Pearson Edexcel International GCSE Biology · specification 4BI1 · Paper 2 | Whole paper: All content including bold B statements · Free · no account needed
2(j) Co-ordination and response (4BI1 specification)
Two control systems — fast electrical and slow chemical — and the plant responses that use neither.
Learn it on Incandio
The 7 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- ADH and the Water Balance of the Blood — One hormone, one adjustable tap at the end of the nephron — and a loop that corrects the very thing that set it off.
- Homeostasis and the Control of Body Temperature — Why the inside of you barely changes while the outside changes constantly — and exactly what the skin does about heat.
- Plant Responses, Tropisms and Auxin — A plant has no eyes, no nerves and no muscles — and still gets its roots down and its shoots up every time. This is how.
- The Nervous System, and the Two Ways a Body Sends a Message — Electrical impulses down a wire, or a chemical posted into the blood — why a body needs both, and which job each one is for.
- Synapses and the Reflex Arc — Neurones do not touch. What crosses the gap between them, why the gap is there at all, and how a hand leaves a hot pan before you know it was hot.
- The Eye — Focusing, and the Pupil Reflex — One sense organ, two adjustments: how the eye sharpens an image and how it controls the amount of light it lets in.
- The Hormones — Sources, Roles and Effects — Eight chemical messengers, three kinds of job: prepare the body for action, hold a condition steady, or run a change that takes years.
The teaching route this belongs to: Topic 2 · Structures and functions in living organisms (Biology) — the lessons in order, with every gate.
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.
This page maps the specification. The pages above teach it, and the Biology lessons hold the whole course — completely free.