Brief description of the subkingdom protozoa. Unicellular organisms - list with names and examples General characteristics of the unicellular subkingdom briefly
Unicellular organisms, or protozoa, include animals whose body morphologically corresponds to one cell, while at the same time being an independent integral organism with all its inherent functions. Total number There are more than 30 thousand species of protozoa.
Emergence single-celled animals were accompanied by aromorphoses: 1. Diploidy (double set of chromosomes) appeared in the nucleus bounded by a shell as a structure separating the genetic apparatus of the cell from the cytoplasm and creating a specific environment for the interaction of genes in the diploid set of chromosomes. 2. Organelles emerged that were capable of self-reproduction. 3. Internal membranes have formed. 4. A highly specialized and dynamic internal skeleton appeared - the cytoskeleton. b. The sexual process arose as a form of exchange of genetic information between two individuals.
Structure. The structural plan of protozoa corresponds to the general features of the organization of a eukaryotic cell.
Genetic apparatus unicellular is represented by one or several nuclei. If there are two nuclei, then, as a rule, one of them, diploid, is generative, and the other, polyploid, is vegetative. The generative nucleus performs functions related to reproduction. The vegetative nucleus provides all vital processes of the body.
Cytoplasm consists of a light outer part, devoid of organelles, - ectoplasm and a darker inner part containing the main organelles, - endoplasm. The endoplasm contains organelles general purpose.
Unlike the cells of a Multicellular Organism, unicellular organisms have organelles for special purposes. These are organelles of movement - pseudopods - pseudopodia; flagella, cilia. There are also osmoregulation organelles - contractile vacuoles. There are specialized organelles that provide irritability.
Unicellular organisms with a constant body shape have permanent digestive organelles: a cell funnel, a cell mouth, a pharynx, as well as an organelle for excreting undigested residues - powder.
INunfavorable under conditions of existence, the nucleus with a small volume of cytoplasm containing the necessary organelles is surrounded by a thick multilayer capsule - a cyst and passes from the active state to rest. When hitting favorable conditions the cysts “open” and protozoa emerge from them in the form of active and mobile individuals.
Reproduction. The main form of reproduction of protozoa is asexual reproduction through mitotic cell division. However, the sexual process is often encountered.
Class Sarcodae. or Roots.
Amoeba
The class includes the amoeba squad. Characteristic sign- the ability to form cytoplasmic projections - pseudopodia (pseudopods), thanks to which they move.
Amoeba: 1 - nucleus, 2 - cytoplasm, 3 - pseudopodia, 4 - contractile vacuole, 5 - formed digestive vacuole
Structure. Body shape is not constant. The hereditary apparatus is represented by one, usually polyploid nucleus. The cytoplasm has a distinct division into ecto- and endoplasm, in which general purpose organelles are located. Free-living freshwater forms have a simply structured contractile vacuole.
Method of nutrition. All rhizomes feed by phagocytosis, capturing food with pseudopods.
Reproduction. For the most primitive representatives of the orders of amoebas and testate amoebae characterized only by asexual reproduction through mitotic cell division.
Class Flagellates
Structure. Flagellates have flagella that serve as organelles of movement and facilitate the capture of food. There may be one, two or many. The movement of the flagellum in the surrounding water causes a whirlpool, due to which small particles suspended in the water are carried to the base of the flagellum, where there is a small opening - the cell mouth, leading to the deep canal-pharynx.
Euglena green: 1 - flagellum, 2 - contractile vacuole, 3 - chloroplasts, 4 - nucleus, 5 - contractile vacuole
Almost all flagellates are covered with a dense elastic membrane, which, along with developed cytoskeletal elements, determines the constant shape of the body.
Genetic apparatus in most flagellates it is represented by a single nucleus, but there are also binucleate (for example, Giardia) and multinucleate (for example, opalina) species.
Cytoplasm It is clearly divided into a thin outer layer - transparent ectoplasm and deeper endoplasm.
Method of nutrition. According to the method of feeding, flagellates are divided into three groups. Autotrophic organisms, as an exception in the animal kingdom, synthesize organic substances (carbohydrates) from carbon dioxide and water with the help of chlorophyll and the energy of solar radiation. Chlorophyll is found in chromatophores, similar in organization to plant plastids. Many flagellates with a plant type of nutrition have special devices that perceive light stimulation - stigmas.
Heterotrophic organisms (trypanosome - the causative agent of sleeping sickness) do not have chlorophyll and therefore cannot synthesize carbohydrates from inorganic substances. Mixotrophic organisms are capable of photosynthesis, but also feed on minerals and organic substances created by other organisms (green euglena).
Osmoregulatory And Partially, excretory functions are performed in flagellates, like sarcodidae, by contractile vacuoles, which are present in free-living freshwater forms.
Reproduction. In flagellates, sexual and asexual reproduction is observed. The usual form of asexual reproduction is longitudinal fission.
Type Ciliates, or Ciliated
General characteristics. TO The type of ciliates includes more than 7 thousand species. Cilia serve as organelles of movement. There are two nuclei: a large polyploid - vegetative nucleus(macronucleus) and small diploid - generative nucleus(micronucleus).
