2aStructures and Functions in Living Organisms
Level of organisation — Edexcel Linear - OL Revision Notes & Topical Questions
5 min read 7 parts Lesson 1 of 25 1 quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Lesson summary
Level of organisation Edexcel O Level Linear Biology notes: describe the levels of organisation in organismsThe order is always cell → tissue → organ → organ system → organism.A tissue contains only one type of cell; an organ contains several tissues.The heart is an organ; the ci…
- Plants have organs too
- Level of organisation Edexcel O Level Linear Biology: what to do next
- Muscle tissue
- Circulatory system
- Give / State / Name
- Evaluate / Assess
Part 1 of 6Key ideas
1The order is always cell2tissue3organ4organ system5organism
A tissue contains only one type of cell; an organ contains several tissues.
The heart is an organ; the circulatory system is an organ system.
Plants have organs too
Plants have organs too leaves, stems, roots and flowers.
Organ systems depend on each other to keep the organism alive.
Part 2 of 6Syllabus points
- describe the levels of organisation in organisms
- organelles, cells
- tissues
- organs and systems
Part 3 of 6Process & sequence
- Cell
- Tissue
- Organ
- Organ system
- Organism
1Cells
Similar cells group together to form a tissue.
2Organ
Different tissues join to form an organ.
3Organ system
Organs work together as an organ system.
4Organism
All organ systems together make an organism.
Part 4 of 6Summary
1
A group of similar cells is a tissue.
2
Different tissues working together form an organ.
3
Organs working together form an organ system.
4
The smallest level is the cell; the largest is the organism.
Part 5 of 6Keep going
Level of organisation Edexcel O Level Linear Biology: what to do next
These Level of organisation Edexcel O Level Linear Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Level of organisation Edexcel O Level Linear Biology understanding with the practice questions below, then reread any Level of organisation Edexcel O Level Linear Biology point you were unsure about before moving on.
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Previous lesson: 1b Variety of living organisms — Notes
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Next lesson: 2b Cell structure — Notes
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Course: Edexcel Linear - OL — all units
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Official syllabus: Pearson Edexcel International GCSEs
Part 6 of 6Compare: Compare
| Level | Made of | Animal example | Plant example | Job of the example | Size |
|---|---|---|---|---|---|
| Cell | Organelles (nucleus, membrane…) | Muscle cell | Palisade cell | Contract / photosynthesise | Microscopic |
| Tissue | Similar cells | Muscle tissue | Xylem tissue | Move body parts / carry water | Very small |
| Organ | Different tissues | Heart, stomach | Leaf, root | Pump blood / make food | Visible |
| Organ system | Several organs | Circulatory system | Shoot system | Transport around body / plant | Large |
| Organism | Organ systems | Human | Sunflower | Carries out all life processes | Whole living thing |
Key terms
Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Cell · Tissue · Organ · Organ system · Organism · Muscle tissue · Xylem · Circulatory system
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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