Cancerous cells often produce tumor markers as well as its own cancer cells that act as antigens that can be recognized by antigen presenting cells and be presented to natural killer (NK) cell progenitors that are found in the spleen, lymph nodes, thymus, and other lymphoid organs. With malignancy, the production of NK cells will be increased. NK cells works by killing cells that do not have an inhibitory signal (i.e. cancer cells) and preserving cells that do have an inhibitory signal (i.e. normal body cells).
<span>Not only does topsoil erosion lead to loss of soil fertility, it can also cause water pollution. Water pollution is a result of the downpour of the fertilizer chemicals to the water contaminating the water in terms of sulfur content, halogen content, and other possible metals.</span>
The offspring had a smaller range of beak depthsfrom smallest to largestthan their parents (black bars).The overall beak depths of the 1978 offspring population are larger the original 1976 population.In 1978, the offspring population is larger than the initial 1976 population before the drought.<span>The finches that survived the drought (black bars) had offspring with much larger beaks.
</span>n both droughts, smallbeaked medium ground finches had the highest survival rates.In both droughts, largebeaked medium ground finches had the highest survival rates.Both droughts events provided strong natural selection on medium ground finch populations.Both droughts resulted in changes to food sources that favored the survival of some medium ground finches over<span>others.</span>
Fish, reptiles, birds, and mammals have very similar embryos with gill slits and tales, but all but fish get rid of the gills as they mature
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AUGUST 28, 2014 -- What does the Sahara Desert in Africa have to do with hurricanes in the Atlantic, Gulf of Mexico, and Eastern Pacific Ocean? You might think this sounds a little crazy because hurricanes are very wet and deserts are very dry, but if it weren't for this huge, hot, dry region in North Africa, we would see far fewer hurricanes in the United States. The Sahara Desert is massive, covering 10 percent of the continent of Africa. It would be the largest desert on Earth, but based strictly on rainfall amounts, the continent of Antarctica qualifies as a desert and is even larger. Still, rainfall in the Sahara is very infrequent; some areas may not get rain for years and the average total rainfall is less than three inches per year. While not the largest or driest of the deserts, the Sahara has a major influence on weather across the Western Hemisphere.
How a Tropical Storm Starts A-Brewin'
The role the Sahara Desert plays in hurricane development is related to the easterly winds (coming from the east) generated from the differences between the hot, dry desert in north Africa and the cooler, wetter, and forested coastal environment directly south and surrounding the Gulf of Guinea in west Africa. The result is a strong area of high altitude winds commonly called the African Easterly Jet. If these winds were constant, we would also experience fewer hurricanes. However, the African Easterly Jet is unstable, resulting in undulations in a north-south direction, often forming a corresponding north to south trough, or wave, that moves westward off the West African Coast. When these waves of air have enough moisture, lift, and instability, they readily form clusters of thunderstorms, sometimes becoming correlated with a center of air circulation. When this happens, a tropical cyclone may form as the areas of disturbed weather move westward across the Atlantic. Throughout most of the year, these waves typically form every two to three days in a region near Cape Verde (due west of Africa), but it is the summer to early fall when conditions can become favorable for tropical cyclone development. Not all hurricanes that form in the Atlantic originate near Cape Verde, but this has been the case for most of the major hurricanes that have impacted the continental United States.
