After swallowing, food is digested in digestive vacuoles. The function of excretion in protozoa is performed by contractile vacuoles, or special holes - powder(in ciliates).
Protozoa live in fresh water bodies, seas and soil. The vast majority of protozoa have the ability to encystment, that is, the formation of a resting stage upon the onset of unfavorable conditions (lower temperature, drying out of the reservoir) - cysts, 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.
Reproduction of protozoa occurs by cell division into two (asexual); many experience sexual intercourse. In the life cycle of most protozoa, asexual and sexual reproduction alternate.
There are over 90,000 species of unicellular organisms. All of them are eukaryotes (have a separate nucleus), but are at the cellular level of organization.
Amoeba
A representative of the rhizome class is amoeba ordinary. 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.
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.
The concentration of dissolved substances in the body of the amoeba is greater than in water, so water continuously accumulates and its excess is removed outside with the help of 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.
Amoeba is a freshwater animal.
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.
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.
If a euglena is in the dark for a long time, then the chlorophyll disappears and it switches to a heterotrophic mode 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
Among flagellates there are colonial species, for example, 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.
Ciliate slipper
Another type of protozoan is often found in fresh water bodies - ciliate-slipper, which got its name due to the peculiarities of the shape of the cell (in the form of a shoe). 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.
Big core regulates all life processes, small- plays an important role in the reproduction of the shoe. Ciliates feed on bacteria, algae and some protozoa. Vibrations eyelashes food gets into mouth opening, then - in throat, at the bottom of which are formed digestive vacuoles where food is digested and nutrients are absorbed. Undigested residues are removed through a special organ - powder. The selection function is performed by contractile vacuole.
It reproduces, like the amoeba, asexually, but the slipper ciliate 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).
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, you should pay special attention to one more property of them - irritability. Protozoa do not have 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
Soil protozoa are representatives of amoebas, flagellates and ciliates, which play an important role in the soil-forming process.
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.
Type of Sarcomastigophora
Sarcodina. Animals with inconsistent body shape.
The body is naked and may have an external shell or an internal skeleton.
Locomotion using pseudopodia of various shapes.
Reproduction is asexual, and in some cases sexual. These include amoebas, testate
amoebas, foraminifera, rayfish and sunfish.
Amoebas (Amoebina)- inhabitants of the soil, fresh water bodies, few
plasmalemma. Monoenergetic and polyenergetic. Organoids of movement
Lobopodia. Heterotrophs. Reproduction is asexual (monotomy), in amoeba
Amoeba marina asexual reproduction is a parasexual process.
Testate amoebas (Testacea)- inhabitants of fresh water bodies, soil,
mosses in swamps. The body is enclosed in a shell of various shapes. Sink
single-chambered from organic matter, in some it is formed
grains of sand are included in silica or in an organic base. Type14
pseudopodia - lobopodia and filopodia. Heterotrophs. Reproduction
asexual - monotomy.
Foraminifera- inhabitants of the seas, inhabit the bottom (benthic forms), a few - the water column (planktonic). The body is placed in an organic shell (usually multi-chambered) impregnated with calcium carbonate. The walls of the shell are permeated with pores through which rhizopodia emerge. Foraminifera are heterotrophs. Reproduction is the alternation of sexual and asexual processes (metagenesis).
(Volvox, for example) consists of many thousands of cells forming a hollow ball. The cells are interconnected by cytoplasmic bridges and differentiated into somatic (vegetative) and generative (parthenogonidia and gametogonidia), differing in structure. Animal sizes and body shapes vary.
The organelles of movement are
flagella (1, 2 or many). In some animals the base of the flagellum
continues beyond the kinetosome, a root thread (rhizoplast) is formed,
which is either attached to the core shell or lies free. Part
flagellates have a parabasal body of various shapes, which
located near the flagellum. This organelle is homologous to the apparatus
Golgi. A kinetoplast may be located next to the kinetosome, it
corresponds to mitochondria, contains a significant amount of DNA.
The integument is a membrane (in a few), pellicle or carapace. Availability
pellicles determine the constancy of the body shape.
