In biology, a large number of species of living organisms have already been studied, which belong to various taxonomic units. Related systematic groups of organisms are separated from other similar species, which simplifies the study of science in general and evolution in particular.
Science Systematics
This branch is engaged in the study and description of the entire diversity of life on planet Earth. Also, the main task of taxonomy is the grouping of organisms according to distinctive features, which further helps to compose competent classification schemes.
When classifying animals, plants, bacteria or protists, the concept of a taxon is often used. This term is understood as a systematic group of organisms related by kinship and common distinctive features.
Features of systematization and classification of all things are the main subjects of study of such a doctrine as taxonomy. The term is used not only in biology, but also in other areas (linguistics, bibliography).
Hierarchical classification systems
In any science that requires the systematization of its objects, it is necessary to single out common classification taxa. These can be large groups (in our case) of living organisms, taking into account common features.
Several systematic groups of related organisms are further formed from such classification taxa. They usually have a number of distinctive and characteristic features, in which they differ from other objects of study by biologists.
If any two taxa do not have common features (do not intersect) or are subordinate to each other, then such a classification system can be called hierarchical.
Here we can give the following examples: the class Amphibians and the class Birds do not intersect, because their representatives have little similarity. If we consider the order Primates within the class Mammals, then both of these taxa are characterized by some common features, but they are subordinate (the order is lower than the class in the biological taxonomy of animals).
Characteristics of a biological taxon
Attributes of any systematic group of organisms related by kinship are diagnosis, rank and volume.
1. The diagnosis is understood as all the distinguishing features of a given taxon, which unite the corresponding species of organisms. Moreover, these distinctive features should be sufficient to limit objects to a separate group.
2. Rank is the level of taxonomicgroups within the considered classification scheme. Depending on it, these groups are subordinate and at the same time may have several common features.
3. If it is necessary to indicate the number of taxa of a lower rank, the concept of the volume of a systematic group is used. It is now rarely used and is usually explained by the Latin expressions sensu stricto or sensu lato (in the narrow sense and in the broad sense, respectively).
Biological classification
The systematization of various types of plants and animals today is firmly established in many textbooks and teaching aids. Based on the above features of the hierarchical classification, all living organisms are divided into 5 kingdoms: plants, animals, fungi, protists and bacteria. There are also non-cellular life forms (viruses, viroids, virusoids, prions), which are considered separately.
Within the kingdoms Plants, Fungi and Bacteria, the following taxonomic units are distinguished, which go in descending order of precedence:
- Kingdom.
- Department
- Class.
- Order.
- Family.
- Born.
- View.
If we consider higher plants (according to the old classification), which include all terrestrial representatives, 4 divisions have been studied: bryophytes, ferns, gymnosperms and angiosperms. Ferns are sometimes divided into three separate taxonomic groups: horsetails, lycopsids, and ferns proper.
Here is another option for the distribution of taxonomic ranks:
- Kingdom.
- Type.
- Class.
- Squad.
- Family.
- Born.
- View.
This hierarchical classification is used in the study of animals and protists.
Relationships within one systematic group of organisms are built vertically, but from the point of view of evolution, scientists are interested in the "horizontal" classification of taxa.
For example, representatives of the type Coelenterates are more primitive in comparison with the type Mollusks, but the latter are clearly inferior in evolutionary terms to the type Mammals. As you can see, the taxonomic rank is the same, but the level of organization of the considered species is different.
