Why is the cell called the basic unit of life (Class 8 Biology)?

What this question is really asking

You need to explain two ideas: (1) every organism is made of cells, and (2) the cell is the smallest unit that can carry out life functions on its own.

Cells make up the body of all organisms

• Unicellular organisms, like Amoeba and many bacteria, have only one cell. That single cell does everything needed for survival.
• Multicellular organisms, like humans and plants, have many cells. These cells form tissues and organs.

A cell performs all basic life processes

A living cell can carry out key functions such as:

• Nutrition and digestion (taking in and using food)
• Respiration (releasing energy from food)
• Excretion (removing wastes)
• Growth and repair (making new cell material)
• Reproduction (making new cells by cell division)

How cells relate to tissues and organs

In multicellular organisms, cells often specialize:

• Similar cells group to form tissues.
• Different tissues combine to form organs.
• Organs work together in organ systems. Even though organs are larger and more complex, the actual life activities happen inside their cells.

Quick example to remember

• An Amoeba is one cell and it is fully alive.
• A brick is not the smallest unit of a house that can "do" house functions, but a cell is the smallest unit that can "do" life functions. That is why it is called the basic unit of life.