It is typical for all representatives of unicellular eukaryotes. Unicellular and multicellular organisms. Tissues and organs. Who are unicellular organisms

Main groups

Main article: Groups

The main groups of unicellular:

• Ciliates (12 microns - 3 mm)...
• Amoeba (up to 0.3 mm)
• Eyelash
• Euglena

prokaryotes

Prokaryotes are predominantly unicellular, with the exception of some cyanobacteria and actinomycetes. Among eukaryotes, protozoa, a number of fungi, and some algae have a unicellular structure. Unicellular organisms can form colonies.

Appearance and evolution

It is believed that the first living organisms of the Earth were single-celled. The most ancient of them are bacteria and archaea. Unicellular animals and prokaryotes were discovered by A. Leeuwenhoek.

eukaryotes

Eukaryotes, or Nuclear (lat. Eucaryota from Greek εύ- - good and κάρυον - core) - the domain (superkingdom) of living organisms whose cells contain nuclei. All organisms except bacteria and archaea are nuclear (viruses and viroids are also not eukaryotes, but not all biologists consider them to be living organisms).

Animals, plants, fungi, and the group of organisms collectively called protists are all eukaryotic organisms. They can be unicellular and multicellular, but all have a common cell plan. It is believed that all these dissimilar organisms have a common origin, so the nuclear group is considered as a monophyletic taxon of the highest rank. According to the most common hypotheses, eukaryotes appeared 1.5-2 billion years ago. An important role in the evolution of eukaryotes was played by symbiogenesis - a symbiosis between a eukaryotic cell, apparently already having a nucleus and capable of phagocytosis, and bacteria swallowed by this cell - precursors of mitochondria and chloroplasts.

Notes

see also

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Class: 5

Presentation for the lesson

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

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

bacteria microscopic unicellular 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 diverse in shape: spherical, rod-shaped, convoluted, in the form of: spiral, comma.

bacteria are ubiquitous, inhabiting all habitats. The greatest 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 organisms of animals and plants. The human body is no exception.

bacteria kind of nurses of our planet. They destroy the complex organic matter of the corpses of animals and plants, 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 the production of alcohols, acids), medical (for the production of hormones, antibiotics, vitamins and enzymes), food (for the production of fermented milk products, pickling vegetables, making wine).

All protozoa They 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.

Infusoria 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, blunt end forward. It feeds on bacteria.

Euglena green- the body is elongated, 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 a muddy bottom (polluted water).

Infusoria slipper- an inhabitant of reservoirs with polluted water.

Euglena green- lives in ponds polluted with rotting leaves, in puddles.

Infusoria slipper- cleans water from bacteria.

After the death of protozoa lime deposits are formed (for example, chalk) food for other animals. The simplest pathogens of various diseases, among which there are many dangerous, leading patients to death.

Concept system

Educational tasks:

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

Lesson type: Lesson learning new material.

Type of lesson: productive (search), using ICT.

Methods and methodological techniques

• Visual- slide show ("Kingdoms of wildlife", "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. Organization of the class (3 min.)

II. Homework (1-2 min.)

III. Actualization of knowledge (5-10 min.)

(The actualization of knowledge begins with a demonstration of a drawing of the Kingdom of Wildlife).

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

Rice. 1 Kingdoms of wildlife

How many kingdoms of wildlife? (4) (the question is asked in order to bring knowledge into the system and come to a scheme, 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 wildlife; 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 opinion, the teacher directs them and “leads” to the topic) (slide 4).

Topic: Unicellular organisms

What do you think is the purpose of our lesson? (Assumptions of students, the teacher directs, corrects).

Target: Acquaintance with the structure of unicellular organisms

In order to fulfill our goal, we will go on a “Journey to the country of bacteria and protozoa” (slide 6)

(Independent work of students with presentations: "Bacteria" ( presentation 2), "The simplest" ( presentation 1) as instructed by the teacher)

(Before starting work, a physical minute "Flies" is held, slide 5)

Table 1: Unicellular animals(slides 7, 8)

This work is followed by a discussion of the table (and, consequently, the new material that the guys got acquainted with during the Journey).

(After discussion, we return to the goal, did you complete it?)

(Students formulate conclusions about whether such unicellular organisms are the same?, slide 9)

V. Summing up the lesson (5 min.)

Reflection on questions:

• Did I enjoy the lesson?
• Whom 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. Grade 5 – M.: Bustard, 2006.
2. Zayats R.G., Rachkovskaya I.V., Stambrovskaya V.M. Biology. Great reference book for schoolchildren. - Minsk: "The Highest School", 1999.

