Why is "Confusing a tissue with an organ" a common mistake in Level of organisation?

Why it happens: Both are described as 'a group of cells working together', so students blur the two. How to avoid it: Use the discriminating words: a **tissue** is **similar cells**; an **organ** is **several DIFFERENT tissues** working together. The word 'different' wins the mark. Source: Edexcel Biology examiner reports

Why is "Calling an organ system an organ (or vice versa)" a common mistake in Level of organisation?

Why it happens: Students see the heart and the circulatory system as the same thing. How to avoid it: An **organ** is a single structure (the heart). An **organ system** is a **group of organs** (the heart + blood vessels = circulatory system). The system is the larger level. Source: Edexcel Biology examiner reports 2023–2024

Why is "Treating an organelle as a cell or as a living organism" a common mistake in Level of organisation?

Why it happens: Both 'organelle' and 'cell' sound like small living units. How to avoid it: An **organelle is a part INSIDE a cell** (e.g. a ribosome) — it is smaller than a cell and not alive on its own. The cell is the basic unit of life. Source: Edexcel Biology examiner reports

Why is "Getting the order of the levels wrong" a common mistake in Level of organisation?

Why it happens: Students memorise the words but not the sequence, or reverse it. How to avoid it: Learn it small → large: **organelle → cell → tissue → organ → organ system → organism**. Each level is built from the one below it. Source: Edexcel Biology examiner reports

Why is "Calling a leaf (or root) a tissue instead of an organ" a common mistake in Level of organisation?

Why it happens: Students apply the hierarchy to animals but forget it works identically for plants. How to avoid it: A leaf contains **several different tissues** (palisade, xylem, epidermal), so it is an **organ** — exactly like the heart. The same definitions apply to plants and animals. Source: Edexcel Biology examiner reports

Why is "Defining a tissue as just 'a group of cells'" a common mistake in Level of organisation?

Why it happens: Students drop the key word 'similar', so the definition becomes too loose. How to avoid it: Always write **'a group of SIMILAR cells with the SAME function'**. 'A group of cells' alone could describe an organ and rarely scores the mark. Source: Edexcel Biology examiner reports

Structure and Functions in Living OrganismsEdexcel IGCSE Science(Double Award)-Biology (4WSD0-1B)

Level of organisation

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Level of Organisation — Edexcel International GCSE Science (Double Award) Biology (4WSD0-1B) Study Notes

How living things are built up in stages — organelles → cells → tissues → organs → organ systems → organism. Each level defined with named examples (ribosome, palisade cell, muscle/xylem tissue, heart/leaf, digestive/circulatory system). Covers Double Award Biology spec 2.1, assessed on Biology Paper 1 (4WSD0/1B).

At a glance

Living things are organised in a hierarchy: organelles → cells → tissues → organs → organ systems → organism.
Organelle = a tiny structure inside a cell that does a specific job, e.g. a ribosome (protein synthesis).
Cell = the smallest unit that can carry out life processes, e.g. a palisade cell in a leaf.
Tissue = a group of similar cells working together on one job, e.g. muscle, epithelial or xylem tissue.
Organ = several different tissues working together, e.g. the heart (animal) or a leaf (plant).
Organ system = a group of organs working together, e.g. the digestive or circulatory system.
Organism = a complete individual living thing built from all the systems together.
Each step gets bigger and is built from the level below it — learn the order and one example for each.

What you’ll learn

Mapped to the Edexcel IGCSE 4SD0 syllabus (2026 onwards).

2.1 — Understand how organisms are organised, from cells (the basic unit of any living organism) up through tissues, organs and organ systems to the whole organism.

The levels of organisation (the big idea)

Living things are built up in stages, each level made from the one below.

Every living organism is organised in a series of levels, each one bigger than the last and built from the level below it:

organelles → cells → tissues → organs → organ systems → organism

A few organelles combine to build a cell.
Many similar cells combine to build a tissue.
Several different tissues combine to build an organ.
Several organs working together make an organ system.
All the organ systems together make the whole organism.

