The scientific study of the different levels of organization of living beings, helps us gain an insight into the complexities of their structure and functioning

Cell: It is considered as the basic unit and building block of life. It is bound by a cell membrane, and possesses a nucleus which acts as its brain. Cytoplasm surrounds the nucleus, which contains cell organelles like mitochondria, ribosomes, vacuole, endoplasmic reticulum, chloroplasts, peroxisomes, and ventricles. The average number of cells in a human body is 100 trillion. They are known to bring about conversion of nutrients into energy, reproduction (cell division), and to carry out specialized functions. Basically, they are of 2 types; prokaryotic and eukaryotic. Prokaryotic cells have a smaller size and simpler form, and lack a nucleus. Eukaryotic cells are more specialized in structure than the prokaryotic ones. Moreover, they are larger in size (by almost 15 times).

Tissue: This level is a combination of different types of cells which perform specialized functions. The group of cells that form a tissue need not be identical, but they should have the same origin. Different types are the nervous, muscle, connective, and epithelial tissues. Connective tissues are fibrous in nature, and they are made up of cells that are separated by an extracellular matrix. Muscle tissues are actively contractile, and useful for producing force and motion. Nervous tissues form organs like the brain and the spinal cord. Epithelial tissues cover the surface of body organs.

Organ System: Organs working together to perform certain functions form organ systems. Examples are the circulatory system in animals, and the vascular system in plants. The organs in an organ system are interdependent, i.e., they work in harmony to carry out various body functions. For example, the digestive system that carries out the process of digestion consists of salivary glands, stomach, esophagus, gallbladder, liver, intestines, pancreas, rectum, and anus.

Population: It is the term used in reference to a group of organisms which belong to the same species. They undergo interbreeding, and share food and space. The population of a particular species indicates a close interaction between its organisms.

Community: Two or more populations together constitute a community. It is characterized by interactions that take place between constituent populations of different species. There are various ways like competition, parasitism, predation, commensalism, and mutualism, by which populations belonging to different species interact with each other. A community can thrive in the same region, but within the territory marked by the particular constituent populations.

Ecosystem: As we move up on this ladder of organization, the complexity tends to increase. The term ecosystem is defined as an area or environment, where one or more communities can thrive and flourish. However, this stage is not the same as community. In fact, it is a greater entity that provides space for different communities. Thus, the populations of many species can together thrive in a particular ecosystem like a desert, grassland, rainforest, etc.

Biosphere: It is simply defined as the place, area, and zone where the entire life on Earth exists. The hydrosphere, lithosphere, and atmosphere, along with all the above-mentioned levels, together constitute the biosphere. It is the amalgamation of all the life forms on Earth, right from the microscopic viruses, bacteria, algae, etc., to the largest animals like blue whales and elephants.

Thus, the above levels present before us the systematic structure and functioning of various components of the organization of life forms. The biological, or precisely the living entities of our planet constitute a very complex and sophisticated system. This article gives a brief idea of the richly varied life on our planet.