tailieunhanh - EARTH Phần 9

Trái Đất cung cấp những tài nguyên có thể được con người sử dụng cho nhiều mục đích. Một vài trong số đó là những nguồn tài nguyên không tái tạo và rất khó tạo ra trong một thời gian ngắn như các loại nhiên liệu hóa thạch. | r-Ịíỳt Giant clam Potato cod 103 Indiat Oceai Gray reef sharks 1 REEF FISH The total weight of fish or biomass on a coral reef is not large compared with some other marine habitats but there is an amazing diversity of species. T They have evolved because there are so many different ways to make a living on the reef. Some such as parrotfish eat the coral itself. Others nibble at algae catch plankton or prey on each other. 4 INVERTEBRATES All kinds of colorful invertebrates live on coral reefs including delicate prawns flamboyant sea slugs and deadly venomous cone shells. The biggest is the giant clam which like corals has masses of photosynthetic organisms called zooxanthellae living within its tissues. These provide the clam with sugar in exchange for nutrients that the clam obtains by filtering plankton from the water. Brightly colored sea slugs nibble at encrusting animals on the reef o CORAL ISLANDS The tropical southwest Pacific is dotted with tens of thousands of coral islands. Most are too small to have names and rise only a nọetre or two above the waves but many are crowned with groves of coconut palm and other trees. These provide nesting sites for seabirds while the beaches are used by breeding sea turtles. A threats AR_R4 F 20-29 C . If the water topical ston corals thrivedrtsea gets warme r thanKnown as aP bleaching3his is posingI an and turn white often withfatal resu t _ n . ean temperatures r se increasing threattocora ofdhoms starfish. t a . a coralheater that can multiply rapidly and . f 4 destroy large areas of coral. Ilk j Ẳ Crown-of-thorns starfish WETLANDS Cattle egret 104 CYPRESS SWAMP Most trees cannot survive in waterlogged conditions but some species like the American bald cypress have special knee roots that gather vital oxygen from above the water. They grow in flooded cypress swamps in the subtropical southern United States famous for the rare beautiful orchids that take root on the tree branches. A MARSH AND FEN Low-lying waterlogged .