Think of it like building a house: bricks (cells) make a wall (tissue), walls make a room (organ), rooms make a floor (organ system), and all the floors make the whole house (organism).

Exam tip. A very common 1-mark question is "Put these in order of increasing size" or "Which level is made of different tissues?". Learn the order and the definition of each level, not just the words.

Order (small → large): organelle → cell → tissue → organ → organ system → organism.
Each level is built from the level directly below it.
Tissues = similar cells; organs = different tissues.

See the full worked example for level of organisation →

Organelles and cells (the smallest levels)

Organelles are parts inside a cell; the cell is the basic unit of life.

Organelle — a small specialised structure inside a cell that carries out a particular job. It is not a living organism on its own.

Example: a ribosome (an organelle where proteins are made).
Other examples you have met: nucleus, mitochondria, chloroplast.

Cell — the basic unit of any living organism; the smallest structure that can carry out all the processes of life. Cells contain organelles.

Animal example: a muscle cell or a red blood cell.
Plant example: a palisade cell (a tall, chloroplast-packed cell near the top of a leaf that does most of the photosynthesis).

So the first two levels are: organelles work inside a cell, and the cell is the basic building block of every tissue, organ and organism.

Watch out. An organelle is part of a cell — it is smaller than a cell. Don't write that a ribosome is a cell.

Organelle = structure inside a cell (e.g. ribosome → makes proteins).
Cell = basic unit of life (e.g. palisade cell, muscle cell).
Organelles are smaller than, and contained within, a cell.

See the full worked example for level of organisation →

Tissues and organs (groups working together)

A tissue = similar cells; an organ = several different tissues.

Tissue — a group of similar cells that work together to carry out one particular function.

Muscle tissue — cells that contract to produce movement.
Epithelial tissue — cells that cover and line surfaces (e.g. lining the gut or covering the skin).
Xylem tissue (in plants) — cells that transport water up the plant and give support.

Organ — a structure made of several different tissues that work together to carry out a specific function.

Heart (animal organ) — contains muscle tissue (to pump), epithelial tissue (lining the chambers) and other tissues; it pumps blood.
Leaf (plant organ) — contains palisade tissue, xylem and other tissues; it carries out photosynthesis.

The key difference to learn:

Level	Made of…	Example
Tissue	similar cells	muscle, epithelial, xylem
Organ	different tissues	heart, leaf

Exam tip. The discriminating word is "different". An organ is different tissues working together; a tissue is similar cells. Examiners reward this exact wording.

Tissue = similar cells, one job (muscle, epithelial, xylem).
Organ = several DIFFERENT tissues, one job (heart, leaf).
Use the words 'similar cells' (tissue) and 'different tissues' (organ).

See the full worked example for level of organisation →

Organ systems and the organism (the largest levels)

Organs combine into systems; all the systems make the organism.

Organ system — a group of organs that work together to carry out a major life process.

Digestive system — mouth, stomach, small intestine, etc., working together to break down and absorb food.
Circulatory system — heart and blood vessels, working together to transport blood around the body.

Organism — a complete individual living thing, made of all its organ systems working together. Examples: a human, an oak tree, a housefly.

So the full picture, top to bottom, is:

Each step is larger and built from the level below it: organelle → cell → tissue → organ → organ system → organism.

Watch out. Don't muddle organ and organ system. The heart is an organ; the heart plus the blood vessels working together is the circulatory system (an organ system).

Organ system = several organs together (digestive, circulatory).
Organism = all the organ systems together (e.g. a human).
Heart = organ; heart + vessels = circulatory system.

See the full worked example for level of organisation →

Organisation works the same way in plants and animals

The same hierarchy applies to plants — just with plant examples.

