Question
According to the UN Inter-agency Group for Child Mortality Estimation, in the year 2000 there were 9.82 million deaths of children under the age of 5. Many of these deaths were caused by infectious diseases. The pie chart shows estimates for the percentages of deaths that were attributable to two of the most frequent pathogens, Streptococcus pneumoniae and Haemophilus influenzae.
(a) Calculate the number of deaths in children under the age of 5 that were attributed to S. pneumoniae in the year 2000.
(b) The deaths due to these two pathogens only included children who were not infected with HIV. Suggest a reason for excluding HIV-infected children from the statistics.
Vaccination programmes have led to decreases in child mortality. The graph shows global trends between 1980 and 2018 in the vaccination of children against seven different pathogens in the first year of their lives.
(c) (i) Using the graph, identify the percentage who had received the tuberculosis vaccine in 2012.
(ii) Calculate the difference in time between 40% of children receiving the hepatitis B vaccine and 40% receiving the pneumococcal vaccine.
Children are immunized against diseases caused by Streptococcus pneumoniae with pneumococcal conjugate vaccine (PCV) and against diseases caused by Haemophilus influenzae with Haemophilus influenzae type b (Hib) vaccine. The graphs show the estimated global percentages of children not vaccinated against S. pneumoniae and H. influenzae by the age of 5 and the estimated global death rates in children under 5 years, due to these pathogens, between 2000 and 2015.
(d) Outline the conclusions that can be drawn from the graph showing data for PCV and S. pneumoniae.
(e) Suggest reasons for the difference between the data for S. pneumoniae and H. influenzae.
Acute respiratory infection (ARI) is a frequent reason for antibiotic use among children in low-income and middle-income countries (LMICs). S. pneumoniae is the predominant, but not the only, cause of ARI in children. In a large-scale study, data were collected in 18 LMICs from 65815 children under the age of 5. The data were analysed to estimate the fraction of ARI cases among the children that could be attributed to S. pneumoniae as shown in the graphs. The upper estimate in the graphs is for all cases, whether or not they were treated with
antibiotics. The lower estimate is for the subset of cases that required antibiotic treatment. The range of estimates is shown by violin plots, with a point for the median estimate and lines for 95% confidence intervals.
(f) Using the data in the violin plots, deduce the age range at which children are most likely to develop ARI due to S. pneumoniae.
(g) Suggest reasons for the difference between the fraction attributed to S. pneumoniae in all cases of ARI and in cases where antibiotics were used to treat the infection.
Estimates were made of the extent of antibiotic use in low-income and middle-income countries. Graphs were constructed to show global estimates for the numbers of cases in LMICs per year of ARI treated with antibiotic in children under the age of 5. The estimates
for LMICs were divided according to income: low income, lower-middle income and upper-middle income.
The graph shows estimates for three levels of vaccination for S. pneumoniae with PCV:
• no vaccination
• 2018 coverage: the vaccine coverage that there was in 2018
• universal coverage: predictions assuming that in the future all children in all LMICs receive the vaccination.
(h) When there is no vaccination, the estimated number of cases for lower-middle income countries is larger than in either low income or upper-middle income countries. Suggest one reason for this.
(i) Using the data, predict the effect of universal PCV vaccination in LMICs.
(j) Outline likely health benefits of universal PCV vaccination of children, other than reducing the incidence of ARI.
Answer/Explanation
Answer:
(a) 736 500;
(b)
a. difficult to know what infection causes death in children with HIV;
b. HIV lowers immunity/fewer T cells/reduces antibody production/more likely to
catch infectious disease;
c. deaths of HIV-infected children should be attributed to HIV;
(c)
(i) 89%;
(ii) 13 years;
(d)
a. number of deaths (due to S. pneumoniae) and percentage of children not vaccinated (with PCV) both fall (along the years)
OR
number of deaths (due to S. pneumoniae) decreases while percentage of
vaccinated children (with PCV) increases (along the years);
b. positive correlation between number of deaths and percentage of children not
vaccinated /
OR
negative correlation between number of deaths and percentage of children
vaccinated / vaccination reduces the number of deaths;
c. increased reduction in the number of deaths from 2010 onwards;
d. still large number of deaths/large number of children unvaccinated in 2015;
(e)
a. Hib vaccination program started earlier/PCV vaccination program started later
OR
Hib vaccine developed before PCV vaccine;
b. deaths due to H. influenzae drop earlier than deaths due to S. pneumoniae
because of earlier vaccination;
c. more deaths due to S. pneumoniae than H. influenzae (in any year) as lower
% of children vaccinated against S. pneumoniae (compared H. influenzae);
(f)
a. 2 – 5 years;
b. higher number/value/percentage/attributable fraction for 2 -5 years (than 0 – 5
years);
(g)
a. highest attributed fraction (in both age groups) is in cases where antibiotic
used;
b. ARI cases due to S. pneumoniae can be severe so antibiotics are often
prescribed;
c. all cases include other causes / viral ARI which may not require antibiotics;
d. antibiotics administered without prescription or physician consultation/to
reduce symptoms;
(h)
a. higher population in lower-middle income countries/subgroup (compared to the other 2 subgroups);
b. low income population may not have/have less access to
medicine/antibiotics/vaccination (compared to lower-middle income
population)/ low-income populations may not report data
OR
upper-middle population may have better living conditions/more adequate
medical diagnoses (compared to lower-middle income population);
(i) (worldwide) drastic/huge/important/significant decrease/decrease of 42 million ARI cases (treated with antibiotics);
(j)
a. less use of antibiotics;
b. less antibiotic resistance (in pathogens) / antibiotics more successful at treating infectious/bacterial diseases;
c. decrease in health care costs / less money spent on antibiotics;
d. decreased mortality / protection of immune-deficient patients/non-vaccinated
population/ achieve herd immunity;
Question
a. Outline how cuts in the skin are sealed to prevent blood loss. [4]
b. Outline how two parents could have a child with any of the four ABO blood groups. [4]
c. Explain how ventilation and lung structure contribute to passive gas exchange. [7]
▶️Answer/Explanation
Markscheme
a. platelets respond to/detect skin/blood vessel damage ✔
b. platelets release clotting factors ✔
c. clotting factors trigger a chain/cascade of reactions ✔
d. «leading to» formation of thrombin ✔
e. thrombin causes fibrinogen conversion into fibrin ✔
f. blood clot seals the wound due to fibrin network of fibres ✔
Accept answers presented as a flow chart.
a. «first set of» gametes/parental genotype IA, i ✔
b. «other set of» gametes/parental genotype IB, i ✔
c. «genotypes of offspring are respectively» IAIB, IBi, IAi, ii ✔ All four correct required.
d. «phenotypes of offspring are respectively» AB, B, A, O ✔ All four correct required linked to genotypes
Award marks only for the first grid if more than one drawn;
e.g. of Punnett grid
Answers can be given in a Punnett grid or in prose.
Accept the four possible blood groups of the offspring anywhere in the answer.
a. air carried through trachea AND bronchi/bronchioles AND alveoli ✔ All three required in correct order.
b. alveoli increase the surface area/thin walled for gas exchange ✔
c. gas exchange carried out through type I pneumocytes ✔
d. type II pneumocytes secrete surfactant to reduce surface tension ✔
e. moist surface/surfactant allows gases to diffuse in solution ✔
f. ventilation/moving blood maintains concentration gradients of oxygen and carbon dioxide ✔
g. between air in alveoli and blood in «adjacent» capillaries
OR
oxygen diffuses from alveoli to capillaries and carbon dioxide from capillaries to alveoli ✔ OWTTE
h. external intercostal muscles/diaphragm contract during inspiration ✔
i. lowering air pressure «in lungs»/increasing thorax volume ✔
j. relaxation of external intercostal muscles/diaphragm enable «passive» expiration ✔
k. internal intercostal «and abdominal muscles» contract «to force» expiration ✔
l. expiration due to increasing air pressure «in lungs»/decreasing thorax volume ✔
Accept correctly annotated diagram.
Question
Multicellular organisms benefit from cell specialization and division of labour.
(a) Outline the processes occurring during interphase in the cell cycle.[4]
(b) Describe what occurs in a neuron when an action potential is propagated along the axon. [4]
(c) Explain how cells in the bloodstream cause a specific immune response.[7]
Answer/Explanation
a a. growth/increase in cell size;
b. division of mitochondria/chloroplasts/production of more organelles/number of organelles doubled;
c. replication of DNA/amount of DNA is doubled;
d. transcription of genes/production of mRNA;
e. protein synthesis;
f. cell respiration/production of ATP;
b a. sodium ions/Na+ enter/diffuse in;
b. depolarization/membrane potential/voltage changes from negative to positive;
c. potassium channels open AND potassium ions/K+ exit/diffuse out;
d. repolarization/membrane potential/voltage changes back from positive to negative;
e. local current due to diffusion of sodium ions along the neuron;
f. (local currents) cause next sodium channels to open/next part of axon to depolarize;
g. opening of sodium channels triggered when threshold potential/-50mV reached;
c a. (specific immune response is) production of antibodies in response to a particular pathogen;
b. antibody is specific to/binds to a specific antigen;
c. macrophages/phagocytes engulf/present antigens from pathogens/viruses/bacteria;
d. T lymphocytes activated by antigens/antigen presentation/antigens presented by macrophage;
e. (activated) T lymphocytes activate B lymphocytes;
f. only B lymphocytes that produce antibodies against the antigen/pathogen are activated;
g. (activated) B lymphocytes clone/divide by mitosis to form plasma cells;
h. plasma cells then secrete (large quantity) of an antibody/secrete antibodies of same type;
i. some B lymphocytes/plasma cells form memory cells;
j. memory cells give long lasting immunity/faster response to a disease/pathogen;