Structure. Ciliates can be of various shapes, most often oval, like the slipper ciliate. Their sizes reach 1 mm in length . The outside of the body is covered with pellicle. Cytoplasm always clearly divided into ecto- and endoderm. The ectoplasm contains the basal bodies of the cilia. Elements of the cytoskeleton are closely associated with the basal bodies of cilia.
Method of feeding ciliates. IN In the front half of the body there is a longitudinal notch - the perioral cavity. In its depth there is an oval opening - a cellular mouth, leading to a curved pharynx, which is supported by a system of skeletal pharyngeal filaments. The pharynx opens directly into the endoplasm.
Osmoregulation. Free-living ciliates have contractile vacuoles.
Ciliates slipper: 1 - cilia, 2 - digestive vacuoles, 3 - small nucleus, 4 - large nucleus, 5 - cell mouth, c - cell pharynx, 7 - powder, 8 - contractile vacuole<
Reproduction. Ciliates are characterized by alternating sexual and asexual reproduction. During asexual reproduction, transverse division of ciliates occurs.
Habitat. Free-living ciliates are found in both fresh waters and seas. Their lifestyle is varied.
The general features of the organization of protozoa are the following:
Most protozoa are unicellular, less often colonial organisms. Their unicellular body has the functions of an entire organism, which are performed by general-purpose organelles (nucleus, endoplasmic reticulum, Golgi complex, lysosomes, mitochondria, ribosomes, etc.) and special ones (digestive and contractile vacuoles, flagella, cilia, etc.). Working in harmony, they obesbake a separate cell the possibility of existence inas an independent organism.
The integuments of protozoa are represented either only plasmatichelic membrane, or also a dense, fairly flexible and elastic shell - pellicle, giving them relative constancy of body shape. In the cytoplasm, two layers are clearly distinguished: superficial, denser - ectoplasma, and internal, more liquid and granular - endoplasma, in which the organelles of the protozoa are located. Due to the colloidal properties of the cytoplasm, these two layers can mutually transform into each other.
Organelles of movement of most species - pseudopods, flagella or numerous short cilia.
Gas exchange occurs over the entire surface of the body.
Irritability in protozoa manifests itself in the form taxis.
9. Most protozoa have the ability to tolerate unfavorable conditions in a dormant stage cysts. In this case, the cell becomes rounded, retracts or discards movement organelles, and becomes covered with a dense protective membrane. The cyst stage allows the protozoan not only to survive unfavorable conditions in an inactive state, but also to spread. Once in favorable conditions, the protozoan leaves the cyst shell and begins to feed and reproduce.
The phylum protozoa includes approximately 25 thousand species of single-celled animals that live in water, soil or the organisms of other animals and humans. Having morphological similarities in the structure of cells with multicellular organisms, protozoa differ significantly from them in functional terms.
If the cells of a multicellular animal perform special functions, then the cell of a protozoan is an independent organism, capable of metabolism, irritability, movement and reproduction.
Protozoa are organisms at the cellular level of organization. Morphologically, a protozoan is equivalent to a cell, but physiologically it is a whole independent organism. The vast majority of them are microscopically small in size (from 2 to 150 microns). However, some of the living protozoa reach 1 cm, and the shells of a number of fossil rhizomes have a diameter of up to 5-6 cm. The total number of known species exceeds 25 thousand.
The structure of protozoa is extremely diverse, but they all have features characteristic of the organization and function of the cell. What is common in the structure of protozoa are the two main components of the body - the cytoplasm and the nucleus.
Cytaplasm
The cytoplasm is bounded by an outer membrane, which regulates the flow of substances into the cell. In many protozoa it is complicated by additional structures that increase the thickness and mechanical strength of the outer layer. Thus, formations such as pellicles and membranes arise.
The cytoplasm of protozoa is usually divided into 2 layers - the outer one is lighter and denser - ectoplasm and internal, equipped with numerous inclusions, - endoplasm.
General cellular organelles are localized in the cytoplasm. In addition, a variety of special organelles may be present in the cytoplasm of many protozoa. Various fibrillar formations are especially widespread - supporting and contractile fibers, contractile vacuoles, digestive vacuoles, etc.
Core
Protozoa have a typical cell nucleus, one or more. The nucleus of protozoa has a typical two-layer nuclear envelope. Chromatin material and nucleoli are distributed in the nucleus. The nuclei of protozoa are characterized by exceptional morphological diversity in size, number of nucleoli, amount of nuclear juice, etc.
Features of the life activity of protozoa
Unlike somatic cells, multicellular protozoa are characterized by the presence of a life cycle. It consists of a number of successive stages, which are repeated with a certain pattern in the existence of each species.
Most often, the cycle begins with the zygote stage, corresponding to the fertilized egg of multicellular organisms. This stage is followed by single or multiple repeated asexual reproduction, carried out by cell division. Then sex cells (gametes) are formed, the pairwise fusion of which again produces a zygote.
An important biological feature of many protozoa is the ability to encystment. In this case, the animals become rounded, shed or retract the organelles of movement, secrete a dense shell on their surface and fall into a state of rest. In the encysted state, protozoa can tolerate sudden changes in the environment while maintaining viability. When conditions favorable for life return, the cysts open and the protozoa emerge from them in the form of active, mobile individuals.
