What is called an organism? Organism: Definition

What is called an organism and how does it differ from other objects in nature? By this concept we mean a living body that has a set of different properties. They distinguish the body from inanimate matter. In translation from Latin, the organismus means "I inform the orderly form", "I arrange". The very name implies a certain structure of any organism. Biology is engaged in this scientific category. Living organisms amaze with their diversity. As separate individuals they are included in the composition of species and populations. In other words, it is a structural unit of a certain standard of living. To understand what is called an organism, it is necessary to consider it from different aspects.

General classification

The organism, whose definition quite fully explains its essence, consists of cells. Specialists distinguish such extrasystematic categories of these objects:

• single-celled;

• multicellular.

A separate group is distinguished by an intermediate category between them, like colonies of unicellular organisms. They are also divided in the general sense into nuclear-free and nuclear ones. For the convenience of studying, all these objects are distributed among numerous groups. Thanks to this division into categories, living organisms (biology of the 6th grade) are brought together in an extensive biological classification system .

The concept of a cell

The definition of the term "organism" is inextricably linked with a category such as a cell. It is the basic unit of life. It is the cell that is the real carrier of all the properties of a living organism. In nature, only viruses that are a non-cellular form do not have them in their structure. This elementary unit of vital activity and the structure of living organisms possesses the whole set of properties and the mechanism of metabolism. The cell is capable of independent existence, development and self-reproduction.

Many bacteria and protozoa, representing a single-celled organism, and multicellular fungi, plants, animals, consisting of many of these units of vital activity, easily fit into the concept of a living organism. Different cells have their own structure. Thus, the structure of prokaryotes includes such organelles as capsule, plasmalemma, cell wall, ribosomes, cytoplasm, plasmid, nucleoid, flagella, and saw. In eukaryotes there are the following organoids: nucleus, nuclear envelope, ribosomes, lysosomes, mitochondria, Golgi apparatus, vacuoles, vesicles, cell membrane.

The biological definition of "organism" is studied by a whole section of this science. The structure and processes of their life is cytology. Recently, it is often called cell biology.

Unicellular organisms

The term "unicellular organism" implies an extrasystemic category of objects whose body has only one cell. It includes:

• Prokaryotes that do not have a decorated cell nucleus and other internal organoids with membranes. They do not have a nuclear envelope. They have a circumscribed and autotrophic type of nutrition (photosynthesis and chemosynthesis).

• Eukaryotes, which are cells containing nuclei.

It is generally accepted that unicellular organisms became the first living objects on our planet. Scientists are sure that the most ancient of them were archaea and bacteria. Unicellular organisms are often called protista-eukaryotic organisms, which are not included in the category of fungi, plants and animals.

Multicellular organisms

A multicellular organism, the definition of which is closely related to the formation of a single whole, is much more complex than single-celled objects. This process consists of differentiation of various structures, which include cells, tissues and organs. The formation of a multicellular organism includes the separation and integration of different functions in ontogenesis (individual) and phylogenesis (historical development).

Multicellular organisms are composed of a multitude of cells, a significant part of which is different in structure and function. The only exception is stem cells (in animals) and cambium cells (in plants).

Multicellularity and coloniality

Biology distinguishes multicellular organisms and colonies of unicellular organisms. Despite some similarity of these living objects, there are fundamental differences between them:

• A multicellular organism is a community of many different cells that have their own structure and special functions. His body consists of different tissues. For such an organism, a higher level of cell aggregation is characteristic. They differ in their diversity.

• Colonies of unicellular organisms consist of identical cells. They are almost impossible to divide into fabrics.

The boundary between colonial and multicellularity is unclear. In nature there are living organisms, for example, volvox, which in their structure are a colony of unicellular animals, but they have somatic and generative cells that differ from each other. It is believed that the first multicellular organisms appeared on our planet only 2.1 billion years ago.

Differences of organisms from inanimate bodies

The term "living organism" implies the complex chemical composition of such an object. It contains proteins and nucleic acids. This is what distinguishes it from the bodies of inanimate nature. They also differ in the totality of their properties. Despite the fact that the bodies of inanimate nature also possess a number of physico-chemical properties, the concept of "organism" includes more numerous characteristics. They are much more diverse.

To understand what is called an organism, it is necessary to study its properties. So he has such characteristics:

• Metabolism, which includes nutrition (intake of useful substances), isolation (withdrawal of harmful and unnecessary products), movement (change of position of the body or its parts in space).

• Perception and processing of information, which includes irritability and excitability, allowing to perceive external and internal signals and selectively react to them.

• Heredity, allowing to transmit its characteristics to descendants and variability, which is the difference between individuals of the same species.

• Development (irreversible changes throughout life), growth (weight and size increase due to biosynthetic processes), reproduction (reproduction of oneself like).

Classification based on cell structure

Experts divide all forms of living organisms into two supra-kingdoms:

• Pre-nuclear (prokaryotes) - evolutionarily primary, the simplest type of cells. They were the first forms of living organisms on Earth.