The levels of organisation are the same idea in both plants and animals — only the examples change:

Level	Animal example	Plant example
Organelle	ribosome, mitochondrion	chloroplast, ribosome
Cell	muscle cell, red blood cell	palisade cell, root hair cell
Tissue	muscle, epithelial	xylem, palisade tissue
Organ	heart, stomach	leaf, root
Organ system	digestive, circulatory	shoot system, root system
Organism	a human	an oak tree

This matters because Paper 1 questions can give you a plant example (e.g. "Is a leaf an organ or a tissue?") and expect you to apply the same definitions you would use for an animal.

Quick check: a leaf contains several different tissues (palisade tissue, xylem, etc.), so a leaf is an organ — exactly like the heart in an animal.

Exam tip. Whenever you are unsure which level something is, ask: "Is it similar cells (tissue) or different tissues working together (organ)?" That one question answers most classification marks.

The same hierarchy applies to plants and animals.
Leaf and root are plant ORGANS (made of different tissues).
Apply the same 'similar cells vs different tissues' test to plants.

See the full worked example for level of organisation →

How it’s examined

Assessed on Biology Paper 1 (4WSD0/1B), 2 hours, 110 marks, untiered. Common question shapes: 'put these levels in order of size' (1 mark), 'define tissue / organ' (1–2 marks each), 'is a leaf a tissue or an organ — explain' (2 marks), and matching named examples (ribosome, palisade cell, muscle, heart, circulatory system) to their level. The keywords 'similar cells' (tissue) and 'different tissues' (organ) are reliable, high-value marks.

Sources: Pearson Edexcel International GCSE Science (Double Award) 4SD0 specification — Issue 4, September 2024 (valid for 2026 onwards); Pearson Edexcel International GCSE Biology 4BI1 specification — Issue 4 (shared Biology Paper 1 content); Pearson Edexcel 4SD0 / 4BI1 examiner reports 2022–2024. Last reviewed 2026-06-04.

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Step-by-step worked examples — Level of organisation

Step-by-step solutions to past-paper-style questions on level of organisation, written exactly the way a tutor would explain them at the board.

