The body of sponges, ranging from 1.5 mm to 1 m in height, consists of a two-layer porous wall surrounding a central cavity. Between the layers of the wall is gelatinous mesoglea, which contains cells various kinds. Sponges lead a sedentary lifestyle, attaching their base to the substrate. Only the mouth and pores can narrow slightly. Under the action of flagellar cells - choanocytes, lining the inner surface of the sponges, water with suspended food particles is pumped through the pores into the internal cavity. Here, various organic substances, as well as bacteria and plankton, are captured by choanocytes. Metabolic products exit along with water through a wide mouth. Some sponges pump up to one and a half tons of water through themselves per day.
Most sponges are hermaphrodites. Reproduction is sexual and asexual. The buds that form on the body, as a rule, are not separated from the mother’s body, which leads to the appearance of colonies of the most bizarre shape. During the sexual process, a sperm fertilizes an egg; A larva emerges from the egg, floats in the water for some time, and then attaches itself to the bottom. Most sponges live from a few weeks to two years; horse sponge can live up to 50 years or more. Sponges have a very well developed ability to regenerate tissue: even if a sponge is cut into pieces, a new sponge will grow from each piece after a while.
The skeleton of sponges develops in the mesoglea. It is composed of fibrillar protein collagen or organic matter spongin and millions of microscopic needles (spicules) formed by silica or lime carbonate. The structure of the skeleton is the main feature of the classification of sponges. About 5,000 species of sponges, found mainly in seas from the surface to a depth of 8 km, are divided into three classes: lime sponges(skeleton made of calcium carbonate), ordinary sponges(skeleton of one- or four-axial silica needles, less often of spongin), glass or six-ray sponges(silica skeleton of six-axial spines). More than 95% of all species are common sponges.
Calcareous sponges have been known since the Precambrian, glass sponges since the Devonian. Currently, most researchers, following Ivan Mechnikov, consider a hypothetical animal, the phagocytella, as the ancestor of sponges. This is evidenced by the structure of the sponge larvae, which is close to the most archaic animals from the subkingdom phagocytelliformes -
Empire - Cellular; kingdom - Animals; subkingdom - Multicellular; type - Sponges.
Today it is known that there are about 8 thousand species. 300 of them inhabit the expanses of the Russian seas. The Sponge Type classification unites all known representatives into four large classes. Karkarea, or Calcareous. Form exoskeleton in the form of deposited calcium salts. Ordinary, or Siliceous. The main representative is the badyaga. Glass (Six-beam). The class size is small. Corals are a very species-poor class. All of these sponges have their own characteristics, not only external, but also internal structure, lifestyle and economic importance In human life. External structure Perhaps the most unusual thing in all the characteristics of the animals in question will be their external appearance. Peculiarities external structure sponges are defined by the variety of body shapes that characterize them. Yes, representatives different classes can be in the form of: glasses; bowls; tree structure. The body symmetry in solitary forms is multipolar axial, while in colonial forms it is mixed. Each individual has a special flat sole, with which it is attached to the bottom or other substrate. Sponges most often lead a sedentary lifestyle. On the upper side of the body there is a special opening called the “osculum”. It serves to remove excess water from the internal cavity. The outside of the body is covered with a layer of cells called pinacoderm. They resemble in their structure the epithelial tissue of higher animals. However, they also have distinctive features- presence of wide pores. The structure of the sponge provides for the absorption of food particles not through the upper hole, but through numerous perforations penetrating the entire body, capable of contracting and expanding. Under the outer layer there are two more, which we will consider in more detail later. The color range of both single and colonial forms is quite diverse. The following color types are available: gray; green; purple; yellow; white; red; brown; mixed. Sponge type is very enlivening undersea world, making it even more bright, colorful and attractive. Moreover, if we consider an individual individual on the surface of land, it will have a very unattractive appearance: a brownish, slippery lump reminiscent of raw liver, emitting a not entirely pleasant aroma. Internal structure representatives The types of structure of sponges are similar, whether it is a single individual or attached to a colony. Immediately under the dermal outer layer of porous cells there is a special intercellular substance that forms a fairly voluminous membrane. In it, the cells are loosely located, and their shape is different. The tissue is somewhat reminiscent of adipose tissue in higher terrestrial representatives. This structure is called "mesohyl". Under this layer there