An extrasolar planet or exoplanet is a planet orbiting a star (or remnant of a
star) beyond our Solar System. As of autumn 2007, about 250 exoplanets had been
discovered around 220 different stars, including nearly two dozen multiple planet
systems. No less than five exoplanets have been discovered orbiting the star 55
Cancri; one of the planets has nearly four times the mass of Jupiter, another is
comparable with Jupiter in mass, two are slightly less massive than Saturn, while
the innermost planet has a mass similar to that of Uranus....
The same amount of water has been present on our planet for about 4 billion years, since shortly after the Earth was formed. Since then it has cycled through evaporation, condensation, precipitation and surface runoff multiple times. Water scarcity as an abiotic factor ranging from moderate to severe stress levels, accompanied by loss of moisture in the soil, is extremely hard for most organisms to cope with, particularly terrestrial plants and their food-chain dependents.
Water contamination weakens or destroys natural
ecosystems that support human health, food production,
and biodiversity. Studies have estimated that the value of
ecosystem services is double the gross national product of
the global economy, and the role of freshwater ecosystems
in purifying water and assimilating wastes has been
valued at US$ 400 billion (2008$) (Costanza et al. 1997).
Freshwater ecosystems are among the most degraded on
the planet, and have suffered proportionately greater species
and habitat losses than terrestrial or marine ecosystems
(Revenga et al. 2000).
Flowering plants now dominate the terrestrial ecosystems of the planet, and there are
good reasons for supposing that the flower itself has been a major contributing factor
to the spread of the Angiosperms. Although the Angiosperm flower is based on four
whorls of organs – petals, sepal, stamens and carpels – the 300 000 odd species exhibit
a huge array of different floral morphologies. Consider, e.g., the humble periwinkle
flower and contrast it with the complex passion flower.