They were an easily found and plentifully available food sourcein farming areas, especially for poor immigrants.
在农业地区，特别是对贫穷的移民来说，它们是一种很容易找到的、丰富的食物来源。
2
Canadian geophysicist Tuzo Wilson realized that this age progression could result if the islands were formed on a surface plate moving over a fixed volcanic sourcein the interior.
加拿大地球物理学家 Tuzo Wilson 意识到，如果一块在内部固定火山源上移动的表面板块形成了岛屿，就会导致岛屿年龄增加。
3
They replaced other minute organisms as a food sourcein the major marine food chain.