Global Challenges

What Global Challenges covers

Global Challenges is examined in Paper 8 (Biology). It covers field investigations and human impact on ecosystems; maintaining biodiversity, monitoring conservation and ecotourism; selective breeding and genetic engineering; health, disease and types of disease; interactions between diseases and how they spread; reducing the spread of disease and named examples; white blood cells, antibodies and platelets; non-specific defences and the immune system; vaccines, medicines and aseptic technique; developing new medicines and non-communicable disease; treating cardiovascular disease and lifestyle factors; cancer and the use of stem cells in medicine; and gene technology in medicine and the human genome.

The 13 subtopics

Each one has its own page.

• Field investigations, and human impact on ecosystemsRandom sampling with quadrats and belt transects, estimating plant numbers from quadrat counts and animal populations by capture-recapture with its assumptions, collecting with pooters and sweep nets, using a dichotomous key, how land use, monoculture and hunting reduce biodiversity, captive breeding, nature reserves and habitat conservation, positive human interactions, and the mean, median, mode and percentiles of survey results.Open →
• Maintaining biodiversity, monitoring conservation and ecotourismThe benefits of high biodiversity to people and why it makes an ecosystem stable, why international conservation agreements are hard to reach, why conservation schemes must be monitored and why that is difficult, what ecotourism is, and how it can both conserve and damage a habitat.Open →
• Selective breeding and genetic engineeringWhat selective breeding is and how it improves wheat and dairy cattle, why it reduces variation and raises disease risk, inbreeding, the economic and ethical arguments, what genetic engineering is, insect-resistant maize, beta-carotene rice and bacterial insulin, the steps using restriction enzymes, sticky ends, ligase, plasmid vectors and antibiotic resistance markers, and the benefits, risks and objections of modified crops.Open →
• Health, disease, and types of diseaseWhat health and disease are and how they relate, other factors such as diet, exercise and stress, how a weak immune system or poor diet raises the risk of infection, links between physical and mental ill health, communicable and non-communicable diseases with their causes and examples in humans and crops, the four types of pathogen, and why crowding spreads disease.Open →
• Interactions between diseases, and how they spreadHow the virus that causes AIDS attacks lymphocytes and makes tuberculosis more likely, how human papillomavirus can lead to cervical cancer and how cases are reduced, how pathogens pass between people, vectors such as mosquitoes, how pathogens spread between plants and through a crop, how fast bacteria multiply, and estimating the number of infections from a sample.Open →
• Reducing the spread of disease, and named examplesReducing the spread of disease by hygiene, isolation, vaccination and controlling insect vectors, identifying pathogens by antigen and DNA tests and plant diseases by symptoms, removing diseased plants, influenza, athlete's foot and Salmonella food poisoning, how the virus that causes AIDS spreads and progresses, preventing sexually transmitted infections, and tobacco mosaic virus, barley powdery mildew and crown gall in plants.Open →
• White blood cells, antibodies and plateletsHow a phagocyte engulfs and digests a pathogen and is adapted to do so, antibodies made by lymphocytes and why each fits only one pathogen, antitoxins, what platelets are, how blood clotting keeps pathogens out, and why too few platelets raise the risk of infection.Open →
• Non-specific defences and the immune systemNon-specific defences including the skin, nose hairs and mucus, cilia in the airways, stomach acid, tears and scabs, why burns lead to infection, what antigens are, how lymphocytes make antibodies that clump pathogens for phagocytes, why a first infection takes days to recover from, memory cells and immunity, and why one strain of a virus may not protect against another.Open →
• Vaccines, medicines and aseptic techniqueWhat a vaccine contains and how it gives immunity, what antibiotics, antivirals, antiseptics and painkillers do and do not do, why drugs that kill viruses are hard to make, antibiotic resistance, aseptic technique with flamed loops, alcohol, autoclaves and taped dishes kept at 25 °C, and testing antiseptics with paper discs on a bacterial lawn, including calculating the area of clear zones.Open →
• Developing new medicines, and non-communicable diseaseWhere early medicines came from, testing new medicines for toxicity, efficacy and dose in preclinical and clinical trials, placebos and double-blind trials, why development is slow and costly, the interacting causes and risk factors of non-communicable diseases such as coronary heart disease, bronchitis, cirrhosis, type 2 diabetes and cancer, and peer review and how trial results are published and communicated.Open →
• Treating cardiovascular disease, and lifestyle factorsLifestyle changes, statins, stents, bypass operations and valve replacements for cardiovascular disease with their advantages and risks, how exercise, saturated fat, alcohol and smoking affect non-communicable disease, why disease patterns differ between places, the rise of type 2 diabetes and the costs of disease, and using bar charts, histograms, modal classes, percentages and scatter diagrams to judge correlation and cause.Open →
• Cancer, and the use of stem cells in medicineWhat cancer and tumours are, why changes in genes cause uncontrolled division, benign and malignant tumours and how secondary tumours form, risk factors and why early detection helps, the benefits and risks of stem cell treatments, bone marrow transplants, embryonic stem cells and the ethical objections to them, therapeutic cloning, and why transplants are rejected and how rejection is reduced.Open →
• Gene technology in medicine, and the human genomeInsulin made by gene technology, gene therapy for disorders such as cystic fibrosis with its practical difficulties and risks, the benefits and the ethical and privacy concerns of genetic testing and changing embryos, sequencing the human genome, and how it helps predict disease risk, target drugs to a patient's genome, trace inherited disorders and develop new medicines.Open →

