<span>The immune system is the body's natural defense mechanism against organisms that can cause infection.There are three types of mechanisms:
1. Cellular :</span><span> refers to the recognition and/or killing of virus and virus-infected cells by leukocytes and the production of different soluble factors (cytokines) by these cells when stimulated by virus or virus-infected cells
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2. Structural: </span>barriers and the immune system defend the body<span> against organisms that can cause infection. </span>Natural<span> barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid.
3. Chemical: </span><span>Some of these include the low pH of the stomach, which inhibits the growth of pathogens; blood proteins that bind and disrupt bacterial cell membranes; and the process of urination, which flushes pathogens from the urinary tract.
</span><span>antibodies - chemical
tissues lining hollow organs - cellular
phagocytes - cellular
skin - structural
antigen - chemical
leukocytes - cellular</span>
There's a shrink to the upward thrust of a sand dune. they do no longer stay interior a similar place yet crawl downwind and are replaced by capacity of latest ones. at last, they attain the factor the place they'd be stabilized by capacity of plant existence. Barrier islands are formed a similar way, different than by capacity of water, somewhat than wind.
Cell division starts with one parent cell and finishes with two cells. Each daughter cell has the same DNA as the parent cell
Since Lithium has one valence electron that means it needs to lose it to form a stable structure. That means it's valence is equal to one. Oxygen has six atoms, in order to form a stable octet structure it needs to accept 2 electrons, therefore it's valence is 2.
Therefore two Lithium atoms bond with one oxygen atom to form Li2O
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Paleontologists study fossils so that we can understand the evolution's from past species to the current ones. It also opens a window to discovering exactly how long earth has been around by finding out the age of the fossil itself. Though paleontology has been in the decline recently, and i'm sure we haven't found out all we need to know from these fossils.
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