1Put the levels in order of size (Getting started)
Getting started• 4WSD0/1B style — short answer• organisation, order, spec-2.1
Question
Put these levels of organisation in order, starting with the smallest: organ, cell, organism, tissue, organ system. (1 mark)
Step-by-step solution
1. Step 1
  Start small. The smallest of these is the cell (the basic unit of life).
2. Step 2
  Build upwards. Similar cells form a tissue; different tissues form an organ; organs form an organ system; all systems form the organism.
Answer
Cell → tissue → organ → organ system → organism.
Examiner tip
All five must be in the correct order for the mark — there is no partial credit on a sequencing question. (If organelles are included, they come before cells.)
2Tell an organelle from a cell (Getting started)
Getting started• 4WSD0/1B style — short answer• organelle, cell, spec-2.1
Question
A ribosome and a palisade cell are both found in a leaf. State which is an organelle and which is a cell, and explain the difference between the two levels. (2 marks)
Step-by-step solution
1. Step 1
  Identify (1). The ribosome is the organelle; the palisade cell is the cell.
2. Step 2
  Difference (1). An organelle is a small structure found inside a cell that does one job (a ribosome makes proteins); a cell is the basic unit of life and contains organelles.
Answer
The ribosome is an organelle (a structure inside a cell that makes proteins); the palisade cell is a cell (the basic unit of life, which contains organelles).
Examiner tip
The key point is that an organelle is smaller than and inside a cell. Don't call a ribosome a cell.
3Tissue versus organ (Building confidence)
Building confidence• 4WSD0/1B style — structured• tissue, organ, spec-2.1
Question
Muscle is a tissue and the heart is an organ. Using these examples, explain the difference between a tissue and an organ. (4 marks)
Step-by-step solution
1. Step 1
  Tissue definition (1). A tissue is a group of similar cells that work together to carry out one function.
2. Step 2
  Tissue example (1). Muscle tissue is made of similar muscle cells that contract to produce movement.
3. Step 3
  Organ definition (1). An organ is made of several different tissues working together for a specific function.
4. Step 4
  Organ example (1). The heart contains muscle tissue, epithelial tissue and others, working together to pump blood.
Answer
A tissue is a group of similar cells with one function — muscle tissue is similar muscle cells that contract. An organ is made of several different tissues working together — the heart contains muscle, epithelial and other tissues that together pump blood.
Examiner tip
The discriminating words are 'similar cells' (tissue) and 'different tissues' (organ). Stating both definitions plus both examples earns all 4 marks.
4Organ or organ system? (Building confidence)
Building confidence• 4WSD0/1B style — structured• organ, organ-system, spec-2.1
Question
A student says 'the heart and the circulatory system are the same thing'. Explain why this is wrong, naming the level of organisation of each. (3 marks)
Step-by-step solution
1. Step 1
  Heart (1). The heart is an organ — a single structure made of several different tissues.
2. Step 2
  Circulatory system (1). The circulatory system is an organ system — a group of organs working together.
3. Step 3
  The link (1). The circulatory system includes the heart plus the blood vessels, so it is a higher (larger) level than the heart alone.
Answer
The heart is an organ; the circulatory system is an organ system (a group of organs). The circulatory system contains the heart AND the blood vessels working together, so it is a larger level of organisation than the heart by itself.
Examiner tip
Examiners want the student to place each at the correct level and to show the system is the heart plus other organs, not just the heart.
5Classify a leaf with full reasoning (Stretch)
Stretch• 4WSD0/1B style — extended• organ, plants, spec-2.1
Question
A leaf contains palisade tissue, xylem tissue and epidermal tissue. State whether a leaf is a tissue or an organ, and explain your reasoning fully. (4 marks)
Step-by-step solution
1. Step 1
  Conclusion (1). A leaf is an organ.
2. Step 2
  Reasoning — tissue rule (1). A tissue is only similar cells; a leaf is not made of one cell type.
3. Step 3
  Reasoning — organ rule (1). A leaf contains several different tissues (palisade, xylem, epidermal).
4. Step 4
  Function (1). These different tissues work together to carry out photosynthesis — that is exactly what defines an organ.
Answer
A leaf is an organ. It is not a tissue because a tissue is just similar cells; a leaf contains several DIFFERENT tissues (palisade, xylem, epidermal) that work together to carry out photosynthesis, which is the definition of an organ.
Examiner tip
The same definitions used for animal organs apply to plant organs. Marks reward applying the 'different tissues working together' rule, not just naming the answer.
6Match named examples to their level (Stretch)
Stretch• 4WSD0/1B style — extended• organisation, examples, spec-2.1
Question
Match each example to the correct level of organisation: ribosome, palisade cell, xylem, leaf, digestive system, oak tree. (6 marks)
Step-by-step solution
1. Step 1
  Ribosome (1) → organelle (a structure inside a cell that makes proteins).
2. Step 2
  Palisade cell (1) → cell (the basic unit of life).
3. Step 3
  Xylem (1) → tissue (similar cells that transport water).
4. Step 4
  Leaf (1) → organ (several different tissues working together).
5. Step 5
  Digestive system (1) → organ system (a group of organs working together).
6. Step 6
  Oak tree (1) → organism (a complete individual living thing).
Answer
Ribosome = organelle; palisade cell = cell; xylem = tissue; leaf = organ; digestive system = organ system; oak tree = organism.
Examiner tip
1 mark per correct match. These are the spec's standard examples — learn one for every level so you can place any example confidently.

Model Answers — Level of organisation

High-scoring sample answers for level of organisation on the Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
4WSD0/1B style3 marks
List the levels of organisation in a multicellular organism, in order from the smallest to the largest. (3 marks)
Model answer
From smallest to largest:

organelle → cell → tissue → organ → organ system → organism

Organelle — a structure inside a cell (e.g. a ribosome).

