TC SIMPLIFIED BIOLOGY

The Unit of Life – Class 11 Biology Simplified Introduction: Life is incredibly diverse, yet every living being—be it a tiny bacterium or a towering tree—is built from the same fundamental unit: the cell. Just like a building is made of bricks, living organisms are made of cells. This chapter from NCERT Class 11 Biology dives deep into the structural and functional unit of life—the cell. --- Discovery of the Cell The story of the cell begins in 1665, when Robert Hooke observed cork under a microscope and described “cellulae” or small compartments. Later, Anton van Leeuwenhoek became the first to observe live cells, laying the groundwork for modern cell biology. --- Cell Theory Two scientists, Schleiden (a botanist) and Schwann (a zoologist), proposed the Cell Theory in 1838-39. It was further refined by Rudolf Virchow, who added: "Omnis cellula e cellula" — meaning “All cells arise from pre-existing cells.” The main points of cell theory are: All living organisms are made of ...

Structural Organisation in Animals – Class 11 Biology Overview The human body, like that of all multicellular animals, is a marvel of structure and function. The Class 11 Biology chapter Structural Organisation in Animals focuses on how cells come together to form tissues, organs, and organ systems that perform specific roles in animal bodies. Understanding this organisation helps us appreciate the complexity and efficiency of animal life. Levels of Organisation 1. Cellular Level: In simple animals like sponges, cells are loosely arranged and perform basic functions independently. 2. Tissue Level: Animals like cnidarians (e.g., Hydra) have cells organized into tissues. 3. Organ Level: In flatworms and onwards, tissues group into organs with defined functions. 4. Organ System Level: Most higher animals (e.g., humans, frogs, earthworms) show a well-developed organ system. Animal Tissues There are four primary types of animal tissues: 1. Epithelial Tissue Covers body surfaces and lines ca...