⚡ 能量流动：每一级都“缩水”十倍⚡ Energy Flow: Shrinking Tenfold at Every Step

上一片里，食物链告诉我们“谁吃谁”。可草里的能量，兔子真的全拿走了吗？这一片跟着能量走一趟，看它一路“缩水”的秘密。 Last leaf, the food chain told us who eats whom. But did the rabbit really get all the grass's energy? Follow the energy on its journey — and watch it shrink at every step.

第 1 步：能量搭起一座金字塔Step 1: Energy builds a pyramid

先看草原上的能量，是怎么一层层传上去的。First, see how energy climbs the grassland, level by level.

能量金字塔：草地 10000 → 兔子 1000 → 猎豹 100 → 鹰 10 — 把草原画成一座金字塔：最底层的草固定了 10000 单位能量；兔子吃到嘴的只剩约 1000；猎豹抓到兔子，约拿到 100；再往上的鹰只剩约 10。每一级都“缩水”十倍——大部分能量在呼吸、奔跑、取暖时散失，再也回不来。 Picture the grassland as a pyramid: the grass at the bottom captures 10,000 energy units; the rabbit gets only about 1,000; the cheetah that catches it gets about 100; and the eagle on top only about 10. Every step shrinks tenfold — most energy is lost to breathing, running and warmth, and never comes back.

你可能会问：那猎豹捕一次猎，到底赚不赚？You might ask: does a cheetah actually profit from a hunt?

第 2 步：捕猎是一笔能量账Step 2: A hunt is an energy deal

猎豹的能量账本：猎物 +100，奔跑 -50，净赚 +50 — 猎豹追兔子，其实是一笔能量买卖：追捕花掉约 50 单位能量，猎物带来约 100 单位，净赚约 50。所以猎豹从不做亏本买卖，追两下没追上就放弃。它跑得那么快，又那么惜力——因为能量来得太不容易了。 A cheetah chasing a rabbit is really an energy deal: the chase costs about 50 units, the prey brings about 100, so the net gain is only about 50. That's why a cheetah never runs at a loss — a few strides and it gives up. It sprints flat out yet saves every stride, because energy is hard-won.

把整条链摊开看，一条规律就浮出来了。Lay the whole chain out, and a famous rule appears.

第 3 步：10% 法则Step 3: The 10% rule

10% 法则：能量每过一级只剩十分之一 — 能量从太阳出发，每过一个营养级（食物链上的一级）只剩约 10%；其余 90% 在呼吸、运动、取暖中变成热散走。这就是“10% 法则”。营养级越高，分到的能量越少——所以鹰、虎、狮子这些顶级掠食者总是稀稀拉拉。“一山不容二虎”，说的就是这座山的能量养不起第二只虎。 Energy starts from the sun and keeps only about 10% at each trophic level (one step on the food chain); the other 90% leaves as heat from breathing, moving and staying warm. That's the 10% rule. The higher the level, the less energy left — so eagles, tigers and lions are always few. “One mountain cannot hold two tigers”: the mountain simply cannot feed a second one.

🎮 你来当能量管家（40 秒）🎮 Your turn: run the energy books (40 seconds)

先拖营养级滑块，看金字塔每一级还剩多少能量；再闯 4 关，把这笔能量账算明白。Drag the trophic-level slider to see how much energy each level keeps; then clear 4 levels and balance the books yourself.

一句话记住它：能量沿食物链单向流动，每过一级只剩约 10%；散失成热的能量，再也回不来了。 Remember it in one line: energy flows one way along the food chain and only about 10% passes each level; what is lost as heat never comes back.

单向流动：太阳能 → 草 → 兔子 → 猎豹，不会倒着流One-way: sun → grass → rabbit → cheetah — never backwards 逐级递减：约 90% 在呼吸等活动中散失，上一级只拿到约 10%Shrinking: about 90% is lost to breathing and activity; the next level keeps only about 10% 肉贵、虎少：养 1 斤肉要耗约 10 斤粮食；顶级掠食者分到的能量太少Pricey meat, rare tigers: 1 kg of meat takes about 10 kg of grain, and top predators get very little energy

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内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。 Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.