Flagellates
monoenergetic and polyenergetic animals. In plant
Flagellates have a sensitive eye - stigma. By food type
Autotrophs (Volvox), mixotrophs (Euglena) and heterotrophs. Maybe
presence of a cellular mouth or animals for catching prey
use a section of sticky cytoplasm. Undigested leftovers
are excreted at the posterior end of the body. Contractile vacuole of different structure.
Flagellates characterized by asexual and sexual reproduction.
Asexual reproduction in the form of monotomy and palintomy. Sexual
reproduction - copulation. Consider the reproduction of euglena,
trypanosomes, volvox, opalina.
Euglena reproduces only asexually, by
longitudinal division of an animal in two. First the nucleus divides, then
starting from the anterior end of the body, and the entire body of the protozoa. The flagellum extends to
one of the daughter individuals or both daughter individuals is formed again. 15
Asexual reproduction can also occur in a cyst, reproduction
palintomy.
Trypanosoma also reproduces asexually by fission
in two or multiple divisions. Part life cycle flows into
the human body, the other part in the body of the tsetse fly. Throughout life
cycle, the animal goes through various stages that differ in structure
(trypanosomal, leptomonas, critidial, leishmanial forms).
Volvox reproduces asexually and sexually. Asexual
reproduction - palintomy. 4-10 parthenogonidy cells divide
sequentially on the surface of the mother colony, then moves
inside. The resulting cells are initially arranged in the form of a plate,
then they take a cup-shaped shape and later a spherical shape. Exit
daughter colonies from the mother colony are accompanied by rupture of the walls
the last one and her death. Volvox colonies are dioecious and
hermaphroditic. Sex cells are formed from gametogonia. Their
not much: 5-10 male and 25-30 female cells. Microgonidia
divide repeatedly, forming microgametes and macrogonidia
increase in volume, macrogametes are formed. Sexual process
oogamous.
Opalins- polynucleate animals with many flagella. They
reproduce asexually (division in two) and sexually
(copulation). Reproduction is associated with a change of hosts, asexual
reproduction leads to the formation of cysts. The most studied life
Opalina ranarum cycle. Cysts containing 3-12 nuclei are excreted from
frogs during the period of laying eggs. Tadpoles ingest cysts in the body
tadpoles undergo gametogony (formation of gametes) and anisogamy
copulation. The zygote encysts and enters the water. Oocyst, ingested
tadpole, develops either into a trophic form, or is formed
new generation of gametes.
Ciliates(Ciliophora)
humans and animals. All ciliates are characterized by nuclear dualism.
Ciliates heterotrophs. Divided into two classes: ciliary
(Ciliata) and sucking (Suctoria) ciliates.
For ciliated ciliates
characteristic:
Body shape is varied. More often animals are longitudinally
oval, inhabitants of sand in the form of long thin ribbons, species in
shaped like a bell, trumpet, etc. Ciliated ciliates
freely mobile or attached to the substrate by a stalk.
The ciliary apparatus (ciliatum) is represented by kinetes, cirri, membranellae and membranes. Many ciliates have immobile tactile cilia.
The ectoplasm contains myonemes and extrusomes - trichocysts.
mouth opening. The structure of the oral apparatus is associated with the character
food. Digestive vacuoles move around the animal's body (cyclosis
vacuoles). Defecation is performed through the cytoproct.
The endoplasm contains nuclei. In the simplest case, the slipper ciliate) has one micronucleus and one macronucleus. Other representatives have several micro- and macronuclei.
The structure of contractile vacuoles and their number varies, they occupy a fixed position in the cell, and open with a vacuoloid pore.
Asexual reproduction - transverse division of the animal (monotomy) or palintomy in a cyst. Sexual reproduction is conjugation. A temporary union of two individuals occurs, resorption of macronuclei in each animal occurs, micronuclei divide twice (meiosis), three nuclei are destroyed, the fourth divides (mitosis). Newly formed nuclei - pronuclei
(stationary and migrating). An exchange of migrating nuclei occurs. The pronuclei fuse to form a synkaryon. Individuals are separated from each other. Conjugants reconstruct the nuclear apparatus. Ciliates
Autogamy is also characteristic - a process in which conjugation occurs in one individual.
