makhluk laut seperti-tas
itu adalah nenek moyang manusia tertua yang dikenal-T-REC semarang--komunitas
reptil-semarang--KSE-komunitas satwa eksotik—komunitas semarang—komunitas
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semarang—komunitas reptil semarang—komunitas semarang—T-REC semarang hari
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budi pradana--berita artikel terkait tentang laut,makhluk laut,nenek moyang
makhluk laut seperti-tas itu adalah nenek moyang manusia tertua yang dikenal
Sebuah makhluk laut kecil diidentifikasi
dari fosil yang ditemukan di Cina mungkin menjadi langkah awal dikenal pada jalur
evolusi yang akhirnya menyebabkan munculnya manusia
Tanggal:
30 Januari 2017
Sumber:
St John College, University of Cambridge
Ringkasan:
Para peneliti telah mengidentifikasi tentang
jejak apa yang mereka percaya adalah awal dikenalnya nenek moyang prasejarah manusia - sebuah mikroskopis,
makhluk laut seperti-tas, yang hidup sekitar 540 juta tahun yang lalu.
...............................
Para peneliti telah mengidentifikasi
jejak apa yang mereka percaya adalah awal dikenalnya nenek moyang prasejarah
manusia - sebuah mikroskopis, makhluk laut seperti-tas, yang hidup sekitar 540
juta tahun yang lalu.
Dinamakan Saccorhytus, setelah fitur seperti-karung
yang dibuat oleh tubuh elipsnya dan mulutnya yang besar, spesies baru bagi ilmu pengetahuan dan
diidentifikasi dari fosil mikro yang ditemukan di Cina. Hal ini dianggap
sebagai contoh yang paling primitif yang disebut "deuterostoma" -
kategori biologis luas yang mencakup sejumlah sub-kelompok, termasuk
vertebrata.
Jika kesimpulan dari penelitian yang
dipublikasikan dalam jurnal Nature, benar, maka Saccorhytus adalah nenek moyang
dari sejumlah besar spesies, dan langkah awal dari belum ditemukannya pada jalur evolusi yang akhirnya menyebabkan adanya
manusia, ratusan juta tahun kemudian.
label
makhluk laut seperti-tas itu adalah nenek moyang manusia tertua yang dikenal,nenek moyang ,prasejarah,mikroskopis,deuterostoma,vertebrata,evolusi,Saccorhytus,deuterostomes
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Bag-like sea
creature was humans' oldest known ancestor
A tiny sea creature identified from fossils found in China may be the
earliest known step on an evolutionary path that eventually led to the
emergence of humans
Date:
January 30, 2017
Source:
St John's College, University of Cambridge
Summary:
Researchers have identified traces of what they believe is the earliest
known prehistoric ancestor of humans -- a microscopic, bag-like sea creature,
which lived about 540 million years ago.
...............................
Researchers have identified traces of
what they believe is the earliest known prehistoric ancestor of humans -- a
microscopic, bag-like sea creature, which lived about 540 million years ago.
Named Saccorhytus, after the
sack-like features created by its elliptical body and large mouth, the species
is new to science and was identified from microfossils found in China. It is
thought to be the most primitive example of a so-called
"deuterostome" -- a broad biological category that encompasses a
number of sub-groups, including the vertebrates.
If the conclusions of the study,
published in the journal Nature, are correct,
then Saccorhytus was the common ancestor of a huge
range of species, and the earliest step yet discovered on the evolutionary path
that eventually led to humans, hundreds of millions of years later.
Modern humans are, however, unlikely to
perceive much by way of a family resemblance. Saccorhytus was about a millimetre in size, and
probably lived between grains of sand on the seabed. Its features were
spectacularly preserved in the fossil record -- and intriguingly, the
researchers were unable to find any evidence that the animal had an anus.
The study was carried out by an
international team of academics, including researchers from the University of
Cambridge in the UK and Northwest University in Xi'an China, with support from
other colleagues at institutions in China and Germany.
