Ans.
Different barriers present in the body prevent entry of disease causing agents or pathogens from entering into body and provide protection against them. These barriers include various physical, chemical, and biological barriers.
Physical barrier include skin and coughing and sneezing. Skin provides first line of defense by preventing entry of pathogens, and coughing and sneezing that expels harmful agents out of the body.
Chemical barriers include lysozyme, acids, and oil secretion. Lysozyme is an enzyme that kills bacteria by targeting their cell wall, while oil and acid prevent microbial growth by providing non-favorable environment for them.
Biological barriers include phagocytes and Langerhans cells. Phagocytes are immune cells that engulf and destroy pathogens and Langerhans cells are antigen-presenting cells that help in elimination of pathogens.
<span>It's because the process is not as organized as we have learned it. We tend to think of intracellular reactions as they're supposed to work. Only thymine is supposed to bond to adenine. Only a specific type of ligand bonds to a certain receptor etc. this type of thinking leaves it hard to imagine what's actually going on. Imagine complete and utter chaos. Enzyme being hit by all the wrong and right molecules many many times per second. Molecules flying off in every which direction and hitting against anything and everything. When we learn about these reactions we tend to think it's ordered based on how specific things are. Not only is an enzyme/protein site made to fit only a specific molecule, it has to be the correct orientation. So even if the right molecules are in the right place hitting against the right enzyme does not mean it will attach, assuming it doesn't approach at the right angle.</span>
B because the prism refracts the light and you see a rainbow effect.
Organisms with more genetic variation are more likely to survive because if something changes in their environments, then they have a larger possibility to survive the changes.
