0The fundamental unit of life is the cell.
All living organisms, whether small like bacteria or large like humans, are made up of cells. A cell is the fundamental unit of life because it is the smallest structure that can perform all the basic functions needed for life, such as growth, respiration, and reproduction. Just like bricks join together to form a building, cells join together to form tissues, organs, and finally an entire organism. The study of cells is called Cytology.
The discovery of the cell was made by Robert Hooke in 1665, when he observed thin slices of cork under a microscope. Later, scientists Schleiden and Schwann proposed the Cell Theory, which states that:
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All living beings are made of cells.
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The cell is the basic structural and functional unit of life.
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All cells arise from pre-existing cells (Virchow).
Organisms can be classified into two main types based on the number of cells in their body:
Unicellular Organisms :Made up of a single cell. The same cell performs all life processes like nutrition, respiration, growth, and reproduction.Examples: Amoeba, Paramecium, Bacteria, Yeast. They are small in size but fully functional because that one cell is independent.
Multicellular Organisms: Made up of many cells.Different groups of cells perform different functions (division of labour).Cells form tissues, tissues form organs, organs form organ systems, and all together make the organism.Examples: Humans, Plants, Animals, Fungi.They are usually larger and more complex.