Simon Conway Morris, Professor of
Evolutionary Palaeobiology and a Fellow of St John's College, University of
Cambridge, said: "We think that as an early deuterostome this may
represent the primitive beginnings of a very diverse range of species,
including ourselves. To the naked eye, the fossils we studied look like tiny
black grains, but under the microscope the level of detail is jaw-dropping. All
deuterostomes had a common ancestor, and we think that is what we are looking
at here."
Degan Shu, from Northwest University, added:
"Our team has notched up some important discoveries in the past, including
the earliest fish and a remarkable variety of other early deuterostomes. Saccorhytus now gives us remarkable insights into
the very first stages of the evolution of a group that led to the fish, and
ultimately, to us."
Most other early deuterostome groups
are from about 510 to 520 million years ago, when they had already begun to
diversify into not just the vertebrates, but the sea squirts, echinoderms
(animals such as starfish and sea urchins) and hemichordates (a group including
things like acorn worms). This level of diversity has made it extremely
difficult to work out what an earlier, common ancestor might have looked like.
The Saccorhytus microfossils were found in Shaanxi
Province, in central China, and pre-date all other known deuterostomes. By
isolating the fossils from the surrounding rock, and then studying them both
under an electron microscope and using a CT scan, the team were able to build
up a picture of how Saccorhytus might have looked and lived. This
revealed features and characteristics consistent with current assumptions about
primitive deuterostomes.
Dr Jian Han, of Northwest University,
said: "We had to process enormous volumes of limestone -- about three tonnes
-- to get to the fossils, but a steady stream of new finds allowed us to tackle
some key questions: was this a very early echinoderm, or something even more
primitive? The latter now seems to be the correct answer."
In the early Cambrian period, the region
would have been a shallow sea. Saccorhytus was so small that it probably lived in
between individual grains of sediment on the sea bed.
The study suggests that its body was
bilaterally symmetrical -- a characteristic inherited by many of its descendants,
including humans -- and was covered with a thin, relatively flexible skin. This
in turn suggests that it had some sort of musculature, leading the researchers
to conclude that it could have made contractile movements, and got around by
wriggling.
Perhaps its most striking feature,
however, was its rather primitive means of eating food and then dispensing with
the resulting waste. Saccorhytus had a large mouth, relative to the
rest of its body, and probably ate by engulfing food particles, or even other
creatures.
A crucial observation are small conical
structures on its body. These may have allowed the water that it swallowed to
escape and so were perhaps the evolutionary precursor of the gills we now see
in fish. But the researchers were unable to find any evidence that the creature
had an anus. "If that was the case, then any waste material would simply
have been taken out back through the mouth, which from our perspective sounds
rather unappealing," Conway Morris said.
The findings also provide evidence in
support of a theory explaining the long-standing mismatch between fossil
evidence of prehistoric life, and the record provided by biomolecular data,
known as the "molecular clock."
Technically, it is possible to estimate
roughly when species diverged by looking at differences in their genetic
information. In principle, the longer two groups have evolved separately, the
greater the biomolecular difference between them should be, and there are
reasons to think this process is more or less clock-like.
Unfortunately, before a point
corresponding roughly to the time at which Saccorhytus was wriggling in the mud, there are
scarcely any fossils available to match the molecular clock's predictions. Some
researchers have theorised that this is because before a certain point, many of
the creatures they are searching for were simply too small to leave much of a
fossil record. The microscopic scale of Saccorhytus, combined
with the fact that it is probably the most primitive deuterostome yet
discovered, appears to back this up.
Story Source:
Materials provided
by St John's College, University of
Cambridge. The original story is licensed under a Creative Commons License. Note:
Content may be edited for style and length.
Journal Reference:
1. Jian
Han, Simon Conway Morris, Qiang Ou, Degan Shu, Hai Huang. Meiofaunal
deuterostomes from the basal Cambrian of Shaanxi (China). Nature,
2017; DOI:10.1038/nature21072