Based on the structure of organelles of movement and characteristics of reproduction, the type of protozoa is divided into 6 classes. The main 4 classes: Sarcodaceae, Flagellates, Sporozoans and Ciliates.
Type of protozoa
Sarcomastigophores
Sarcodaceae
Amoeba proteus (common), amoeba dysentery, radiolaria
Flagellates
Euglena green, Volvox, African trypanosoma, Leishmania, Trichomonas, Giardia hepatica
Sporozoans
Coccidia
Malarial plasmodium
Ciliates
Ciliary
Balantidium ciliate, slipper ciliate, trumpeter ciliate
Trichophriasis
Used Books:
1.Biology: a complete reference book for preparing for the Unified State Exam. / G.I. Lerner. - M.: AST: Astrel; Vladimir; VKT, 2009 2.Biology: Animals: textbook. for 7-8 grades. general education Institutions. - 7th ed. - M.: Education, 2000. 3. Biology: textbook / reference manual / A.G. Lebedev. M.: AST: Astrel. 2009. 4.Biology. Full course of general secondary school: a textbook for schoolchildren and applicants / M.A. Valovaya, N.A. Sokolova, A.A. Kamensky. - M.: Exam, 2002. 5. Biology for applicants to universities. Intensive course / G.L.Bilich, V.A.Kryzhanovsky. - M.: Onyx Publishing House, 2006.
Internet resources used:
Protozoa are unicellular animals whose body consists of one cell. However, they cannot be considered as simply organized forms, because morphologically, a protozoan cell is equivalent to a cell of a multicellular organism. Physiologically, a protozoan cell is an integral organism, which is characterized by all manifestations of life: metabolism, irritability, growth, reproduction, etc. The role of organs in them is performed by organelles.
Protozoa were discovered in 1675 by the Dutch naturalist Antoine van Leeuwenhoek. In the first classification of animals, proposed in 1759 by the Swedish botanist Carl Linnaeus, protozoa were combined into one genus called Chaos, which was part of the phylum worms. Only in 1845 Kölliker and Siebold identified them as an independent type of animal. And only very recently, in 1980, Levine established a separate sub-kingdom for protozoa
There are from 5 to 7 types of protozoa, each type includes several classes. To date, more than 30 thousand species have been described, but there are many more of them.
Origin of unicellular organisms
As is known, the first living beings arose in the primeval oceans and looked like tiny mucous lumps. They had neither nuclei, nor vacuoles, nor other parts of cells, but they could grow, absorbing nutrients from the environment, and multiply. As a result of natural selection, these organisms gradually became more complex. From them came the first single-celled organisms with nuclei. As has been established, at the earliest stages of the evolution of living nature they gave rise to single-celled animals and primitive fungi. Their ancestors were the most ancient single-celled organisms - the simplest flagellates (as many biologists believe).
Conclusions:
1. The first animals to appear on Earth were single-celled animals belonging to the protozoa.
2. Among the protozoa there are not only unicellular forms, but also colonial ones (Volvox).
General characteristics of protozoa
1. Protozoa are unicellular animals whose body consists of one cell. Morphologically, a protozoan cell is equivalent to a cell of a multicellular organism. Physiologically, a protozoan cell is an integral organism, which is characterized by all manifestations of life: metabolism, irritability, growth, reproduction, etc. The role of organs in them is performed by organelles.
2. This is a widespread group of animals in a state of biological progress. During evolution, they acquired numerous adaptations to living conditions in different habitats (sea, fresh water bodies, damp soil, liquid environment of other organisms).
3. The sizes of protozoa are microscopically small. Their body (cell) consists of cytoplasm, in which there is an outer layer - ectoplasm and an inner layer - endoplasm. In most species, the outside of the cell is covered with a membrane, which gives the animal a permanent shape (the exception is sarcodae). In the endoplasm, in addition to the organelles inherent in all cells, there are organelles that perform the functions of digestion, excretion, movement (flagella, cilia), protection (trichocysts in ciliates), and a light-sensitive eye (in free-living flagellates).
4. According to the method of nutrition, these are typical heterotrophic organisms (with the exception of green euglena).
5. Breathe with the entire surface of the body.
7. Reproduction is carried out asexually or sexually.
8. Protozoa, as full-fledged living organisms, react to the influence of the external environment, i.e. have irritability, which manifests itself in various movements (taxis). There are positive taxis (when animals move towards the stimulus) and negative taxis (when they move away from the stimulus).
9. Encystation is an important biological feature of protozoa - this is the ability to form a cyst when exposed to unfavorable conditions. Encystment not only ensures survival of unfavorable conditions, but also contributes to widespread dispersal.
10. This is the most ancient type of animal. The most ancient classes of this type include flagellates and sarcodae, which originated from a primitive, now extinct group of eukaryotic heterotrophic organisms. Ciliates are related in their origin to flagellates. All multicellular animals originated from flagellates (via colonial forms).
The type includes the following classes:
flagellates, sarcodes or rhizomes, ciliates, sporozoans and others.
