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 eat 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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Instructions

More than 3.5 billion years ago, the first living organisms consisting of a single cell appeared in the depths of the sea. Some believe that unicellular spores could have ended up on Earth with the help of meteorites arriving from outer space. Most scientists associate the origin of life with chemical reactions occurring in the atmosphere and oceans.

The body, consisting of only one cell, is a complete organism with microscopic dimensions, but in the classes of protozoa there are species that reach lengths of several millimeters and even centimeters. Among these organisms, separate classes are distinguished, characterized by certain characteristics.

Amoeba is a colorless lump that constantly changes shape and lives in fresh water. The pseudopods help this organism living in the mud and on the leaves of rotting plants to move imperceptibly to another place. Amoebas feed on algae and bacteria, and they reproduce by dividing into two parts.

The structure of other representatives of the protozoa - ciliates - is more complex. The cell of these organisms contains two nuclei that perform different functions, and the cilia they have are a means of transportation.

Resembling the appearance of elegant women's shoes, the slipper ciliate has a constant body shape and lives in shallow stagnant water. Arranged in regular rows, numerous eyelashes oscillate in waves, and the shoe moves. Ciliates feed on bacteria, unicellular algae, and dead organic matter (detritus). The cilia help guide food into the mouth, which then moves toward the pharynx. The shoe can be voracious if it lives in favorable conditions. During asexual reproduction, the body of the ciliate is divided in half in the transverse direction, and the daughter individuals begin to develop anew. But after a few generations, such reproduction will be replaced by a sexual process called conjugation.

The body of representatives of the flagellate class, covered with an elastic membrane, determines its shape. These protozoa have one or more flagella and nuclei. Reproduction depends on the type of single-celled organism.

Green Euglena lives in stagnant fresh water bodies. She swims quickly due to the streamlined shape of her body. A single flagellum, located in front and screwed into the water, facilitates movement. This simple organism eats in a special way, which helps it survive under different living conditions. The most illuminated areas, where the chlorophyll-containing body of the euglena is arranged for favorable photosynthesis, are found by it using a light-sensitive red eye. If euglena remains in the dark for a long time, the chlorophyll is destroyed. In such cases, organic substances serve as food. It reproduces by dividing the cell longitudinally into two parts. If conditions are favorable, this single-celled creature is capable of reproducing every day.

You will find out who discovered single-celled organisms from this article.

Who discovered single-celled organisms?

Unicellular organisms are organisms that have only one cell in their body, which has a nucleus. They are both a cell and an independent organism. These include unique and invisible to the naked eye protozoa and bacteria. Single-celled organisms range in size from 0.2 to 10 microns.

The study of protozoa began later than other groups of animals. This is due to their small size, so only the invention of the microscope moved everything forward.

Dutchman Anthony Leeuwenhoek in 1675 he examined a drop of water under a microscope and was the first to discover a large number of microscopic organisms in water, which were the simplest single-celled organisms.

This discovery aroused great interest in them. Back then they were called “liquor small animals.” In the 17th-18th centuries, knowledge about them was chaotic and uncertain, which gave rise to Carl Linnaeus, another scientist, in his “System of Nature”, united all unicellular organisms into one genus of protozoa, which he called “Chaos infusorium”.

He made a huge contribution to the development of single-celled, microscopic organisms Muller. In his essay, he described 377 of their species. The scientist proposed species and generic names in the system of protozoa.

In the 18th and early 19th centuries, the study of unicellular organisms acquired the opposite diametrical character. For example, Ehrenberg described single-celled organisms as complex creatures that have different organ systems. Another scientist, Dujardin, on the contrary, argued that they have no internal organization and their body is built on sarcode - a structureless semi-liquid living substance.

A mysterious group of microscopic single-celled organisms, considered as a subkingdom of the kingdom Animalia, and sometimes separated into a separate kingdom.

Protozoa unicellular

People first learned about the existence of protozoa in the 7th century from the discovery of a Dutch naturalist; he was the first to observe them in a drop of water, using a microscope he invented.

Over many years of the development of biology, with the advent of electron microscopy and genetics, this group of organisms was increasingly studied and its systematics underwent significant changes.

