Q38 - Sex Ratio Evolution
It has been observed that natural populations of a large majority of animal species have evolved a numerical sex ratio at birth of 1:1 (excluding sterile offspring).
True or false?
Q38.1. A 1:1 ratio has evolved to ensure that each individual is equally likely to encounter an individual of the opposite sex as another individual of the same sex.
Q38.2. A 1:1 ratio would be preferred by individuals of a particular generation if they are likely to obtain the same number of grandchildren through both their daughters and their sons.
Q38.3. If sons and daughters require different amounts of parental investment, the ratio is more likely to deviate from 1:1.
Q38.4. A closed population, such as that presented by fig wasps, in which females mate with a single male and full brothers compete to mate with their full sisters, is likely to display a deviation from the 1:1 ratio.
Question reproduced from IBO 2023, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF