The origin of atmospheric oxygen on Earth: The innovation of oxygenic photosynthesis

The evolution of O2-producing cyanobacteria that use water as terminal reductant transformed Earth's atmosphere to one suitable for the evolution of aerobic metabolism and complex life. The innovation of water oxidation freed photosynthesis to invade new environments and visibly changed the face of the Earth. We offer a new hypothesis for how this process evolved, which identifies two critical roles for carbon dioxide in the Archean period. First, we present a thermodynamic analysis showing that bicarbonate (formed by dissolution of CO2) is a more efficient alternative substrate than water for O2 production by oxygenic phototrophs. This analysis clarifies the origin of the long debated “bicarbonate effect” on photosynthetic O2 production. We propose that bicarbonate was the thermodynamically preferred reductant before water in the evolution of oxygenic photosynthesis. Second, we have examined the speciation of manganese(II) and bicarbonate in water, and find that they form Mn-bicarbonate clusters as the major species under conditions that model the chemistry of the Archean sea. These clusters have been found to be highly efficient precursors for the assembly of the tetramanganese-oxide core of the water-oxidizing enzyme during biogenesis. We show that these clusters can be oxidized at electrochemical potentials that are accessible to anoxygenic phototrophs and thus the most likely building blocks for assembly of the first O2 evolving photoreaction center, most likely originating from green nonsulfur bacteria before the evolution of cyanobacteria.

Carrot red leaf and carrot mottle viruses : observations on the composition of the particles in single and mixed infections

Particles of carrot red leaf virus (CRLV; luteovirus group) purified from chervil (Anthriscus cerefolium) contain a single ssRNA species of mol. wt. about 1.8 x 106 and a major protein of mol. wt. about 25000. CRLV acts as a helper for aphid transmission of carrot mottle virus (CMotV; ungrouped) from mixedly infected plants. Virus preparations purified from such plants possess the infectivity of both viruses but contain particles indistinguishable from those of CRLV; some of the particles are therefore thought to consist of CMotV RNA packaged in CRLV coat protein. When RNA from such preparations was electrophoresed in agarose/polyacrylamide gels, CMotV infectivity was associated with an RNA band that migrated ahead of the CRLV RNA band and had an estimated mol. wt. of about 1.5 x 106, similar to that previously found for the infective ssRNA extracted directly from Nicotiana clevelandii leaves infected with CMotV alone. Preparations of dsRNA from CMotV-infected N. clevelandii leaves contained two species: one of mol. wt. about 3.2 x 106, presumably the replicative form of the infective ssRNA, and the other, mol. wt. about 0.9 x 106, of unknown origin and function. The infective agent in buffer extracts of CMotV-infected N. clevelandii was resistant to RNase (although the enzyme acted as a reversible inhibitor of infection at high concentrations) and is therefore not unprotected RNA. It may be protected within the approximately 52 nm enveloped structures previously reported.

Effects of seed origin latitude on the timing of height growth cessation and field performance of silver birch

The aim of this thesis was to increase our knowledge about the effects of seed origin on the timing of height growth cessation and field performance of silver birch from different latitudes, with special attention paid to the browsing damage by moose in young birch plantations. The effect of seed origin latitude and sowing time on timing of height growth cessation of first-year seedlings was studied in a greenhouse experiment with seven seed origins (lat. 58º - 67ºN). Variation in critical night length (CNL) for 50 % bud set within two latitudinally distant stands (60º and 67ºN) was studied in three phytotron experiments. Browsing by moose on 5-11 -year-old silver birch saplings from latitudinally different seed origins (53º - 67ºN) was studied in a field experiment in southern Finland. Yield and stem quality of 22-year-old silver birch trees of Baltic, Finnish and Russian origin (54º - 63ºN) and the effect of latitudinal seed transfers were studied in two provenance trials at Tuusula, southern and Viitasaari, central Finland. The timing of height growth cessation depended systematically on latitude of seed origin and sowing date. The more northern the seed origin, the earlier the growth cessation and the shorter the growth period. Later sowing dates delayed growth cessation but also shortened the growth period. The mean CNL of the southern ecotype was longer, 6.3 ± 0.2 h (95 % confidence interval), than that of the northern ecotype, 3.1 ± 0.3 h. Within-ecotype variance of the CNL was higher in the northern ecotype (0.484 h2) than in the southern ecotype (0.150 h2). Browsing by moose decreased with increasing latitude of seed origin and sapling height. Origins transferred from more southern latitudes were more heavily browsed than the more northern native ones. Southern Finnish seed origins produced the highest volume per unit area in central Finland (lat. 63º11'N). Estonian and north Latvian stand seed origins, and the southern Finnish plus tree origins, were the most productive ones in southern Finland (lat. 60º21'N). Latitudinal seed transfer distance had a significant effect on survival, stem volume/ha and proportion of trees with a stem defect. The relationship of both survival and stem volume/ha to the latitudinal seed transfer distance was curvilinear. Volume was increased by transferring seed from ca. 2 degrees of latitude from the south. A longer transfer from the south, and transfer from the north, decreased the yield. The proportion of trees with a stem defect increased linearly in relation to the latitudinal seed transfer distance from the south.

