The Fundamental Unit of Life

What are Living Organisms Made Up Of?

Living organisms, whether plants, animals, or microorganisms, are composed of fundamental units called cells. These cells are microscopic in size and are the smallest structural and functional units of life. Every living organism, from the tiniest bacteria to the largest animals and plants, is made up of one or more cells. Cells carry out all the essential processes that sustain life, such as metabolism, growth, and reproduction. The concept that all living things are made of cells forms the basis of the cell theory, a fundamental principle in biology. Cells can exist independently as single-celled organisms like amoeba, or they can be part of a complex multicellular organism like humans, where cells specialize to perform different functions. This specialization allows for the formation of tissues, organs, and organ systems, which work together to maintain the life of the organism. The study of cells is crucial to understanding the structure, function, and processes of all living beings. **Table on page 17 (7×5)** | S. No. | Property | Solution | Suspension | Colloid | | --- | --- | --- | --- | --- | | 1. | Nature (homogeneous/heterogeneous) | | | | | 2. | Particle size | | | | | 3. | Visibility | | | | | 4. | Separation by filtration | | | | | 5. | Settling | | | | | 6. | Tyndall effect | | | | **Table on page 19 (3×3)** | Solution | Suspension | Colloid | | --- | --- | --- | | Properties | Properties | Properties | | Examples | Examples | Examples | **Table on page 20 (8×3)** | Mixture | Method of separation | Reason for selection | | --- | --- | --- | | Mud from muddy water | | | | Plasma from other components in the blood sample | | | | Naphthalene and sand | | | | Chalk powder and common salt | | | | Common salt and water | | | | Oil from water | | | | Pigments of the flower | | | **Table on page 21 (6×7)** | Salts | Temperature (°C) | | | | | | | --- | --- | --- | --- | --- | --- | --- | | | 10 °C | 20 °C | 30 °C | 40 °C | 60 °C | 80 °C | | Potassium nitrate | 21 | 32 | 45 | 62 | 106 | 167 | | Sodium chloride | 36 | 36 | 36.3 | 36.5 | 37 | 37 | | Potassium chloride | 35 | 35 | 37.4 | 40 | 46 | 54 | | Ammonium chloride | 24 | 37 | 41 | 41 | 55 | 66 | **Table on page 22 (2×6)** | Solvent | Water | Acetone | Alcohol | Chloroform | Benzene | | --- | --- | --- | --- | --- | --- | | Temperature (°C) | 100 °C | 56 °C | 78 °C | 61 °C | 80 °C |

• Cells are the basic structural and functional units of all living organisms.
• Living organisms can be unicellular or multicellular.
• Cells perform essential life processes like metabolism, growth, and reproduction.
• Specialization of cells leads to tissues and organs in multicellular organisms.
• The cell theory states that all living organisms are made up of cells.
• Understanding cells is key to understanding life.
• 📌 Cell: The smallest structural and functional unit of life.
• 📌 Unicellular organism: An organism made up of a single cell.
• 📌 Multicellular organism: An organism made up of many specialized cells.

Discovery of the Cell

The discovery of the cell is a landmark event in the history of biology. In 1665, Robert Hooke, an English scientist, observed thin slices of cork under a microscope. He noticed tiny, box-like structures which he called 'cells' because they resembled the small rooms, or 'cells,' in a monastery. These were actually the dead cell walls of cork tissue. Later, Antonie van Leeuwenhoek, a Dutch scientist, improved the microscope and observed living cells in pond water, blood, and other materials. He discovered single-celled organisms, which he called 'animalcules.' The development of better microscopes allowed scientists to observe cells in greater detail, leading to the formulation of the cell theory by Matthias Schleiden and Theodor Schwann in the 19th century. They proposed that all plants and animals are composed of cells, and that the cell is the basic unit of life. This discovery revolutionized biology by providing a unifying concept for the structure and function of all living organisms.

• Robert Hooke discovered cells in cork tissue in 1665.
• Hooke named the structures 'cells' due to their resemblance to small rooms.
• Antonie van Leeuwenhoek observed living cells and microorganisms.
• Improved microscopes enabled detailed study of cells.
• Matthias Schleiden and Theodor Schwann formulated the cell theory.
• Cell theory states that all living organisms are made of cells.
• 📌 Cell theory: The concept that all living organisms are composed of cells.
• 📌 Microscope: An instrument used to observe objects too small for the naked eye.
• 📌 Animalcules: Term used by Leeuwenhoek for microscopic living organisms.