Key term
OCR GCSE Biology A J247
Cell Level Systems
Topic overviewMicroscopy, and sub-cellular structuresDNA structure: polymer, double helix and nucleotidesProtein synthesis and the triplet codeEnzyme action, and investigating enzymesCellular respiration as an exothermic processAerobic and anaerobic respiration comparedSynthesis and breakdown of carbohydrates, proteins and lipidsPhotosynthesis: producers and the processPhotosynthesis as endothermic, and investigating itLimiting factors in photosynthesis
Community Level Systems
Genes, Inheritance and Selection
Topic overviewGenetic terms, and the genomeGenome, environment and mutationsHow genetic variants influence phenotypeAsexual and sexual reproduction comparedHaploid, diploid and meiosisSingle gene inheritance and Punnett squaresSex determination, multiple genes and Mendel's workVariation within a population, and classificationNatural selection and evolutionEvidence for evolution, and the work of Darwin and Wallace
Global Challenges
Topic overviewField investigations, and human impact on ecosystemsMaintaining biodiversity, and evidence for environmental changeFood security, agricultural and biotechnological solutionsSelective breeding and genetic engineeringHealth, disease, and types of diseaseInteractions between diseases, and how they spreadReducing the spread of disease, and named examplesPhysical and chemical plant defencesDetecting plant disease; white blood cells and plateletsNon-specific defences and the immune systemMonoclonal antibodies and their usesVaccines, medicines and aseptic techniqueDeveloping new medicines, and non-communicable diseaseTreating cardiovascular disease, and lifestyle factorsCancer, and the use of stem cells in medicineGene technology in medicine, and the human genome
Organism Level Systems
Topic overviewThe nervous system and coordinated responsesThe reflex arcThe eye and its common defectsThe structure and function of the brainInvestigating and treating the brainHormonal coordination, thyroxine and adrenalineHormones in reproduction and the menstrual cycleContraception and treating infertilityPlant hormones and their commercial usesHomeostasis, and the skin in temperature controlInsulin and glucagon in blood sugar controlType 1 and type 2 diabetesOsmotic changes in body fluids, and the kidneysThe kidney tubule and the effect of ADHResponding to temperature and osmotic challenges
Scaling Up
Topic overviewDiffusion, osmosis and active transportMitosis, the cell cycle and cell differentiationStem cells in animals and meristems in plantsSurface area to volume ratio and exchange surfacesThe circulatory system, the heart and blood vesselsRed blood cells and plasmaRoot hair cells, transpiration and translocationXylem and phloemFactors affecting water uptake, and the potometer
Organism Level Systems
- 15 subtopics
- 45 things to know
- Paper 3
What Organism Level Systems covers
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.
Where it is assessed
Paper 3
Biology A Paper 3: 1 hour 45 minutes, 90 marks, 50% of the GCSE.
Check the OCR specification ↗The 15 subtopics
Each one has its own page.
- The nervous system and coordinated responsesThe 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.Open →
- The reflex arcWhat 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.Open →
- The eye and its common defectsThe 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.Open →
- The structure and function of the brainThe 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.Open →
- Investigating and treating the brainWhy 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.Open →
- Hormonal coordination, thyroxine and adrenalineWhat 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.Open →
- Hormones in reproduction and the menstrual cycleTestosterone 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.Open →
- Contraception and treating infertilityHow 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.Open →
- Plant hormones and their commercial usesWhat 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.Open →
- Homeostasis, and the skin in temperature controlWhat 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.Open →
- Insulin and glucagon in blood sugar controlThe 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.Open →
- Type 1 and type 2 diabetesWhat 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.Open →
- Osmotic changes in body fluids, and the kidneysWhat 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.Open →
- The kidney tubule and the effect of ADHThe 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.Open →
- Responding to temperature and osmotic challengesHow 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.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
A person's body temperature rises above normal and then returns to normal. Explain how this shows the body correcting a change.
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Give an external change and an internal change that the body must respond to in order to keep conditions constant.
