你是一名资深科学老师，现在你根据我提供的知识点复习资料对知识点进行复习讲解。---Here is the extracted content from the image: 1. 绿色开花植物几乎都是从种子开始新生命的，有的是用根、茎、叶繁殖后代的。 2. 种子是由种皮和胚构成的。胚包括胚芽、胚根和子叶。 3. 观察种子的外部特征：综合运用感官并用比较的方法能观察到种子的更多特征。 (1) 看：用肉眼观察种子的颜色、大小、形状及其他显著特征，然后用放大镜观察颗粒较小的种子的特征。 (2) 摸：用手摸一摸种子的软硬、光滑程度。 (3) 闻：用鼻子闻一闻种子的气味。 (4) 测量：了解种子的重量、体积等。 (5) 观察记录：观察不同植物的种子，可以发现它们的形状、大小、颜色等特征各不相同。将观察到的结果记录下来。 4. 种皮保护种子的内部结构；胚是种子的重要部分，发育成一株植物；胚芽将来发育成茎和叶；胚根将来发育成根；子叶具有储存营养物质的作用。有的种子有一片子叶，有的种子有两片子叶。 **Chart/Diagram Description:** * Type: Biological diagram illustrating the structure of a seed. * Main Elements: * The main object is a seed, labeled "种子". * A bracket on the left indicates that the seed is composed of "种皮" (seed coat) and "胚" (embryo). * A bracket under "胚" indicates that the embryo is composed of "胚根" (radicle), "胚芽" (plumule), and "子叶" (cotyledon). * The diagram shows a cutaway view of the seed, revealing its internal structure. * The outer layer is labeled "种皮". * Inside the seed coat is the embryo, which consists of two large structures labeled "子叶" (cotyledons). * Between the two cotyledons, the "胚芽" (plumule) and "胚根" (radicle) are shown attached to the base of the cotyledons. * The overall diagram illustrates the major components of a typical dicotyledonous seed (having two cotyledons).