Life begins with a cell

"Where did life begin?" Most probably in water. Some researchers think it began in small pools where conditions kept changing, such as hot springs.

India has such a place. The hot springs of Puga Valley in Ladakh stay close to the boiling point of water even though the land around them is freezing cold. That is a lot like the early Earth, about 3.5 billion years ago. Tiny one-celled bacteria live in this hot water. They love heat, so they are called thermophiles (thermo = heat, phile = loving).

Scientists from the Birbal Sahni Institute of Palaeosciences, Lucknow, found calcium carbonate (the mineral in chalk) forming quickly around these springs. Such deposits may have protected the first molecules of life and helped form the first membrane: the thin wall that separates a cell from everything outside it.

Every living thing is made of cells. The smallest thing in matter is an atom; the smallest living thing is a cell.

• Unicellular (one cell): bacteria, yeast.
• Multicellular (many cells): plants, fish, birds, you.

Think of a house. Bricks make a wall, walls make a room, rooms make a house. In the body:

• similar cells together make a tissue;
• tissues together make an organ;
• organs working together make an organ system.

Your nose openings, nasal cavity, windpipe (trachea) and lungs together form the respiratory system.

However big the house, the brick is still the basic unit. In the same way, the cell stays the basic unit of structure (what the body is built from) and function (what the body does).