Compare the four eukaryote kingdoms
Outline diagnostic features of Protoctista, Fungi, Plantae and Animalia.
Section 18.1 · Classification
A Level; Cambridge International Biology 9700, 2028–2030. Written responses are self-checked; this does not certify supervised fieldwork or practical competence.
Before you begin
- Classification compares shared characteristics; populations occupy environments and contain variation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which cell-wall material is characteristic of fungi?
What you will learn
- Outline characteristic features of Protoctista and Fungi
- Outline characteristic features of Plantae and Animalia
Build the explanation
Protoctists are a diverse group of eukaryotes; many are unicellular, while some are multicellular, and nutrition may be autotrophic or heterotrophic. Fungi include unicellular yeasts and multicellular hyphae forming mycelia; their cell walls contain chitin and they digest food externally before absorption. Plants are generally multicellular, with cellulose walls and photosynthetic tissues.
Use evidence within scope
Animals are multicellular eukaryotes without cell walls and obtain nutrients by ingestion. Kingdom features are broad patterns, not rules that every specialised cell must show: root cells, for example, may lack chloroplasts. Identify the organism-level pattern and note relevant exceptions.
Pause and explain
A learner says fungi photosynthesise because they have cell walls. Correct the reasoning.
Worked example
An organism is multicellular, has chitin walls and absorbs products after external digestion. Which kingdom is supported?
Show the worked solution
- Chitin walls are characteristic of fungi.
- External digestion and absorption support the same group.
Answer Fungi.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A unicellular eukaryote has a nucleus and photosynthetic chloroplasts. Which kingdom could it belong to?
Give me a hint
Identify the required evidence and sequence the reasoning.
Compare my reasoning
- Some protoctists are unicellular and photosynthetic.
- Protoctista is diverse.
Protoctista is consistent with the evidence; the group includes unicellular eukaryotes with varied nutrition.
Look for these in your work
- Relevant evidence selected
- Reasoning linked to conclusion
A multicellular organism has cellulose walls and photosynthetic tissues. Which kingdom is supported?
Give me a hint
Use the supplied example or data to justify a conclusion.
Compare my reasoning
- Cellulose walls and photosynthetic tissues are plant features.
- Use the combined evidence.
Plantae, because cellulose walls and photosynthetic tissues are characteristic features of plants.
Look for these in your work
- Concept applied
- Limit or assumption stated
A learner says fungi photosynthesise because they have cell walls. Correct the reasoning.
Give me a hint
Apply the concept in a new context and qualify its limits.
Compare my reasoning
- A wall does not establish photosynthesis.
- Fungi have chitin walls and obtain nutrients by absorption.
Cell walls alone do not show photosynthesis. Fungi have chitin walls and digest food externally before absorbing nutrients; plants typically have cellulose walls and photosynthetic tissues.
Look for these in your work
- New context handled
- Conclusion appropriately bounded
Common mistakes
- Calling fungi plants because both can have cell walls
- Assuming every plant cell contains chloroplasts
What can you explain now?
Which cell-wall material is characteristic of fungi?
Compare with the explanation
Chitin
Plants have cellulose cell walls; fungi have chitin.
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Make it stick
How do fungal walls and nutrition differ from those of plants?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.