Sucking ciliates lead an attached lifestyle. Adults lack cilia. They are characterized by both non-branching and branching tentacles. The tentacles are used to catch prey: the prey sticks to the tentacle, the prey pellicle dissolves and the contents of the victim flow inside through a channel located in the tentacle
ciliates. These ciliates are also characterized by nuclear dualism. Reproduction is asexual - budding (vagrants with cilia are formed) and sexual - conjugation.
Sporozoa
Sporozoans are represented by gregarines and coccidia. All
or the animal becomes infected with the help of animal carriers,
are called transmission. There are three groups of transmissible
diseases: anthroponoses, anthropozoonoses, zoonoses. In the life cycle
distinguish endogenous and exogenous parts.
The intestine is divided into sections (2 or 3): epimerite, protomerite and deuterite with one core. The body of animals inhabiting cavities, gonads, is spherical or worm-shaped. Nutrition is saprophytic. Paraglycogen is deposited in the endoplasm. Reproduction - alternation of gametogony and sporogony, some also have asexual reproduction
Subkingdom Unicellular animals includes animals whose body consists of one cell. This cell is a complex organism with its own physiological processes: breathing, digestion, excretion, reproduction and irritation.
Their cell shapes are varied and can be constant(flagellates, ciliates) and fickle(amoeba). The organelles of movement are pseudopods, flagella And cilia. Protozoa have food autotrophic(photosynthesis) and heterotrophic(phagocytosis, pinocytosis). Reproduction in unicellular organisms asexual(nuclear division - mitosis, and then longitudinal or transverse cytokinesis, as well as multiple division) and sexual: conjugation (ciliates), copulation (flagellates).
About 30,000 species of unicellular organisms are grouped into several types. The most numerous are types of Sarcoflagellates And ciliate type.
Type of Ciliates totals more than 7,500 species. This is in highly organized protozoa that have a constant body shape.
A typical representative of the type is ciliate-slipper. The body of the ciliate is covered with a dense shell. It has two cores: large ( macronucleus), which regulates all life processes, and small ( micronucleus), which plays a major role in reproduction. Ciliate slipper feeds on algae, bacteria, and some protozoa. The cilia of the ciliate oscillate, which “promotes” food into the mouth 
e, and then into the pharynx, at the bottom of which digestive vacuoles where food is digested and nutrients are absorbed. Through powder– a special organ – undigested residues are removed. Selection functions are carried out contractile vacuoles. Reproduces ciliate-slipper, like amoeba, asexually(transverse division of the cytoplasm, the small nucleus divides mitotically, the large nucleus divides amitotically). Characteristic and sexual process– conjugation. This is a temporary connection between two individuals, between which a cytoplasmic bridge, through which they exchange separated small nuclei. The sexual process serves to update genetic information.
Ciliates are link in food chains. Living in the stomachs of ruminants, ciliates contribute to their digestion.
A typical representative is common amoeba.
Amoeba lives in freshwater bodies. Her body shape is not constant. The pseudopods also serve to capture food - bacteria, unicellular algae, and some protozoa. Undigested residues are thrown out from any place in the amoeba. The animal breathes with its entire body surface: oxygen dissolved in water penetrates into the amoeba’s body through diffusion, and carbon dioxide formed during respiration in the cell is released outside. The animal is irritable. Amoeba reproduces division: First, the nucleus divides mitotically, and then the cytoplasm divides. Under unfavorable conditions it occurs encystment.
Typical presentation 
tel Zhgutikov - green euglena– has a spindle-shaped shape. A long thin flagellum extends from the front end of the euglena's body: by rotating it, the euglena moves, as if screwing into the water. In the cytoplasm of euglena there is a nucleus and several colored oval bodies - chromatophores(20 pieces) containing chlorophyll(in the light, euglena feeds autotrophically). Photosensitive peephole helps euglena find illuminated places. When kept in the dark for a long time, euglena loses its chlorophyll and switches to feeding on ready-made organic substances, which it absorbs from the water over the entire surface of its body. Euglena breathes through the entire surface of its body. Reproduction is carried out division in two(longitudinal).
