Castle, W. E. Heredity, in relation to evolution and animal breeding

Ohne Zusammenfassung

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Castle, W. E. Heredity, in relation to evolution and animal breeding

     

Mimicry: Ecology,evolution, and development

1 IntroductionMimicry occurs when one species (the mimic)evolves to resemble a second species (the model) because of the selective benefits associated with confusing a third species (the receiver).For example,natural selection can favor phenotypic convergence between completely unrelated species when an edible species receives the benefit of reduced predation by resembling an inedible species that predators avoid.     

Salaman, R.N. Heredity and the Jew

Ohne Zusammenfassung

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Salaman, R.N. Heredity and the Jew

     

Inflorescences: concepts,function, development and evolution

Background

Inflorescences are complex structures with many functions. At anthesis they present the flowers in ways that allow for the transfer of pollen and optimization of the plant''s reproductive success. During flower and fruit development they provide nutrients to the developing flowers and fruits. At fruit maturity they support the fruits prior to dispersal, and facilitate effective fruit and seed dispersal. From a structural point of view, inflorescences have played important roles in systematic and phylogenetic studies. As functional units they facilitate reproduction, and are largely shaped by natural selection.

Scope

The papers in this Special Issue bridge the gap between structural and functional approaches to inflorescence evolution. They include a literature review of inflorescence function, an experimental study of inflorescences as essential contributors to the display of flowers, and two papers that present new methods and concepts for understanding inflorescence diversity and for dealing with terminological problems. The transient model of inflorescence development is evaluated in an ontogenetic study, and partially supported. Four papers present morphological and ontogenetic studies of inflorescence development in monophyletic groups, and two of these evaluate the usefulness of Hofmeister''s Rule and inhibitory fields to predict inflorescence structure. In the final two papers, Bayesian and Monte-Carlo methods are used to elucidate inflorescence evolution in the Panicoid grasses, and a candidate gene approach is used in an attempt to understand the evolutionary genetics of inflorescence evolution in the genus Cornus (Cornaceae). Taken as a whole, the papers in this issue provide a glimpse of contemporary approaches to the study of the structure, development, and evolution of inflorescences, and suggest fruitful new directions for research.     

Genomics and the evolution of aminoacyl-tRNA synthesis.

Translation is the process by which ribosomes direct protein synthesis using the genetic information contained in messenger RNA (mRNA). Transfer RNAs (tRNAs) are charged with an amino acid and brought to the ribosome, where they are paired with the corresponding trinucleotide codon in mRNA. The amino acid is attached to the nascent polypeptide and the ribosome moves on to the next codon. Thus, the sequential pairing of codons in mRNA with tRNA anticodons determines the order of amino acids in a protein. It is therefore imperative for accurate translation that tRNAs are only coupled to amino acids corresponding to the RNA anticodon. This is mostly, but not exclusively, achieved by the direct attachment of the appropriate amino acid to the 3'-end of the corresponding tRNA by the aminoacyl-tRNA synthetases. To ensure the accurate translation of genetic information, the aminoacyl-tRNA synthetases must display an extremely high level of substrate specificity. Despite this highly conserved function, recent studies arising from the analysis of whole genomes have shown a significant degree of evolutionary diversity in aminoacyl-tRNA synthesis. For example, non-canonical routes have been identified for the synthesis of Asn-tRNA, Cys-tRNA, Gln-tRNA and Lys-tRNA. Characterization of non-canonical aminoacyl-tRNA synthesis has revealed an unexpected level of evolutionary divergence and has also provided new insights into the possible precursors of contemporary aminoacyl-tRNA synthetases.     

Coidingham Loch, S.E. Scotland

SUMMARY. 1. Coidingham Loch (Berwickshire. Scotland) (area. 8.4 ha, mean depth 2.9 m, max. depth 12.3 m) belongs to Hakansson's convex shape category. It lies in a basin of Silurian Greywackes rock within 0.25 km of coastal sea cliffs (c. 133 m a.s.l.). The theoretical hydraulic replacement time is 3.17 years. 2. The loch stratifies intermittently in summer. Fluctuations in oxygen concentration generally correspond to spells of mixing and stratification; low values of 10% saturation occur at the bottom. 3. The sum of the concentrations of major cations (Na+, K+, Ca²⁺, Mg²⁺) is in accordance with measured conductivities ranging between 380 μS cm^?1 and 420 μS cm^?1 (k.₂₅). The ratios (by equivalents) of Na⁺/Cl^? (0.04) are similar to those in sea-water, whilst values for Ca+²⁺/Cl^? (0.85–1.01) and Mg²⁺/Cl^? (0.79–0.88) reflect the bedrock. 4. Nitrate concentrations were lowest (<0.05 mg N1^?1) in summer following losses from the column of 107 mg N m^?2 1^?1, a rate corresponding well with published figures on microbial nitrate reduction. Nitrate increased at a rate of 8μg N I^?1 d^?1 to a winter maximum of 1.55 mg N I^?1. Mass balance calculations show that if this rise is attributed to run-off from surrounding land, a loss rate of 11.1 kg N ha^?1 yr^?1 would be required; this value is also commensurate with published figures. 5. Changes in phosphorus and factors controlling them contrast markedly with those of nitrate. The minimum concentration of 55 μg total P l^?1 (mainly in soluble reactive form) occurs in spring. An increase to the maximum ofc. 300 μg l^?1 in summer is sustained mainly by release from the sediments at a regular rate of 3 μg P l^?1 d^?1 (8.7 mg m^?2 d^?1). Adsorption by the sediments is considered to be the major process accounting for autumnal losses of phosphorus of 2.6 mg P M^?2d^?1. 6. Silica showed a less regular seasonal pattern, but varied some 45-fold with a maximum of 2.25 mg SiO₂, l_?1 in August.