Today they are increasingly defined as a separate kingdom, since among the simplest unicellular organisms there are organisms that have characteristics different from those of animals. For example, Euglena greena has the ability for photosynthesis, characteristic of plants. Or, for example, the Labyrinthula type - previously classified as mushrooms.

The cell of the simplest unicellular organism has an organization common to eukaryotic cells. But most protozoa also have specific organelles:

• contractile vacuoles, which serve to remove excess fluid and maintain the desired osmotic pressure;
• various organelles of movement: flagella, cilia and pseudopodia (pseudopods). Pseudopaedes, as the name implies, are not real organelles; they are just protrusions of the cell.

Subkingdom (or kingdom) Protozoa unicellular represented by 7 main types:

Let's look at the types in more detail

Type of Sarcomastigophora

It is divided into three subtypes: Flagellates, Opalines, Sarcodaceae.

Flagellates- a group of organisms, as the name suggests, they are characterized by common organelles of movement - flagella.

Habitats: fresh waters, seas, soils. There are flagellates that live in multicellular organisms. Flagellates are characterized by maintaining a constant body shape, thanks to the pellicle, or shell.

They reproduce mainly asexually: by longitudinal division in two.

Types of nutrition: heterotrophic, autotrophic, mixotrophic.

Let's look at the structure using an example Euglena green.

• It is characterized by a mixotrophic (mixed) type of nutrition.
• There are special organelles - chlorophyll-containing chromatophores, in which the process of photosynthesis occurs, similar to the photosynthesis of plants.
• Due to the ability to photosynthesize, Euglena greena has a light-sensitive organelle - stigma, it is also sometimes called a light-sensitive ocellus.
• Removal of excess fluid occurs due to the work of the contractile vacuole.

Some types of trypanosomes cause sleeping sickness. The carrier of African trypanosomiasis (as this disease is scientifically called) is the tsetse fly. This is a blood-sucking insect.

Trypanosomes. They float and cause a dangerous disease.

Giardia. Looks like a pear. Mnemonic rule: Giardia is in the shape of a pear, so to avoid getting infected, you need to wash the pear.

Sarcodidae are protozoans that do not have a constant body shape.

The organelles of movement are pseudopodia (pseudopods). Previously, sarcodids and flagellates were classified into two different types, contrasting their organelles of movement: pseudopodia and flagella. But it turned out that at some stages of development, sarcodids have flagella, and some organisms have characteristics of both flagella and sarcodids.

The Sarcodaceae subtype includes the following classes: Roothoppers, Radiolarians (Radiants), Solarians.

Roots. This class includes the orders: Amoebas, testate amoebas, foraminifera.

• Amoebas feed by phagocytosis. A digestive vacuole forms around the captured piece of food.
• They reproduce by dividing in two.
• If Euglena green moves towards the light (since it needs it for photosynthesis), then Amoeba vulgaris, on the contrary, moves away from the light. The amoeba also avoids other irritants.

Usually the following experiment is considered: a salt crystal is placed on one side of a drop of water with an amoeba, and one can observe the movement of the amoeba in the opposite direction.

Testate amoebas. They have a similar structure to amoebas, only they have a shell with a hole (mouth) from which pseudopodia “look out.” All testate amoebae are free-living and live in fresh waters. Since the shell cannot split in two, division occurs in a special way: a daughter individual is formed, but it is not immediately separated from the mother. A new shell is formed around the daughter shell. Then the amoebas separate.

Foraminifera are one of the most numerous orders of the simplest unicellular organisms - rhizomes. They are part of marine plankton. Foraminifera, like testate amoebae, have a shell.

Radiolarians very interesting microorganisms that are part of marine plankton. They are characterized by the presence of an internal skeleton. Radiolarians have the largest number of chromosomes of any living creature.

Radiolarians, Foraminifera and testate amoebae die, leaving behind shells and internal skeletons. The accumulation of all this goodness forms deposits of limestone, chalk, quartz and other things.

Solnechniki - a small group of protozoa. They got their name due to the similarity in appearance of the pseudopodia with the rays of the sun. Such pseudopodia are called axopodia.

