Answers to school textbooks
Characteristic features of the structure of unicellular animals:
Most are microscopic;
The body consists of one cell and is a whole organism with many functions inherent in it;
The cytoplasm is bounded by a membrane, which may be covered by a cell wall or shell;
Some species contain several nuclei per cell;
There are organelles of movement - flagella, cilia or pseudopodia, which can be temporary or permanent;
The digestive vacuole, formed as a result of pinocytosis or phagocytosis, carries out digestion. The vacuole may be absent in species that absorb nutrients through the entire surface of the body by diffusion; undigested food residues are thrown out of the vacuole;
The contractile (otherwise called excretory, pulsating, osmoregulatory) vacuole performs an excretory and osmoregulatory function; it occurs only in freshwater species;
There are no special respiratory organs; respiration occurs due to the diffusion of gases through the surface of the cell;
Under unfavorable conditions, they form a cyst (a dense shell is isolated on the surface, which makes it possible to protect the cell from external influences as much as possible).
2. Prove that the body plan of unicellular organisms corresponds to the general features of the organization of nuclear (eukaryotic) cells.
For all eukaryotic cells, both unicellular and multicellular organisms, it is characteristic:
The presence of the main parts: nucleus, cytoplasm and plasma membrane;
In the cytoplasm there are multi-membered organelles that perform special functions: the endoplasmic reticulum, the Golgi apparatus, mesosomes, ribosomes, mitochondria;
Plastids (in plants and some unicellular organisms), cell center, basal bodies of flagella and cilia;
The cell nucleus is surrounded by a nuclear membrane consisting of two membranes;
Any eukaryotic cell is characterized by a cytoskeleton - a system of microtubules and protein fibers that form the inner frame of the cell.
3. What special purpose organelles are found in unicellular organisms?
In Sarcodidae, for movement and capturing food, if necessary, pseudopodia are formed - pseudopodia. They are outgrowths of the cytoplasm, strengthened by the fibers of the cytoskeleton.
Flagellates move with the help of one or more flagella, and ciliates - thanks to numerous cilia.
In freshwater species, the contractile vacuole performs the excretory and osmoregulatory function.
In flagellates, the ability to move directionally under the influence of light is due to the activity of a light-sensitive eye - stigma.
4. What group of unicellular animals is the most ancient?
The most ancient classes are Flagellates and Sarcods. This is evidenced by the relative simplicity of their organization.
5. Tell us about the types of nutrition found in flagellates.
According to the way of feeding, flagellates are divided into three groups:
Autotrophic organisms that synthesize organic substances (carbohydrates) using the energy of sunlight, that is, they feed like real plants (all colored flagellates);
Heterotrophic organisms that use organic substances that have already been created by other organisms (colorless flagellates);
Mixotrophic organisms with a mixed type of nutrition, they are capable of photosynthesis, but also feed on organic substances, absorbing bacteria and other protozoa by phagocytosis (euglena green).
6. What animals do not have a permanent body shape?
Due to the underdeveloped and very mobile cell skeleton, formed by protein fibers and microtubules, many sarcoflagellates (for example, amoeba) do not have a permanent body shape. In addition, rapid rearrangements of the internal frame make it possible to easily change the shape of the body and quickly form pseudopodia.
7. How do protozoa reproduce?
As a rule, under favorable conditions, unicellular animals reproduce asexually - by cell division, and when unfavorable conditions occur - sexually.
8. What is the role of protozoa in nature? In human life?
Many protozoa play a significant role in the food chains of the reservoir: they absorb bacteria and some algae, and they, in turn, serve as food for many invertebrates, fish fry, and tadpoles.
In the seas and oceans, the shells of dead rhizomes, settling to the bottom, form layers of chalk.
9. What are pseudopodia?
Pseudopodia (pseudopodia) - organelles of movement. They are outgrowths of the cytoplasm, reinforced with elements of the cytoskeleton.
10. Can protozoa have shells?
Yes. The body of testate amoebae and foraminifera is enclosed in a single-chamber shell equipped with a hole - a mouth through which pseudopodia enter the environment. Shells are made of a chitin-like substance and can have a variety of shapes. In some representatives, the shells are purely organic, in others they are impregnated with calcium salts or encrusted with grains of sand.
