参考答案:Certain species disappeared or became extinct as new forms arose that were better adapted to the Earth’s changing environment./...when new forms arose that were better adapted to the Earth’s changing environment. 答案解析:[译文] 一些物种消失或灭绝,是由于产生了新的物种形式,它们可以更好地适应当时不断变化的地球环境。