How can the skin be considered part of the immune system?

Me the formula cacl2 represents the compound

What is an example of a scientific question that galileo could not have answered with out this new tool?

The genetic code is essentially the same for all organisms. based on this information, one can logically assume which of the following statements to be correct? a. dna was the first genetic material. b. the same codons in different organisms translate into the different amino acids. c. different organisms have different numbers of different types of amino acids. d. a gene from an organism can theoretically be expressed by any other organism. e. all organisms have experienced convergent evolution.