11. What are the main features of the organization of foraminifera.
Foraminifera are mostly represented by sea rhizomes.
The main features of the organization of foraminifera:
They have a multi-chamber shell, consisting of calcium carbonate (due to which their remains form chalk deposits);
Pseudopodia extend from the shell, providing locomotion and food capture.
12, What protozoa have skeletal formations?
All eukaryotic cells have a cytoskeleton. In some cases, it is weakly expressed (as in rhizopods). In other representatives, the cell skeleton ensures the maintenance of a constant body shape over a long life cycle. The cytoskeleton is most pronounced in ciliates. The constant shape of the body is provided by thick bundles of fibers of the cytoskeleton adjacent to the membrane.
13. What organisms are called autotrophic?
Aetotrophs are organisms that can synthesize organic substances from inorganic substances.
Photosynthetic autotrophs form organic substances (carbohydrates) from carbon dioxide and water due to the energy of solar radiation.
Chemosynthetic autotrophs form organic molecules from inorganic ones due to the energy of chemical bonds of inorganic molecules.
14. What are colonies and how do they form in protozoa?
Colonies are large or small clusters of cells of single-celled organisms. The cells of the colony do not have permanent specialization. Colonies can form as a result of the division of individual cells that do not move away from each other and continue to coexist. Also, colonies can form as a result of incomplete cell division, when individuals that are not completely separated from each other remain connected to each other. Colonies differ both in form and in the way of development. The number of individuals that make up the colony ranges from 4 to 20 thousand cells.
In their structure, the protozoa are extremely diverse. The smallest ones are 2-4 microns in diameter (a micrometer is 0.001 mm). Their most common sizes are in the range of 50-150 microns, some reach 1.5 mm and are visible with the naked eye.
The amoeba has the simplest structure. The body of the amoeba is a lump of semi-liquid cytoplasm with a nucleus in the middle. The entire cytoplasm is divided into two layers: the outer, viscous - ectoplasm and the inner, much more liquid - endoplasm. These two layers are not sharply demarcated and can turn into each other. The amoeba does not have a hard shell, and it is able to change the shape of the body. When an amoeba crawls over a leaf of an aquatic plant, protrusions of the cytoplasm are formed in it in the direction in which it moves. Gradually, the rest of the cytoplasm of the amoeba flows into them. Such protrusions are called pseudopodia or pseudopodia. With the help of pseudopodia, the amoeba not only moves, but also captures food. With pseudopodia, it covers a bacterium or microscopic algae, soon the prey is inside the body of the amoeba, and a bubble is formed around it - a digestive vacuole. Undigested food remains are thrown out after a while.
Amoeba proteus: 1 - core; 2 - digestive vacuoles; 3 - contractile vacuole; 4 - pseudopods; 5 - undigested food remnants thrown out.
In the cytoplasm of the amoeba, a light bubble is usually visible, which either appears or disappears. This is a contractile vacuole. It collects excess water that accumulates in the body, as well as the liquid waste products of the amoeba. The amoeba, like all other protozoa, breathes over the entire surface of the body.
Euglena green: 1 - flagellum; 2 - eye spot; 3 - contractile vacuole;
The most complex structure of the simplest ciliates. Unlike the amoeba, their body is covered with the thinnest shell and has a more or less constant shape. The support fibers that run in different directions also support and determine the shape of the body. However, the body of ciliates can quickly contract, change its shape, and then return to its original shape. The contraction is carried out with the help of special fibers, similar in many respects to the muscles of multicellular animals.
Infusoria shoe: 1 - cilia; 2 - digestive vacuoles; 3 - large nucleus (macronucleus); (micronucleus); 5 - mouth opening and pharynx; 6 - undigested food residues thrown out; 7 - trichocysts; 8 - contractile vacuole.
