Extinction of widespread species is common in evolutionary time (millions of years) but rare in ecological time (hundreds or thousands of years). In the fossil record, there appears to be a smooth continuum between background and mass extinction; and the clustering of extinctions at mass extinctions cannot be explained by the chance coincidence of independent events. Although some extinction is selective, much is apparently random in that survivors have no recognizable superiority over victims. Extinction certainly plays an important role in evolution, but whether it is constructive or destructive has not yet been determined.

The atmospheric oxygen reserve is so huge that, in the short term of hundreds or thousands of years, only minor changes can be expected due to fossil fuel burning and deforestation. Each oxygen molecule passes through a living organism, on average, only once in 9000 years. As a consequence, the fastest regulating system must take of the order of hundreds of years. Nevertheless, it is possible that the actual oxygen level is not necessarily at the optimum level for life, but is just an accidental one in the course of the earth's history. Tropical forests are not the ‘lungs’ of the earth in terms of hundreds of years, but only on a much longer time scale, likewise for all other vegetation which produce humus and the long-term fossil carbon. The driving force is related to the slight differences caused by external factors between photosynthesis and respiration, with subsequent organic matter deposition or consumption for short time regulation of hundreds of years; while, for periods of millions of years, the regulation depends on changes of weathering or burial of fossil sedimentary organic matter.

Surface tension effects, due to the accumulation of minor components in the surface, play an important part in the processing and properties of materials. The ‘tears of wine’ is an example of such processes.

The greatest problem of civilization is the inexorable growth in population. This essay examines the problems in the context of two recent books concerned with the development of birth control pills.

One way that the American government has changed in the past 50 years is through the establishment and expansion of organizations providing technical expertise for decisionmaking. This essay reviews the performance of current structures from the diverse vantage points of elites, bureaucracies, the general public and activist minorities, drawing on studies of the Carnegie Commission on Science, Technology and Government, and the cultural theory of Mary Douglas et al. The apparently mature institutional landscape may well be ripe for change.

Museums have been increasing in number and the attendance at them has grown tremendously in recent years. During the same period the concept of what constitutes a museum has underdone considerable evolution. This article discusses the changing ideas of museums.

At a time when nationalism grows more strident, the role of national museums assumes great importance. National museums encourage not only an understanding of national identity, but also patriotism. While this is natural, it has dangers in that the museum can be used politically to endorse racial and other charged emotions. The great international museums have provided an antidote to such tendencies by providing a universal view of the culture and natural history of the world from the earliest times. Because these museums have important material from other countries they are often attacked as odious relics of colonialism. Rather they should be seen as representative of internationalism and encouraged to collect as widely as possible—within the law. They should not be pressurized into returning material to its country of origin for narrow nationalistic purposes. National museums should themselves collect outside their own national boundaries so that countries can see themselves against the background of other cultures. As nationalism grows, internationalism must be stressed in national museums so that countries may understand each others' culture and points of view.

Archaeological sites can be excellent alternative museums. They need appropriate enclosures and an imaginative arrangement of archaeological objects or replicas.

Habitat dioramas are natural history scenarios which typically feature mounted zoological specimens arranged in a foreground that replicates their native surroundings in the wild. Ideally, the three-dimensional foreground merges imperceptibly into a painted background landscape, creating an illusion—if only for a moment—of atmospheric space and distance. More profoundly, some of the major controversies hidden in the diorama concept are: taxonomic versus ecologic understanding; art versus science; popular education versus scientific documentation; culturally biased perception versus ‘objectivity’; and ‘Omni-max’ versus diorama.