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The Simplest

The simple - a heterogeneous group of eukaryotic organisms. Previously, simply refers to the animal kingdom. But after some time in 1977 in a separate new tsarstvo.Prosteyshie - paraphyletic group. For organisms that belong to this group can not specify any positive common characteristics.

It's simple - unicellular and colonial, with no highly organized tissue.

General characteristics of protozoa

Most elementary - small organisms. Their average size is measured in several tens of micrometers.

The smallest simplest - intracellular parasites - reach 4.2 mCi, and the length of the largest species, such as some gregarines may be up to 1 millimeter.

the simplest form of the body is extremely diverse. Among them are species with variable shape of the body as an amoeba. Diverse types of symmetry in the elementary. Widespread form with radial symmetry: Radiolarians, Dory (Heliozoa). It basically floating planktonic protozoa. Bilateral symmetry is observed in some flagellates, foraminifera, radiolarians. Translational and rotational symmetry characteristic of foraminifera from spiralnozakruchennoy sink. Some species are observed MetaSubway - repeatability structures along the longitudinal axis.

various life forms of protozoa, or morfoadaptivnye types. The most common forms are amoeboid that are crawling lifestyle different substrates in water or in a liquid medium in the body of the host, the sink - benthic inactive form; actively swimming ciliates flagellates and, floating in the plankton groove or rayed, shape, chairs - stalked; uzkotelye or ploskotelye inhabiting the substrates - interstitial and rounded still, resting forms (cysts, spores).

Structure and life cycles:

Simple have the finest morphophysiological adaptations to living in different environmental conditions. Typically, microscopic size, are found in water, moist soil, or in the body of animals and humans. The shape of their body is very diverse - from uncertain (like an amoeba) to an elongated, streamlined, fusiform. Some of the simplest have an outer shell, and those that live in the water column - bizarre appendages.

most elementary body consists of a single cell comprising one or more cores. In some body wearing only the thinnest membrane, other than a cell membrane developed a series of structures forming a membrane with a more or less thick shell, generally elastic - pellicle. The cytoplasm in the simplest can be divided into external (ectoplasm, plazmagel) and internal (endoplasm, plazmozol), distinguishable under a microscope.

just the ability to move through lozhnonozhek, flagella or cilia respond to different stimuli (phototaxis, chemotaxis, thermotaxis, etc.). They feed on the smallest simplest animal, vegetable organisms and decaying organic matter, parasitic forms live on the surface of the body, in body cavities or tissues of organisms for their owners. Routes of food into the body cells are also different: pinocytosis, phagocytosis, osmotic way, the active transport of substances through the membrane. In doing they digest food in the digestive vacuoles filled with digestive enzymes. Some of them having photosynthetic intracellular symbiont - chlorella or chloroplasts (for example, Euglena) capable of synthesizing organic matter from the inorganic substances by photosynthesis.


simplest is sexually and asexually, depending on the conditions of existence. At first asexual reproduction of the core is divided into two or more parts, and then divided the cytoplasm into two (equal or unequal) or a lot of parts (corresponding to the number of newly formed nuclei). As a result of a single organism produces two (the same or unequal in value) or more new organisms. In sexual reproduction two equal or different in size and structure (male and female) individuals merge with each other to form a zygote, which then begins to reproduce asexually. Sometimes between two individuals is part of the exchange of nuclei in contact individuals (zygote formation is not observed).

Under adverse conditions, can form the simplest tsysty: their body is rounded and covered with a thick protective shell in which they can spend a lot of time. Under favorable conditions, the simplest is released from the shell and begins to lead sedentary lives.

Classification simple:

prostitution traditionally be classified in three groups:

  • Sarkomastigofory - are able to help with the movement of flagella or pseudopodia (lozhnonozhek)
  • ciliates - with plenty of cilia.
  • Spore - still or moving through a special sliding motion due to penetration into the cell a special material such as Plasmodium falciparum.

classification of protists is experiencing a period of turbulent change permanent. With the exception of ciliated and aquatic fungi, traditional groups polifiletichny and often overlap. New classification criteria, including those based on data from biochemistry and genetics, can distinguish monophyletic group. However, the understanding of the evolutionary relationships between protists began to clear only recently, and the position of many groups are still controversial.