Ciliates can move very quickly. So, a shoe in a second overcomes a distance exceeding the length of its body by 10-15 times. At the same time, many cilia that cover the entire body of the ciliate make fast rowing movements, up to 30 per second (at room temperature). In the ectoplasm of the shoe there are many trichocyst sticks. When irritated, they are thrown out, turning into long threads, and hit the enemy attacking the ciliate. Instead of those thrown out in the ectoplasm, new trichocysts are formed. On one side, approximately in the middle of the body, the shoe has a deep oral cavity leading to a small tubular pharynx. Through the pharynx, food enters the endoplasm, where it is digested in the resulting digestive vacuole. In ciliates, unlike amoebas, undigested food residues are thrown out in a certain place in the body. Their contractile vacuole is more complex and consists of a central reservoir and conducting channels. The ciliates have two types of nuclei: large - macronucleus and small - micronucleus. Some ciliates may have several macro- and micronuclei. The macronucleus differs from the micronucleus in a significantly larger number of chromosomes. And therefore, it contains a lot of deoxyribonucleic acid (DNA), which is part of the chromosomes.
Different types of ciliates: 1 - ciliates trumpeter; 2-5 - planktonic ciliates.
The simplest have irritability and therefore are able to choose the most favorable environmental conditions for themselves, reacting to light, heat, various chemicals, electric current, magnetic field and other stimuli.
Under adverse conditions, for example, when a reservoir dries up or freezes, the protozoa take on a spherical shape, lose cilia or flagella, form a hard shell on their surface and turn into an immobile cyst. Protozoan cysts survive both desiccation and sudden changes in temperature. Cysts are easily carried by the wind, with grass, hay, etc., which contributes to the spread of the species. If the cyst is in suitable conditions, its shell bursts or holes appear in it, and the organism passes to an active existence.
The sub-kingdom of unicellular or protozoa includes the smallest creatures whose body consists of one cell. These cells are an independent organism with all its characteristic functions (metabolism, irritability, movement, reproduction).
The body of unicellular organisms can have a constant (infusoria-shoe, flagella) or a non-permanent form (amoeba). The main components of the body of protozoa - nucleus and cytoplasm. In the cytoplasm of protozoa, along with general cellular organelles (mitochondria, ribosomes, the Galji apparatus, etc.), there are special organelles (digestive and contractile vacuoles) that perform the functions of digestion, osmoregulation, and excretion. Almost all protozoa are able to actively move. The movement is carried out with prolegs(in amoeba and other rhizopods), flagella(euglena green) or cilia(ciliates). Protozoa are able to capture solid particles (amoeba), which is called phagocytosis. Most protozoa feed on bacteria and decaying organic matter. Food after swallowing is digested into digestive vacuoles. The function of selection in protozoa is performed contractile vacuoles, or special holes - powder(for ciliates).
The simplest live in fresh water, seas and soil. The vast majority of protozoa have the ability to encystment, that is, the formation of the dormant stage upon the onset of adverse conditions (lowering temperature, drying up of the reservoir) - cysts covered with a dense protective sheath. Cyst formation is not only an adaptation to survival under adverse conditions, but also to the spread of protozoa. Once in favorable conditions, the animal leaves the cyst shell, begins to feed and multiply.
Reproduction of protozoa occurs by cell division into two (asexual); many have sexual intercourse. In the life cycle, most protozoa alternate between asexual and sexual reproduction.
There are over 90,000 unicellular species. All of them are eukaryotes (have a separate nucleus), but are at the cellular level of organization.
Amoeba
A representative of the rhizopod class is amoeba ordinary. Unlike many protozoa, it does not have a permanent body shape. It moves with the help of pseudopods, which also serve to capture food - bacteria, unicellular algae, and some protozoa.
Surrounding the prey with pseudopods, the food is in the cytoplasm, where a digestive vacuole is formed around it. In it, under the influence of the digestive juice coming from the cytoplasm, digestion occurs, as a result of which digestive substances are formed. They penetrate the cytoplasm, and undigested food residues are thrown out.
The amoeba breathes the entire surface of the body: oxygen dissolved in water directly penetrates into its body by diffusion, and carbon dioxide formed in the cell during respiration is released outside.
The concentration of dissolved substances in the body of an amoeba is greater than in water, so water continuously accumulates and its excess is excreted through contractile vacuole. This vacuole is also involved in the removal of decay products from the body. The amoeba reproduces by division. The nucleus divides in two, its two halves diverge, a constriction is formed between them, and then two independent, daughter cells arise from one mother cell.