is an internal cavity lined with a special row of cells. This is the gastric layer. All food ends up here, and this is where digestion takes place. All waste products, along with excess water, are directed to the upper opening of the body and discharged out through it. Also, the structure of a sponge necessarily includes a kind of skeleton. It is formed from limestone, phosphorus, organic salts, which are produced in special mesochyl cells. It not only gives the sponges a certain body shape, but is also important for the safety of the internal cavity from mechanical damage. Characteristics of the Sponge type will be incomplete if you do not indicate main feature these animals - their body does not have tissues, but only includes cells of different shapes and structures that form layers. This is the main difference between the animals in question and all others. The aquifer system of the individuals is also interesting. It may not be the same for different classes. In total, there are three main types of it: Askon - all communication with external environment carried out through a system of tubes through which water moves into special chamber cells. The most simplified aquifer system, found in only a few representatives. Sicon. A more advanced system that includes a network of branched tubules and tubes flowing into special chamber cells with flagella. Leukon is a whole network of osculums; this type of aquifer system is characteristic only of colonial forms. The most complicated option compared to all the previous ones. Reproduction in sponges occurs both sexually and asexually. Germ cells are formed in the mesochyl layer. Then the products come out through the pores of the body and, with a stream of water, enter the bodies of other sponges, where fertilization occurs. As a result, a zygote is formed, giving rise to a larva. The fry can be called differently: amphiblastula, parenchymulus, celloblastula. If we talk about asexual reproduction, then it is based on the process of budding, that is, the detachment of a part of the body with the subsequent regeneration of missing structures. Most of the Sponge type includes hermaphroditic animals.
Sponges are very peculiar animals, so researchers for a long time solved the question of whether to classify these organisms as plants or animals. About 4,500 species of sponges are known. All of them, except large number freshwater, live in seas and oceans. Sponges are the most primitive multicellular organisms.
The body shape of the sponges resembles a glass or a bag (Fig. 1). These are sessile solitary or more often colonial forms. The entire body of the sponge is riddled with pores. Through them, water with dissolved oxygen and floating small organisms penetrate into the sponge, which the sponge uses as food. Water comes out of the sponge through the outlet - the mouth (osculum).
The outer layer of the body (ectoderm) consists of flat surface cells. The inner layer (endoderm) is built of flagellated collar cells (choanocytes), similar to the cells of colonial flagellates. Choanocytes capture food, which is then digested inside the cells. In addition, special mobile amoeboid cells also capture food and digest it. Consequently, sponges have intracellular digestion and do not yet have a digestive system. Between the outer and inner layer of cells there is a gelatinous substance called mesoglea. Cells of different functions are scattered in it: amoeboid cells, which serve for digestion, mature and immature gametes, skeletoblasts, i.e., forming the skeleton. The skeleton is built from the organic matter of spongin or from one-, three- and four-axial calcareous and flint needles (spicules), also located in the mesoglea.
Sponges reproduce asexually (by budding) and sexually. They have a well-expressed ability to regenerate.
During the development of sponges, a peculiar process occurs. The outer layer of flagellar cells formed in larvae later turns into endoderm (and not into ectoderm, as in other animals), and the inner layer of embryonic cells, which usually gives rise to endoderm, turns into the outer cells of an adult animal. This phenomenon is not observed in any type of multicellular animal, except sponges.
From the above description it is clear that, unlike protozoa, in which all vital functions are performed by one cell, in sponges there is a division of functions between cells and associated morphological differentiation. But there are still no or almost no connections between cells, no coordination of functions.
There are two points of view regarding the origin of sponges. The presence of collar cells in sponges gives reason to assume their origin from some ancient colonial collar flagellates, regardless of the rest of the animal world. However, their origin is more likely from the hypothetical ancestor of all multicellular organisms - the phagocytella, with which the larva found in most sponges - the parenchymula - is very similar in structure. The progressive development of sponges due to a sedentary lifestyle has stopped, and their structure may have become simpler. Development and structure show that sponges stand apart from other types of multicellular organisms and, phylogenetically, represent a blind branch of the family tree of animals.