Cell — the basic unit of life (e.g. a palisade cell).

Tissue — similar cells working together (e.g. muscle).

Organ — different tissues working together (e.g. the heart).

Organ system — organs working together (e.g. the circulatory system).

Organism — the whole individual living thing.
Why this scores
The order is the marked content — examiners typically award marks for the correct sequence cell → tissue → organ → organ system → organism (organelles before cells if included).
Question 2
4WSD0/1B style4 marks
Define the terms 'cell' and 'tissue', giving one example of each. (4 marks)
Model answer
Cell — the basic unit of any living organism; the smallest structure that can carry out the processes of life. Example: a palisade cell (plant) or a muscle cell (animal).

Tissue — a group of similar cells that work together to carry out one particular function. Example: muscle tissue (contracts to produce movement) or xylem tissue (transports water in plants).
Why this scores
1 mark for each definition + 1 for each valid example. The phrase 'similar cells' is essential for the tissue mark.
Question 3
4WSD0/1B style6 marks
Explain the difference between a tissue, an organ and an organ system, using one named example of each. (6 marks)
Model answer
Tissue — a group of similar cells working together to carry out one function. Example: muscle tissue, made of muscle cells that contract.

Organ — a structure made of several different tissues working together for a specific function. Example: the heart, which contains muscle tissue, epithelial tissue and others, and pumps blood.

Organ system — a group of organs working together to carry out a major life process. Example: the circulatory system, made of the heart and blood vessels, which transports blood around the body.

Each level is larger than the one before and is built from it: similar cells → a tissue; different tissues → an organ; several organs → an organ system.
Why this scores
Up to 2 marks per level (definition + named example). Keyword credits: 'similar cells' (tissue), 'different tissues' (organ), 'group of organs' (organ system).
Question 4
4WSD0/1B style5 marks
A leaf is made of palisade tissue, xylem tissue and epidermal tissue. Using this information, explain why a leaf is described as an organ and not a tissue. (5 marks)
Model answer
A tissue is a group of similar cells that carry out one function.

A leaf is not a single tissue because it is not made of just one type of cell — it contains several different tissues (palisade, xylem and epidermal tissue).

An organ is defined as several different tissues working together to carry out a function.

In the leaf, these different tissues work together to carry out photosynthesis (and to transport water and gases).

Because a leaf is built from different tissues working together, it fits the definition of an organ, just like the heart in an animal.
Why this scores
Marks reward applying the definitions (tissue = similar cells; organ = different tissues) to the plant example, plus naming photosynthesis as the leaf's function.
Question 5
4WSD0/1B style — extended open response8 marks
Describe the levels of organisation in a multicellular organism, from organelles to the whole organism. For each level, give a clear definition and one named example. (8 marks)
Model answer
Organelle — a small specialised structure found inside a cell that carries out one job. Example: a ribosome, where proteins are made.

Cell — the basic unit of any living organism; the smallest unit that can carry out the processes of life, and which contains organelles. Example: a palisade cell in a leaf.

Tissue — a group of similar cells that work together to perform one function. Example: muscle tissue (contracts), epithelial tissue (covers/lines surfaces) or xylem tissue (transports water in plants).

Organ — a structure made of several different tissues working together for a specific function. Example: the heart (animal) or a leaf (plant).

Organ system — a group of organs that work together to carry out a major life process. Example: the digestive system (breaks down and absorbs food) or the circulatory system (transports blood).

Organism — a complete individual living thing made of all its organ systems working together. Example: a human or an oak tree.

Each level is larger than the previous one and is built from the level below it.
Why this scores
Roughly 1 mark per level for a correct definition + named example, with credit for showing each level is built from the one below. Use of keywords ('basic unit', 'similar cells', 'different tissues', 'group of organs') secures the marks.

