Which of these paleozoic periods is the youngest?
a. permian
b. devonian
c. ordovician
d. pennsylvanian

stratosphere: as the altitude increases, the air temperature increases. the stratosphere has a layer of ozone, called the ozone layer. this layer absorbs most of the ultraviolet radiation from sunlight. this results in the stratosphere being warmer.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

ya the other dude is right

its temperature is increasing. this causes molecular vibrations to increase.