Amoeba is a freshwater animal.
Euglena green
Another widespread species of protozoan animals lives in fresh water bodies - euglena green. It has a spindle shape, the outer layer of the cytoplasm is compacted and forms a shell that helps to maintain this shape.
From the front end of the body of the green euglena, a long thin flagellum departs, 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 (autotrophically). A light-sensitive eye helps to find the illuminated places of the euglena.
If Euglena is in the dark for a long time, then chlorophyll disappears and it passes to a heterotrophic mode of nutrition, that is, it feeds on ready-made organic substances, absorbing them from the water with the entire surface of the body. Respiration, reproduction, division in two, cyst formation in green euglena are similar to those in amoeba.
Volvox
Among the flagella there are colonial species, for example, volvox.
Its shape is spherical, the body consists of a gelatinous substance, in which individual cells are immersed - members of the colony. They are small, pear-shaped, have two flagella. Thanks to the coordinated movement of all flagella, Volvox moves. In a Volvox colony there are few cells capable of reproduction; from which daughter colonies are formed.
Infusoria shoe
In fresh water, another type of protozoa is often found - infusoria-shoe, which got its name because of the peculiarities of the shape of the cell (in the form of a shoe). The organelles of locomotion are cilia. The body has a constant shape, as it is covered with a dense shell. Infusoria-shoes have two nuclei: large and small.
big core regulates all life processes, small- plays an important role in the reproduction of shoes. The infusoria feeds on bacteria, algae and some protozoa. With vibrations cilia food gets into mouth opening, then - in throat, at the bottom of which digestive vacuoles where food is digested and nutrients are absorbed. Undigested residues are removed through a special organ - powder. The selection function is performed contractile vacuole.
It reproduces, like the amoeba, asexually, however, the sexual process is also characteristic of the ciliates-shoes. 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 shoe has the most complex structure.
Irritability
Characterizing the simplest organisms, one should pay special attention to one more of their properties - irritability. The simplest 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
Soil protozoa are representatives of amoebae, flagellates and ciliates, which play an important role in the soil-forming process.
In nature, protozoa participate in the circulation of substances, perform a sanitary role; in food chains they are one of the first links, being 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.
A basic level of
For each question, choose one correct answer from the four given.
A1. Almost all animals eat
- autotrophically
- heterotrophically
- during photosynthesis
- in the process of chemosynthesis
A2. The nervous system is present in representatives of the kingdom
- mushrooms
- bacteria
- plants
- animals
AZ. The body is made up of one cell
- lichens
- cap mushrooms
- protozoa
A4. Pseudopods of the simplest animals are
- plastids
- nuclear matter
- cytoplasmic outgrowth
- supply of nutrients
A5. The organelle of excretion of undigested food residues in protozoa is
- cyst
- flagellum
- powder
A6. Protozoa reproduce mainly by
- phagocytosis
- pinocytosis
- cell division
- cyst formation
A7. There is no permanent body shape
- foraminifera
- ciliates-shoes
- euglena green
- amoeba vulgaris
A8. Only in the cells of the simplest animals that feed autotrophically, there is
- chlorophyll
- cytoplasm
- flagellum
A9. Two nuclei are found in animal cells
- ciliates
- euglena
- volvox
- amoeba
- - - Answers - - -
A1-2; A2-4; A3-4; A4-3; A5-4; A6-3; A7-4; A8-1; A9-1.
Increased difficulty level
B1. Are the following statements true?
A. Many protozoa are part of plankton.
B. Phagocytosis of protozoa is associated with the formation of a contractile vacuole.
- Only A is true
- Only B is true
- Both statements are correct
- Both statements are wrong
B2. Are the following statements true?
A. Amoeba captures food with pseudopods.
B. Among the representatives of the simplest animals there are multicellular organisms.
- Only A is true
- Only B is true
- Both statements are correct
- Both statements are wrong
BZ. Choose three true statements. Not found in animal cells
- cell wall
- chloroplast
- cytoplasm
- outer membrane
- large vacuole
B4. Establish a correspondence between the structural features of the animal and its type.
