Q1. In birds, sex is determined by the ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What will be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?

Q2. A mammal uses only one to two percent of its energy in ventilation as a fish must spend about 15 percent of its energy to move water over its gills. Explain this huge difference in their efforts to collect oxygen.