Principles of organisation
Joe Wolfensohn
Teacher
Contents
Recall Questions
This topic requires prior knowledge of the structure and functions of specialised cells and an understanding of cell organisation.
What is the function of a root hair cell?
It absorbs water and minerals from the soil using its large surface area.
What is meant by cell specialisation?
It is when a cell develops features that allow it to carry out a specific function.
Give one example of a specialised cell and describe its function.
A sperm cell – it fuses with an egg cell at fertilisation and has a tail to swim towards the egg cell.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains principles of organisation, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Principles of Organisation
The Hierarchy of Biological Organisation
Living organisms are made of systems organised into increasing levels of complexity:
1. Cells
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The basic unit of structure and function in living organisms.
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E.g. muscle cells, nerve cells.
2. Tissues
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A group of similar cells that work together to perform a specific function.
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The cells that form the tissue all come from the same source.
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E.g. muscular tissue contracts to move, epithelial tissue covers surfaces.
3. Organs
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An organ is made of different tissues working together to carry out a specific function.
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E.g. the stomach (an organ in the digestive system) contains muscular tissue (for churning food and mixing it with digestive juices), glandular tissue (which produces and secretes enzymes and hydrochloric acid), and epithelial tissue (for lining and protection of the inner surface).
4. Organ Systems
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Organs are organised into systems to perform broader functions essential for survival.
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E.g. the digestive system includes the stomach, intestines, and liver to digest food and absorb nutrients.
5. Organism
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A complete living thing where all organ systems work together.
A diagram showing the organisational hierarchy of the circulatory system.
Key Terms:
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Cell – Basic unit of life.
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Tissue – Group of similar cells with a specific function.
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Organ – Made up of different tissues working together for a specific function.
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Organ system – A group of organs working together.
- Organism – A living thing.
No answer provided.
Practice Question
Describe why a leaf is an example of an organ (2 marks)
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A leaf is made of different tissues.
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Which work together to carry out a specific function (photosynthesis).
More Practice
Try to answer the practice question from the TikTok video on your own, then watch the video to see how well you did!