Oxidation of methanol on the surfaces of model Cu/ZnO catalysts containing Cu1+ and Cu-0 species

Interaction of CH3OH with Cu clusters deposited on ZnO films grown on a Zn foil as well as on a ZnO(0001)Zn crystal, has been examined by X-ray photoelectron spectroscopy. On clean Cu clusters, reversible molecular adsorption or formation of CH3O is observed. However if the Cu clusters are pretreated with oxygen, both CH3O and HCOO- species are produced. Model Cu/ZnO catalyst surfaces, containing both Cu1+ and Cu-0 species, show interesting oxidation properties. On a Cu-0-rich catalyst surface, only CH3O species is formed on interaction with CH3OH. On a Cu1+-rich surface, however, HCOO- ion is the predominant species.

Examining the effects of species richness on community stability: an assembly model approach

We build dynamic models of community assembly by starting with one species in our model ecosystem and adding colonists. We find that the number of species present first increases, then fluctuates about some level. We ask: how large are these fluctuations and how can we characterize them statistically? As in Robert May's work, communities with weaker interspecific interactions permit a greater number of species to coexist on average. We find that as this average increases, however, the relative variation in the number of species and return times to mean community levels decreases. In addition, the relative frequency of large extinction events to small extinction events decreases as mean community size increases. While the model reproduces several of May's results, it also provides theoretical support for Charles Elton's idea that diverse communities such as those found in the tropics should be less variable than depauperate communities such as those found in arctic or agricultural settings.

On the origin and foundation of the concept “The Person” metaphysical realism on interpersonal recognition

Resumen: De acuerdo con el autor, la capacidad del alma de conocerse a sí misma está en la raíz del problema de la persona. Más aún, el entendimiento deber ser interpretado antológicamente como una actividad del alma. Se lleva a cabo un análisis del concepto de persona en algunos filósofos medievales y modernos. También hay referencias a pensadores contemporáneos. El autor sostiene que la noción que Spaemann introduce, considerando la intencionalidad como meramente un sentimiento o negatividad, es insuficiente. El mencionado sentimiento subjetivo es idéntico al concepto de ‘intuición experienciante’ en la fenomenología; pero es insuficiente para permitirnos comprender la esencia de la persona como una entidad espiritual. El autor afirma que cada ser humano debería ser reconocido, no sólo como una creatura racional, sino también como persona, en especial cuando nos referimos a este ser humano o a esta alma. Agrega que las consecuencias prácticas de esta perspectiva son de gran importancia.

On the relationship of the genus Aulacocarpus, with description of a new Panamanian species

pages 1-4

Observations on the spawning of four species on tuna (Neothunnus macropterus, Katsuwonus pelamis, Auxis thazard and Euthynnus lineatus) in the Eastern Pacific Ocean, based on the distribution of their larvae and juveniles

ENGLISH: Knowledge of spawning habits is useful in the elucidation of the life history, ecology and population structure of tropical tunas, and is essential to the sound management of these resources. Until recently, little was known concerning the spawning of tunas, or about the distribution of their larval and juvenile stages, in the Eastern Pacific Ocean. Nichols and Murphy (1944) reported the capture off Colombia of young scombroids ultimately identified as frigate mackerel, Auxis thazard (Schaefer and Marr, 1948a). Fowler (1944) reported the capture off Manzanillo, Mexico of two young tunas, one of which is definitely and the other most likely Neothunnus macropterus (Klawe, 1959). In 1947, young of N. macropterus, K. pelamis, A. thazard and E. lineatus were caught offshore from Central America (Schaefer and Marr, 1948a, 1948b, and Schaefer, 1948). Further collections of young N. macropterus, A. thazard and E. lineatus were made in the same general area in the spring of 1949 (Mead, 1951). In January and February 1955, Clemens (1956) carried Out experiments in rearing young tunas, E. lineatus and A. thazard, in shipboard aquaria, using fish caught off Central America. Matsumoto (1958) reported captures of larval N. macropterus and K. pelamis in the area along the 120th meridian of west longitude. Klawe (1958 and 1961b) reported captures of larval N. macropterus and Auxis from the Revillagigedo Islands. Captures of young Auxis and E. lineatus in the Gulf of Panama in January 1922 during the Dana Expedition have recently been reported by Matsumoto (1959). Capture of juveniles of K. pelamis, E. lineatus and Auxis in the area off tropical Mexico and in the area of outlying islands during the SCOT Expedition has been reported by Klawe (1960a). SPANISH: El conocimiento sobre los hábitos del desove es útil para el esclarecimiento de la historia natural, ecología y estructura de las poblaciones de atunes tropicales, y es esencial para la acertada administración de estos recursos. Hasta hace poco tiempo no se sabía mucho sobre el desove de los atunes o acerca de la distribución de sus larvas y juveniles en el Océano Pacífico Oriental. Nichols y Murphy (1944) informaron sobre la captura frente a Colombia de escómbridos jóvenes últimamente identificados como melva, Auxis thazard (Schaefer y Marr, 1948a). Fowler (1944) también informó sobre la captura de dos atunes jóvenes frente a Manzanillo, México, uno de los cuales era definitivamente Neothunnus macropterus y el otro era lo más probable que también lo fuera (Klawe, 1959). En 1947 se capturaron especímenes juveniles de N. macropterus, K. pelamis, A. thazard y E. lineatus frente a la América Central (Schaefer y Marr, 1948a, 1948b, y Schaefer, 1948). Otras recolecciones de ejemplares jóvenes de N. macropterus, A. thazard y E. lineatus fueron hechas en la misma área general durante la primavera de 1949 (Mead, 1951). En enero y febrero de 1955, Clemens (1956) efectuó experimentos de crianza de atunes jóvenes, E. lineatus y A.. thazard, en acuarios a bordo para lo que empleó peces capturados frente a la América Central. Matsumoto (1958) informó sobre capturas de larvas de N. macropterus y K. pelamis en el área a lo largo del meridiano 120 de longitud oeste. Klawe (1958 y 1961b) ha dado cuenta también de capturas de larvas de N. macropterus y Auxis en las Islas Revillagigedo. Matsumoto (1959) ha informado recientemente acerca de capturas de ejemplares jóvenes de Auxis y E. lineatus en el Golfo de Panamá en enero de 1922 durante la Expedición Dana. Klawe (1960a) informó así mismo que durante la Expedición SCOT se capturaron juveniles de K. pelamis, E. lineatus y Auxis en el área frente a la zona tropical de México y en la región de las islas alejadas del continente.

