Science class 10

What processes would you consider essential for maintaining life?

An organism needs a source of energy for its movement and maintenance of the body. Carbon compounds like starch, cellulose, glucose, sucrose and fats found in the environment fill that requirement. We generally call them food.

We look for some form of movement like walking, talking, breathing etc. or growth in the body part like height, size to confirm the organism is live. But this is not always true. For example, we can not detect a movement in plants and unicellular organism easily.

A cell of a unicellular organism is in direct contact with the environment and intake of oxygen occurs directly by diffusion. While Many cells of multi-cellular organisms like human are not in contact with the external environment.