Arctic Sea Ice reaches Record Lows
Abstract: Arctic sea ice during the 2007 melt season plummeted to the lowest levels since satellite measurements began in 1979.

Source: National Snow and Ice Data Centre (NSIDC) www.nsidc.org


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A plant that lives for two years, generally germinating and producing leaves in the first year, to flower and produce seeds (and then die) in the second year.

The offspring of a cross between individuals of different genotypes. Hybrids may be intraspecific (parents from the same species) of interspecific (parents from different species). Most hybrid plants and animals are infertile (sterile).

The growth of a plant or part of plant in a particular direction as a result of an outside stimulus. Growth toward the stimulus is positive tropism; away from it is negative tropism. For example, in geotropism (gravitropism) gravity acts to make roots grow downward whereas phototropism makes shoots grow toward the light.

A logarithmic scale numbered from 0 to 14 for expressing acidity or alkalinity. A pH of 7.0 indicates neutrality, below 7 is acidic, and above 7 is alkaline.

The study of the plant and animal life which has left its records as fossils in the stratigraphic record – the layers of rock and sediment laid down over geological time. It includes analyses of plant and animal from, growth and development, of evolutionary changes; and of the relationship of all these factors to environmental variations with time.

A crescent shaped sand dune in which the convex face lies upwind and the concave face downwind.

Either of the two points where the ecliptic crosses the celestial equator. The Sun reaches these positions on or about 21 March (vernal equinox in the Northern Hemisphere) and 21 September (autumnal equinox). On these days the day and night are of equal length throughout the world, 12 hours each.

An organic chemical compound consisting predominantly of hydrogen and carbon. Coal, oil and natural gas are three commonly occurring hydrocarbons.

The process by which oceanic crust is thrust over the leading edge of a continental plate as huge slabs, in contrast with the more usual process in which the crust is subducted beneath the edge.

An enclosed flat basin in a desert, usually occupied in part by an ephemeral lake or lakes, often with salt encrustations.

The study of the ways in which species can be preserved within their habitats. There are three main approaches to conservation : by legislation against the sale of their produce; by setting aside habitats as managed national parks and placing the threatened species into captive breeding programmes.

Describes the deepest part of the ocean, below about 2,000 m (6,500 feet), and the organisms living there.

The dry, eroded and uneven landscape where the scanty rainfall results in runoff that causes rills and gullies. There is little or no vegetation in badland areas.

The upper level of mature forest or woodland formed by the highest branches and foliage of trees. The level below is shrub level.