The extraordinary diversity of living beings on the planet forces us to find different criteria for their classification. Thus, they are classified as cellular and non-cellular forms of life, since cells are the structural unit of almost all known organisms - plants, animals, fungi and bacteria, while viruses are non-cellular forms.

unicellular organisms

Depending on the number of cells that make up the body, and the degree of their interaction, single-celled, colonial and multicellular organisms are distinguished. Despite the fact that all cells are morphologically similar and capable of performing the usual functions of a cell (metabolism, maintaining homeostasis, development, etc.), the cells of unicellular organisms perform the functions of an integral organism. Cell division in unicellular organisms entails an increase in the number of individuals, and there are no multicellular stages in their life cycle. In general, unicellular organisms have the same cellular and organismal levels of organization. The overwhelming majority of bacteria, part of animals (protozoa), plants (some algae) and fungi are unicellular. Some taxonomists even propose to distinguish unicellular organisms into a special kingdom - protists.

colonial organisms

Colonial organisms are called organisms in which, in the process of asexual reproduction, the daughter individuals remain connected to the mother organism, forming a more or less complex association - a colony. In addition to colonies of multicellular organisms, such as coral polyps, there are also colonies of unicellular organisms, in particular pandorina and eudorina algae. Colonial organisms, apparently, were an intermediate link in the process of the emergence of multicellular organisms.

Multicellular organisms

Multicellular organisms undoubtedly have a higher level of organization than unicellular organisms, since their body is formed by many cells. Unlike colonial cells, which can also have more than one cell, in multicellular organisms, cells specialize in performing various functions, which is also reflected in their structure. The price for this specialization is the loss of their cells' ability to exist independently, and often to reproduce their own kind. The division of a single cell leads to the growth of a multicellular organism, but not to its reproduction. Ontogeny of multicellular organisms is characterized by the process of fragmentation of a fertilized egg into many blastomere cells, from which an organism with differentiated tissues and organs is subsequently formed. Multicellular organisms are generally larger than unicellular organisms. An increase in the size of the body in relation to their surface contributed to the complication and improvement of metabolic processes, the formation of the internal environment and, ultimately, provided them with greater resistance to environmental influences (homeostasis). Thus, multicellular organisms have a number of advantages in organization compared to unicellular organisms and represent a qualitative leap in the evolutionary process. Few bacteria are multicellular, most plants, animals and fungi.

Differentiation of cells in multicellular organisms leads to the formation of tissues and organs in plants and animals (except for sponges and coelenterates).

Tissues and organs

Tissue is a system of intercellular substance and cells that are similar in structure, origin and perform the same functions.

There are simple tissues, consisting of cells of one type, and complex, consisting of several types of cells. For example, the epidermis in plants consists of the actual integumentary cells, as well as guard and side cells that form the stomatal apparatus.

Organs are formed from tissues. The organ consists of several types of tissues related structurally and functionally, but usually one of them predominates. For example, the heart is formed mainly by muscle, and the brain - by nervous tissue. The composition of the leaf blade of a plant includes the integumentary tissue (epidermis), the main tissue (chlorophyll-bearing parenchyma), conductive tissues (xylem and phloem), etc. However, the main tissue prevails in the leaf.

Organs that perform common functions form organ systems. In plants, educational, integumentary, mechanical, conductive and basic tissues are distinguished.

Plant tissues

Educational fabrics

Cells of educational tissues (meristems) retain the ability to divide for a long time. Due to this, they take part in the formation of all other types of tissues and ensure the growth of the plant. Apical meristems are located at the tips of shoots and roots, and lateral meristems (for example, cambium and pericycle) are located inside these organs.

Integumentary tissues

Integumentary tissues are located on the border with the external environment, i.e., on the surface of roots, stems, leaves and other organs. They protect the internal structures of the plant from damage, the effects of low and high temperatures, excessive evaporation and desiccation, the penetration of pathogens, etc. In addition, integumentary tissues regulate gas exchange and water evaporation. Covering tissues include the epidermis, periderm and cortex.

mechanical fabrics

Mechanical tissues (collenchyma and sclerenchyma) perform supporting and protective functions, giving strength to organs and forming the "internal skeleton" of the plant.

Conductive tissues

Conductive tissues ensure the movement of water and substances dissolved in it in the plant body. Xylem delivers water with dissolved minerals from the roots to all organs of the plant. Phloem transports solutions of organic substances. Xylem and phloem are usually located side by side, forming layers or vascular bundles. In the leaves, they can be easily seen in the form of veins.