• Nuclear (eukaryotes), originating from prokaryotes. This more progressive type of cells has a nucleus. Most of the living organisms on our planet, including humans, are eukaryotic.

The nuclear supercarship, in turn, is divided into four kingdoms:

• protists (paraphilithic group), which are ancestral to all other living organisms;

• mushrooms;

• plants;

• Animals.

Prokaryotes include:

• bacteria, including cyanobacteria (blue-green algae);

• Archaean.

The characteristic features of these organisms are:

• lack of a developed core;

• presence of flagella, vacuoles, plasmids;

• presence of structures in which photosynthesis is carried out;

• Form of reproduction;

• Size of the ribosome.

Despite the fact that all organisms differ in the number of cells and their specialization, all eukaryotes are characterized by a certain similarity in the structure of the cell. They differ in their common origin, therefore this group is a monophyletic taxon of the highest rank. According to scientists, eukaryotic organisms appeared on the earth about 2 million years ago. An important role in their emergence was played by symbiogenesis, which is a symbiosis between a cell that has a nucleus and is capable of phagocytosis, and its absorbed bacteria. They became the precursors of such important organelles as chloroplasts and mitochondria.

Mesocariotes

In nature, there are living organisms, which are an intermediate link between prokaryotes and eukaryotes. They are called mesocaryotes. They differ from them by the organization of the genetic apparatus. To this group of organisms are dinoflagellates (dinophyte algae). They have a differentiated nucleus, but in the cell structure there are preserved the features of primitiveness that are inherent in the nucleoid. The type of organization of the genetic apparatus of these organisms is viewed not only as a transitional, but also as an independent branch of development.

Microorganisms

Microorganisms are called a group of living objects, extremely small in size. They can not be seen with the naked eye. Most often their size is less than 0.1 mm. This group includes:

• denuclearized prokaryotes (archaea and bacteria);

• eukaryotes (protists, fungi).

The vast majority of microorganisms are a single cell. Despite this, there are unicellular organisms in nature that can easily be seen without a microscope, for example, the giant polycarion Thiomargarita namibiensis (marine gram-negative bacterium). The life of such organisms is studied by microbiology.

Transgenic organisms

Recently, more often on the ear is a word combination, like a transgenic organism. What is it? It is an organism in which the genome of another living object is artificially introduced into the genome. It is introduced in the form of a genetic construct, which is a sequence of DNA. Most often it is a bacterial plasmid. Thanks to such manipulations, scientists receive living organisms with qualitatively new properties. Their cells produce a protein of the gene that was introduced into the genome.

The concept of "human body"

Like any other living objects people study the science of biology. The human body is an integral, historically developed, dynamic system. It has a special structure and development. And the human body is in constant communication with the environment. Like all living objects on Earth, it has a cellular structure. They form tissues:

• Epithelial, located on the surface of the body. It forms the skin and lays the walls of hollow organs and blood vessels from the inside. Also, these tissues are present in closed body cavities. There are several types of epithelium: cutaneous, renal, intestinal, respiratory. The cells that form this tissue are the basis of such altered structures as nails, hair, enamel of teeth.

• Muscular, with the properties of contractility and excitability. Due to this tissue motor processes inside the organism and its movement in space are carried out. Muscles consist of cells in which microfibrils (contractile fibers) are located. They are divided into smooth and striated muscle.

• Connective, which includes bone, cartilaginous, adipose tissue, as well as blood, lymph, ligaments and tendons. All its varieties have a common mesodermal origin, although each of them has its own functions and features of the structure.

• Nervous, which is formed by special cells - neurons (structural-functional unit) and neuroglia. They differ in their structure. So the neuron consists of a body and 2 processes: branching short dendrites and long axons. Covered by shells, they make up nerve fibers. Functional neurons are divided into motor (efferent), sensitive (afferent), intercalary. The place of transition from one of them to another is called a synapse. The main properties of this tissue: conductivity and excitability.

What is called the human body in a broader sense? Four types of tissues form organs (part of the body with a certain shape, structure and function) and their system. How are they formed? Since with the performance of certain functions one body can not cope, their complexes are formed. What are they? Such a system is a collection of several organs with a similar structure, development and functions. All of them form the basis of the human body. These include:

• musculoskeletal (skeleton, muscles);

• Digestive (glands and tract);

• respiratory (lungs, respiratory tract);

• sense organs (ears, eyes, nose, mouth, vestibular apparatus, skin);

• Sexual (female and male sexual organs);

• nervous (central, peripheral);

• the blood (heart, blood vessels);

• endocrine (endocrine glands);

• Cover (skin);

• urinary (the kidneys that lead the way).

The human organism, the definition of which can be imagined as the totality of different organs and their systems, has a basic (deterministic) origin - the genotype. It is a genetic constitution. In other words, it is a set of genes of a living object, received from parents. Any kind of microorganisms, plants, animals has a characteristic genotype for it.