2.1 Cell Structure

New Cells are Produced by Division of Existing Cells

All living organisms are made up of cells. These cells are the basic units of life. New cells are not created from scratch; they arise from the division of existing cells. This process is essential for growth, repair, and reproduction.

Cell Division

Cell division is the process by which a parent cell divides into two or more daughter cells. This ensures that the organism can grow and replace damaged cells.

Types of Cell Division

There are two main types of cell division:

• Mitosis: This type of cell division produces two identical daughter cells. It's used for growth and repair.
• Meiosis: This type of cell division produces four daughter cells with half the number of chromosomes as the parent cell. It's used for sexual reproduction.

Table: Comparison of Mitosis and Meiosis

Feature	Mitosis	Meiosis
Purpose	Growth and repair	Sexual reproduction
Number of divisions	One	Two
Daughter cells	Two identical cells	Four genetically different cells
Chromosome number in daughter cells	Same as parent cell	Half the number of chromosomes as the parent cell

Importance of Cell Division

Cell division is vital for:

• Growth: Increases the number of cells in an organism, leading to growth.
• Repair: Replaces damaged or worn-out cells.
• Reproduction: In single-celled organisms, it's the primary mode of reproduction. In multicellular organisms, it's involved in the development of new individuals.

Equation for growth: $Growth = Rate of cell division \times Number of cells$

Understanding how cells divide is fundamental to understanding how living things function and develop.