Principles of organisation: A tissue is a group of cells with a similar structure and function.

The idea

A tissue is formed when many cells of similar structure work together to carry out a shared function. In animals, examples include muscular tissue, which contracts to move parts of the body, and glandular tissue, which secretes substances such as enzymes or hormones. In plants, examples include palisade mesophyll tissue, whose cells are packed with chloroplasts for photosynthesis, and xylem tissue, which transports water and mineral ions. Tissues are the next level of organisation above cells: several tissues combine to form an organ, and organs work together in organ systems. Recognising a tissue therefore depends on identifying a group of similar cells and the common job they perform, not simply on the number of cells present.

What earns the marks

• Defines a tissue as a group of cells with a similar structure and function.
• Gives named animal examples such as muscular, glandular or epithelial tissue and states their function.
• Gives named plant examples such as palisade mesophyll, xylem or phloem tissue and states their function.
• Explains that tissues are made of similar cells working together, distinguishing this from a single cell or an organ.
• Places tissues in the hierarchy: cells form tissues, tissues form organs, organs form organ systems.
• Uses microscope images or diagrams to identify a tissue from the appearance and arrangement of its cells.

Common mistakes and how to put them right

• Calling any group of cells a tissue regardless of similarity.

  Put it right: The cells must have a similar structure and function.

• Confusing a tissue with an organ.

  Put it right: An organ contains several different tissues working together.

• Giving an organ example such as the stomach or leaf when asked for a tissue.

  Put it right: Name the tissue, such as muscular tissue or palisade mesophyll tissue.

• Assuming all cells in a tissue are identical in every detail.

  Put it right: They are similar in structure and share a function, but may differ slightly.

Exam tips

• Always name the tissue and state its function together, for example 'muscular tissue contracts to move parts of the body'.
• Use one animal and one plant example to show the definition applies to both.
• When identifying a tissue in a diagram, describe the cells' shape, arrangement and any special features.
• Link tissue answers to the next level of organisation to show understanding of the hierarchy.