however, as is most often the case with film adaptations, differences do exist between the film and source material. certain scenes from the book were cut from the film, such as a biology room scene where bella's class does blood typing. hardwicke explains, "well [the book is] almost 500 pages—you do have to do the sweetened condensed milk version of that... we already have two scenes in biology: the first time they're in there and then the second time when they connect. for a film, when you condense, you don't want to keep going back to the same setting over and over. so that's not in there." the settings of certain conversations in the book were also changed to make the scenes more "visually dynamic" on-screen, such as bella's revelation that she knows edward is a vampire—this happens in a meadow in the film instead of in edward's car as in the novel. a biology field trip scene is added to the film to condense the moments of bella's frustration at trying to explain how edward saved her from being crushed by a van. the villainous vampires are introduced earlier in the film than in the novel. rosenberg said that "you don't really see james and the other villains until to the last quarter of the book, which really won't work for a movie. you need that ominous tension right off the bat. we needed to see them and that impending danger from the start. and so i had to create back story for them, what they were up to, to flesh them out a bit as characters." rosenberg also combined some of the human high school students, with lauren mallory and jessica stanley in the novel becoming the character of jessica in the film, and a "compilation of a couple of different human characters" becoming eric yorkie. about these variances from the book, mooradian stated, "i think we did a really judicious job of distilling [the book]. our greatest critic, stephenie meyer, loves the screenplay, and that tells me that we made all the right choices in terms of what to keep and what to lose. invariably, you're going to lose bits and pieces that certain members of the audience are going to desperately want to see, but there's just a reality that we're not making 'twilight: the book' the movie."