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Organs are connected to cells, tissues, organ systems and organisms by cells that are grouped together which are called tissues.
Tissues and organs are made of cells
tissues
cells to tissues to organs to organ systems to organisms... cells to tissues to organs to organ systems to organisms...
cells are to tissue are to organs are to organ systems are to organisms
Unicellular organisms have to complete all tasks to survive, and obviously have no specialised cells, while a multi cellular cell would be specialised and be made for a specific task such as a lung cell.
In unicellular organisms, a single cell performs all the basic functions such as respiration, movement, excretion, digestion, etc. But in multicellular organisms, cells are grouped to form tissues. These tissues are specialised to carry out a particular function at a definite place in the body. For example, the muscle cells form muscular tissues which helps in movement, nerve cells form the nervous tissue which helps in transmission of messages. This is known as division of labour in multicellular organisms. It is because of this division of labour that multicellular organisms are able to perform all functions efficiently.
Tissues are connected to the cells organism by small molecules called cells.
cells, tissues, organs, organ systems, and organisms
tissues
They are made by tissues which were formed by cells
Stem cells are important cells found in all multi-celled organisms, that can divide and recognise problems. In mammals, there are two types of stem cells: embryonic cells, and adult stem cells, which are found in various tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, renewing and restoring adult tissues.