In the presence of poison-laced glucose, cockroaches that refuse glucose will have a much higher survival rate than cockroaches that feed indiscriminately. This explains why the glu– allele frequency increases over time in a population exposed to poison + glucose bait. However, energy from carbohydrates is required for growth and reproduction, and glucose is commonly found in non-poison foods that cockroaches encounter in human dwellings. By refusing to eat glucose, are glu–/glu– roaches missing out on an essential energy source?
One way to answer this question is to measure the relative fitness of glu–/glu– roaches. Relative fitness is the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals. Relative fitness is affected by diet and environmental hazards. To determine the relative fitness of a particular genotype, you average the fitness values of a group of individuals with that genotype.
Suppose you raise populations of each homozygous genotype in captivity with three different food sources (plus supplemental rat chow) and collect data about how many individuals survive from egg to adulthood (survivorship) and how many offspring each adult female produces over her lifetime (fecundity). The survivorship and fecundity data are shown in the table below.
From this data, you can calculate fitness values.
The absolute fitness of each genotype is calculated by multiplying the survivorship by the fecundity (only those individuals that survive will reproduce).
The fitness of one relative to the other is the ratio of the two absolute fitness values.
Use the following data to complete the table of fitness calculations. Convert percentage values to decimals before you do the calculations. Round absolute fitness values to the nearest whole number; round relative fitness values to one decimal place.