Read before you practise · 3 min
Read What Belongs to a Population
Rates and ratios such as birth, death and sex ratio describe populations rather than individuals.
NSEJS · Organisms and Populations · 5 linked questions · 100% coverage
Know this first
Population Attributes is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Study deeper: NCERT Science · Organisms and Populations
Identify population-level measures
Birth rate, death rate, sex ratio and age distribution are population attributes. Rates should be normalised by the population and the stated time interval.
Calculate a per-capita death rate
Divide deaths by the starting population and time. Four deaths from forty flies in one week gives 4/40 = 0.1 per individual per week.
OlympIQ exam lens
- ✓Population attributes include rates, ratios and age structure.
- ✓Per-capita rate = event count / population / time.
OlympIQ trap
Keep the time unit in the answer; a weekly rate is not a yearly rate.
Ready to try the pattern?
100% coverage across the 5 linked questions.
Practise 5 linked questionsSign in to practise — your XP, streak and analysis update as you solve.