OCR · A-Level · Biology
Course version: H420 · Version from Sept 2025
(i) the organisation of cells into tissues, organs and organ systems
Full specification wording
Cell division, cell diversity and cellular organisation: (i) the organisation of cells into tissues, organs and organ systems
Cells are organised in a hierarchy of increasing complexity.
Checked against the OCR H420 specification (opens in a new tab) on .
- Point 9 of 13
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Cells are organised in a hierarchy of increasing complexity. Similar cells specialised for the same function group together as a tissue, such as squamous epithelium, ciliated epithelium, cartilage or xylem. Different tissues combine to form an organ with a particular overall function, for example the stomach contains epithelium, muscle and connective tissue. Organs then work together as an organ system, such as the digestive system, to carry out a major body function. Learn the order: cell, then tissue, then organ, then organ system, then organism. A single named cell type is not a tissue; a tissue is not an organ; and an organ is not a system. Watch for options that place a structure at the wrong level of the hierarchy.
What earns the marks
- A tissue is a group of similar cells specialised to carry out the same function.
- An organ is formed from several different tissues working together for a particular function.
- An organ system is a group of organs working together to carry out a major function of the body.
- The hierarchy runs from cell to tissue to organ to organ system to organism.
- A correct option must place the named structure at the level described in the question stem.
Common mistakes and how to put them right
Calling a single cell type a tissue.
Put it right: A tissue is a group of similar cells, not one cell.
Describing an organ as a group of organs.
Put it right: An organ is made of tissues, while a group of organs forms an organ system.
Reversing the hierarchy order.
Put it right: Recall cell, tissue, organ, organ system, organism in that sequence.
Exam tips
- Identify the level named in the stem before evaluating the options.
- Check each option against the definition of that level, not just whether the structure is familiar.
- Reject options that mix levels, such as calling an organ system a tissue.
Try the lesson
The start of the Cell division, cell diversity and cellular organisation: (i) the organisation of cells into tissues, organs and organ systems lesson, made from checked teaching notes for this specification point.
Have a go first
Which of these is an example of a tissue rather than an organ or an organ system?
Listen
Cells are organised in a hierarchy of increasing complexity. Similar cells specialised for the same function group together as a tissue, such as squamous epithelium, ciliated epithelium, cartilage or xylem. Different tissues combine to form an organ with a particular overall function, for example the stomach contains epithelium, muscle and connective tissue. Organs then work together as an organ system, such as the digestive system, to carry out a major body function. Learn the order: cell, then tissue, then organ, then organ system, then organism. A single named cell type is not a tissue; a tissue is not an organ; and an organ is not a system. Watch for options that place a structure at the wrong level of the hierarchy. A strong answer earns marks for these points. A tissue is a group of similar cells specialised to carry out the same function. An organ is formed from several different tissues working together for a particular function. An organ system is a group of organs working together to carry out a major function of the body. The hierarchy runs from cell to tissue to organ to organ system to organism. A common slip: Calling a single cell type a tissue. Instead, a tissue is a group of similar cells, not one cell. Exam tip: Identify the level named in the stem before evaluating the options.
See it
Put it in order
Put these steps in the order they happen.
- 1. Tissue
- 2. Organ
- 3. Cell
- 4. Organism
- 5. Organ system
Key words
Say what each word means before you turn the card.
Tissue
Try answering aloud or in your head before turning the card.
Organ
Try answering aloud or in your head before turning the card.
Organ system
Try answering aloud or in your head before turning the card.
Levels of organisation
Try answering aloud or in your head before turning the card.
See every definition
- Tissue
- A group of similar cells specialised to carry out the same function.
- Organ
- Formed from several different tissues working together for a particular function.
- Organ system
- A group of organs working together to carry out a major function of the body.
- Levels of organisation
- The hierarchy runs from cell to tissue to organ to organ system to organism.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Cell division, cell diversity and cellular organisation: (i) the organisation of cells into tissues, organs and organ systems
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge