IB DP Biology SL- Data-Based Questions- IB Style Questions For Paper 1B -FA 2025
Question
▶️ Answer/Explanation
(a)
• The mean total energy of the study diet is slightly lower than that of the habitual diet.
• However, the standard deviations overlap, so there is no clear difference in total energy content between the two diets.
(b)
• The diets differ in the proportions of saturated and unsaturated fats, not in total fat.
• The study diet contains a higher percentage of saturated fats and a lower percentage in the habitual diet.
• (Mono- and poly-)unsaturated fats are reduced in the study diet compared with the habitual diet (polyunsaturated fats in the study diet are roughly half those in the habitual diet).
• The study diet has slightly less carbohydrate than the habitual diet.
(c)
Initial mean cholesterol level = \(150\ \text{mg dL}^{-1}\)
Mean cholesterol after 1 week on the study diet = \(165\ \text{mg dL}^{-1}\)
\[ \text{Percentage change} = \frac{\text{new value} – \text{old value}}{\text{old value}} \times 100 = \frac{165 – 150}{150} \times 100 = \frac{15}{150} \times 100 = 10\% \]
✅ Percentage change in mean cholesterol level after one week = 10% increase.
(d) (i)
• Before and after the study diet, plasma insulin levels show the same general pattern: a rapid rise, then a leveling and gradual decrease.
• Both sets of values are very similar at each time point, with overlapping error bars, indicating no significant difference in insulin levels before and after the study diet.
• In both cases, insulin rises for about the first 30–45 minutes after glucose intake.
(d) (ii)
• Insulin is secreted by the β (beta) cells of the islets of Langerhans in the pancreas.
(d) (iii)
• After glucose is consumed, blood glucose concentration rises.
• This stimulates the pancreatic β cells to secrete more insulin to reduce blood glucose levels by increasing glucose uptake into cells.
Markscheme (summary):
(a)
a. Energy is not effectively changed between the two diets;
b. Study diet slightly lower in energy than habitual diet (but means/SD overlap);
c. Habitual diet shows slightly greater variation / higher SD.
(b)
a. They differ in percent of saturated vs unsaturated fats, not total fat;
b. Percent of saturated fats higher in study diet / lower in habitual diet;
c. (Mono/poly)unsaturated fats decreased in study diet compared to habitual diet;
d. Slightly less carbohydrate in the study diet.
(c)
a. \(((165 – 150) \div 150) \times 100\);
b. = 10%;
(d)(i)
a. Both show same pattern of rise, level, then decrease;
b. Both show similar insulin levels at all times (overlapping error bars);
c. Both rise for about 30–45 minutes.
(d)(ii)
a. β cells of pancreas / islets of Langerhans.
(d)(iii)
a. As blood glucose rises, insulin secretion increases to reduce the blood glucose level.
Question
(i) the largest number of Ebola cases. [1]
(ii) the largest number of deaths. [1]
▶️ Answer/Explanation
(a)
(i) Country with the largest number of Ebola cases: Sierra Leone.
(ii) Country with the largest number of deaths: Liberia.
(b)
Evidence that the number of deaths is not related to total population size:
• Liberia has the smallest population among the four countries but the highest number of deaths.
• Mali has a relatively large population, yet very few deaths from Ebola.
Any one of these contrasting examples shows there is no simple link between population size and deaths.
(c)
• Ebola spreads through close contact with infected individuals, their body fluids or contaminated equipment.
• In countries with higher population density, people are more likely to be in frequent, close contact with each other and with infected individuals, so more opportunities exist for the virus to be transmitted.
(d) Compare and contrast the progress of the epidemic in Liberia and Guinea:
• In both countries, the overall pattern is similar: the number of new cases rises to a peak and then falls again.
• The epidemic in Guinea starts earlier (around April 2014), while in Liberia it starts later (around June 2014).
• Liberia reaches its peak number of new cases earlier (around September 2014), whereas Guinea peaks later (around December 2014).
• After the peak, Liberia shows a sharp drop in new cases after October 2014, while Guinea shows more fluctuating numbers and a slower decline.
• The epidemic lasts longer in Guinea (cases continue until at least May 2015), whereas in Liberia the last cases are recorded by about February 2015.
• In general, the number of new cases is higher in Liberia than in Guinea throughout much of the epidemic.
(e) Two possible reasons for the drop in daily numbers of newly infected cases after October 2014 in Liberia:
• Improved control measures: quarantine, isolation of infected individuals, better contact tracing, safer burial practices, and stricter infection control in hospitals.
• Better medical support and public awareness: more trained healthcare workers, improved hygiene and use of protective equipment, health education campaigns teaching people how to avoid contact with infected body fluids.
Other acceptable ideas include international aid arriving, changes in people’s behaviour (avoiding gatherings), or vaccination programmes (if used), etc.
(f) Evidence that T-705 has potential as a treatment:
• As the concentration of T-705 increases, the virus concentration falls markedly, showing the drug is effective at reducing or inhibiting viral replication.
• The percentage of live cells remains high even at high T-705 concentrations, indicating that the drug is not highly toxic to the host cells in vitro.
Together, these results suggest T-705 can reduce Ebola virus levels without killing many host cells, so it has potential as a treatment for EVD.
(g)
One way international organizations can assist (any one):
• Provide healthcare workers, training and expertise to support local staff.
• Supply personal protective equipment, disinfectants and medical equipment.
• Fund and organize vaccination campaigns or clinical trials.
• Support logistics for quarantine, contact tracing and distribution of supplies.
• Provide financial aid and coordination for emergency response.
Any one clearly described method gains the mark.
Markscheme (key points):
(a)(i) Sierra Leone
(a)(ii) Liberia
(b)
• Country with biggest population (e.g. Mali) has very few deaths;
• Country with smallest population (Liberia) has the greatest number of deaths.
(c)
• Greater population density → more frequent contact with infected people/animals → more transmission.
(d) (examples of valid points)
a. Overall pattern similar in both (rise then fall).
b. Both countries increase during 2014; neither shows an increase in 2015.
c. Sudden drop occurs earlier (Oct–Nov 2014) in Liberia than in Guinea (Dec 2014–Jan 2015).
d. Guinea shows fluctuations; Liberia rises to a peak then falls more smoothly.
e. Epidemic starts earlier (April 2014) in Guinea than in Liberia (June 2014).
f. Epidemic peaks earlier in Liberia (Sept 2014) than in Guinea (Dec 2014).
g. Epidemic lasts longer in Guinea (cases to at least May 2015) than in Liberia (last cases Feb 2015).
h. Numbers of cases generally lower in Guinea than in Liberia.
(e) (any two)
a. Improved medical care/support/supplies/equipment/training of staff/hygiene;
b. Improved public understanding/education/awareness of how to avoid infection;
c. Effect of control measures: quarantine, isolation, travel restrictions;
d. International aid arriving; vaccine use; seasonal or behavioural changes, etc.
(f)
a. Few cells killed, even at high drug concentration;
b. Virus concentration much reduced at 100 μM and especially 1000 μM;
c. Virus concentration decreases as T-705 concentration increases;
d. Therefore, T-705 has high potential as a treatment at adequate dose.
(g)
• Raise awareness/provide information; supply health workers/equipment; train local staff; provide financial support; provide vaccines; issue travel alerts, etc.