Effects of some environmental factors on the fecundity of Tilapia species (Family Cichlidae) in Kigera Reservoir, New Bussa

The effects of some environmental factors on the fecundity of Tilapia species (Family Cichilidae) was carried out at the Kigera dam. Four Tilapia species caught were Tilapia zilli, Hemichromis fasciatus, Sarotherodon galilaeus and Oreochromis niloticus while the environmental factors considered were water temperature, Dissolved Oxygen, pH value, level of rainfall and rate of sunshine and range of time. 43 fish comprising of 25 male with (58.1%) and 18 females having (41.9%) were studied with 74.42% been sexually matured. Both high levels of rainfall and dissolved oxygen favoured fecundity. The spawning peak occurred in (July), environmental factors monitored indicated that dissolved oxygen ranges from 3.7 to 4.45mg/lit rainfall ranges from (34.90mm to 237.80mm) sunshine ranges from (5hrs-8hrs) and pH ranges from (7.35-7.45). The spawning of these species in their natural or hatchery condition is therefore best achieved during the peak of raining season

On the little known species of threadfin breams Nemipterus mesoprion (Bleeker) and Nemipterus delagoae (Smith)

Among the fish species of the family Nemipteridae, the two little known species, namely, Nemipterus mesoprion (Bleeker) and Nemipterus delagoae (Smith) are recorded from the Cochin waters. Nemipterus mesoprion is a new distributional record from the west coast of India. N. delagoae is described with adequate numbers of specimen for the first time from Indian waters. Moreover, the results of the present study show that the colour of the viscera, the number of pyloric caeca and the gill rakers can also be used for the diagnosis of the species of the genus Nemipterus. The affinity of the above species with other related species of the genus Nemipterus and their geographical distribution are presented.

Observations on the durability of fifteen species of CCA treated timber in the Cochin harbour

Observations on the durability of fifteen species of common Indian timber treated with CCA at two absorption levels, for eight years are presented. CCA treatment has improved the durability of this timber to a great extent. T. grandis, D. indicus and X. xylocarpa give maximum durability on treatment with CCA. Less durable A. kurzi, T. nudiflora and P. longifolia when treated with CCA showed results comparable to the best species.

Adaptive evolution of energy metabolism genes and the origin of flight in bats

Bat flight poses intriguing questions about how flight independently developed in mammals. Flight is among the most energy-consuming activities. Thus, we deduced that changes in energy metabolism must be a primary factor in the origin of flight in bats. The respiratory chain of the mitochondrial produces 95% of the adenosine triphosphate (ATP) needed for locomotion. Because the respiratory chain has a dual genetic foundation, with genes encoded by both the mitochondrial and nuclear genomes, we examined both genomes to gain insights into the evolution of flight within mammals. Evidence for positive selection was detected in 23.08% of the mitochondrial-encoded and 4.90% of nuclear-encoded oxidative phosphorylation (OXPHOS) genes, but in only 2.25% of the nuclear-encoded nonrespiratory genes that function in mitochondria or 1.005% of other nuclear genes in bats. To address the caveat that the two available bat genomes are of only draft quality, we resequenced 77 OXPHOS genes from four species of bats. The analysis of the resequenced gene data are in agreement with our conclusion that a significantly higher proportion of genes involved in energy metabolism, compared with background genes, show evidence of adaptive evolution specific on the common ancestral bat lineage. Both mitochondrial and nuclear-encoded OXPHOS genes display evidence of adaptive evolution along the common ancestral branch of bats, supporting our hypothesis that genes involved in energy metabolism were targets of natural selection and allowed adaptation to the huge change in energy demand that were required during the origin of flight.