The epidermis of a leaf is considered an example of a tissue because the cells

1. Analyze the question The question asks why the epidermis counts as a tissue. So we need the definition of a tissue.

2. Explain the concept A tissue is a group of cells that have a similar structure and work together to perform a specific function. Examples are the epidermis, xylem, phloem and muscle tissue. The levels of organization run:

Cell → Tissue → Organ → System → Organism

3. Go through the options

• A. Allow sunlight to pass through. This is a property of the epidermis (it is transparent), but it does not define a tissue.
• B. Are covered by a waxy cuticle. The cuticle is a secretion on the outside of the epidermis. It does not explain why the epidermis is a tissue.
• C. All possess a similar structure and function. This matches the definition of a tissue exactly. The epidermal cells are flat, closely packed and all protect the leaf and reduce water loss.
• D. Allow water to enter them by osmosis. All living cells do this, so it is not specific to tissues.

4. Answer

5. Exam tip Whenever you see "why is X a tissue?", look for the option that says similar cells doing the same function. Remember: Tissue = same cells + same job. An organ, by contrast, is made of different tissues working together (the leaf is an organ made of epidermis, mesophyll, xylem and phloem).