Responses of the haploid-to-diploid ratio of isomorphic biphasic life cycles to time instability

Previous modelling of the haploid-to-diploid ratio (H:D) in biphasic life cycles relied on estimates of the stable population growth rate and structure. This is a projective analysis that estimates the population dynamics given current conditions. However, the environment is rarely constant and has both periodicity and random instabilities. The objective of this work was to unveil how the H:D responds to them. It was found that ploidy phase dissimilarities on the demographic matrix and/or in the initial population structure cause an inevitable H:D time variability as a consequence of the life-cycle structure and independent of the environmental seasonal cycle. This variability depends on the type of life strategy, demographic processes involved and ploidy dissimilar vital rates. Furthermore, ploidy dissimilar fertility or growth rates cause cyclic oscillations mismatching the seasonal cycle, whereas ploidy dissimilarities in the ramet looping rates (survival related) induce a monotonical variation.     

Functional unit influence on building life cycle assessment

Purpose

The building sector is one of the most relevant sectors in terms of environmental impact. Different functional units (FUs) can be used in life cycle assessment (LCA) studies for a variety of purposes. This paper aimed to present different FUs used in the LCA of buildings and evaluate the influence of FU choice and setting in comparative studies.

Methods

As an example, we compared the “cradle to grave” environmental performance of four typical Brazilian residential buildings with different construction typologies, i.e., multi-dwelling and single dwelling, each with high and basic standards. We chose three types of FU for comparison: a dwelling with defined lifetime and occupancy parameters, an area of 1 m² of dwelling over a year period, and the accommodation of an occupant person of the dwelling over a day.

Results and discussion

The FU choice was found to bias the results considerably. As expected, the largest global warming indicator (GWi) values per dwelling unit and occupant were identified for the high standard dwellings. However, when measured per square meter, lower standard dwellings presented the largest GWi values. This was caused by the greater concentration of people per square meter in smaller area dwellings, resulting in larger water and energy consumption per square meter. The sensitivity analysis of FU variables such as lifetime and occupancy showed the GWi contribution of the infrastructure more relevant compared with the operation in high and basic standard dwellings. The definition of lifetime and occupancy parameters is key to avoid bias and to reduce uncertainty of the results when performing a comparison of dwelling environmental performances.

Conclusions

This paper highlights the need for adequate choice and setting of FU to support intended decision-making in LCA studies of the building sector. The use of at least two FUs presented a broader picture of building performance, helping to guide effective environmental optimization efforts from different approaches and levels of analysis. Information regarding space, time, and service dimensions should be either included in the FU setting or provided in the building LCA study to allow adjustment of the results for subsequent comparison.

     

Differential reattachment capacity of isomorphic life history phases of Gelidium sesquipedale

Vegetative reproduction is an important phenomenon in the propagation of Gelidium species, having significant implications for its ecology and commercial cultivation. This work is an experimental study of one of five sequential processes included in the vegetative propagation of Gelidium sesquipedale: the reattachment of rhizoidal filaments differentiated from apical fragments.Two different factors: light (25 µmol m^–2 s^–1 and long-day conditions, and 50 µmol m^–2 s^–1 and short-day conditions) and life history phases (female gametophytes and tetrasporophytes) were combined in a 2 × 2 factorial experiment. Reattachment of apical portions was induced in the laboratory under spray cultivation conditions and occurs mainly at the first stage of development when in contact with the substratum. Light conditions in these experiments (photoperiod + instantaneous photon flux densities) had no effect on the percentage of reattached neofilaments per fragment. Significant differences between percentages corresponding to both phases suggest, however, a probable competitive advantage of sporophytic fronds.     

Developmental modularity and phenotypic novelty within a biphasic life cycle: morphogenesis of a cone snail venom gland

The venom gland of predatory cone snails (Conus spp.), which secretes neurotoxic peptides that rapidly immobilize prey, is a proposed key innovation for facilitating the extraordinary feeding behaviour of these gastropod molluscs. Nevertheless, the unusual morphology of this gland has generated controversy about its evolutionary origin and possible homologues in other gastropods. I cultured feeding larvae of Conus lividus and cut serial histological sections through the developing foregut during larval and metamorphic stages to examine the development of the venom gland. Results support the hypothesis of homology between the venom gland and the mid-oesophageal gland of other gastropods. They also suggest that the mid-region of the gastropod foregut, like the anterior region, is divisible into dorsal and ventral developmental modules that have different morphological, functional and ontogenetic fates. In larvae of C. lividus, the ventral module of the middle foregut transformed into the anatomically novel venom gland of the post-metamorphic stage by rapidly pinching-off from the main dorsal channel of the mid-oesophagus, an epithelial remodelling process that may be similar to other cases where epithelial tubes and vesicles arise from a pre-existing epithelial sheet. The developmental remodelling mechanism could have facilitated an abrupt evolutionary transition to the derived morphology of this important gastropod feeding innovation.     

