How is the spread of a disease carried by an insect reduced?

By destroying the insect and its breeding sites, and by using barriers such as nets so it cannot reach people.

How is testing DNA used to identify the cause of an infection?

DNA from the sample is checked for base sequences found only in that pathogen, giving a certain identification even when very few pathogens are present.

How does a grower identify a diseased crop plant by eye in the field?

By looking for typical symptoms such as mottled or discoloured leaves, spots, growths or stunted growth.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Protein synthesis and the triplet code Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

Community Level Systems

Topic overview Cycling materials, and the role of microorganisms The carbon and water cycles, and decomposition Levels of organisation, and abiotic and biotic factors Interdependence, competition and trophic levels Pyramids of biomass and the efficiency of transfer

Genes, Inheritance and Selection

Topic overview Genetic terms, and the genome Genome, environment and mutations How genetic variants influence phenotype Asexual and sexual reproduction compared Haploid, diploid and meiosis Single gene inheritance and Punnett squares Sex determination, multiple genes and Mendel's work Variation within a population, and classification Natural selection and evolution Evidence for evolution, and the work of Darwin and Wallace

Global Challenges

Topic overview Field investigations, and human impact on ecosystems Maintaining biodiversity, and evidence for environmental change Food security, agricultural and biotechnological solutions 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 Physical and chemical plant defences Detecting plant disease; white blood cells and platelets Non-specific defences and the immune system Monoclonal antibodies and their uses 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 Gene technology in medicine, and the human genome

Organism Level Systems

Topic overview 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 Responding to temperature and osmotic challenges

Scaling Up

Topic overview Diffusion, osmosis and active transport Mitosis, the cell cycle and cell differentiation Stem cells in animals and meristems in plants Surface area to volume ratio and exchange surfaces The circulatory system, the heart and blood vessels Red blood cells and plasma Root hair cells, transpiration and translocation Xylem and phloem Factors affecting water uptake, and the potometer

Global Challenges

Reducing the spread of disease, and named examples

3 things to know
Paper 4

Overview

Reducing 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.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Give three ways the spread of an infectious disease between people can be reduced.

Key term

Explain how vaccinating most of a population protects the people who are not vaccinated.

Key term

How does testing a sample for a pathogen's antigens help control the spread of a disease?

Questions from this subtopic

Each one with the model answer underneath.

1
Give three ways the spread of an infectious disease between people can be reduced.
Model answer
Washing hands and keeping surfaces clean, isolating people who are infectious, and vaccinating the population.
2
Explain how vaccinating most of a population protects the people who are not vaccinated.
Model answer
So few people can catch and pass on the pathogen that it cannot spread, so unvaccinated people are unlikely ever to meet it.
3
How is the spread of a disease carried by an insect reduced?
Model answer
By destroying the insect and its breeding sites, and by using barriers such as nets so it cannot reach people.
4
How does testing a sample for a pathogen's antigens help control the spread of a disease?
Model answer
The antigens are unique to that pathogen, so the disease is confirmed quickly and the infected individual can be treated or isolated before others are infected.
5
How is testing DNA used to identify the cause of an infection?
Model answer
DNA from the sample is checked for base sequences found only in that pathogen, giving a certain identification even when very few pathogens are present.
6
How does a grower identify a diseased crop plant by eye in the field?
Model answer
By looking for typical symptoms such as mottled or discoloured leaves, spots, growths or stunted growth.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

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Algae and .

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AThe blood becomes too dilute.

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Egestion means passing out of undigested food as faeces.

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