ÜDS-Fen 2011-1 Soru=59

One learns from the passage that ultraviolet radiation from the sun —.

Ozone molecules in the stratosphere absorb incoming solar ultraviolet radiation. With depletion of the ozone layer, more ultraviolet radiation reaches the Earth's surface. Excessive exposure to ultraviolet radiation is linked to a number of human health problems. These include cataracts, skin cancer, and a weakened immune system. However, this is not the end of the list. Much scientific evidence also documents crop damage from exposure to high levels of ultraviolet radiation. Moreover, biologists are seriously concerned that the ozone hole over Antarctica could damage plankton that forms the base of the food web for the surrounding ocean. A 1992 study confirmed that increased ultraviolet radiation is penetrating surface waters around Antarctica. Tnis extra amount o* ultraviolet radiat on is negatively affecting Antarctic phytoplankton. The productivity of Antarctic phytoplankton has declined by at least 6% to 12% as a result. If the productivity of phytoplankton continues to decline, the complex food web of Antarctica, which includes fishes, seals, penguins, whales, and vast populations of birds, will beat risk.