Some ways in which communicable diseases spread are by: physical contact with an infected person, such as through touch (staphylococcus), sexual intercourse (gonorrhea, HIV), fecal/oral transmission (hepatitis A), or droplets (influenza, TB) travel through the air, such as tuberculosis or measles.
Cell division is simpler in prokaryotes than eukaryotes because prokaryotic cells themselves are simpler. Prokaryotic cells have a single circular chromosome, no nucleus, and few other organelles. Eukaryotic cells, in contrast, have multiple chromosomes contained within a nucleus, and many other organelles.
New disease that affects the younger of a population, shortage of availability of food, new competitor for food, new predator of jaguars (though there arent many of those)
Water treatment is any process that improves the quality of water to make it more acceptable for a specific end- use. The end use may be drinking, industrial water supply, irrigation,river flow maintenance, water recreation or many other uses, including being safely returned to the enviroment