• Journal of Life Science
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• v.25 no.5
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• pp.601-606
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• 2015

Hutchinson (1961) proposed that the large number of species in most plankton communities is remarkable in review of the competitive exclusion principle, which suggests that in homogeneous, well-mixed environments species that compete for the same resources cannot coexist. The principle of competitive exclusion would lead us to conclude that only a few species could coexist in such circumstances. Nevertheless, numerous competing species in most natural habitats are able to coexist, while generally only few resources (niches) limit these communities. It is coined “the paradox of plankton” by Hutchinson. We reviewed some literature of the proposed solutions and give a brief overview of the mechanisms proposed so far. The proposed mechanisms that we discuss mainly include spatial and temporal heterogeneity in physical and biological environment, externally imposed or self-generated spatial segregation, horizontal mesoscale turbulence of ocean characterized by coherent vortices, oscillation and chaos generated by several internal and external causes, stable coexistence and compensatory dynamic under fluctuating temperature in resource competition, and finally the role of toxin-producing phytoplankton in maintaining the coexistence and biodiversity of the overall plankton populations. Especially we sited Roy and Chattopadhyay’s reviews and their toxin-producing hypothesis by phytoplankton. This review may be some information to study plankton communities and effect to put the solutions to the paradox that have been proposed over the years into perspective.

• Advances in Traditional Medicine
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• v.5 no.2
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• pp.124-136
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• 2005

Two popular ethnomedicines of the Onge, a Negrito tribe of Andaman Islands, were evaluated for analgesic and antiinflammatory activity. The methanol extract as well as the different fractions of methanol extract of both Alstonia macrophylla and Mallotus peltatus leaves were studied using Swiss albino mice and Wistar albino rats. Acetic acid induced writhing, Tail flick and Tail immersion; Carrageenin- and Dextran-induced paw oedema tests were used. Dose-dependent analgesic and antiinflammatory activity were demonstrated for both methanol leaf extracts as well as fractions. Results were highly comparable with that of the standard drug pethidine.