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海绵可能是地球上第一个生物

Sea sponge could be the first animal on Earth

在地球历史上
There is a specific moment in
有这样一个特殊时期
Earth’s history in which most
大部分动物掌管了这个星球
animals took over the planet,
被称为寒武纪生命大爆发
known as the Cambrian Explosion,
发生在大约
which took place approximately
5亿4千万年前
540 million years ago.
海绵一直被
While sea sponges have been
认为是地球上
widely thought to be the first
第一个动物,最近的基因
animal on Earth, recent genetic
证据表明更为
evidence suggests that the more
复杂的栉水母或许
complex comb jelly might claim
夺得此次冠军
this title.
但麻省理工学院的科学家的新研究
But new research by MIT
可能支持海绵
scientists may side with the
他们着眼于一种
sea sponge. They looked at a
被发现于岩石中
molecule found in rocks that
有6亿4千万年的分子
are 640 million years old,
并且确认是由
and confirmed that it was
海绵最初生产的
originally produced by sea
1亿年前
sponges, 100 million years before
寒武纪时期开始了
the Cambrian Period began.
证据显示
The evidence suggests that
海绵也许的确是
sea sponges may indeed have
第一个动物
been the first animals to
栖息在地球上
inhabit Earth.
非常少的化石在
Very few fossils exist from
寒武纪生命大爆发前保存完好
well before the Cambrian
使其非常
explosion, making it extremely
困难去确定
difficult to determine what the
第一个动物是什么
first animals were like. So
所以麻省理工学院的研究人员
researchers at MIT have been
寻找答案于
looking for the answer in
分子化石
molecular fossils, which are
这是微量的分子
trace amounts of molecules that
幸存在古老的岩石中
have survived in ancient rocks,
在动物
long after the actual animal
彻底腐烂很久以后
has decayed away.
研究人员把精力集中在
The researchers focus on
24-异丙基甘油酸酯或
24-isopropylcholesterol, or
简称24-ipc,一种脂类分子
24-ipc for short, a lipid molecule
是胆固醇的一种改良版
that is a modified version of
因为这种
cholesterol. Because this
分子已经被发现于
molecule has been found in
6.4亿年的岩石中
rocks that are 640 million years
并且是由现今的海绵制造的
old, and is produced today by
这或许是
sea sponges, it could be the
解锁最古老的动物生活
key to unlocking evidence of
证据的关键
the oldest animal life.
在这项研究中,科学家们
In this study, the scientists
分析了基因和脂质
analyzed genes and lipids
在一大群生物
across a large group of organisms,
包括多种类型的植物
including multiple types of plants,
真菌和海绵
fungi, and sponges, trying to
试图确定
determine how many times the
这种制造24-ipc的能力进化了多少次
ability to produce 24-ipc has
他们辨认出一种基因
evolved. They identified a gene
负责这种分子
responsible for this molecule,
并且发现
and discovered that the number
每个物种所拥有基因副本的数量
of gene copies each species has
能预测它们
can predict what kind of
制造哪种分子
molecules they can produce.
他们发现只有两种
They found that only two
生物——海绵和海藻
organisms – sea sponges and
有足够的
algae – have enough copies of
这种基因来制造24-ipc
this gene to produce 24-ipc.
无论他们如何操作
No matter how they manipulated
进化树的时间
the timing of the evolutionary
研究人员发现
tree, the researchers found that
海绵进化出额外的
sea sponges evolved the extra
基因副本比海藻更早
copy of the gene much earlier
它们确实是这样
than algae, and they did so
大约6.4亿年前
around 640 million years ago
同期24-ipc
the same period in which 24-ipc
被发现于岩石中
was found in rocks.
他们的研究结果提供了有力的证据
Their results provide strong
简单的海绵
evidence that the simple sea
并且因此动物
sponge, and thus animals,
出现在地球上比
appeared on Earth much earlier
目前的化石表明更早
than fossils currently suggest.

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https://www.youtube.com/watch?v=cKfNVYCu6Us

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