1. The first animals on this living sphere, the Earth, were primitive marine animals, and then around 500 million years ago these sea animals developed shells.
    在地球这个有生命的星球上，最早的动物是原始海洋动物。后来，在大约5亿年前，这些海洋动物进化成甲壳动物。

2. He drew a world map on a sphere.
    他在球上面画一幅世界地图.

3. And to exercise such initiative as falls within their sphere, then administrative overheads will be low.
    在各自的工作范围内发挥主动性，行政管理费用就会降低。