What is common in the structure of the simplest in the opinion of biologists

Animals that can only be seen with a microscope are the simplest. They form their sub-kingdom, containing up to 40 thousand species. And although their number is so great, the scientists met representatives protist only in the 17th century thanks to the inventor of the microscope, Antoni van Leeuwenhoek. In this article we will study their morphology by finding out what they are different from each other and what is common in the structure of the protozoa.

Biology about the role of unicellular animals in nature

According to the systematics data, this group of eukaryotic organisms includes representatives of the Sarcodov, Sporoviki, Infuzorii and Zhgutikovy classes. Having settled ecological niches in the hydro- and lithosphere, they became capable of different types of food. Among the protozoa are autotrophs, for example euglena green, heterotrophs - infusorians, foraminifers and radiolarians, parasites such as malarial plasmodium or dysentery amoeba.

Most of them serve as the main food base for multicellular animals: coelenterates, arthropods, fish. Protozoa enter all trophic chains, playing the role of producers or consumers of the first order. Let's consider what is common in the structure of the protozoa.

Cell as a whole organism

The protista body consists of a single cell and, although it does not have organs, tissues and systems, but is able to fully perform the functions of respiration, secretion, nutrition, reproduction.

Outwardly, animals are very different from each other, which is due to the phenomenon of divergence. It arose as a result of the action of natural selection and hereditary variability. Nevertheless, according to most scientists, all unicellular animals originate from one ancient and extinct group of eukaryotic cells. This explains the similarity of their morphological plan. Let us consider what is common in the structure of protozoa, in more detail. For example, freshwater inhabitants: amoeba proteus, infusoria-shoe, euglena green - have contractile vacuoles. They periodically throw out excess water and protect the animal from death, regulating the osmotic pressure of the liquid in the body.

Digestive vacuoles also have a similar structure, splitting organic substances. The cells include the Golgi apparatus, mitochondria and lysosomes. These examples clearly show what is common in the structure of the protozoa.

The flagellar class is characterized by an intracellular structure similar to the infusoria and amoeba. But in its composition it has species containing chloroplasts, such as euglena green. In the light, such protozoa are capable of photosynthesis - an autotrophic way of feeding, like plants.

Cell membrane

Its composition and properties can be considered as a criterion, which is common in the structure of the protozoa. The membrane consists of molecules of proteins and lipids and provides transportation of substances, and above it is located glycocalyx. It contains signaling proteins and is responsible for irritability. To form a body, a pellicle is formed, and in the sarcodic - dense near-wall layer of the cytoplasm. In marine rhizomes, the membrane is covered from above with a shell serving as a supporting function.

Despite the external differences of organisms, conditioned by adaptations to the environment, their cellular level of organization is a criterion that is common in the structure of protozoa.