Scientists have long noticed the extreme diversity of our world and therefore they began to study the manifestations, origin and distribution of all forms of life on Earth. The science that studies all living organisms, their functions, structure, and their classification is called biology. In addition, she explores the relationship of the animate world with the inanimate.
Distinctive properties that only living organisms possess are the following: a high degree and complexity of their organization; each part has its own meaning and certain functions; the ability to use, extract and transform the energy of the environment for their life; the ability to respond to external stimuli and environmental changes. They are also well adapted to their habitat (adaptive properties are developed); can self-reproduce (reproduce), have heredity and a tendency to variability. In addition, they are characterized by evolutionary processes, as a result of which such a variety of living beings arose.
There are several levels of life organization that are in complex subordination to each other. The lowest step isthe line that separates living organisms from non-living ones and is a molecular structure. Next comes the cellular level, at which the cells and the main structural features are the same for everyone. A more complex organo-tissue level applies only to multicellular organisms, in which the parts of the body formed from cells have already developed sufficiently. The next step is a holistic organism, here, no matter how different the creatures are, they have one thing in common - they are all made up of cells.
Further on, all the diversity of life is classified according to a different principle. In biology, there is even a whole section called systematics, in which they describe and group all creatures. So, the systematics of living organisms divides them according to the form of life into non-cellular (viruses) and cellular. The latter are further subdivided into: simple and complex bacteria, plants, animals and fungi. To systematize all these objects, they need to be identified, and for this a number of features are used, which include: morphological, biochemical, physiological and other features.
Great attention in biology is paid to the study of the structure of living beings. They contain a lot of chemical components that form organic and inorganic compounds. The chemical elements in the cells of living organisms contain carbon atoms, which are the hallmark of life. In general, of all organic compounds, only a few classesare essential for development. These include nucleic acids, proteins, lipids and carbohydrates. Living organisms can contain up to 70 components of the periodic system of Mendeleev in their cells, but only 24 are constantly included in their composition (phosphorus, potassium, sulfur, calcium, iron, magnesium, zinc, aluminum, iodine, etc.)
