Human Population Dynamics · 人口动态
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| birth rate/bɜːθ reɪt/ | 出生率 | chū shēng lǜ |
| death rate/deθ reɪt/ | 死亡率 | sǐ wáng lǜ |
| growth rate/ɡrəʊθ reɪt/ | 增长率 | zēng zhǎng lǜ |
| doubling time/ˈdʌblɪŋ taɪm/ | 倍增时间 | bèi zēng shí jiān |
A crowded planet
- For most of history, humans were few and grew slowly.
- Then, in the last 200 years, our numbers exploded.
- From one billion to eight billion in a couple of centuries.
- Understanding why is the study of human population dynamics.
一个拥挤的星球
- 历史上大部分时间,人类数量很少,增长缓慢。
- 然后,在过去 200 年里,我们的数量爆发了。
- 从十亿到八十亿,只用了两个世纪。
- 理解为什么,就是人口动态的研究。
Births versus deaths
- The birth rate 出生率 is how many are born per 1000 people each year.
- The death rate 死亡率 is how many die per 1000 each year.
- The growth rate 增长率 is the birth rate minus the death rate, plus migration.
- When births outnumber deaths, the population grows.
出生对死亡
- 出生率(birth rate)是每年每 1000 人中有多少出生。
- 死亡率(death rate)是每年每 1000 人中有多少死亡。
- 增长率(growth rate)是出生率减去死亡率,加上迁移。
- 当出生多于死亡时,人口增长。
A population's growth rate is set mainly by… · 一个人口的增长率主要由……决定。
Growth rate = (birth rate − death rate) plus net migration. · 增长率 = (出生率 − 死亡率)加上净迁移。
Why growth exploded
- For most of history, high birth rates were matched by high death rates.
- Then medicine, sanitation, and food supply cut the death rate sharply.
- Birth rates stayed high for a while, so the population surged.
- The gap between falling deaths and high births drove the explosion.
增长为什么爆发
- 历史上大部分时间,高出生率被高死亡率抵消。
- 然后医药、卫生和食物供应急剧削减了死亡率。
- 出生率保持高了一段时间,所以人口激增。
- 下降的死亡与高出生之间的差距推动了爆发。
Human population growth · 人口增长
growth rate = births - deaths (+ migration) · 增长率 = 出生数 - 死亡数 (+ 迁移)
Growth depends on the gap between birth rate and death rate; a small rate still doubles the population over time. · 增长取决于出生率与死亡率之间的差距;一个小的增长率随时间仍然使人口翻倍。
Why did the human population grow so fast in the last century? · 为什么上个世纪人口增长这么快?
Falling death rates (medicine, sanitation, food) with high birth rates caused rapid growth. · 下降的死亡率(医药、卫生、食物)加上高出生率导致快速增长。
Doubling time
- Even a small growth rate compounds over time.
- The doubling time 倍增时间 is how long a population takes to double.
- A handy shortcut: doubling time ≈ 70 ÷ (growth rate as a percent).
- At 2% per year, a population doubles in only about 35 years.
倍增时间
- 即使小的增长率随时间也会复利增长。
- 倍增时间(doubling time)是一个人口翻倍所需的时间。
- 一个方便的捷径:倍增时间 ≈ 70 ÷(百分比增长率)。
- 按每年 2%,一个人口只用约 35 年就翻倍。
The time it takes a population to double in size is its ____ time. · 一个人口翻倍所需的时间是它的____时间。
Doubling time ≈ 70 ÷ (growth rate in percent) — even a small rate doubles a population over time. · 倍增时间 ≈ 70 ÷(百分比增长率)——即使小的增长率随时间也使人口翻倍。
Even a small yearly growth rate can double a population within a lifetime. · 即使小的年增长率也能在一个生命周期内使人口翻倍。
At 2% per year, a population doubles in only about 35 years (70 ÷ 2). · 按每年 2%,一个人口只用约 35 年就翻倍(70 ÷ 2)。
Select all · 所有 true statements about human population dynamics. · 选出关于人口动态的所有正确说法。
A growing population puts rising pressure on resources. The other three are correct. · 增长的人口对资源施加越来越大的压力。其余三条正确。
A "small" growth rate is not small over time. Because growth compounds, even 2% per year doubles a population in about 35 years. This is why a growth rate that sounds tiny can lead to enormous numbers within a single lifetime.
一个"小"的增长率随时间并不小。因为增长复利,即使每年 2% 也能在约 35 年内使人口翻倍。这就是为什么一个听起来微不足道的增长率能在一个生命周期内导致巨大的数量。
The rule of 70 in action:
- Suppose a country grows at 2% per year.
- Doubling time ≈ 70 ÷ 2 = 35 years.
- A country of 50 million would reach 100 million in just 35 years — and 200 million in 70 — from a rate that sounds modest.
70 法则在起作用:
- 假设一个国家以每年 2% 增长。
- 倍增时间 ≈ 70 ÷ 2 = 35 年。
- 一个 5000 万的国家将在仅 35 年内达到 1 亿——70 年达到 2 亿——从一个听起来温和的增长率。
Human population dynamics depend on the growth rate = birth rate − death rate (plus migration). Rapid growth came from falling death rates while birth rates stayed high. Doubling time ≈ 70 ÷ (growth rate percent), so even a small rate can double a population within a lifetime.
人口动态取决于增长率 = 出生率 − 死亡率(加上迁移)。快速增长来自下降的死亡率而出生率保持高。倍增时间 ≈ 70 ÷(百分比增长率),所以即使小的增长率也能在一个生命周期内使人口翻倍。