B2.2.1

Large multicellular organisms develop systems for exchanging materials. During the development of a multicellular organism, cells differentiate so that they can perform different functions.

A tissue is a group of cells with similar structureand function. Examples of tissues include:

• muscular tissue, which can contract to bring about movement
• glandular tissue, which can produce substances such as enzymes and hormones
• epithelial tissue, which covers some parts of the body.

Organs are made of tissues. One organ may contain…