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More than 2 million animals live on Earth, and this list is constantly growing.
The science that studies the structure, behavior, and vital functions of animals is called zoology.
The sizes of animals range from a few microns to 30 m. Some of them are visible only through a microscope, such as amoeba and ciliates, while others are giants. These are whales, elephants, giraffes. The habitat of animals is very diverse: water, land, soil and even living organisms.
Having common features with other representatives of eukaryotes, animals also have significant differences. Animal cells lack membranes and plastids. They feed on ready-made organic substances. A significant part of animals actively move and have special organs of movement.
animal kingdom divided into two sub-kingdoms: unicellular (protozoa) And multicellular.
Rice. 77. Protozoa: 1 - amoeba; 2 - green euglena; 3 - foraminifera (shells); 4 - ciliate-slipper ( 1 - large core; 2 - small core; 3 - cell mouth; 4 - cell pharynx; 5 - digestive vacuole; 6 - powder; 7 - contractile vacuoles; 8 - eyelashes)
Protozoa are divided into several types, the most widespread and significant of which are Sarcodaceae, Flagellates, Sporozoans and Ciliates.
Sarcodaceae (Rhizopods). A typical representative of Sarcodaceae is the amoeba. Amoeba is a freshwater, free-living animal that does not have a constant body shape. When an amoeba cell moves, it forms pseudopodia, or pseudopods, which also serve to capture food. In the cell, the nucleus and digestive vacuoles are clearly visible, which are formed at the site where the amoeba captures food. In addition, there is also contractile vacuole, through which excess water and liquid metabolic products are removed. Amoeba reproduces by simple division. Respiration occurs across the entire surface of the cell. Amoeba has irritability: a positive reaction to light and food, a negative reaction to salt.
Testate amoebas - foraminifera have an external skeleton - a shell. It consists of an organic layer impregnated with limestone. The shell has numerous openings - holes through which pseudopodia protrude. The size of the shells is usually small, but in some species it can reach 2-3 cm. The shells of dead foraminifera form sediments on the seabed - limestones. Other shell amoebas also live there - radiolarians (rays). Unlike foraminifera, they have an internal skeleton, which is located in the cytoplasm and forms needles - rays, often of an openwork design. In addition to organic matter, the skeleton contains strontium salts - this is the only case in nature. These needles form the mineral celestine.
Flagellates. These microscopic animals have a constant body shape and move with the help of flagella (one or more). Euglena green - a single-celled organism that lives in water. Its cell is spindle-shaped and has one flagellum at its end. At the base of the flagellum there is a contractile vacuole and a light-sensitive eye (stigma). In addition, the cell contains chromatophores containing chlorophyll. Therefore, euglena photosynthesizes in the light and feeds on ready-made organic substances in the dark.
After several asexual generations, cells appear in erythrocytes from which gametes develop. For further development, they must enter the intestines of the Anopheles mosquito. When a mosquito bites a person with malaria, gametes are carried through the blood into the digestive tract, where sexual reproduction and sporozoite formation occur.
Ciliates- the most complex representatives of protozoa, there are more than 7 thousand species. One of the most famous representatives - ciliate-slipper. This is a fairly large single-celled animal that lives in fresh water bodies. Its body is shaped like the footprint of a shoe and is covered with a dense shell with cilia, the synchronous movement of which ensures the movement of the ciliate. It has a cellular mouth surrounded by cilia. With their help, the ciliate creates a current of water, with which bacteria and other small organisms on which it feeds enter the “mouth”. A digestive vacuole is formed in the body of the ciliate, which can move throughout the cell. Undigested food remains are thrown out through a special place - powder. Ciliates have two nuclei - large and small. The small nucleus takes part in the sexual process, and the large one controls protein synthesis and cell growth. The slipper reproduces both sexually and asexually. Asexual reproduction after several generations is replaced by sexual reproduction. Next (§ 58-65) multicellular organisms of the Animal Kingdom are considered.
