Symbiosis
Mutualism, commensalism, parasitism, host–parasite interactions and co-evolution.
How to study Higher Biology
Move from accurate biological mechanisms to unfamiliar data, experimental evidence and justified conclusions. Use current official materials for the written, extended-response and controlled-assignment formats that this question bank does not reproduce.
Core concepts
Concept 1
Classify close species interactions from the fitness effects on each partner.
Exam cue: Classify close species interactions from the fitness effects on each partner.
Concept 2
Explain transmission, host defence, parasite exploitation and virulence as interacting selective pressures.
Exam cue: Explain transmission, host defence, parasite exploitation and virulence as interacting selective pressures.
Concept 3
Use reciprocal adaptation to explain co-evolution.
Exam cue: Use reciprocal adaptation to explain co-evolution.
Risk pitfalls and guardrails
Commensalism benefits one partner without a significant effect on the other.
Guardrail: Check vocabulary, sequence, direction, compartment, units and whether the evidence supports causation or only an association.
A parasite normally depends on a living host and does not necessarily benefit from rapid host death.
Guardrail: Check vocabulary, sequence, direction, compartment, units and whether the evidence supports causation or only an association.
Memory anchors
Symbiosis signs
Mutualism +/+; commensalism +/0; parasitism +/−.
Co-evolution
Each species changes the other’s selection pressures.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is symbiosis?
A tick gains nutrients by feeding on a mammal and lowers the mammal's fitness. Which outcome defines this relationship?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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