The game-changing amniotic egg - April Tucker

改变游戏规则的羊膜卵 - 艾普丽尔·塔克

翻译人员: Binglei Shea 校对人员: Ning Zhang

Would you believe that walruses,

你相信海象

rattlesnakes,

响尾蛇

and parakeets

和鹦鹉

all once lived in the same house?

曾经在同一个屋檐下居住吗？

Let's go back about 350 million years.

让我们回到3.5亿年前。

Look around.

看

Steamy swamps and rain forests of horsetails and ferns

潮湿的沼泽，马尾松的热带雨林以及各种蕨类植物

cover the region.

覆盖了地面

Amphibians are the dominant land vertebrates.

两栖动物在陆地上占主导地位。

They range in size from newts

它们从最小的蝾螈

to crocodiles.

到巨大的鳄鱼。

And all require water to do their egg laying.

但是都需要水来产下他们的蛋。

If they don't go to the water,

如果他们远离水，

their shell-less, jelly-like eggs will dry out.

他们没有外壳，像果冻一样的卵会变干。

Because of this hazard,

由于这种危险，

they spend most of their time

他们大部分时间

都生活在水中或者附近。

living in or near fresh water.

That is, until a breakthrough

也就是说，直到一个突破性的进化

in evolution changes everything:

改变了这一切：

the amniotic egg.

羊膜卵。

The amniotic egg is shelled,

羊膜卵有外壳

waterproof,

防水

and can be laid on dry land.

并且可以被产在干燥的土地上。

It is produced by the amniotes,

正是由于羊膜動物产生，

a new group of animals named after their revolutionary egg.

他们革命性的卵创造了一种新的生物种类。

The first amniote is a tetrapod,

第一种羊膜动物是四足動物,

a four-legged animal,

一种四条腿的动物,

resembling a small lizard.

类似于小蜥蜴。

While some amphibians can walk around on land

虽然有些两栖类动物也可以在陆地上生活

and bury their eggs in wet soil or highly humid areas,

把他们的蛋埋在潮湿的土壤中

nothing before the amniotes has the ability

但是在羊膜动物之前没有生物有能力

to lay its eggs on completely dry land.

在完全干燥的土地上产卵。

Because of this evolved egg,

由于这种进化的卵，

the amniotes are the first animals

羊膜动物是第一种

with the ability to live a fully terrestrial life.

完全具备陆地生活的能力的动物。

But, despite their move inland,

虽然，他们向大陆挺近，

the amniotes have not abandoned

羊膜动物没有放弃

their pond-dwelling upbringing.

他们曾经生长的池塘环境。

In fact, the amniotic egg brings the pond with them

事实上，羊膜卵把池塘的水生环境

by enclosing the aquatic environment within its shell.

用壳包裹起来。

This is achieved by four main upgrades

这是由四个主要的升级实现的

that are unique to amniotic eggs.

这些升级是羊膜卵的特征。

Let's take a closer look.

让我们仔细看看。

The first development is the most obvious:

首先最明显的是：

the egg's protective shell.

蛋的保护壳。

It's tough but flexible,

它坚韧而灵活，

and has a leathery surface,

有一个貌似皮革的表面，

still seen in reptile eggs today.

今天仍然可以从爬行动物的卵中看到。

The shell protects the eggs from predators,

壳保护卵免受掠食者

细菌，

bacteria,

damage,

冲击，

and drying out.

和干燥。

But, unlike the walls of a fish tank,

但不同于鱼缸壁的全封闭

the shell of the amniotic egg is porous,

羊膜卵壳有很多细小的孔

allowing oxygen to pass through

允许氧气通过

so that the growing amniote inside doesn't suffocate.

因此，胚胎能在里面发育而不会窒息而死。

The next two developments are two separate membranes

其次是两个单独的膜

that work together like a pair of lungs.

他们能像肺一样协同工作。

They bring oxygen into the embryo

它们把氧气带入胚胎

while removing carbon dioxide.

同时排出二氧化碳。

The first is the chorion,

第一个是绒毛膜，

which is the protective layer that oxygen passes through

这是氧气通过的保护层

after entering the shell's tiny pores.

紧贴着外壳。

You may recognize the chorion

你很容易找到绒毛膜

as the thin skin you peel away on a hard boiled egg.

从一个煮熟的鸡蛋上剥掉的那层薄皮就是。

Think of this waterproof membrane

想想这个防水薄膜

as the in and out doors of the egg.

作为蛋于外界交换气体的门户

It's the entrance for oxygen

它是氧气的入口

and exit for carbon dioxide.

和二氧化碳的出口。

The membrane working with the chorion

与绒毛膜协同工作的

is the allantois.

是尿膜。

If the chorion is the doors,

如果绒毛膜是门

then the allantois is essentially the lobby of the building.

那么尿膜就是大厅。

It directs the oxygen and carbon dioxide

它为氧气和二氧化碳指明方向

while simultaneously storing

同时存储

unneeded waste from the embryo.

胚胎的产生的废物。

The chorion and the allantois make sure the embryo

绒毛膜和尿膜确保胚胎

has everything it needs

获得它所需要的一切

and gets rid of anything it doesn't.

并且摆脱它不需要的排泄物。

The last and perhaps the most important development

最后，但却是最重要的发展是羊膜

is the amnion, the membrane for which the egg is named.

羊膜卵就是以其命名的。

The amnion is also contained within the chroion

羊膜也包含在绒毛膜内

and holds the fluid in which the embryo floats.

使得胚胎能够在液态环境中漂浮。

Because it has left the watery world of the amphibians,

因为它要离开两栖动物赖以生存的水底世界

the amnion is necessary for preventing

羊膜对于胚胎来说

the embryo from drying out.

是必不可少的保护。

It is the transportable pond

这个可移动的池塘

that allows the amniote to lay the egg on dry land.

让羊膜动物能够在干燥的土地上产卵。

Its fluid also protects the embryo

它内部的液体还可以保护胚胎

from any collisions or rough landings,

免于碰撞或坠落的损伤，

like a shock absorber on your bike or car.

就像你自行车或汽车上的减震器。

Together, the shell and these four membranes

外壳和这些膜，共同

create a safe, watery environment

为胚胎成长和发展

for the embryo to grow and develop.

创建了一个安全的水环境。

The new amniote offspring will continue

新的羊膜动物的后代将继续

the process of vertebrate evolution

他们向脊椎动物的进化

as it explores new land away from the water.

去探寻远离水域的新大陆。

They will spend the next million years

他们将用下一个百万年

splitting into two distinct groups:

分化成两个不同的组：

the synapsids and sauropsids.

下孔类 和 蜥形类。

Synapsida is the group of animals

下孔类动物

that contain mammals,

包括哺乳动物，

while sauropsida is the group that contains

蜥形类动物有

reptiles,

爬行动物，

birds,

鸟，

and dinosaurs.

和恐龙。

These two amniotic groups collectively contain

这两个羊膜腔组的联系是，

the walruses,

rattlesnakes,

海象，

响尾蛇，

and parakeets we know today.

和我们今天所熟知的鹦鹉。

Like a family reunion,

就像家庭的团聚，

with relatives of every shape and size,

虽然长相迥异，

coming together from different corners of the Earth,

来自地球的不同角落，

these animals can all call one place home:

但他们有一个共同的归宿：

the amniotic egg.

羊膜卵。