Question 6

4WSD0/1B style — extended open response9 marks

Show that the levels of organisation apply in the same way to plants and animals by giving a worked example of each level for both a flowering plant and a mammal. (9 marks)

Model answer

The hierarchy organelle → cell → tissue → organ → organ system → organism is identical in plants and animals; only the examples differ.

Level	Definition	Plant example	Animal (mammal) example
Organelle	structure inside a cell	chloroplast / ribosome	ribosome / mitochondrion
Cell	basic unit of life	palisade cell	muscle cell
Tissue	similar cells, one function	xylem (transports water)	muscle (contracts)
Organ	different tissues together	leaf (photosynthesis)	heart (pumps blood)
Organ system	group of organs	shoot system	circulatory system
Organism	whole individual	an oak tree	a human

In both cases a tissue is similar cells, an organ is several different tissues working together, and an organ system is a group of organs. For example, a leaf is a plant organ for the same reason the heart is an animal organ — both are built from several different tissues working together to carry out one function.

Why this scores

Credit a correct plant AND animal example for each level, plus the explicit point that the same definitions (similar cells / different tissues) apply to both kingdoms.

Key Definitions and Keywords — Level of organisation

Definitions to memorise and the exact keywords mark schemes credit for level of organisation answers — sharpened from recent examiner reports for the 2026 Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) sitting.

Organelle
Examiner keyword
A small specialised structure found inside a cell that carries out a particular function, e.g. a ribosome (protein synthesis). An organelle is smaller than, and contained within, a cell.
Cell
Examiner keyword
The basic unit of any living organism — the smallest structure able to carry out the processes of life. Cells contain organelles. Examples: palisade cell, muscle cell.
Tissue
Examiner keyword
A group of similar cells that work together to carry out one particular function, e.g. muscle, epithelial or xylem tissue.
Organ
Examiner keyword
A structure made of several different tissues working together to carry out a specific function, e.g. the heart (animal) or a leaf (plant).
Organ system
Examiner keyword
A group of organs that work together to carry out a major life process, e.g. the digestive system or the circulatory system.
Organism
Examiner keyword
A complete individual living thing, made of all its organ systems working together, e.g. a human or an oak tree.
Levels of organisation
Examiner keyword
The hierarchy in which living things are built up: organelles → cells → tissues → organs → organ systems → organism, each level larger than and built from the one below.
Palisade cell
A tall, chloroplast-packed cell near the top of a leaf that carries out most of the photosynthesis — a worked example of the 'cell' level of organisation in plants.

Common Mistakes and Misconceptions — Level of organisation

The traps other students keep falling into on level of organisation questions — taken from recent Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) examiner reports and mark schemes — and how to avoid them.

✕Confusing a tissue with an organ
Edexcel Biology examiner reports
Why it happens
Both are described as 'a group of cells working together', so students blur the two.
How to avoid it
Use the discriminating words: a tissue is similar cells; an organ is several DIFFERENT tissues working together. The word 'different' wins the mark.
✕Calling an organ system an organ (or vice versa)
Edexcel Biology examiner reports 2023–2024
Why it happens
Students see the heart and the circulatory system as the same thing.
How to avoid it
An organ is a single structure (the heart). An organ system is a group of organs (the heart + blood vessels = circulatory system). The system is the larger level.
✕Treating an organelle as a cell or as a living organism
Edexcel Biology examiner reports
Why it happens
Both 'organelle' and 'cell' sound like small living units.
How to avoid it
An organelle is a part INSIDE a cell (e.g. a ribosome) — it is smaller than a cell and not alive on its own. The cell is the basic unit of life.
✕Getting the order of the levels wrong
Edexcel Biology examiner reports
Why it happens
Students memorise the words but not the sequence, or reverse it.
How to avoid it
Learn it small → large: organelle → cell → tissue → organ → organ system → organism. Each level is built from the one below it.
✕Calling a leaf (or root) a tissue instead of an organ
Edexcel Biology examiner reports
Why it happens
Students apply the hierarchy to animals but forget it works identically for plants.
How to avoid it
A leaf contains several different tissues (palisade, xylem, epidermal), so it is an organ — exactly like the heart. The same definitions apply to plants and animals.
✕Defining a tissue as just 'a group of cells'
Edexcel Biology examiner reports
Why it happens
Students drop the key word 'similar', so the definition becomes too loose.
How to avoid it
Always write 'a group of SIMILAR cells with the SAME function'. 'A group of cells' alone could describe an organ and rarely scores the mark.