What you need to know

Answer each one before you reveal it.

Take Global Challenges further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Communicable disease vs Non-communicable disease

  Communicable disease: illness caused by a pathogen that can pass from one organism to another. Non-communicable disease: illness that cannot be passed on, developing from inherited and lifestyle factors.

• Antigen vs Antibody

  Antigen: molecule on a cell surface that the immune system recognises as own or foreign. Antibody: protein made by a lymphocyte that binds to one specific foreign molecule.

• Phagocyte vs Lymphocyte

  Phagocyte: white blood cell that engulfs a pathogen and digests it with enzymes. Lymphocyte: white blood cell that produces antibodies against a specific antigen.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Why is random sampling used when estimating the abundance of a plant in a field?

   Model answer

   It removes bias in choosing where to sample, so the samples represent the whole area and the estimate is reliable.

2. 2

   How can random positions for quadrats be chosen in a grassy field?

   Model answer

   The field is divided into a numbered grid and pairs of random numbers are used as coordinates for each quadrat.

3. 3

   What is a quadrat and what is it used to measure?

   Model answer

   A square frame of known area placed on the ground, used to count the number of organisms or estimate the percentage cover in that area.

4. 4

   What is a belt transect and when would it be the better sampling method?

   Model answer

   A line across a habitat along which quadrats are placed at set intervals, used where a factor changes gradually, such as from the sea up a rocky shore.

5. 5

   A student places 10 quadrats each of 0.25 m² at random in a field of 2000 m² and counts 30 daisies in total. Estimate the number of daisies in the field.

   Model answer

   The quadrats cover 2.5 m², so the mean density is 12 daisies per m² and the estimate is 24000 daisies.

6. 6

   In a capture-recapture study 40 woodlice are caught, marked and released. The next day 50 are caught and 10 of them are marked. Estimate the size of the population.

   Model answer

   The estimate is 40 × 50 ÷ 10, which is 200 woodlice.

What is inside Levo

Six ways to work the same material.

Global Challenges revision questions

What does Global Challenges cover in OCR GCSE Combined Science Biology?

13 subtopics: field investigations, and human impact on ecosystems, maintaining biodiversity, monitoring conservation and ecotourism, selective breeding and genetic engineering, health, disease, and types of disease, interactions between diseases, and how they spread, reducing the spread of disease, and named examples, white blood cells, antibodies and platelets, non-specific defences and the immune system, vaccines, medicines and aseptic technique, developing new medicines, and non-communicable disease, treating cardiovascular disease, and lifestyle factors, cancer, and the use of stem cells in medicine and gene technology in medicine, and the human genome. Each one has its own page with questions and model answers.

How is Global Challenges organised?

By the OCR J250 specification, subtopic by subtopic, so it matches the order you are taught it in.