TUGAS MATAKULIAH KKH II

Kerjakan tugas terjemahan ini dan ditumpuk hari Jumat tgl.20 Maret 2009.

CHARACTRISTIC.
The chordates are bilaterally symmetrical, with three germ layers, a segmented body, complete digestive tract, and well-developed coelom. Three outstanding characteristics distinguish them from other animals- a single dorsal tubular nerve cord, the notochord, and gill slits in the pharynx.
These features all from in the early embryo of a chordate, and they persist, are altered, or may disappear in the adult.
The notochord is the first supporting structure of the chordate body, in the early embryo it forms above the primitive gut as a slender rod of cells containing a gelatinous matrix and is sheathed in fibrous connective tissu. In tunicates, it is present in the tail and only during the larval stages. In the lancelets and higher forms, it extends almost the length of the body. it persists throughout life as the main axial support in lancelets and lampreys, but in the fishes to mammals is later surrounded or replaced by the vertebral column.
The nerve cord forms on the dorsal surface of the early embryo soon after the gastrula stage. In folding of the ectoderm produces the hollow tubular cord that lies above the notochord. The anterior end becomes enlarged as simple "cerebral vesicle" in tunicate larvae and in lancelets, but in all vertebrates it thickens and differentiates as the brain, to becomes progressively more complex in higher forms. In tunicates the cord and vesicle degenerate to a ganglion at metamorphosis. From the lampreys onward the nerve cord later becomes surrounded ny neural arches of the vertebrae that protect it from injuy, and the brain is enclosed by a brain box, or cranium.
Paired gill pouches develop on the sides of the embryonic pharynx (digestive tract). Each is formed by an aotpocketing of endoderm in the pharynx and a corresponding inpocketing of ectoderm on the outside of the body; the intervening wall breaks through to form a gill slit. The characteristic development is seen in a shark or fish in which each slit is margined bt many slender filaments containing blood vessels, to form a gill. Water containing dissolved oxygen passes into the mouth and pharynx and out over the filaments, where the blood gives up its carbon dioxide acquires oxygen, so that the gill servesthe process of external respiration. All aquatic chordates from tunicates to amphibians respire by gills. In amphibians which transform from aquatic larvae to air-breathing adults, the gills are lost at metamorphosis. The reptiles, birds, and mammals all develop several pairs of gill pouches during early embryonic life, but they are never functional and soon close; all these animals later acquire lungs for breathing air when they hatch or are born.

Ilmu Pengetahuan Lingkungan

Kerjakan Tugas terjemahan (mk IPL) ini dan ditumpuk hari Kamis 26 Februari 09

Global Issues.

In temporal context human community began to exert a major influence on global environments with the onset of permanen agriculture 10 000 years ago. Although this was not the "revolution" that it has often been called,as it grew out ofsophisticated hunter-gatherer strategies,it created environmental and cultural changes of an unprecedented nature. It developed in tandem with permanent settlement, facilitated the division of labour and marked the emergence of society as a significant force on the landscape. The onset of permanent agriculture also marked the first stage of global deforestation, a process that began in localized areas but which is now a global problem. Deforetstation together with fosisil fuel energy production are among the most important issues of the 1990s, not least because of their efffect on global climate via their impact on the biogeochemical cycle of carbon. Global warming could influence all aspects of of environmental and cultural processes, although it remains controversial because, as yet, there is no definitive evidence that it is becoming reality. Deforetstation is also linked with spesies extinction and declining gene pools; both represent the deminution of resources, the potential of which has not been fully realized. What is perhaps most disconcerting about the current deforestation of tropical forest is the fact that many of the agricultural systems replacing them are also failing. For example, large-scale ranching ranching in Central and South America has, in general, not provided the salvation to national economies that it initially promised.

Population growth and demographic trends are also global issues. Burgeoning population in the developing world and changing demographic patterns in the developed world, are both a matter for concern. Increasing populations inevitably mean greater pressure on resources, but the relationship with environmental damage is complex. Individuals in the developing world exert different pressures on resources than do those in the developed world, where income, age and family structures will influence environmental impacts in the 1990s. At the sama time there are scientific and technologycal developments that may offset some of the problems that affect humanity. Biotechnology and genetic engineering provide new opportunities for agriculture which, in principle, could lead to the tailoring of crops to the environment rather than vice versa, which has been the traditional approach. Biotechnology is providing new ways to treat watste, including the recycleing of useful materials. In the longer term such developments should contribute to sustainable resource use.