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Explain why blood glucose falls in the hour after a large meal.
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Explain how insulin and glucagon work together to hold blood glucose steady.
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Explain why the concentration of the blood must be kept steady to protect the body's cells.
Process
Explain the sequence of events that corrects blood which has become too concentrated.
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Explain what happens to ADH release after a person drinks a large volume of water.
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Describe how the body responds after several hours of heavy sweating in the heat.
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Explain the body's response to drinking far more water than it needs.
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Explain what happens in the body after a very salty meal.
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Which two organs make up the central nervous system?
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What is a reflex action?
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What is the pupil?
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Which is the largest part of the human brain and what is it responsible for?
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Why is it hard to collect enough case studies of people with damage to one region of the brain?
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What is a hormone?
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Which is the main male reproductive hormone and where is it made?
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What is a tropism?
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What is type 1 diabetes?
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What is a sensory receptor?
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Name the parts of a reflex arc in the order an impulse passes through them.
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Name the two kinds of light receptor cell in the retina and say what each detects.
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The cerebrum is made of two halves. What does each half control?
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Why are the results from a patient with brain damage difficult to interpret?
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What is an endocrine gland?
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Which is the main female reproductive hormone and where is it made?
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Name three hormonal methods of contraception other than the pill.
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What are phototropism and gravitropism?
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What is type 2 diabetes?
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What happens to a body cell placed in a solution with a lower water potential than its cytoplasm?
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What is an effector?
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Where is the relay neurone of a spinal reflex arc found, and why does this matter?
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Explain how the ciliary body and suspensory ligaments let the eye focus on a nearby object.
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What is the cerebral cortex?
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Why can consent be a difficulty when studying a patient with severe brain damage?
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A hormone reaches every organ, so why does it affect only some of them?
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What does FSH do, and where is it released from?
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Which methods of contraception are the most effective, and how do condoms compare?
Evaluation
Why is it an advantage to a plant for its shoots to grow towards the light?
Key term
What is homeostasis?
Key term
Which hormone is released when the blood glucose concentration is too high, and from where?
Process
At what stage of life does each type of diabetes usually first appear?
Key term
What happens to an animal cell placed in a solution more dilute than its own contents?
Key term
Name the regions seen when a kidney is cut in half from top to bottom.
Take Organism Level Systems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Insulin vs Glucagon
Insulin: pancreatic hormone that makes cells take up glucose and store it as glycogen. Glucagon: pancreatic hormone that makes the liver turn glycogen back into glucose.
Vasodilation vs Vasoconstriction
Vasodilation: widening of the vessels supplying skin capillaries so more heat is lost. Vasoconstriction: narrowing of the vessels supplying skin capillaries so less heat is lost.
FSH vs LH
FSH: pituitary hormone that makes an egg mature inside a follicle. LH: pituitary hormone whose surge makes the follicle burst and release the egg.
Questions from this topic
Each one with the model answer underneath.
- 1
Which two organs make up the central nervous system?
Model answer
The brain and the spinal cord.
- 2
What is the job of a sensory neurone?
Model answer
It carries electrical impulses from a sensory receptor to the central nervous system.
- 3
What is the job of a motor neurone?
Model answer
It carries electrical impulses from the central nervous system to an effector.
- 4
Where are relay neurones found and what do they do?
Model answer
They lie inside the central nervous system and pass impulses from sensory neurones on to motor neurones.
- 5
What is a sensory receptor?
Model answer
A cell that detects a stimulus such as light, sound, touch, temperature or a chemical, and starts an electrical impulse.
- 6
What is an effector?
Model answer
A muscle or a gland that carries out the response when an impulse arrives from a motor neurone.
What is inside Levo
Six ways to work the same material.
Organism Level Systems revision questions
- What does Organism Level Systems cover in OCR GCSE Biology A?
- 15 subtopics: 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. Each one has its own page with questions and model answers.
- How is Organism Level Systems organised?
- By the OCR J247 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Organism Level Systems, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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