Type of Ciliates

Characteristics:

• constant body shape due to the presence of pellicle;
• Some ciliates are characterized by specific protective organelles;
• nuclear dualism, i.e. the presence of two nuclei: a polyploid macronucleus (vegetative nucleus) and a diploid micronucleus (generative nucleus). This situation with the nuclei is necessary for the sexual process to occur: . And direct reproduction is only asexual: by longitudinal division in two.
• The organelles of movement are cilia. The structure of cilia is the same as that of flagella.

Let's look at the structure using the example of the slipper ciliate. This is a classic, you need to know this.

The slipper ciliate is a predator. Feeds on bacteria. The prey is captured by specialized cilia and directed into the cell mouth, followed by the cell pharynx, then the digestive vacuole. Undigested residues are released through the powder into the external environment.

The digestive system of ruminants contains symbiotic ciliates that help digest fiber:

Trumpeter ciliate

Suvoiki are ciliates leading an attached lifestyle.

Type Apicomplexa

For example, protozoa of the genus Plasmodium cause a dangerous disease - malaria.

Type Labyrinthula

Protozoa are single-celled, free-living colonial protozoa that live on seaweed. Previously classified as mushrooms. They got this name because the colony really resembles a labyrinth.

Type Ascetosporidia

Type Myxosporidium

Microsporidia type

So, we have looked at the types of kingdom (sub-kingdom) of the simplest single-celled organisms. To consolidate all the knowledge, let's look at the taxonomy:

Despite their small size, the simplest unicellular organisms are of great importance:

• protozoa are included in food chains;
• form plankton;
• act as saprophytes, absorbing decaying remains;
• protozoa clean water bodies not only of rotting residues, but also of bacteria;
• participate in the formation of soils and deposits of chalk and limestone.
• are good indicators of water purity.
• autotrophic and mixotrophic protozoa, together with plants, perform a very important mission - replenishing the atmosphere with oxygen.

Back forward

Attention! Slide previews are for informational purposes only and may not represent all the features of the presentation. If you are interested in this work, please download the full version.

All living organisms are divided according to the number of cells: unicellular and multicellular.

Single-celled organisms include: unique and invisible to the naked eye bacteria and protozoa.

Bacteria microscopic single-celled organisms ranging in size from 0.2 to 10 microns. The body of bacteria consists of one cell. Bacterial cells do not have a nucleus. Among bacteria there are mobile and immobile forms. They move with the help of one or more flagella. Cells are varied in shape: spherical, rod-shaped, convoluted, in the form of a spiral, a comma.

Bacteria are found everywhere, inhabiting all habitats. The largest number of them is found in the soil at a depth of up to 3 km. Found in fresh and salt water, on glaciers and in hot springs. There are many of them in the air, in the bodies of animals and plants. The human body is no exception.

Bacteria unique orderlies of our planet. They destroy the complex organic substances of animal and plant corpses, thereby contributing to the formation of humus. Convert humus into minerals. They absorb nitrogen from the air and enrich the soil with it. Bacteria are used in industry: chemical (for producing alcohols, acids), medical (for producing hormones, antibiotics, vitamins and enzymes), food (for producing fermented milk products, pickling vegetables, making wine).

All the simplest consist of one cell (and are simply arranged), but this cell is a whole organism leading an independent existence.

Amoeba (microscopic animal) looks like a small (0.1-0.5 mm), colorless gelatinous lump, constantly changing its shape (“amoeba” means “changeable”). It feeds on bacteria, algae and other protozoa.

Ciliate slipper(a microscopic animal, its body is shaped like a shoe) - has an elongated body 0.1-0.3 mm long. She swims with the help of cilia covering her body, with the blunt end first. Feeds on bacteria.

Euglena green– elongated body, about 0.05 mm long. Moves with the help of a flagellum. It feeds like a plant in the light and like an animal in the dark.

Amoeba can be found in small shallow ponds with muddy bottoms (contaminated water).

Ciliate slipper- inhabitant of reservoirs with polluted water.

Euglena green– lives in ponds contaminated with rotting leaves, in puddles.