Comparative life cycle assessment of a commercial algal multiproduct biorefinery and wild caught fishery for small pelagic fish

Purpose

The purpose of this study was to compare the environmental impacts of omega-3 fatty acid (n-3), high protein feed and biofuel production from algae to the impacts of the production of those products from fish.

Methods

The functional unit was the production of one metric ton of omega-3 fatty acids from algae (fish) and the accompanying co-products of biofuel and high protein feed. This was a cradle to gate LCA. Four scenarios were used in this model. The algae multiproduct model (MPM) scenario was the baseline using only unit operations currently in use at the reference facility (Cellana LLC). A low-energy centrifuge replaced the existing conventional centrifuge (MPM (LE)) to reduce energy consumption. The MPM was improved in a different manner, employing membrane filtration prior to centrifugation (MPM (MF)). These three scenarios were compared to the conventional production of the same products from fish (conventional product model: CPM). This life cycle assessment investigated the following impacts: ozone depletion potential, global warming potential, smog formation potential, acidification potential, and eutrophication potential.

Results and discussion

The environmental impacts of producing omega-3 fatty acids from algae were higher than producing omega-3 fatty acids from fish if membrane filtration was not used. Membrane filtration reduced most of the environmental impacts of the algae system by more than 50%. Fuel consumption was the only factor that caused the fish systems to change by greater than 10% from the baseline. Productivity, membrane filtration electricity, and annual operating days could each affect the environmental impacts of the algae system by greater than 10% from the baseline. Improvements to the algae system depend on improvements to cultivation and harvesting, with the impacts from processing being very small.

Conclusions

This study presented results comparing the environmental impacts from a multiproduct system from algae and from fish. The results of this study can serve as a benchmark for the environmental impacts of an algal multiproduct biorefinery compared to the conventional production of those same products from fish. Areas of improvement have been identified for the algae production system for dewatering and cultivation. The amount of n-3 had little impact on the n-3 market but had a significant effect on the existing algal n-3 market. The amount of fuel and feed produced had a negligible effect on both markets.

     

Comparative life cycle assessment and life cycle costing of lodging in the Himalaya

Purpose

The main aim of the study is to assess the environmental and economic impacts of the lodging sector located in the Himalayan region of Nepal, from a life cycle perspective. The assessment should support decision making in technology and material selection for minimal environmental and economic burden in future construction projects.

Methods

The study consists of the life cycle assessment and life cycle costing of lodging in three building types: traditional, semi-modern and modern. The life cycle stages under analysis include raw material acquisition, manufacturing, construction, use, maintenance and material replacement. The study includes a sensitivity analysis focusing on the lifespan of buildings, occupancy rate and discount and inflation rates. The functional unit was formulated as the ‘Lodging of one additional guest per night’, and the time horizon is 50 years of building lifespan. Both primary and secondary data were used in the life cycle inventory.

Results and discussion

The modern building has the highest global warming potential (kg CO_2-eq) as well as higher costs over 50 years of building lifespan. The results show that the use stage is responsible for the largest share of environmental impacts and costs, which are related to energy use for different household activities. The use of commercial materials in the modern building, which have to be transported mostly from the capital in the buildings, makes the higher GWP in the construction and replacement stages. Furthermore, a breakdown of the building components shows that the roof and wall of the building are the largest contributors to the production-related environmental impact.

Conclusions

The findings suggest that the main improvement opportunities in the lodging sector lie in the reduction of impacts on the use stage and in the choice of materials for wall and roof.

     

The life cycle of the peroxisome

Peroxisomes are highly adaptable organelles that carry out oxidative reactions. Distinct cellular machineries act together to coordinate peroxisome formation, growth, division, inheritance, turnover, movement and function. Soluble and membrane-associated components of these machineries form complex networks of physical and functional interactions that provide supramolecular control of the precise dynamics of peroxisome biogenesis.     

