Synthetic Writing
5-minute workshop
From Hobbie et al. 2006:
Whether earthworms in this site are responding directly to higher
litter Ca or to the concomitant higher concentrations of soil Ca
(Reich et al. 2005) is unknown (Ponge et al. 1999). Regardless,
the positive relationship between forest floor removal and litter Ca
likely arises from the nutritional requirements of the earthworms at
the site. Although there are several species of earthworms in the
Siemianice Experimental Forest (Reich et al. 2005), earthworm
biomass is dominated by Lumbricus terrestris (C. M. Hale,
unpublished data). Lumbricus is an anecic species that makes
deep burrows, but consumes litter on the soil surface. Lumbricus
has well-developed calciferous glands that produce calcium
carbonate (Robertson 1936, Canti and Piearce 2003). It has been
suggested that Lumbricus and other species with well-developed
calciferous glands produce calcium carbonate to reduce their
blood CO2 levels and regulate blood pH when faced with high soil
CO2 levels, and thus they have a high Ca requirement (Crang et
al. 1968, Robertson 1936, Piearce 1972b).
What is the topic of this
paragraph?
What is the conclusion?
Which of the following results would enhance this paragraph?
Why?
(1) Holdsworth et al. (2008) found that decomposition of oak litter, a
species with Ca-poor litter, was unaffected by earthworm
abundance, while decomposition of basswood, a species with Carich litter, was accelerated by earthworms.
(2) Silver and Miya (2001) reviewed as many studies of root
decomposition as they could find, and found that across multiple
studies, root Ca concentration was positively related to root
decomposition rates.
(3) In a study that manipulated grassland biodiversity, higher
earthworm densities accelerated the decomposition of nitrogen-rich
legume litter (Milcu et al. 2008).
References
Hobbie, S. E., P. B. Reich, J. Oleksyn, M. Ogdahl, R. Zytkowiak, C. M.
Hale, and P. Karolewski. 2006. Tree species effects on
decomposition and forest floor dynamics in a common garden.
Ecology 87:2288-2297.
Holdsworth, A. R., L. E. Frelich, and P. B. Reich. 2008. Litter
decomposition in earthworm-invaded northern hardwood forests:
Role of invasion degree and litter chemistry. Ecoscience 15:536544.
Milcu, A., S. Partsch, C. Scherber, W. W. Weisser, and S. Scheu. 2008.
Earthworms and legumes control litter decomposition in a plant
diversity gradient. Ecology 89:1872-1882.
Silver, W. L. and R. K. Miya. 2001. Global patterns in root
decomposition: comparisons of climate and litter quality effects.
Oecologia 129:407-419.
From Lane et al. 2010:
Apart from being counter-intuitive, the most remarkable feature of
chemiosmosis is how universal, how fundamental, proton gradients are
across all of life. Mitchell appreciated that proton gradients frequently power
active transport in bacteria, along with the rotating motor of the bacterial
flagellum; and they are as central to ATP synthesis in photosynthesis as they
are to oxidative phosphorylation in mitochondria or bacteria.(51) The fact
that a proton-motive force powers chloroplasts, mitochondria and bacteria is
already a startlingly diverse heritage; but we now know that proton gradients
are ubiquitous in archaea as well as bacteria. Both archaea and bacteria
generate proton gradients across their plasma membranes; both synthesise
ATP via oxidative phosphorylation; both share similar membrane-bound
rotor-stator-type ATP synthase enzymes, albeit with a few minor differences
(the bacterial F-type and archaeal A-type ATPases share a number of
unquestionably homologous subunits, as well as others apparently
unrelated).(52)) Thus the deep and broad phylogenetic distribution of
chemiosmosis is precisely the opposite of that of fermentation. Just as we can
say that LUCA had a ribosome, which will not startle anyone, we can say that
LUCA obtained energy by chemiosmotic coupling.
Which of the following results would enhance this paragraph?
Why?
(1) Bacteria and archaea differ markedly in the gene sequences
and crystal structures of enzymes that catalyse the individual steps
of fermentation (Siebers & Schonheit 2005).
(2) Both archaea and bacteria conduct electrons and pump protons
using ferredoxins, quinones and cytochromes that are closely
related in chemical structure (Baymann et al. 2003).
(3) Bada (2004) asserts that RNA was once the only catalyst as
well as the only replicator and so all the basic chemistry of life was
invented by RNA.
References
Bada JL. 2004. How life began on earth: a status report. Earth Planet
Science Letters 226: 1–15.4.
Baymann F, Lebrun E, Brugna M, et al. 2003. The redox protein
construction kit: pre-last universal common ancestor evolution of
energy conserving enzymes. Philosophical Transactions of the
Royal Society of London B 358: 267-74.
Lane, N, J.F. Allen, & W. Martin. 2010. How did LUCA make a living?
Chemiosmosis in the origin of life. BioEssays 32:271-280.
Siebers B, Schonheit P. 2005. Unusual pathways and enzymes of
central carbohydrate metabolism in Archaea. Current Opinions in
Microbiology 8:695–705.13.