Sponge Type, structural features
Type Sponges, the structural features of which we consider in our article, to this day are Yes, and in the textbooks on zoology about them there is not so much information. But sponges are a type of multicellular animals and are widely distributed in nature.
Over time, as a result of evolutionary transformations, along with protozoa in nature, multicellular animals also appeared. They have a number of more complex structural features. And the matter is not only in the number of cells, but in their specialization to perform various functions. Some of them are used for breeding, others - provide movement, and others - the processes of splitting substances, etc.
Groups of cells that are the same in structure and function are combined into tissues, and they, in turn, form organs.
Type of Sponge: general characteristics
Sponges are the most primitive multicellular animals. They do not yet form real tissues, but the cells are distinguished by strict specialization.
Sponges are ancient animals.Some of their species have been known since the Precambrian and Devonian periods. Scientists believe that their ancestors are calcareous flagellates. But the branch of the evolution of sponges was a dead end.
For a long time, taxonomists could not determine their position in the system of the organic world. Therefore, sponges were called zoophytes - organisms that have signs of both animals and plants. Everything changed only at the beginning of the 19th century. Sponge finally attributed to the animal kingdom. But scientists are still arguing: whether it is a colony of the simplest, or real multicellular organisms.
Basics of Classification
By type of structure sponges are combined into several classes:
- Ordinary. Among them are single and colonial forms. They have the appearance of growths, plates, lumps, small bushes, whose height can reach half a meter. Representatives of this class are badyagi, toilet and drilling sponges.
- Limy. Characterized by the presence of an internal skeleton, the needles of which consist of calcium carbonate. Body shape - in the form of a barrel or tube. Representatives are sikon, ascetta, leukandra.
- Coral. Exclusively colonial forms.The inner skeleton consists of calcite or silicon. The size of the colonies in width reach a meter. Named due to the fact that they live among the coral reefs of the Indian and Pacific Oceans.
- Glass, or Aisle. Single goblet-shaped individuals. Have a skeleton of silicon in the form of needles. They live exclusively in ocean waters. Thanks to the aesthetic appearance they are used to make jewelry.
Most representatives such as Sponges have a goblet body. With its base, the animal attaches to the substrate - stones, the bottom of ponds or shells. The upper part opens outwards with a hole leading into the body cavity. It is called atrial.
All classes like Sponges are two-layer animals. The ectoderm is located outside. This layer is formed by flat cells of the covering epithelium. The internal endoderm consists of flagellated cells called hoanocytes.
The walls are not solid, but pierced with a large number of pores. Through them, the metabolism of sponges with the environment. Between the layers of the body is gelatinous substance - mesogliya. It contains three types of cells.These are the anchors that form the skeleton, the genital and the amoeboid. With the help of the latter is the process of digestion. They also provide the regeneration of sponges, because they can turn into all types of cells.
The sizes of sponges vary from 1 cm to 2 m, and the color varies from dull brown to bright purple. The variety is different and the shape of the body. Sponges can be like a plate, a ball, a fan or a vase.
According to the method of feeding, representatives of the Sponge type are heterotrophic filter feeders. Through their body cavity, water moves continuously. Due to the activity of flagellated cells, it enters the pores of the layers of the body, enters the atrial cavity and comes out through the mouth.
At the same time, protozoa, bacteria, phytoplankton and remnants of dead organisms are captured by amoebocytes. This happens through phagocytosis - intracellular digestion. Unprocessed leftover food enters the cavity again and is thrown out through the mouth.
Among the sponges are found predators. They lack an aquifer filtration system. As food they are served by small crustaceans and fry of fish that stick to their sticky threads. Further, they are shortened, pulling up to the body of the predator.Sponge envelops prey and digests it.
Breathing and excretion
Animals belonging to the Sponge type are not found on land. Therefore, they are adapted to absorb oxygen only from water. This happens through diffusion. Absorb oxygen, as well as remove carbon dioxide, are capable of all cells of the sponge body.
Despite the primitive structure, methods of reproduction of sponges are quite diverse. They can multiply by budding. At the same time on the body of the animal appears protrusion, which over time increases in size. When all types of cells have formed on such a kidney, it detaches from the maternal individual and goes on to an independent existence.
The next breeding method for sponges is fragmentation. As a result, the body of the sponge is divided into parts, each of which gives rise to a new organism. This process is also called gemlogenesis. It usually occurs with the onset of adverse conditions.
The parts of the sponges formed during this process are called gemmules. Each of them is covered with a protective sheath, and inside contains a supply of nutrients. Gemmules are considered resting stages of sponges.Their ability to survive is incredible. They remain viable after exposure to low temperatures down to -100 degrees and prolonged dehydration.
The sexual process is carried out by specialized cells. In this case, the sperm comes out of the mouth of one sponge and with a stream of water enters the other. There amoebocytes deliver it to the egg.
According to the type of development, there are egg and viviparous sponges. In the former, the division of the fertilized egg and the formation of the larva occurs outside the maternal organism. Such organisms are always dioecious. Among the viviparous representatives often hermaphroditic. They develop zygotes in the atrial cavity.
For the distribution of sponge-type animals, the presence of a particular substrate is of great importance. It must be hard, because the sludge can become clogged in the pores. This leads to the mass death of animals.
The characteristic of the Sponge type would be incomplete without mentioning the symbiosis. In nature, there are cases of their mutually beneficial cohabitation with other aquatic inhabitants. These can be algae, bacteria or fungi.
With this form of existence, the metabolism of sponges occurs more intensively. For example, when cohabiting with algae, they emit several times more oxygen and organic matter. Since adult sponges are inedible, many animals use them to protect against enemies. There are cases when crustaceans settle in them. And crabs prefer to wear sponges on their shell.
Value in nature and human life
Sponges are very important for cleaning ponds. By filtering, they not only feed, but also remove contaminants. Their role is played by these animals in trophic chains. Sponge larvae feed on shellfish and certain species of fish.
For humans, sponges are raw materials for pharmacology. Everyone knows the bruise and bruise ointment on the basis of sponge - badyagi, as well as iodine-containing drugs. The value of these animals is associated with their name. They are really used for a long time to wash the body and various surfaces. And now we call these synthetic sponges.
So, in the article we looked at the representatives of the sub-kingdom Multicellular - Sponge type. These are multicellular aquatic animals that lead an attached lifestyle. In their body, there are two layers - ecto-and endoderm. Each of them is formed by specialized cells.These sponge tissues do not form.