join多指参加某组织,成为其中的一个成员.
take part in指参加群众性活动、会议等,往往指参加者持有积极的态度,起一份作用.
join 例句:①I will never forget the day when I joined the Party.我永远也忘不了入党的那一天。
②Will you join us for dinner?请你和我们一起吃饭好吗?
take part in 例句:①Will you take part in the English evening?同我们一起参加英语晚会好吗?
②All the students took an active part in the thorough cleaning.所有的学生都积极参加了大扫除。
③We should take an active part in school activities.我们应该积极参加学校的活动。
参考资料:http://zhidao.baidu.com/question/118024703.html