Which of the following describes the levels of structural organization approach to studying the human body ? A) a way of classifying body components such as cells, tissues, and organs according to their shared origin and function
B) a collection of organs or structures whose coordinated activities perform one or more vital functions
C) a focus on studying body systems
D) a way of studying the body without focusing on cells

Which of the following best reflects what we know about how the flu virus moves between species? a) the flu virus in a pig is mutated and replicated in alternate arrangements so that humans who eat the pig products can be infected.b) a flu virus from a human epidemic or pandemic infects birds; the birds replicate the virus differently and then pass it back to humans.c) an influenza virus gains new sequences of dna from another virus, such as a herpesvirus; this enables it to be transmitted to a human host.d) an animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.