Monday, January 22, 2007
Terrestrial weather
On Earth, regularly happening weather phenomena include such things as wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes and ice storms. Almost all standard weather phenomena on Earth occur in the troposphere. Weather does occur in the stratosphere and does affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.
The Earth's atmosphere is one large chaotic system so small changes to one part can have large effects elsewhere. This makes it very difficult to exactly predict short term weather changes more than a few days in advance, though weather forecasters are continually working to extend this limit through the science of the study of weather, Meteorology. Chaos theory explains that there are an infinite number of variables which affect the weather. The slightest variation in the motion of any molecule in the air influences the atmospheric situation. The slightest difference could affect the troposphere sufficiently to lead to utterly different conditions. Thus it will never be possible to forecast perfectly
Thursday, January 11, 2007
Multicellular organism
Multicellular organisms are those organisms consisting of more than one cell, and having differentiated cells that achieve specialized functions. Most life that can be seen with the naked eye is multicellular, as are all animals and plants. A group of similarly differentiated cells performing a function in a multicellular organism is known as a tissue. Although some single-celled organisms, such as mycobacteria, have differentiated cells, the differentiation is less dramatic than that usually found in multicellular organisms.
A multicellular organism can work on a number of levels. For instance, a sponge works on a cellular level as the different cells are almost like many separate organisms co-operating jointly for a common goal. This is illustrated by the fact you can put a sponge in a blender and the cells of the sponge will aggregate again to form another sponge. They have no tissues, organs or organ systems which require a higher level of organization. More advanced organisms such as jellyfish, coral and sea anemones work on a tissue level of organization, as their cells can aggregate to form different tissues. For instance, a jellyfish has an outer epidermis and an inner gastrodermis, an example of different tissues to serve a different purpose.
