Stem Cell Research Controversy: An Argumentative Essay Introduction Few topics in science and religion have been as hotly contested in recent years as stem cell research, largely because it involves the fate of, disposition of, and research on the human embryo. There are two basic types of stem cell research—that involving adult cells AS cells and that involving human embryonic cells ESCs or hES cells ; only the latter is a source of controversy. In both cases, research is still at the early stages regarding the programming and uses of these cells, and there is comparatively little data about the efficacy of AS and hES cells for human therapies.
Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se. All groups below are crown groups, nearly all are extant.
Characters mentioned are those of the immediate common ancestor of the group,  contains explanatory material, features common in clade, exact status unclear. B class], mitochondrial rps2 gene lost. In all node characterizations, boldface denotes a possible apomorphy, Note that the particular node to which many characters, particularly the more cryptic ones, should be assigned is unclear.
This is partly because homoplasy is very common, in addition, basic information for all too many characters is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed see above.
Stem-group ages for Fabaceae the ages just mentioned offered by H. A number of species in the nitrogen-fixing clade, practically alone among land plants, have associations with N-fixing bacteria and play a key role in the terrestrial nitrogen cycle see below. The ability to fix N is uncommon elsewhere in seed plants, although Nostoc, a N-fixing blue-green algae, is associated with Gunneraceae and Cycadales, and also with hypnalean feather mosses and particulary hornworts, Anthocerophyta.
In vitro nitrogen fixation by Azotobacteria vinelandii endophytic in Mammillaria has been recorded Lopez et al.
N fixation in this group of four orders would seem to be a classic example of a "tendency" or "predisposition" e. Be this as it may, it has been suggested there have been some nine independent establishments of symbioses with Frankia alone H.
Swensen ; Clawson et al. Doyle ; Santi et al. N-fixing angiosperms have more aquaporins compared to plants that cannot fix N, the number having been increased by tandem duplications; the channel was "a good candidate to be a key molecular innovation for the emergence of N-fixing symbiosis.
However, there have been recent suggestions van Velzen et al. Given the ecological importance of N-fixing plants, the timing of their evolution is of considerable interest. Under the multiple origins on N-fixation hypothesis, Jeong et al.
Under the single origin hypothesis, the minimum time at which N fixation appeared would be the crown-group age of the N-fixing clade. This is commonly estimated to be m. However, the stem group age of the N-fixing clade, i.
Using age estimates of Bell et al. Doyle noted that the common ancestor of the N-fixing clade was about m. Particularly old N-fixing clades may be Datiscaceae and Elaeagnaceae, but since both have very long stems exactly when N-fixing actually evolved there is anyone's guess.
Nitrogen-fixing members of the four orders of the N-fixing clade grow throughout the world and are very important in the global N cycle, moving N from the atmospheric to terrestrial and ultimately aquatic parts of the cycles. Nitrogen-fixing plants are usually not members of closed l.
Frankia-associated plants are woody, and favour high light and soils with low available N, and are early successional for the most part H. Indeed, there are major geographic patterns in the kinds of N fixation.
The vast range of maximum lifespan differences between species provides convincing evidence that longevity is genetically influenced. An elephant lives about 10−20 times longer than a mouse, yet both animals have roughly the same number of lifetime heartbeats — the elephant at 30 per minute and the mouse at per minute. The purpose of this RFI is to solicit feedback from industry, academia, research laboratories, government agencies, and other stakeholders to assist in further defining the scope and priorities of EERE’s commercialization and entrepreneurship activities. Stem cell research and cloning are controversial. Scientists claim medical necessity. Opponents argue it's unethical. This sample expository essay explores the argument against stem cell research.. Arguments against stem cell research and cloning/5(5).
Interestingly, strains of Bradyrhizobium, close to Rhizobium, are the dominating bacteria in pine forests across North America, and although they are unable to fix nitrogen other strains can and N-fixing plants are vanishingly uncommon there, they seem to be able to metabolize aromatic carbon sources - VanInsberghe et al.
N-fixing plants in general - although Fabaceae make up the majority of these - have very high concentrations of nitrogen in the leaf, and this has been linked with high levels of both carbon fixation and photosynthesis see M.
However, Adams et al. There is no evidence that Fabaceae in general have a high demand for nitrogen, moreover, inoculation of plants with crushed rhizobia affected plant nitrogen concentrations independently of any fixation, which suggests a rather complex interaction between the plant and bacterium Wolf et al.
Species forming ectomycorrhizal ECM associations are also common in the N-fixing clade, and this association has evolved here at least seven times as well as in other seed plantsbut apparently not in Cucurbitales.
Plants with ECM fungi rarely fix nitrogen, although Casuarinaceae are an exception. Interestingly, ECM associations also involve a perturbation of the nitrogen cycle in that nitrogen may move directly from humus to the fungus, and then to the plant, rather than moving in inorganic form from the soil into the root hairs see also below.
There are associations of particular groups of butterflies and plants as food sources for caterpillars within Fabales and Rosales in particular AckeryScience topics are interesting to write and easy to research because there are so many current and reputable journals online.
Start by browsing through the topic questions below, then look at some of the linked articles or continue your search online with the links provided. A Conservative Argument against Stem Cell Research For the past few years stem cell research has been a widely debated topic; however, former President Clinton?s stance?allowing federal money to be spent on tightly controlled stem cell research?lead to intense debates over federal funding for stem cell research.
Stem Cell Research Controversy: An Argumentative Essay Stem Cell Research Controversy: An Argumentative Essay Introduction Few topics in science and religion have been as hotly contested in recent years as stem cell research, largely because it involves the fate of, disposition of, and research on the human embryo.
The goal of Sudoku is to fill in a 9×9 grid with digits so that each column, row, and 3×3 section contain the numbers between 1 to 9. At the beginning of the game, . Aug 09, · Scientists largely agree that stem cells may hold a key to the treatment, and even cure, of many serious medical conditions.
But while the use of adult stem cells is widely accepted, many religious groups and others oppose stem cell research involving the use and destruction of human embryos.
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