Past paper style quiz

Get a report showing which sub-topics you've nailed and which ones still need work.

Level of Organisation — Edexcel International GCSE Science (Double Award) Biology (4WSD0-1B) Study Notes

Level

Made of…

Example

Tissue

similar cells

muscle, epithelial, xylem

Organ

different tissues

heart, leaf

Level

Animal example

Plant example

Organelle

ribosome, mitochondrion

chloroplast, ribosome

Cell

muscle cell, red blood cell

palisade cell, root hair cell

Tissue

muscle, epithelial

xylem, palisade tissue

Organ

heart, stomach

leaf, root

Organ system

digestive, circulatory

shoot system, root system

Organism

a human

an oak tree

Organelle — a small specialised structure found inside a cell that carries out one job. Example: a ribosome, where proteins are made.

Cell — the basic unit of any living organism; the smallest unit that can carry out the processes of life, and which contains organelles. Example: a palisade cell in a leaf.

Tissue — a group of similar cells that work together to perform one function. Example: muscle tissue (contracts), epithelial tissue (covers/lines surfaces) or xylem tissue (transports water in plants).

Organ — a structure made of several different tissues working together for a specific function. Example: the heart (animal) or a leaf (plant).

Organ system — a group of organs that work together to carry out a major life process. Example: the digestive system (breaks down and absorbs food) or the circulatory system (transports blood).

Organism — a complete individual living thing made of all its organ systems working together. Example: a human or an oak tree.

Each level is larger than the previous one and is built from the level below it.

Level

Definition

Plant example

Animal (mammal) example

Organelle

structure inside a cell

chloroplast / ribosome

ribosome / mitochondrion

Cell

basic unit of life

palisade cell

muscle cell

Tissue

similar cells, one function

xylem (transports water)

muscle (contracts)

Organ

different tissues together

leaf (photosynthesis)

heart (pumps blood)

Organ system

group of organs

shoot system

circulatory system

Organism

whole individual

an oak tree

a human

Level of organisation

Detailed Notes

What you’ll learn

How it’s examined

1Put the levels in order of size (Getting started)

2Tell an organelle from a cell (Getting started)

3Tissue versus organ (Building confidence)

4Organ or organ system? (Building confidence)

5Classify a leaf with full reasoning (Stretch)

6Match named examples to their level (Stretch)

Organelle

Cell

Tissue

Organ

Organ system

Organism

Levels of organisation

Palisade cell

✕Confusing a tissue with an organ

✕Calling an organ system an organ (or vice versa)

✕Treating an organelle as a cell or as a living organism

✕Getting the order of the levels wrong

✕Calling a leaf (or root) a tissue instead of an organ

✕Defining a tissue as just 'a group of cells'

Past paper style quiz

Level of organisation

Detailed Notes

What you’ll learn

How it’s examined

1Put the levels in order of size (Getting started)

2Tell an organelle from a cell (Getting started)

3Tissue versus organ (Building confidence)

4Organ or organ system? (Building confidence)

5Classify a leaf with full reasoning (Stretch)

6Match named examples to their level (Stretch)

Organelle

Cell

Tissue

Organ

Organ system

Organism

Levels of organisation

Palisade cell

✕Confusing a tissue with an organ

✕Calling an organ system an organ (or vice versa)

✕Treating an organelle as a cell or as a living organism

✕Getting the order of the levels wrong

✕Calling a leaf (or root) a tissue instead of an organ

✕Defining a tissue as just 'a group of cells'

Past paper style quiz