This mini-lesson covers OCR B6 — Global challenges: sampling & monitoring ecosystems, human impact, food security, health & disease, pathogens and the immune system, drug development and biotechnology.
Make a guess: what does it take to feed a growing population?
Mission 1How do we keep a growing world fed?
Mission 2How does a vaccine protect you?
Mission 3Why keep patients and doctors in the dark?
Work through each screen, answer the questions as you go and collect ⭐ stars. Watch for the Higher tier flags. Press Start when you're ready.
Sampling & monitoring ecosystems
Sampling & monitoring
We monitor ecosystems to spot changes and pollution:
Quadrats (placed randomly) and transects (along a line) estimate populations and how they change.
Indicator species reveal pollution — e.g. bushy lichens are only found where the air is clean, and mayfly larvae only where the water is clean.
Scale up the mean per quadrat to estimate the whole population; more, random samples = more reliable.
Indicator species: their presence or absence is a quick, cheap sign of environmental quality.
Quick check
What is an indicator species?
?Why are lichens useful as indicator species?
Human impact & food security
Human impact & food security
A growing human population increases demand and impact:
Human impact: deforestation, pollution, and greenhouse-gas emissions reduce biodiversity and change the climate.
Food security is having enough safe food for everyone. It is threatened by a rising population, changing diets, pests, disease and climate change.
Ways to improve yield: fertilisers, pest control, and biotechnology (e.g. GM crops).
Sustainability: we must increase food production without permanently damaging ecosystems or biodiversity.
Mission 1 check
How do we keep a growing world fed?
?A country's population is rising fast, and a new pest is spreading through its wheat. Which plan would best improve its food security?
Mission 2 of 3
How does a vaccine protect you?
Make a guess: how can a dead or inactive germ keep you safe?
Health · pathogens
Health, disease & pathogens
Health is a state of physical and mental wellbeing. Diseases can be:
Communicable (infectious) — caused by pathogens that spread between organisms.
Non-communicable — not spread; e.g. many cancers, heart disease.
The four pathogen groups: bacteria (e.g. Salmonella), viruses (e.g. measles, HIV), fungi (e.g. rose black spot) and protists (e.g. Plasmodium, which causes malaria and is spread by mosquitoes).
Bacteria vs viruses: bacteria release toxins that make you feel ill; viruses invade cells and reproduce inside them, damaging the cell. Antibiotics kill bacteria but not viruses.
Quick check
What do antibiotics kill?
?A patient has a viral infection. Why won't antibiotics help?
Health · plant disease
Plant diseases & defences
Plants catch communicable diseases too. Learn one of each:
Barley powdery mildew (Erysiphe graminis) — fungus; white powdery patches on leaves; spores spread by wind.
Crown gall disease (Agrobacterium tumefaciens) — bacterium; tumour-like growths (galls) on stems and roots.
Plant defences: physical — a waxy leaf cuticle and cellulose cell walls; chemical — antimicrobial substances.
Higher tier — spotting plant disease: in the field, by observing symptoms and using a microscope; in the lab, by detecting the pathogen's DNA or antigens.
The immune system
The immune system & vaccination
White blood cells defend the body against pathogens by:
Phagocytosis — engulfing and digesting pathogens.
Producing antibodies that lock onto specific pathogens.
Producing antitoxins that neutralise toxins.
Vaccination: a dead or inactive form of the pathogen, carrying its antigens, is introduced, so white blood cells make antibodies and memory cells. If the real pathogen invades later, the response is faster and larger — you are immune.
Herd immunity: if enough people are vaccinated, the pathogen can't spread easily, protecting those who aren't vaccinated.
Quick check
How does a vaccine work?
?How does a vaccine protect you from a disease?
Mission 2 check
How does a vaccine protect you?
?A child is given a vaccine containing a dead form of a virus. Later, the live virus gets into her body, but she does not become ill. Why not?
Match it
Match each pathogen to its group
Tap a disease, then its pathogen type.
Statement
Answer
Mission 3 of 3
Why keep patients and doctors in the dark?
Make a guess: why don't patients or doctors know who got the drug?
Drug development
Developing new drugs
New drugs are tested in stages before use:
Preclinical — tested on cells, tissues and then animals.
Clinical trials — tested on healthy volunteers (for safety) then patients (for safety and effectiveness), finding the best dose.
Placebo and double-blind trials (neither doctor nor patient knows who gets the real drug) reduce bias.
Why so thorough? testing checks a drug is safe, effective and given at the right dose before it reaches patients.
Quick check
What is a double-blind trial?
?In a double-blind drug trial, who knows which patients receive the real drug?
Mission 3 check
Why keep patients and doctors in the dark?
?A new painkiller is tested. Patients and doctors both know who got the real pill and who got a placebo. The real-pill group reports less pain. Why can't this result be trusted?
Health · non-communicable disease
Non-communicable disease
Many non-communicable diseases are caused by an interaction of several factors (genes, lifestyle, environment):
Examples: cardiovascular disease, many cancers, lung disease (bronchitis), liver disease (cirrhosis), type 2 diabetes.
Lifestyle factors: diet, exercise, alcohol and smoking.
Cancer: changes in cells lead to uncontrolled growth and division.
Treating cardiovascular disease — weigh them up:lifestyle (diet, exercise, stop smoking: cheap, no side effects, but slow); medical (e.g. statins lower cholesterol: effective, but long-term and possible side effects); surgical (e.g. stents, bypass: quick effect, but risks such as infection).
Diseases interact: HIV weakens the immune system, so tuberculosis is more likely; infection with HPV can lead to cervical cancer.
Biotechnology
Biotechnology & genetic engineering
Biotechnology uses living organisms to make useful products:
Genetic engineering — transferring a gene from one organism to another (e.g. inserting the human insulin gene into bacteria so they make insulin).
GM crops — modified for pest resistance or higher yield to help food security.
Enzymes and microorganisms are used to make foods, medicines and fuels.
Evaluate GM: benefits include higher yields and insulin production, but there are concerns about long-term effects, ethics and reduced biodiversity.
Sort it
Sort each into its group
Tap each item, then tap which theme it belongs to.
🦠 Fighting disease
🌾 Food & environment
🧫 Biotechnology
Recap
The big ideas to know
Monitoring: quadrats, transects & indicator species (e.g. lichens)
Food security: enough safe food; threatened by population, pests, climate