Tissue and Other Levels of Organization: Levels of Organisation – Cell to Organism (For CBSE, ICSE, IAS, NET, NRA 2022)

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Levels of Organisation – Cell to Organism

The cell has a very complex system of its organelles, each organelle concerned with a particular task or activity, and each activity contributing to the total performance of the cell. Thus, there is a division of labour at the cellular level. As evolution progressed and larger and larger organism appeared with enormous number of cells in the body, it became necessary that the bodily functions are distributed among different groups of cells or tissues even among groups of tissues. Such higher and higher stages or grouping are known the levels of organization; these levels are as follows:

  • Cellular level of Organization: The cell is the lowest level of organisation that is alive and has an independent existence. It is the structural and functional unit of life. That is why these are called the building blocks of life. The organisation of the activities by different organelles in a single cell. Example- white blood cells or a green cell of a leaf.
  • Tissue level: The aggregates of cells of same origin and having same function including extracellular substance between them, example- the surface epithelium of our skin or the dividing cells at the root cap of a plant.
  • Tissue system: Organisms which consist of two or more cells are called multi-cellular organisms. Example- vascular tissue of a leaf, consisting of xylem and phloem, for transport of water and food materials.
  • Organ level: Different types of tissues work together to form an organ and is called organ level of organisation. An organ performs a specific function in the body. In the case of plants, root, stem and leaf are the organs. In an animal body there are different organs like heart, stomach, liver, lungs etc. Each organ is made up of more than one type of tissues. It is higher than the tissue level of organisation.
  • Organ system: Several organs form a system which is responsible for performing specific functions. This is called organ system level of organisation. It is higher than organ level of organisation. In higher plants the body is divided into root system and root system. The root absorbs fixes the plant in the soil and also absorbs water and minerals. The shoot system with stem, leaf, flower and fruit performs various other functions. In animals, several organs combine to form at least ten different systems.
  • Organism: An organism is also unit. It consists of cells, tissues, organs and organ systems. Because of this organisation, the organisation leads and independent life. The complete individual made of different organ system. Examples- man, monkey, or a mustard plant.
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