2(j) Co-ordination and response
Pearson Edexcel International GCSE Biology · 4BI1
Paper 2 | Whole paper: All content including bold B statements
Two control systems — fast electrical and slow chemical — and the plant responses that use neither.
Specification coverage
Topic 2 Structures and functions in living organisms (j) Co-ordination and response — statements 2.79–2.94B (includes bold B statements assessed on Paper 2 only)
Assessment objectives: AO1, AO2, AO3. Suggested learning time: 100 minutes.
Required knowledge
- The nervous system: receptors, sensory neurones, relay neurones, motor neurones and effectors
- The reflex arc and why reflexes are involuntary
- The structure and function of the eye, including accommodation and the pupil reflex
- Hormones as chemical messengers, and the roles of named hormones including adrenaline, insulin and testosterone or oestrogen
- Comparison of nervous and hormonal coordination
- Tropic responses in plants: phototropism and gravitropism, and the role of auxin
- Bold B statements: homeostasis, including the control of blood glucose and body temperature, in greater depth
Required skills
- Trace a stimulus to a response through the correct sequence of structures
- Compare nervous and hormonal control on speed, duration and specificity
- Explain a tropism in terms of unequal auxin distribution
- Describe and evaluate the required practical: Investigate the effect of light or gravity on the growth of newly germinated seedlings.
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
- Practical questions on method, variables, data and sources of error
Common mistakes
- Missing out the relay neurone in a reflex arc.
- Saying auxin makes cells divide. In shoots it causes cell elongation, and it accumulates on the shaded side.
- Describing hormones as fast. Their advantage is duration and wide distribution, not speed.