Structural feature
A. Presence of eyelashes
B. Photosensitive eye
B. Pseudopods
G. Chloroplast
D. Two cores
Kind of animal
- Amoeba
- Euglena
- Infusoria shoe
Write down the corresponding numbers in the table.
- - - Answers - - -
B1-1; B2-1; B3-126; B4-32123.
Protozoa in a drop of pond water (under a microscope).
Rhizome class unites the simplest unicellular animals, the body of which is devoid of a dense shell, and therefore does not have a permanent shape. They are characterized by the formation of pseudopods, which are temporarily formed outgrowths of the cytoplasm that promote movement and capture of food.
Habitat, structure and movement of the amoeba. The common amoeba is found in the silt at the bottom of the ponds with contaminated water. It looks like a small (0.2-0.5 mm), colorless gelatinous lump, barely visible to the naked eye, constantly changing its shape ("amoeba" means "changeable"). The details of the structure of the amoeba can only be examined under a microscope.
The body of the amoeba consists of a semi-liquid cytoplasm with a small vesicle enclosed inside it core. Amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
Cytoplasm cells are in constant motion. If the current of the cytoplasm rushes to one point on the surface of the amoeba, a protrusion appears on its body in this place. It increases, becomes an outgrowth of the body - a pseudopod, the cytoplasm flows into it, and the amoeba moves in this way. Amoeba and other protozoa capable of forming pseudopods are classified as rhizopods. They got this name for the external resemblance of the pseudopods to the roots of plants.
Vital activity of Amoeba.
Food. An amoeba can simultaneously form several pseudopods, and then they surround food - bacteria, algae, and other protozoa. Digestive juice is secreted from the cytoplasm surrounding the prey. A vesicle is formed - a digestive vacuole. Digestive juice dissolves some of the substances that make up food and digests them. As a result of digestion, nutrients are formed that seep from the vacuole into the cytoplasm and go to build the body of the amoeba. Undissolved residues are thrown out anywhere in the body of the amoeba.
Amoeba Breath. Amoeba breathes oxygen dissolved in water, which penetrates into its cytoplasm through the entire surface of the body. With the participation of oxygen, complex food substances of the cytoplasm are decomposed into simpler ones. In this case, the energy necessary for the life and activity of the body is released.
Release of harmful substances life activity and excess water. Harmful substances are removed from the body of the amoeba through the surface of its body, as well as through a special bubble - the contractile vacuole. The water surrounding the amoeba constantly penetrates into the cytoplasm, liquefying it. The excess of this water with harmful substances gradually fills the vacuole. From time to time the contents of the vacuole are thrown out. So, from the environment, food, water, oxygen enter the body of the amoeba. As a result of the life of the amoeba, they undergo changes. The digested food serves as material for building the body of the amoeba. The substances harmful to the amoeba are removed outside. There is a metabolism. Not only amoeba, but also all other living organisms cannot exist without metabolism both inside their body and with the environment.
Amoeba reproduction. The feeding of the amoeba leads to the growth of its body. The grown amoeba begins to reproduce. (? Probably due to exceeding a certain mass of her body.) Reproduction begins with a change in the nucleus. It is stretched, the transverse groove is divided into two halves, which diverge in different directions - two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction. Each of them gets one nucleus. The cytoplasm between both parts is torn, and two new amoebas are formed. The contractile vacuole remains in one of them, while in the other it reappears. So the amoeba reproduces by dividing in two. During the day, division can be repeated several times.
Division (reproduction) of Amoeba.
Cyst. The amoeba feeds and reproduces throughout the summer. In autumn, when cold weather sets in, the amoeba stops eating, its body becomes rounded, a dense protective shell is released on its surface - a cyst is formed. The same thing happens when the pond dries up where amoebas live. In the state of a cyst, the amoeba endures unfavorable living conditions for it. When favorable conditions occur, the amoeba leaves the cyst shell. She releases pseudopods, begins to feed and multiply. Cysts carried by the wind contribute to the dispersal (spread) of amoebae.
Possible additional questions for self-study.
- What makes the Cytoplasm systematically flow from one part of the Amoeba to another, forcing it to move in a given direction?
- How does the membrane of the Amoeba cytoplasm recognize nutrients, as a result of which the amoeba purposefully forms pseudopods and a digestive vacuole?
