Organism Level Systems | OCR GCSE Biology A, Higher tier (J247)

Organism Level Systems

221 questions
15 subtopics
Paper 3
Paper 3

Organism Level Systems is examined in Biology A Paper 3.

It covers the nervous system and coordinated responses, the reflex arc, the eye and its common defects, the structure and function of the brain, investigating and treating the brain, hormonal coordination, thyroxine and adrenaline, hormones in reproduction and the menstrual cycle, contraception and treating infertility, plant hormones and their commercial uses, homeostasis, and the skin in temperature control, insulin and glucagon in blood sugar control, type 1 and type 2 diabetes, osmotic changes in body fluids, and the kidneys, the kidney tubule and the effect of ADH and responding to temperature and osmotic challenges.

Sample questions from Organism Level Systems

Answer each one closed book first, then open the answer.

The nervous system and coordinated responses

What is an effector?

Show the answer
A muscle or a gland that carries out the response when an impulse arrives from a motor neurone.
The reflex arc

In the blinking reflex, what is the stimulus and what is the effector?

Show the answer
The stimulus is an object touching the eye or moving quickly towards it, and the effector is the eyelid muscle.
The structure and function of the brain

Where is the cerebellum and what does it do?

Show the answer
It lies at the back of the brain beneath the cerebrum, and it coordinates muscle movement, balance and posture so movements are smooth.
Investigating and treating the brain

Why can many drugs not be used to treat disease in the brain?

Show the answer
The blood-brain barrier stops most substances carried in the blood from passing into brain tissue.
Hormones in reproduction and the menstrual cycle

What is the role of progesterone in the menstrual cycle?

Show the answer
It maintains the thick lining of the uterus so it is ready for a fertilised egg to implant.
Contraception and treating infertility

Why is a woman given FSH and LH before eggs are collected for in vitro fertilisation?

Show the answer
So that several eggs mature and are released at the same time, giving more eggs to fertilise and a better chance of success.
Homeostasis, and the skin in temperature control

A person's body temperature rises above normal and then returns to normal. Explain how this shows the body correcting a change.

Show the answer
The rise is detected, and the responses it triggers, such as sweating and widening of the skin blood vessels, act against the rise and bring the temperature back down to its normal level.
Insulin and glucagon in blood sugar control

Explain how insulin and glucagon work together to hold blood glucose steady.

Show the answer
Insulin is released when glucose is too high and lowers it by having it stored as glycogen, while glucagon is released when glucose is too low and raises it by breaking glycogen down, so the level is corrected whichever way it moves.

The 15 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
The nervous system and coordinated responses	The central nervous system, what sensory, motor and relay neurones, receptors and effectors do, how sensory and motor neurones differ in shape, synapses and neurotransmitters, what a coordinated response is and why many receptors and connections help, the stages from stimulus to response, catching a falling glass, and why nervous responses are faster than hormonal ones.	16
The reflex arc	What a reflex action is and why it protects the body, the parts of a reflex arc in order, why a reflex is faster than a voluntary action, the relay neurone in the spinal cord, how synapses slow an impulse, the hot pan and blinking reflexes, why a person is aware of a reflex, and why the same stimulus always gives the same response.	10
The eye and its common defects	The cornea, pupil, iris, retina with its rods and cones, and optic nerve, how the ciliary muscles and suspensory ligaments change the lens to focus on near and distant objects, red-green colour blindness, the causes of short- and long-sightedness and the concave and convex lenses that correct them, and contact lenses and surgery.	16
The structure and function of the brain	The cerebrum and its two hemispheres, the cerebral cortex, the cerebellum and its control of balance and movement, the medulla and why damage to it is life-threatening, the role of the hypothalamus, the pituitary gland as the master gland, and working out which region an injury has damaged.	10
Investigating and treating the brain	Why brain damage case studies are scarce and hard to interpret, consent and ethics, MRI scans and their limits, animal and surgical studies, and why brain and spinal injuries and tumours are hard to treat.	16
Hormonal coordination, thyroxine and adrenaline	What hormones and endocrine glands are and how hormones affect only their target organs, the main endocrine glands and sex hormones, how hormonal and nervous responses compare, thyroxine and how thyroid stimulating hormone and negative feedback control it, and how adrenaline prepares the body for action.	16
Hormones in reproduction and the menstrual cycle	Testosterone and oestrogen and what each does at puberty, the roles of FSH, LH, oestrogen and progesterone across the 28-day cycle, what triggers ovulation, the corpus luteum, and how a new cycle begins.	16
Contraception and treating infertility	How the combined pill, implants, injections, patches, condoms, sterilisation and natural methods prevent pregnancy, their effectiveness, advantages and drawbacks, how FSH and LH given as fertility drugs help a woman conceive, the stages, drawbacks, multiple births and ethical objections of in vitro fertilisation, and injecting a single sperm into an egg.	16
Plant hormones and their commercial uses	What tropisms are and how auxin makes shoots bend towards light and roots grow downwards, why these responses help the plant, the processes plant hormones control, the roles of ethene, gibberellins and auxins, and their commercial uses in selective weedkillers, rooting powder, seedless fruit and ending seed dormancy for brewing.	21
Homeostasis, and the skin in temperature control	What homeostasis is and the conditions it keeps constant, why body temperature and blood water content must be controlled, the receptor, coordination centre and effector of a control system, how the skin and hypothalamus detect temperature, and how sweating, vasodilation, vasoconstriction and shivering correct body temperature, with why sweating works poorly on a humid day.	16
Insulin and glucagon in blood sugar control	The pancreas monitoring blood glucose, how insulin makes cells take up glucose and the liver and muscles store it as glycogen, why blood glucose must be controlled, negative feedback, how glucagon releases glucose from glycogen, insulin and glucagon as antagonistic hormones, what happens after a meal, between meals and during a long run, and the part the liver plays.	16
Type 1 and type 2 diabetes	What type 1 and type 2 diabetes are, when each usually appears, insulin injections and why insulin cannot be swallowed, diet and exercise for type 2, risk factors, symptoms, and glucose in the urine.	10
Osmotic changes in body fluids, and the kidneys	What happens to animal, red blood and plant cells in dilute and concentrated solutions, lysis, why blood concentration must stay steady, the kidneys' roles in controlling water and salt and removing urea made in the liver, how urine changes with water intake and on hot days, filtration and selective reabsorption, and the path of urine to the bladder.	16
The kidney tubule and the effect of ADH	The cortex, medulla and renal pelvis, the renal artery and vein, what a kidney tubule is and how many a kidney holds, filtration at the Bowman's capsule, reabsorption in the proximal convoluted tubule, the loop of Henlé and the collecting duct, ADH from the pituitary and its effect on the collecting ducts, how it corrects blood concentration by negative feedback, and the effect of alcohol.	16
Responding to temperature and osmotic challenges	How ADH, urine output and thirst respond to heavy sweating, dehydration, drinking too much water and a salty meal, the signs of dehydration, why drinking a very large volume of water is dangerous and salty drinks help after exercise, how the body responds to a falling core temperature, and why sweating challenges both temperature control and water balance.	10

Organism Level Systems is 221 of the 1,137 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.