1、第三章 能量流动Chapter 3 Energy flow * 1国家级精品资源共享课* 国家级精品资源共享课 2一、 能量转移二、 农业生态系统遵守能量流动的基本规律三、 食物是农业生态系统中的能量载体四、 农业生态系统的能源、能流途径和能效五、 农业生态系统的能流调控主要内容* 国家级精品资源共享课 3（一）能量转移植物利用太阳能，通过光合作用生产食物能，食物能通过食物链和食物网，从一个营养级传递到另一个营养级。太阳能 绿色植物 食草动物食肉动物一、能量转移食草动物 食肉动物* 4国家级精品资源共享课The relationship between matter and energyOnc
2、e energy is transformed into heat, it can no longer be used by living organisms to do work or to fuel the synthesis of biomass, the heat is lost to the atmosphere and can never be recycled. Life on Earth is possible because a fresh supply of solar energy is made available every day. In contrast, nut
3、rients such as carbon can be reused. Chemical nutrients, the building blocks if biomass, can be used again, and recycling is a critical feature. Unlike the energy in solar radiation, nutrients are not in unalterable supply. If plants, and their consumers were not eventually decomposed, the supply of
4、 nutrients would become exhausted and life on Earth would cease.* 5国家级精品资源共享课* 国家级精品资源共享课 61.流 生态系统中能量和物质不断地被吸收、贮存和转移的运动状态。 能量的转移 能量流。物质的转化 物质流。流量要多，流速要快增加流量的方法： 提高能量转化效率、减少消耗增加流速的方法： 缩短周转周期、提高周转速率（二）流、库、环的概念及应用* 国家级精品资源共享课 72.库 能量和物质在运动过程中暂时被吸收和贮存的单位。 库要大、库效率要高。（ 1） 植物库 ： 库大 土地利用充分、植物产品多；库效率高 光合效率高
5、（ 2） 动物库 ： 库大 种群多数量大、动物产品多；库效率高 出栏率高，产肉蛋奶多（ 3） 土壤库 ： 库大 土壤肥力高而稳库效率高 养分损失少，利用率高 * 国家级精品资源共享课 83.环 各种库将流连接起来形成的整体。 环结构要合理环流库是相互联系的。库要大、效率高；环结构要合理；流要多且流畅。* 国家级精品资源共享课 9（一）热力学第一定律 二、农业生态系统遵守能量流动的基本规律（二）热力学第二定律1.能量传递有一定的方向，是不可逆的。2.能量转化过程中存在着衰变现象，必然有能量的耗散。3.为了判断能量流动的方向和限度，用 自由能 和 熵 来描述。* 国家级精品资源共享课 10The
6、first law of thermodynamics states that energy can neither be created nor destroyed. The second law of thermodynamics states that every transformation results in a reduction of the free energy of the system. Because energy transformation cannot be 100% efficient (from the second law), heterotrophs must have less energy, and must therefore be rarer than the plants they feed on. The complexity of ecological interactions means that it is not possible to construct predictive mathematical models of living systems based on these laws of thermodynamics.Ecosystems and the laws of thermodynamics
