Class 9 Science: The Fundamental Unit of Life

Robert Hooke was the first to observe cells. He used a self-made microscope and examined thin slices of cork, where he noticed small, box-like compartments that he named 'cells.'

Antonie van Leeuwenhoek, a Dutch scientist, observed tiny living organisms in pond water using his self-made microscopes. These were the first observations of living cells.

Robert Brown is credited with discovering the nucleus, a dense, spherical body present within the cell. He observed it in plant cells using his microscope.

Theodor Schwann, a German scientist, contributed significantly to the cell theory by proposing that all living organisms, both plants and animals, are made up of cells.

Rudolf Virchow, a German pathologist, added to the Cell Theory by stating that all cells arise from pre-existing cells. This idea contradicted spontaneous generation theories.

Every cell has three key features that define it: the plasma membrane, the nucleus, and the cytoplasm. These components work together to maintain cell function.

Endocytosis is a process where the cell membrane engulfs substances from the outside environment and brings them inside. This allows cells to take in nutrients and other necessary materials.

Diffusion is the movement of solute molecules from a region of high concentration to low concentration, while osmosis is the movement of water molecules across a semipermeable membrane from a region of high water concentration to low concentration.

Every multicellular organism starts as a single cell, which then divides and differentiates into various types of cells that form tissues, organs, and systems. The process of development is how this single cell becomes a complex organism.

The Golgi apparatus is an organelle that acts like a factory or distribution center within the cell. It packages, modifies, and sorts proteins and lipids that are made in the endoplasmic reticulum, preparing them for use in the cell or for export.