Every organism that we see in the surrounding reality is defined in biology as an individual.
An individual (or individual) is the basic unit of various life forms (plants, animals, fungi).
Each individual has its own individual characteristics. However, individuals can be similar to each other, for example, all cats. They should never be confused with dogs, for example. They are different because they belong to different species.
A species is a group of individuals with a similar structure that are able to interbreed with each other, providing fertile offspring.
Many species, similar in lifestyle, diet and habitat, can be combined into larger groups.
The need to unite living beings into various groups or to systematize them appeared in ancient times. This is how the biological science – systematics – was formed. Its founder is the Swedish naturalist Karl Linnaeus.
In different periods of time, different scientists subdivided living beings in different ways. Currently, there are several kingdoms of living organisms: Animals, Plants, Fungi, Bacteria, etc.
The kingdom is a very large group of organisms that have similar characteristics of structure, nutrition and life in nature.
Representatives of these kingdoms have a cellular structure. Non-cellular organisms are also known – viruses.
In this course we will study the kingdoms: Plants, Bacteria, Mushrooms. Of these three kingdoms of living nature, the largest and most diverse is the kingdom of the Plant. It includes about 350 thousand species, while about 100 thousand species of fungi are known to date, and about 20 thousand species of bacteria. Bacteria and fungi were isolated into separate kingdoms only in the twentieth century, when they were found to be significantly different from plants.
Plants are currently the basis of life for the entire organic world. It is the plants that create the conditions for the existence of all life on Earth. Living plants and their obsolete and fallen parts – leaves, fruits, branches, trunks – provide food for animals, fungi and bacteria.
Also of great importance in nature are bacteria and fungi – many of them turn plant and other organic residues into humus, which is reused by plants.
Realizing the great importance of living organisms, we must treat them very carefully in order to preserve all their diversity and wealth on Earth. For this, each person needs to know biology well.