The practical value of sponges is small. A number of sea sponges, called toilet sponges, have been extracted from the bottom of the sea since ancient times and, after drying, are used for washing. In our fresh waters There is also a bodyaga sponge that forms growths on underwater objects. It is used in folk medicine as an external antirheumatic agent.
Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.
Subkingdom multicellular
Multicellular animals are descendants of ancient protozoa. Their body consists of a large number of cells. Groups of cells differ in structure and function.
The cells of multicellular animals are combined into tissues and organs that perform various functions in the whole organism. True, this is not observed in all multicellular organisms. U lower representatives In this sub-kingdom, tissues and organs are still in the formation stage.
It is typical for multicellular animals individual development – processes of complex transformations occurring from the birth of an individual to the end of its life.
Multicellular organisms are more fully adapted to different conditions environment. Consequently, the emergence of multicellular animals is qualitatively new stage in the development of the animal world on Earth. Multicellular organisms are united into a large subkingdom, which includes over 20 types of animals.
Sponge Type
Sponges- a type of invertebrate animal.
Currently, about 8,000 species have been described. Although the vast majority of sponges live in the seas, freshwater representatives (for example, badyagi) are found in the inland waters of all continents except Antarctica.
Classification
Calcareous sponges (Calcarea, or Calcispongia)
The skeleton is composed of carbonated lime needles, which can be tetraaxial, triaxial or uniaxial. Exclusively marine, predominantly shallow-water small sponges. They can be built according to the asconoid, siconoid or leuconoid type. Typical representatives- genera Leusolenia, Sycon, Leuconia.
Glass sponges (Hyalospongia)
Marine predominantly deep-sea sponges up to 50 cm in height. The body is tubular, bag-shaped, sometimes in the form of a glass. Almost exclusively solitary forms of the syconoid type. The flint needles that make up the skeleton are extremely diverse and are basically triaxial. Often soldered at the ends to form lattices of varying complexity. Characteristic glass sponges - poor development of mesoglea and fusion of cellular elements into syncytial structures. Typical genus Euplectella. In some species of this genus, the body is cylindrical, up to 1 m in height, the needles at the base, sticking into the ground, reach 3 m in length.
Common sponges (Demospongia)
Most modern sponges belong to this class. The skeleton is flint, spongine, or a combination of both. This includes the order of four-rayed sponges, the skeleton of which is composed of four-axial spines with an admixture of uniaxial ones. Characteristic representatives: globular large geodia, brightly colored orange-red sea oranges (Tethya), lumpy bright corky sponges, boring sponges and many others. The second order of the Demospongia class is the flint-horned sponges. The skeleton contains spongin as the sole component of the skeleton or in varying proportions with flint spines.
Structure
The body shape of sponges can be different: like a bowl, a tree, etc. Moreover, all sponges have a central cavity with a fairly large hole (mouth) through which water comes out. The sponge absorbs water through smaller holes (tubules) in its body.
The figure shows three variants of the structure of the aquifer system of sponges. In the first case, water is sucked into a common large cavity through narrow side channels. In this common cavity, the water is filtered nutrients(microorganisms, organic remains; some sponges are predators and are capable of capturing animals). The capture of food and the flow of water are carried out by the cells shown in red in the figure. In the figure in the second and third cases, the sponges have more complex structure. There is a system of channels and small cavities, the inner walls of which form cells responsible for nutrition. The first variant of the sponge body structure is called ascon, second - sicon, third - lacon.
Cells shown in red are called choanocytes. They have cylindrical shape, flagellum facing the chamber-cavity. They also have what is called plasma collar., which traps food particles. Choanocyte flagella push water in one direction. 
Nutrition
Sponges feed by filtering water. They absorb water through pores located throughout the body wall in the central cavity. The central cavity is lined with collar cells, which have a ring of tentacles surrounding the flagellum. The movement of the flagellum creates a current that holds water flowing through the central cavity into an opening at the top of the sponge called the osculum. As water passes through the collar cells, food is captured by the rings of tentacles. Next, food is digested in food vacuoles or amoeboid cells in the middle layer of the wall. The flow of water also provides a constant supply of oxygen and removes nitrogenous waste. Water exits the sponge through a large hole at the top of the body called the osculum.