Herbivorous nutrition of Cyclops vicinus: the effect of a pure algal diet on feeding, development, reproduction and life cycle

Nutritional requirements, functional response, development andreproduction of Cyclops vicinus were studied with exclusivelyalgal food. Phytoflagellates were found to be adequate foodresources for both juvenile development and egg production.Ingestion measurements were performed with Chlamydomonas reinhardii.The functional response data give evidence for low feeding efficiency,especially for the naupliar stages. A difference between naupliiand older instars was also found in their quantitative foodneeds. A higher threshold food concentration was observed fornaupliar development (0.4 mg C l^–1) than for copepoditedevelopment (0.2 mg C l^–1). The calculation of assimilationefficiencies suggests that the high food requirements are dueto low specific ingestion rates rather than poor assimilationefficiency. Development time decreased as algal density increasedand males developed more quickly than females at all food concentrations.Body size and carbon content increased with increasing foodconcentration. Continuous egg production was observed abovea food concentration of 0.5 mg C l^–1. The results haveimplications for the life cycle of C. vicinus. Summer diapauseis interpreted as a strategy to avoid starvation of the juvenilestages. The facultative herbivory of the adults might be anadvantage when competing against other more carnivorous cyclopoidcopepods. ¹Present address: Agricultural University of Wageningen, Departmentof Mathematics, Dreijenlaan 4, NL-6703 HA Wageningen, The Netherlands     

Optimal seasonal schedules and the relative dominance of heteromorphic and isomorphic life cycles in macroalgae

Marine macroalgae (seaweed) show diverse life cycles. Species with a heteromorphic life cycle have a large multicellular algal body in one generation but have a very small body in the second generation of the same year. In contrast, the diploid and haploid life forms of isomorphic species have similar morphology, and these species often have more than two generations in a year. Here, we first study the optimal life cycle schedule of marine macroalgae when daily mortality changes seasonally, and then we discuss the conditions for coexistence and relative dominance of different life cycles. According to the optimal life cycle schedule, heteromorphic species tend to have a generation with a large algal body when mortality is low, and a microscopic-sized generation when mortality is high. In contrast, isomorphic species tend to mature when body size reaches a threshold value that is the same for different generations. We then examine the coexistence of the two life cycles when growth rate decreases with biomass. The model predicts that (1) at high latitudes (i.e., in strongly seasonal environments), heteromorphic species are likely to dominate over isomorphic species, and (2) species with a heteromorphic life cycle should dominate in the supratidal and upper intertidal zones where macroalgae tend to suffer high mortality, and also in the subtidal zone, where mortality is low, whereas isomorphic species are likely to be more successful when mortality is intermediate. These predictions are consistent with the observed distribution patterns of the two life cycles in macroalgae.     

Using GaBi 3 to perform life cycle assessment and life cycle engineering

The growing availability of software tools has increased the speed of generating LCA studies. Databases and visual tools for constructing material balance modules greatly facilitate the process of analyzing the environmental aspects of product systems over their life cycle. A robust software tool, containing a large LCI dataset and functions for performing LCIA and sensitivity analysis will allow companies and LCA practitioners to conduct systems analyses efficiently and reliably. This paper discusses how the GaBi 3 software tool can be used to perform LCA and Life Cycle Engineering (LCE), a methodology that combines life cycle economic, environmental, and technology assessment. The paper highlights important attributes of LCA software tools, including high quality, well-documented data, transparency in modeling, and data analysis functionality. An example of a regional power grid mix model is used to illustrate the versatility of GaBi 3.     

The evolution of the chelicerate life cycle

A comparative study is made of the life-cyle in Chelicerata, and its evolution. Various types of forms or instars, and various evolutionary phenomena are distinguished. They are arranged in a chronological diagram constituting a general model of the evolution of the chelicerate life-cycle. A glossary is added in which terminology is defined.In the present paper, Chelicerata are classified according to van der Hammen (1977); the classification of Mites is based on van der Hammen (1972b).     

Thermoregulation in the life cycle of nematodes

An unanswered question in the biology of many parasites is the mechanism by which environmental (or external) and intrinsic signals are integrated to determine the switch from one developmental stage to the next. This is particularly pertinent for nematode parasites, many of which have a free-living stage in the environment prior to infection of the mammalian host, or for parasites such as filarial nematodes, which utilise an insect vector for transmission. The environmental changes experienced by a parasite upon infection of a mammalian host are extremely complex and poorly understood. However, the ability of a parasite to sense its new environment must be intrinsically linked to its developmental programme, as progression of the life cycle is dependent upon the infection event. In this review, the relationship between temperature and development in filarial nematodes and in the free-living species Caenorhabditis elegans is summarised, with a focus on the role of heat shock factor and heat shock protein 90 in the nematode life cycle.     

Integrating life cycle assessment and life cycle cost: a review of environmental-economic studies

The International Journal of Life Cycle Assessment - The purpose of this document is to carry out a critical review of the existing literature by specifically addressing the following: (i) the...