Main fabrics

The underlying tissues, or parenchyma, make up the bulk of the plant's body. Depending on the location in the plant's body and the characteristics of its habitat, the main tissues are able to perform various functions - carry out photosynthesis, store nutrients, water or air. In this regard, chlorophyll is distinguished between the nasal, storage, aquiferous and air-bearing parenchyma.

As you remember from the 6th grade biology course, vegetative and generative organs are isolated from plants. The vegetative organs are the root and shoot (stem with leaves and buds). Generative organs are divided into organs of asexual and sexual reproduction.

The organs of asexual reproduction in plants are called sporangia. They are located singly or combined into complex structures (for example, sori in ferns, spore-bearing spikelets in horsetails and club mosses).

The organs of sexual reproduction provide the formation of gametes. Male (anteridia) and female (archegonia) organs of sexual reproduction develop in mosses, horsetails, club mosses and ferns. Gymnosperms are characterized only by archegonia, which develop inside the ovule. Antheridia are not formed in them, and male sex cells - spermine - are formed from the generative cell of pollen grains. Flowering plants lack both antheridia and archegonia. Their generative organ is a flower, in which the formation of spores and gametes, fertilization, the formation of fruits and seeds take place.

Animal tissues

epithelial tissues

Epithelial tissues cover the body from the outside, line the body cavities and walls of hollow organs, and are part of most glands. The epithelial tissue consists of cells that are tightly adjacent to each other, the intercellular substance is not developed. The main functions of epithelial tissues are protective and secretory.

Connective tissues

Connective tissues are characterized by a well-developed intercellular substance, in which cells are located singly or in groups. The intercellular substance, as a rule, contains a large number of fibers. The tissues of the internal environment are the most diverse group of animal tissues in structure and function. These include bone, cartilage and adipose tissues, connective tissues proper (dense and loose fibrous), as well as blood, lymph, etc. The main functions of the tissues of the internal environment are supporting, protective, and trophic.

Muscle tissues

Muscle tissues are characterized by the presence of contractile elements - myofibrils located in the cytoplasm of cells and providing contractility. Muscle tissue performs a motor function.

nervous tissue

Nervous tissue consists of nerve cells (neurons) and glial cells. Neurons are capable of being excited in response to the action of various factors, generating and conducting nerve impulses. Glial cells provide nutrition and protection for neurons, the formation of their membranes.

Animal tissues are involved in the formation of organs, which, in turn, are combined into organ systems. In the body of vertebrates and humans, the following organ systems are distinguished: bone, muscle, digestive, respiratory, urinary, reproductive, circulatory, lymphatic, immune, endocrine and nervous. In addition, animals have various sensory systems (visual, auditory, olfactory, gustatory, vestibular, etc.), with the help of which the body perceives and analyzes various stimuli from the external and internal environment.

It is common for any living organism to obtain building and energy material from the environment, metabolism and energy conversion, growth, development, ability to reproduce, etc. In multicellular organisms, various life processes (nutrition, respiration, excretion, etc.) are realized through interaction certain tissues and organs. At the same time, all life processes are under the control of regulatory systems. Thanks to this, a complex multicellular organism functions as a single whole.

In animals, the regulatory systems include the nervous and endocrine systems. They ensure the coordinated work of cells, tissues, organs and their systems, determine the integral reactions of the body to changes in the conditions of the external and internal environment, aimed at maintaining homeostasis. In plants, vital functions are regulated by various biologically active substances (for example, phytohormones).

Thus, in a multicellular organism, all cells, tissues, organs and organ systems interact with each other, function smoothly, due to which the organism is an integral biological system.

Unicellular organisms are organisms whose body consists of only one cell with a nucleus. They combine the properties of a cell and an independent organism.

Single-celled plants are the most common among algae. Unicellular algae live in fresh water, seas, soil.

Spherical unicellular chlorella is widespread in nature. It is protected by a dense shell, under which there is a membrane. The cytoplasm contains the nucleus and one chloroplast, which in algae is called the chromatophore. It contains chlorophyll. In the chromatophore, under the action of solar energy, organic substances are formed, as in the chloroplasts of land plants.

The spherical alga Chlorococcus ("green ball") is similar to chlorella. Some species of Chlorococcus also live on land. It is they who give the trunks of old trees growing in humid conditions a greenish color.

There are also mobile forms among unicellular algae, for example. The organ of its movement are flagella - thin outgrowths of the cytoplasm.

Unicellular fungi

Packs of yeast sold in stores are compressed unicellular yeast. The yeast cell has a typical fungal cell structure.