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§ 56. Seed plants§ 58. Animal Kingdom. Multicellular organisms: sponges and coelenterates
Organisms whose body contains only one cell are classified as protozoa. They can have different shapes and all kinds of methods of movement. Everyone knows at least one name that the simplest living organism has, but not everyone realizes that it is exactly such a creature. So, what are they, and what types are the most common? And what kind of creatures are these? Like the most complex and coelenterate organisms, unicellular organisms deserve detailed study.
Subkingdom unicellular
Protozoa are the smallest creatures. Their bodies have all the functions necessary for life. Thus, the simplest single-celled organisms are capable of showing irritability, moving and reproducing. Some have a constant body shape, while others constantly change it. The main component of the body is the nucleus surrounded by cytoplasm. It contains several types of organelles. The first are general cellular. These include ribosomes, mitochondria, the Galgi apparatus, and the like. The second ones are special. These include digestive and almost all protozoan single-celled organisms can move without much difficulty. In this they are helped by pseudopods, flagella or cilia. A distinctive feature of organisms is phagocytosis - the ability to capture solid particles and digest them. Some can also carry out photosynthesis.
How do unicellular organisms spread?
Protozoa can be found everywhere - in fresh water, soil or sea. Their ability to encyst provides them with a high degree of survival. This means that under unfavorable conditions the body enters a resting stage, becoming covered with a dense protective shell. The creation of a cyst promotes not only survival, but also proliferation - this way the organism can end up in more comfortable environment, where it will receive food and the opportunity to reproduce. Protozoan organisms accomplish the latter by dividing into two new cells. Some also have the ability to reproduce sexually, and there are species that combine both.
Amoeba
It is worth listing the most common organisms. Protozoa are often associated with this particular species - amoebas. They do not have a permanent body shape, and use pseudopods for movement. With them, the amoeba captures food - algae, bacteria or other protozoa. Surrounding it with pseudopods, the body forms a digestive vacuole. From it, all substances obtained enter the cytoplasm, and undigested substances are thrown out. The amoeba carries out respiration throughout the body using diffusion. Excess water is removed from the body by the contractile vacuole. The process of reproduction occurs through nuclear division, after which two cells are produced from one cell. Amoebas are freshwater. Protozoa are found in humans and animals, in which case they can lead to a variety of diseases or worsen the general condition.
Euglena green
Another organism common in fresh water bodies is also a protozoa. Euglena green has a spindle-shaped body with a dense outer layer of cytoplasm. The anterior end of the body ends with a long flagellum, with the help of which the body moves. In the cytoplasm there are several oval chromatophores in which chlorophyll is located. This means that in the light, euglena feeds autotrophically - not all organisms can do this. Protozoa navigate with the help of an eye. If the euglena stays in the dark for a long time, the chlorophyll will disappear and the body will switch to a heterotrophic method of nutrition with the absorption of organic substances from the water. Like amoebas, these protozoa reproduce by division and also breathe throughout the body.
Volvox
Among unicellular organisms there are also colonial organisms. A protozoan called volvox lives this way. They have a spherical shape and gelatinous bodies formed by individual members of the colony. Each Volvox has two flagella. The coordinated movement of all cells ensures movement in space. Some of them are capable of reproduction. This is how daughter Volvox colonies arise. The simplest algae known as Chlamydomonas also have the same structure.
Ciliate slipper
This is another common inhabitant of fresh water. The ciliates get their name from the shape of their own cell, which resembles a shoe. The organelles used for movement are called cilia. The body has a constant shape with a dense shell and two cores, small and large. The first is necessary for reproduction, and the second controls all life processes. Ciliates use bacteria, algae and other single-celled organisms as food. Protozoa often create a digestive vacuole; in slippers it is located on certain place at the mouth opening. To remove undigested residues, powder is present, and excretion is carried out using a contractile vacuole. This is typical for ciliates, but it can also be accompanied by the union of two individuals to exchange nuclear material. This process is called conjugation. Among all freshwater protozoa, the slipper ciliate is the most complex in its structure.
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