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sequenced and analysed the genome of the
unicellular choanoflagellate Monosiga
brevicollis. The genome contains
approximately 9,200 intron-rich genes,
including a number that encode cell adhesion
and signalling protein domains that are
otherwise restricted to metazoans. Here we
show that the physical linkages among protein
domains often differ between M. brevicollis
and metazoans, suggesting that abundant
domain shuffling followed the separation of
the choanoflagellate and metazoan lineages.
The completion of the M. brevicollis genome
allows us to reconstruct with increasing
resolution the genomic changes that
accompanied the origin of metazoans.
古 生 态 学
2009020048
海 床 上 捕 食 胜 于 竞 争 = Predation defeats
competition on the seafloor. ( 英 文 ). Stanley S
M. Paleobiology, 2008, 34(1): 1-21
For many decades, ecology textbooks
presented classical competition theory without
reservation. The central principle here is that
two species sharing an essential resource that
is in limited supply cannot coexist for long
because the competitively superior species
will eliminate the other one. The implication
is that ecological communities should be
characterized by division of resources among
species, or niche partitioning. Thus, it is
understandable that many paleontologists have
continued to invoke concepts of competitive
exclusion and niche partitioning in their
studies of ancient guilds and communities. By
now, however, there is a large body of
neontological literature demonstrating that
interspecific competition and resource
partitioning play only a minor role in many
ecological communities— especially benthic
marine communities, which are the primary
focus of the following discussion. Predation
and physical disturbance inflict so much
damage on biotas of the seafloor that
populations of one species seldom monopolize
a potentially limiting resource, except
sporadically and locally. As a result, it is
uncommon for any species to drive another to
extinction through competitive exclusion—or
even to force another species to drastically
change its exploitation of any environmental
resource throughout its geographic range.
Furthermore, what particular species or group
of species occupies a particular microhabitat is
often simply a matter of time of arrival.
2009020049
阿 根 廷 前 科 迪 勒 拉 石 炭 纪 和 下 二 叠 统 贝 壳
层 : 时 间 变 化 和 与 显 生 宙 趋 势 的 关 系 =
Carboniferous and Lower Permian shell beds
in Precordillera Argentina. Temporal
variations and relationships with the trends
proposed for the Phanerozoic. ( 其 他 ). Sterren
A F. Ameghiniana, 2008, 45(2): 303-320
Taphonomic and biodiversity studies of
Carboniferous and Permian shell beds
recorded in several sections from the Rio
Blanco-Paganzo and Calingasta-Uspallata
basins are carried out. Two parameters of
bioclastic accumulations are analyzed:
taxonomic composition and thickness. The
analysis of the taxonomic composition
revealed that molluscan-dominated
concentrations predominate in both periods,
being rhynchonelliform-dominated ones more
abundant during the Carboniferous than
during the Early Permian. The distribution of
thickness ranges exhibits a relative increase
through the studied interval, reaching a
maximum of 30 cm. Studied bioclastic
deposits, are relatively thin and are composed
of distinctive elements of the Modern Fauna;
hence they could be included in a "mixed"
style. On taxonomic grounds the transition
between styles appeared to take place toward
the ending of the Paleozoic, and might have
been driven by a biotic factor related to the
relatively early diversification of infaunal
bivalves. The increase in thickness
documented in the studied interval is the result
of the sedimentary dynamics in different areas
of the basins. Patterns of biodiversity among
mollusks and brachiopods show significantly
higher levels of richness in the Permian than
in the Carboniferous, a feature that is also
evident in the composition of fossiliferous
concentrations. The superposition of styles
herein documented suggests that the
Neopaleozoic is a key interval to test the local
expressions of global models.
2009020050
3.76 亿 年 前 泥 盆 纪 化 石 形 态 变 化 的 气 候 控
制 的 记 录 = Record of climate-driven
morphological changes in 376 Ma Devonian
fossils. ( 英 文 ). Balter V; Renaud S; Girard C;
Joachimski M M. Geology, 2008, 36(11): 907-
910
The Lower and Upper Kellwasser horizons
represent two anoxic events that mark the
mass extinction at the Frasnian-Famennian (F-
F) boundary. Among other groups, conodont
animals were severely affected, but the genus
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