What is Growth and Development?
Living organisms are remarkable in their ability to grow and change over time. But growth and development are actually two different things — and understanding the difference is key to understanding biology.
A permanent increase in size, mass, or number of cells in an organism.
The process by which an organism changes in structure, complexity, and function over time — not just getting bigger, but becoming more organised and specialised.
Think of it this way: a balloon gets bigger when you blow air into it — that's just an increase in size, not growth. True biological growth involves the production of new cells and new living material. Development goes even further — it involves an organism changing what it can do as well as how it looks.
Imagine building a city. Growth is like adding more buildings. Development is like adding roads, electricity, hospitals, and schools — making the city more complex and functional, not just larger.
How Do Organisms Grow? Cell Division
At the heart of all biological growth is cell division. Organisms grow because their cells divide, producing more cells.
The process by which a parent cell splits into two or more daughter cells, increasing the total number of cells in an organism.
The most common type of cell division in growth is called mitosis. During mitosis:
- The cell copies all of its genetic material (DNA)
- The cell divides into two identical daughter cells
- Each daughter cell receives a full copy of the organism's genetic information
This means every new cell formed during growth carries the same genetic instructions as the original cell. This is extremely important — it means all the trillions of cells in your body (except red blood cells and sex cells) contain the same DNA.
An adult human body contains approximately 37 trillion cells, all derived from a single fertilised egg cell through repeated cell division. Every one of those cells (with a few exceptions) carries an identical copy of your DNA.
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