The unicellular phytophthora fungus infects living leaves and tubers of potatoes, leaves and fruits of tomatoes.

unicellular animals

Like unicellular plants and fungi, there are animals in which the functions of the whole organism are performed by one cell. Scientists have united everyone in a large group - the simplest.

Despite the diversity of organisms in this group, their structure is based on one animal cell. Since it does not contain chloroplasts, the protozoa are not able to produce organic substances, but consume them in finished form. They feed on bacteria. single-celled, pieces of decaying organisms. Among them are many pathogens of serious diseases in humans and animals (dysentery, Giardia, malarial plasmodium).

The protozoa, widely distributed in fresh water, include the amoeba and the ciliate shoe. Their body consists of cytoplasm and one (amoeba) or two (infusoria-shoe) nuclei. In the cytoplasm, digestive vacuoles are formed, in which food is digested. Excess water and metabolic products are removed through contractile vacuoles. Outside, the body is covered with a permeable membrane. Oxygen and water enter through it, and various substances are released. Most protozoa have special organs of movement - flagella or cilia. In ciliates-shoes, the entire body is covered with cilia, there are 10-15 thousand of them.

The movement of the amoeba occurs with the help of pseudopods - protrusions of the body. The presence of special organoids (organs of movement, contractile and digestive vacuoles) allows the cells of the simplest to perform the functions of a living organism.

Organisms whose body includes only one cell are protozoa. They can have a different shape and all kinds of ways of movement. Everyone knows at least one name that the simplest living organism bears, but not everyone realizes that this is just such a creature. So, what are they, and what types are most common? And what are these beings? Like the most complex and coelenterates, unicellular organisms deserve detailed study.

Subkingdom of unicellular

The simplest are the smallest creatures. Their bodies have all the functions necessary for life. So, the simplest unicellular organisms are able to show irritability, move and multiply. Some are distinguished by 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 Galji apparatus, and the like. The second is special. These include the digestive and almost all the simplest unicellular organisms can move around without much difficulty. In this they are helped by pseudopods, flagella or cilia. A hallmark of organisms is phagocytosis - the ability to capture solid particles and digest them. Some can also carry out photosynthesis.

How do unicellular organisms spread?

The simplest can be found everywhere - in fresh water, soil or the sea. The ability to encyst provides them with a high degree of survival. This means that under unfavorable conditions, the body falls into a dormant stage, being covered with a dense protective shell. Creating a cyst contributes not only to survival, but also to spread - this way the organism can find itself in a more comfortable environment, where it will receive food and the opportunity to reproduce. Protozoa carry out the latter by dividing into two new cells. Some also have the ability to sexually reproduce, there are species that combine both options.

Amoeba

It is worth listing the most common organisms. The simplest are often associated with this particular species - with amoebas. They do not have a permanent body shape, and instead use pseudopods for locomotion. With them, the amoeba captures food - algae, bacteria or other protozoa. Surrounding it with pseudopods, the body forms a digestive vacuole. From it, all the received substances enter the cytoplasm, and undigested is thrown out. The amoeba breathes through the whole body with the help of diffusion. Excess water is excreted from the body by the contractile vacuole. The process of reproduction occurs with the help of nuclear division, after which two cells are obtained from one cell. Amoebas are freshwater. There are protozoa in the body of 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, also belongs to the simplest. Euglena green has a spindle-shaped body with a dense outer layer of cytoplasm. The front 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 Euglena feeds autotrophically in the light - far from all organisms can do this. The simplest navigate with the help of an eye. If the euglena stays in the dark for a long time, chlorophyll will disappear and the body will switch to a heterotrophic mode of nutrition with the absorption of organic substances from the water. Like amoeba, these protozoa reproduce by fission and also breathe through their whole body.

Volvox

Colonial organisms are also found among unicellular organisms. The simplest, called Volvox, live just like that. 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 provides movement in space. Some of them are capable of reproduction. This is how volvox daughter colonies arise. The simplest algae, known as chlamydomonas, differ in the same structure.

Infusoria shoe

This is another common inhabitant of fresh water. The name of ciliates is due to the shape of their own cell, resembling a shoe. The organelles used for movement are called cilia. The body has a constant shape with a dense shell and two nuclei, small and large. The first is necessary for reproduction, and the second controls all life processes. Infusoria uses bacteria, algae and other single-celled organisms as food. The simplest often create a digestive vacuole; in shoes, it is located in a certain place at the mouth opening. Powder is present to remove undigested residues, and excretion is carried out using a contractile vacuole. It is typical for ciliates, but it can also be accompanied by the union of two individuals for the exchange of nuclear material. This process is called conjugation. Among all freshwater protozoa, the ciliate shoe is the most complex in its structure.