Drosophila may be monosomic for chromosome 4, yet remain fertile. a recessive mutant for bent bristles is identified on chromosome 4. determine the genotypes of the f1 and f2 progeny for the following crosses.
the following cross is conducted of true-breeding adult flies: monosomic bent bristles x diploid normal bristles. select the two f1 genotypes that will be produced from this cross
a. -/b+
b. -/b
c. b/b
d. b/b+
e. b+/b+

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.