托福听力背景知识:SEA

托福听力背景知识:SEA

　SEA

　　The distribution of marine organisms depends on the chemical and physical properties of seawater (temperature, salinity, and dissolved nutrients), on ocean currents (which carry oxygen to subsurface waters and disperse nutrients, wastes, spores, eggs, larvae, and plankton), and on penetration of light. Photosynthetic organisms (plants, algae, and cyanobacteria), the primary sources of food, exist only in the photic, or euphotic, zone (to a depth of about 300 ft/90 m), where light is sufficient for photosynthesis.

　　Ant

　　Typically they include three castes: winged, fertile females, or queens; wingless, infertile females, or workers; and winged males. Those ordinarily seen are workers.

　　Whenever a generation of queens and males matures it leaves on a mating flight; shortly afterward the males die, and each fecundated queen returns to earth to establish a new colony. The queen then bites off or scrapes off her wings, excavates a chamber, and proceeds to lay eggs for the rest of her life (up to 15 years), fertilizing most of them with stored sperm.

　　Females develop from fertilized and males from unfertilized eggs. The females become queens or workers, depending on the type of nutrition they receive. The first-generation larvae are fed by the queen with her saliva; all develop into workers, which enlarge the nest and care for the queen and the later generations

　　Leaf-cutter Ant’s Feeding Habits: Cultivation is practiced by certain ants that feed on fungi grown in the nest. Some of these, called leaf-cutter, or parasol, ants, carry large pieces of leaf to the nest, where the macerated leaf tissue is used as a growth medium for the fungus. Most leaf cutters are tropical, but the Texas leaf-cutting ant is a serious crop pest in North America.

　　Ant Hill: All species show some degree of social organization; many species nest in a system of tunnels, or galleries, in the soil, often under a dome, or hill, of excavated earth, sand, or debris. Mound-building ants may construct hills up to 5 ft (1.5 m) high. Other species nest in cavities in dead wood, in living plant tissue, or in papery nests attached to twigs or rocks; some invade buildings or ships.

　　在寒溫帶的森林地區，地底的溫度一般都比較低，因此木蟻便將大部分的蟻巢建築在地面上，一方面可減少因地面潮濕所帶來的寒氣，另一方面也能增加陽光照射的面積。