Energy Flow and Food Webs in Ecosystems | 生态系统中的能量流动与食物网

📚 Energy Flow and Food Webs in Ecosystems | 生态系统中的能量流动与食物网

In Cambridge Stage 8 Science, you learn how living organisms depend on each other through feeding relationships. Energy from the Sun enters ecosystems, passes through food chains and food webs, and is eventually lost as heat. Understanding energy flow helps explain why ecosystems cannot support unlimited numbers of top predators.

在剑桥 Stage 8 科学中，你将学习生物之间如何通过取食关系相互依存。来自太阳的能量进入生态系统，沿食物链和食物网传递，最终以热的形式散失。理解能量流动有助于解释为什么生态系统无法养活无限数量的顶级捕食者。

1. What is an Ecosystem? | 什么是生态系统？

An ecosystem is a community of living organisms interacting with each other and with the non-living parts of their environment, such as water, soil, air, and sunlight. The living parts are called biotic factors, and the non-living parts are called abiotic factors. A pond, a forest, and a desert are all examples of ecosystems.

生态系统是由一群生物彼此之间以及与环境中的水、土壤、空气和阳光等非生物部分之间相互作用的整体。生物部分称为生物因素，非生物部分称为非生物因素。池塘、森林和沙漠都是生态系统的例子。

Biotic factors include plants, animals, fungi, bacteria, competition, and predation. Abiotic factors include light intensity, temperature, water availability, and soil pH. Both sets of factors determine which organisms can survive in an ecosystem.

生物因素包括植物、动物、真菌、细菌、竞争和捕食。非生物因素包括光照强度、温度、水分供应和土壤 pH。这两类因素共同决定哪些生物可以在一个生态系统中生存。

2. Feeding Relationships: Producers, Consumers, and Decomposers | 取食关系：生产者、消费者和分解者

Producers are organisms that make their own food using energy from sunlight through photosynthesis. Green plants and algae are producers. Consumers cannot make their own food, so they must eat other organisms. Primary consumers eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers.

生产者是利用阳光通过光合作用制造自身食物的生物。绿色植物和藻类是生产者。消费者不能制造自身食物，因此必须取食其他生物。初级消费者取食生产者，次级消费者取食初级消费者，三级消费者取食次级消费者。

Decomposers break down dead organisms and waste, returning nutrients to the soil. Bacteria and fungi are the main decomposers. They release enzymes that digest dead material outside their cells, then absorb the small nutrient molecules.

分解者分解死去的生物和排泄物，将养分归还到土壤中。细菌和真菌是主要的分解者。它们释放酶在细胞外消化死亡物质，然后吸收小分子养分。