一自然界中的水、土、光、热、气等非生物因素及植物、动物、微生物等生物因素,彼此之间是相互联系、相互制约的。这些因素在自然界构成一个不可分割的综合体——生态系统。森林、农田、湖泊、草原,可分别称作不同的生态系统。一个生态系统在相对稳定的正常情况下,各种物质要素不断地循环,能量不断地转化。如森林生态系统中的乔木、灌木、草本植物,在一定温度和日光下,吸取大气中的二氧化碳和土壤中水分而生长。一些动物靠植物生活,而另一些动物又靠吃草食动物而生存;动植物残体经过微生物分解后,变为矿物养分,又被植物吸收利用。整个过程中的物质不断地循环,生物量和生产量不断地增加,形成了生态系统中的平衡。但是,这个生态系统一旦遭到外界不合理的干扰,就会出现相反的情况,如过量采伐森林,以林中植物为生的动物则失去生存条件,而另一些靠草食动物为生的动物也不会存在。久而久之,形成恶性循环,生物量和生产量不断减少,生态平衡遭到破坏,人 A biological nature of water, soil, light, heat, gas and other biological factors such as plants, animals, microorganisms and other biological factors are interrelated and mutual restraint. These factors constitute an indivisible complex in nature - the ecosystem. Forests, farmland, lakes, grasslands, can be called different ecosystems. Under the relatively stable and normal conditions of an ecosystem, various material elements are continuously recycled, and energy is continually transformed. Such as forest ecosystem trees, shrubs, herbs, under a certain temperature and sunlight, absorb the atmosphere of carbon dioxide and soil moisture and grow. Some animals live on plants, while others live on herbivores. After animal and plant debris is decomposed by microorganisms, they become mineral nutrients and are absorbed by plants. Throughout the process of material recycling, biomass and production continue to increase, forming a balance of ecosystems. However, once the ecosystem has been disturbed irrationally by the outside world, the opposite happens. For example, over-deforestation, animals that live on forest plants lose their living conditions, and other animals that depend on herbivores also Will not exist. As time passes, a vicious cycle has taken shape, biomass and production have been declining, ecological balance has been destroyed, and people