Gce Model Questions Vol1 2023 Biology Question 6

A population of a short‑lived insect is divided into three age classes: juveniles (0-1 yr), sub‑adults (1-2 yr) and adults (2-3 yr). The probability of surviving from one class to the next is 0.5 for juveniles and 0.7 for sub‑adults, while adults survive to the next year with probability 0.9 (which is not needed for the calculation). The average number of female offspring produced per individual is 0 for juveniles, 1.2 for sub‑adults and 2.5 for adults. (i) Calculate the net reproductive rate \(R_{0}\). (ii) State whether the population is expected to increase or decrease. (iii) Calculate the generation time \(G\) (in years) using \(G=\frac{\sum x\,l_{x}m_{x}}{R_{0}}\) where \(x\) is the age (in years) of the reproductive class.