四年级科学 花 果实及种子教学设计 Microsoft PowerPoint 演示文稿.ppt

花、果实和种子 １７ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 想一想，　　　　　　 　生活中，你见过哪些花？　　　　　　　　　　你能描述一下吗？ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 雌蕊 雄蕊 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 你能找出雄蕊和雌蕊吗？ 动动手－小组实验 它们有什么共同特点？ 　（观察桃花，月季花） Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 　　　　　　　　　　仔细观察，沉着思考。 实验中…… Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 柱头 花药 子房 花柱 花丝 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 提示：可以用手触摸，认真观察。 雌蕊的柱头，和雄蕊的花药有　　　　什么特点？ 想一想： Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 对一对 雄蕊的花药中有许多花粉，用手轻轻抖动，会散落。 雌蕊的柱头有许多黏液，用手可以感觉的到，它们在传粉过程中都发挥非常重要的作用。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 花药 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 小组讨论： 你能根据花药和柱头的特点，推测出花传粉的方式和过程吗？ 提示（蜜蜂菜花的生物意义，苍耳外形结构和传播种子的关系。） Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 动动手－－给花授粉　（验证假设） １用棉签轻触雄蕊花药。 ２用接触过雄蕊花药的棉签在雌蕊柱头上轻 　涂。 ３用放大镜观察雌蕊柱头是否沾上了花粉。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 教师小结： 当蜜蜂或其他昆虫在花中飞舞，爬行时，就会把雄蕊的花粉传播到雌蕊的柱头上去，就会使雌蕊子房中的胚珠受精，胚珠受精以后，果实和种子开始成长，花朵开始凋谢。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Lt