Reproduction
In sponges, both sexual and asexual reproduction. Sponges can be oviparous or viviparous. Ovoviviparous sponges are usually dioecious, and in the second case they are often hermaphrodites. However, there is a known case of a sponge changing its gender within a year.
The first multicellular organisms on Earth were sponges that led an attached lifestyle. However, some scientists classify them as complex colonies of protozoa.
general description
Sponges are a separate phylum of the animal kingdom, numbering about 8,000 species.
There are three classes:
- Limestone - have a calcareous skeleton;
- Glass - have a silicon skeleton;
- Ordinary - have a silicon skeleton with spongin filaments (the spongin protein holds the parts of the skeleton together).
Rice. 1. Sponge colony.
General characteristics of sponges are given in the table.
|
Sign |
Description |
|
Lifestyle |
Attached. They form colonies. There are single representatives |
|
Habitats |
Fresh and salt water bodies in different climatic zones |
|
Can reach 1 meter in height |
|
|
Heterotrophic. They are filter feeders. Internal flagella create a current of water that penetrates into the body. Organic particles, plankton, and detritus deposited on the walls are absorbed by cells |
|
|
Reproduction |
Sexual or asexual. During sexual reproduction, they lay eggs or form larvae. There are hermaphrodites. When asexual, they form buds or reproduce by fragmentation |
|
Lifespan |
Depending on the species, they can live from several months to several hundred years. |
|
Natural enemies |
Turtles, fish, gastropods, sea stars. Poison and needles are used for protection |
|
Relationships |
They can form symbiosis with algae, fungi, eyelash worms, molluscs, crustaceans, fish and other aquatic life |
The main representatives of sponges are Neptune's cup, badyaga, Venus's basket, and the luminous sponge of Clion.
Rice. 2. Kliona.
Structure
Despite the fact that these are symmetrical animals with all the signs of a living organism, they are conventionally classified as multicellular organisms, because they do not have specific tissues and organs.
The structure of sponges is primitive, limited to two layers of cells permeated with pores and a skeleton. Visually, sponges look like bags attached to the substrate with a sole. The walls of the sponge form the atrial cavity. The external opening is called the orifice (osculum).
There are two layers , between which there is a jelly-like substance - mesoglea:
- ectoderm - outer layer, formed by pinacocytes - flat cells resembling epithelium;
- endoderm - the inner layer formed by choanocytes - cells resembling funnels with flagella.
Mesoglea contains:
- mobile amoebocytes that digest food and regenerate the body;
- germ cells;
- supporting cells containing spicules - silicon, limestone or horny needles.
Rice. 3. The structure of sponges.
Sponge cells are formed from undifferentiated cells - archaeocytes.
Physiology
Despite the lack of organ systems, sponges are capable of feeding, respiration, reproduction, and excretion. Obtaining oxygen, food and excretion carbon dioxide and other metabolic products occurs due to the inward flow of water, which is created by vibrations of the flagella.
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Fertilization occurs in the same way during sexual reproduction. The flow of water absorbs the sperm of one sponge, which fertilizes the eggs in the body of the other sponge. As a result, larvae are formed that come out. Some species produce eggs. They attach to the substrate and, as they grow, transform into an adult.
Every five seconds, a volume of water equal to the internal volume of its body passes through the sponge. Water enters through the pores and leaves through the mouth.
Meaning
For humans, the importance of sponges lies in the use of their hard skeleton for industrial, medical and aesthetic purposes. The ground skeleton was used as an abrasive and for cleaning. Soft-skeleton sponges were used to filter water.
Currently, dried and crushed badyaga is used in folk medicine to treat bruises and rheumatism.
In nature, sponges are natural water purifiers. Their disappearance leads to pollution of the reservoir.
What have we learned?
From a report for a 7th grade biology lesson, we learned about the features of the lifestyle, structure, significance, nutrition, and reproduction of sponges. These are primitive multicellular animals that lead an attached lifestyle and are formed by two layers of cells. They filter water, obtaining food, oxygen and germ cells from it for fertilization. Metabolic products, sperm and fertilized cells or larvae enter the water. Thanks to rapid regeneration, they are able to reproduce by fragmentation.
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