Answer:
Sigma factors bind to the promoter region of a particular gene and facilitating the binding of RNA Polymerase to the promoter region (formation of the RNA polymerase holoenzyme complex) in order initiate transcription of the gene.
Put simply - Helps RNA Polymerase do it's job.
He observed 15 different finch species that originated as one ancestral bird. all differing in body shape, beak size, and mating habbits
Altitude decreases the temperature in the troposphere....