熱血背包客莊ㄟ

 During the Pleistocene epoch, several species of elephants isolated on islands underwent rapid dwarfing. This phenomenon was not necessarily confined to the Pleistocene, but may have occurred much earlier in the Southeastern Asian islands, although evidence is fragmentary. Several explanations are possible for this dwarfing. For example, islands often have not been colonized by large predators or are too small to hold viable predator populations. Once free from predation pressure, large body size is of little advantage to herbivores. Additionally, island habitats have limited food resources, a smaller body size and a need for fewer resources would thus be favored. Interestingly, the island rule is reversed for small mammals such as rodents, for which gigantism is favored under insular conditions.

Larvae of many marine invertebrate species delay their metamorphosis into juveniles when cues signaling an appropriate juvenile environment are absent, thereby increasing their likelihood of thriving as juveniles and of ultimately reaching adulthood. Nevertheless, delayed metamorphosis has potential costs for juveniles, including reduced growth and increased mortality. Nearly all evidence of such costs involves species whose larvae do not feed but rather subsist stored nutrients, indicating that insufficient energy reserves may be an underlying cause of these costs. Supporting this “ hypothesis" are laboratory studies showing that in a certain “bryozoan’, the prolonged larval swimming that results from delayed metamorphosis is associated with size reductions in the juvenile feeding organ (the lophophore) and that one factor influencing the size of juveniles of certain “ barnacle species “ is how long larvae delay metamorphosis. However, other studies show that while significantly fewer juvenile “ Capitella worms “ survived to adulthood when metamorphosis had been delayed, prolonged larval swimming had no significant effect on juvenile size, suggesting, perhaps, that in some species, factors other than insufficient energy reserves account for the negative effects of the larval stresses that result from delayed metamorphosis.

Biologists generally agree that birds and dinosaurs are somehow related to one another. The agreement ends there. Hypotheses regarding dinosaurian and avian evolution are unusually diverse—and often at odds with one another. Confusion consequently reigns over a broad spectrum of unanswered questions dealing with avian origins and the biology of dinosaurs and early birds. This confusion has been exacerbated by a paucity of serious attempts to synthesize and evaluate available data on the details of avian and dinosaurian evolution. Too often, the job of summarizing current knowledge of these subjects has fallen to well-meaning but naïve lay authors or reporters. Consequently, both the public and the scientific community have often been misled by widespread dissemination of sensational but weakly founded hypotheses.

Although the passenger pigeons, now extinct, were abundant in eighteenth- and nineteenth century America, archaeological studies at twelfth-century Cahokian sites in the present day United States examined household food trash and found that traces of passenger pigeon were quite rare. Given that the sites were close to a huge passenger pigeon roost documented by John James Audubon in the nineteenth century and found that Cahokians consumed almost every other animal protein source available, the archaeologists conducting the studies concluded the passenger pigeon population had once been very limited before increasing dramatically in post-Columbian America. Other archaeologists have criticized those conclusions on the grounds that passenger pigeon bones would not be likely to be preserved. But all the archaeological projects found plenty of bird bones- and even tiny bones from fish.

According to the conventional view, serfdom in nineteenth-century Russia inhibited economic growth. In this view Russian peasants’ status as serfs kept them poor through burdensome taxes in cash, in labor, and in kind; through restrictions on mobility; and through various forms of coercion. Melton, however, argues that serfdom was perfectly compatible with economic growth, because many Russian serfs were able to get around landlords’ rules and regulations. If serfs could pay for passports, they were usually granted permission to leave the estate. If they could pay the fine, they could establish a separate household; and if they had the resources, they could hire laborers to cultivate the communal lands, while they themselves engaged in trade or worked as migrant laborers in cities.

Benjamin Franklin is portrayed in American history as the quintessential self-made man. In “Self-reliance”, Emerson asks, “Where is the master who could have instructed Franklin...?” In fact, Franklin took instruction widely, and his scientific work was highly collaborative. Friends in England sent equipment needed for his electrical experiments, others, in Philadelphia, helped him set up his workshop there. Philip Syng constructed a device for generating electrical charges, while Tomas Hopkinson demonstrated the potential of pointed conductors. Franklin, in addition to being the group’s theoretician, wrote and published its results. His fame as an individual researcher is partly a consequence of the shorthand by which when one person writes about a group’s discoveries, history sometimes grants singular credit for collective effort.

Few central textiles from the Timurid period (1370-1526 C.E.) have survived to be dated. However, scholars have long assumed that Timurid rugs with geometric patterns were replaced in royal courts by floral-patterned rugs only at the end of the 1400s, under the influence of the painter Behzad (circa 1455- circa 1536). Nevertheless, the presence of floral-patterned rugs in court scenes of from two paintings in a 1440s Timurid manuscript suggests that floral-patterned rugs were already being used at that time. Whether the occasional presence of geometric rugs in similar painting after the 1440s means the tradition of weaving rugs with geometric patterns also continued, or whether here the painters simply followed a well-established “formula”, is still an open question.

Computers cannot accurately predict climate change unless the mathematical equations fed into them adequately capture the natural meteorological processes they are intended to simulate. Moreover, there are processes that influence climate, such as modifications in land use, that scientists do not know how to simulate. The failure to incorporate such a process into a computer climate model can lead the model astray because a small initial effect can initiate a feedback cycle: a perturbation in one variable modifies a second variable, which in turn amplifies the original disturbance. An increase in temperature, for example, can boost the moisture content of the atmosphere, which then causes further warming because water vapor is a greenhouse gas.

While chocolate was highly esteemed in Mesoamerica, where it originated, its adoption in Europe was initially slow. There is a common belief that Europeans needed to “transform" chocolate to make it appetizing. However, while Spaniards did put sugar, which was unknown to indigenous Americans, into chocolate beverages, this additive was not completely innovative. Mesoamericans were already sweetening chocolate with honey, and the step from honey to sugar—increasingly more available than honey because of expanding sugar plantations in the Americas—is a small one. Likewise, although Spaniards adjusted Mesoamerican recipes by using European spices, the spices chosen suggest an attempt to replicate harder-to-find native flowers. There is no indication the Spaniards deliberately tried to change the original flavor of chocolate.