藻类要比真正意义上的植物出现得早很多。现今,它们仍然在有水和阳光的地方繁茂地生长着。大多数种类的藻类生长在海洋或淡水中,也有一些种类生长在潮湿的土地上。不同于植物的是,藻类不具有实根、茎或叶片。最小的藻类只有一个单细胞大,并且漂浮生活。最大的藻类为褐海藻,它们看上去更像是植物,并且长度能超过50米。藻类作为食物对于动物来说十分重要,并且一些动物还通过同藻类共生而获得益处。 Algae appear much earlier than real plants. Nowadays, they still flourish in the places where water and sunshine are. Most species of algae grow in the ocean or freshwater, and some species grow on moist soil. Unlike plants, algae do not have roots, stems or leaves. The smallest algae have only one single cell, and float to life. The largest algae, brown algae, look more like plants and can be more than 50 meters in length. Algae are very important for animals as food, and some animals also benefit from symbiosis with algae.