下列各类动物中，最先出现呼吸系统的是( )。
- A.环节动物
- B.节肢动物
- C.软体动物
- D.鱼类动物
正确答案及解析
正确答案
解析
按照进化等级，选项中的顺序是软体动物→环节动物→节肢动物→鱼类动物。软体动物一般生活在水中，用鳃呼吸，是在进化过程中首先具有了专门的呼吸器官的动物。环节动物一般靠体壁进行呼吸；节肢动物呼吸系统呈现多样性，可以用鳃(虾、蟹)、书肺(蜘蛛)、气管(昆虫)呼吸；鱼类动物用鳃呼吸。
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