What causes diffusion? i have a test to study for in biology and the only thing i dont get is what causes diffusion.?

Which of the following is most important in making the typical seed more resistant to adverse conditions than the typical spore? a) a different type of sporopollenin b) an internal reservoir of liquid water c) integument(s) d) ability to be dispersed e) waxy cuticle

How are mutations continually being generated in a population (what are some of the causes of mutatuions? ) explain

People with one sickle cell allele are not likely to get malaria. what is this an example of?