Name at least 4 things our atmosphere does for us

Alaska and northern canada have a diet rich in vitamin d and their skin color is darker than predicted on the basis of iv intensity at their latitude. explain the observation:

Genetic disorders can result when sister chromatids fail to seperate properly. during what phase is this problem most likely to occur?

Ineed to get this test done which of the following statements is correct in hour our immune system responds to a potential pathogen? a.) the skin will be the first line of defense, and then the many phagocytes in the bloodstream will attempt to consume the possible pathogen. b.) b cells will start reading the antigen code immediately and call t cells to assist in destroying the pathogen. c.) the adapted immune system will call on the innate immune system to destroy the pathogen. d.) the t-cells in the adapted immune systems are the first to recognize the pathogen