Ciliate slipper– cleans water bodies of bacteria.

After the death of the protozoa limescale deposits (for example, chalk) are formed; food for other animals. Protozoa are the causative agents of various diseases, including many dangerous ones that lead patients to death.

System of concepts

Educational tasks:

1. introduce students to representatives of single-celled organisms; their structure, nutrition, meaning;
2. continue to develop communication skills, work in pairs (groups);
3. continue to develop skills: compare, generalize, draw conclusions when completing tasks (aimed at consolidating new material).

Lesson type: A lesson in learning new material.

Lesson type: productive (search), using ICT.

Methods and methodological techniques

• Visual– slide show (“Kingdoms of Living Nature”, “Bacteria”, “Protozoa”);
• Verbal– conversation (instructive conversation); survey: frontal, individual; explanation of new material.

Means of education: Slide presentations: “Bacteria”, “Protozoa”, textbook.

During the classes

I. Class organization (3 min.)

II. Homework (1-2 min.)

III. Updating knowledge (5-10 min.)

(Updating knowledge begins with demonstrating a drawing of the Kingdom of Living Nature).

Look carefully at the picture, to which kingdoms do the organisms shown in the picture belong? (presentation 16 slide 1), (to bacteria, fungi, animals, plants).

Rice. 1 Kingdoms of Wildlife

How many kingdoms of living nature are there? (4) (the question is asked in order to bring knowledge into the system and come to a diagram, slide 2)

What are all living organisms made of? (from cells)

How many and into what groups can all living organisms be divided? (slide 3), (depending on the number of cells)

*students may not name representatives of unicellular organisms (** most likely they will not name protozoa because they are not yet familiar with them).

IV. Lesson progress (20-25 min.)

We remembered: the kingdoms of living nature; and what groups organisms are divided into (according to the number of cells), let's make assumptions about what we will study today. (Students express their opinions, the teacher guides them and “leads” them to the topic) (slide 4).

Topic: Unicellular organisms

What do you think is the purpose of our lesson? (Students’ assumptions, the teacher guides and corrects).

Target: Introduction to the structure of single-celled organisms

In order to achieve this goal, we will go on a “Journey to the Land of Bacteria and Protozoa” (slide 6)

(Independent work of students with presentations: “Bacteria” ( presentation 2), "The simplest" ( presentation 1) according to the teacher's instructions)

(Before starting work, a physical exercise “Flies” is carried out, slide 5)

Table 1: Unicellular animals(slides 7, 8)

Name of unicellular organisms (name: protozoa; bacteria)	Habitat (where do they live?)	Nutrition (who or what do they eat?)	Structure, body dimensions (in mm)	Meaning (benefit, harm)
Bacteria	everywhere (soil, air, water, etc.)	most bacteria feed on ready-made organic matter	small sizes; cells do not have a nucleus	orderlies, increase soil fertility, used in the food industry, to obtain medicines
Protozoa:
Amoeba	in ponds	bacteria, algae, other protozoa	0.1-0.5, gelatinous lump	food for other animals, causative agent of human and animal diseases
Ciliate slipper	in reservoirs	bacteria	0.1-0.3; looks like a shoe, the body is covered with eyelashes	food for other animals, cleans water bodies of bacteria
Protozoa:
Euglena green	in ponds, puddles	Feeds like a plant in the light and like an animal in the dark	0.05, elongated body, with flagellum	food for other animals

This work is followed by a discussion of the table (and, therefore, the new material with which the children became acquainted during the “Journey”).

(After discussion, we return to the goal, have you completed it?)

(Students formulate conclusions about whether these are single-celled organisms?, slide 9)

V. Lesson summary (5 min.)

Reflection on questions:

• Did I like the lesson?
• Who did I enjoy working with most in class?
• What did I understand from the lesson?

Literature:

1. Textbook: A. A. Pleshakov, N. I. Sonin. Nature. 5th grade. – M.: Bustard, 2006.
2. Zayats R.G., Rachkovskaya I.V., Stambrovskaya V.M. Biology. Great reference book for schoolchildren. – Minsk: “Higher School”, 1999.