Since pathogens are easily passed from person to person, they need large populations to spread and survive. If they did not have a large population, the pathogens would die out.
Answer:
To allow for the passage of light in a microscope.
3. PR.
It stands for per rectum
It works according to the guidelines set by the authorities
Gradually, came sushi and karate from Japan, and delicatessens from Italy and Germany, and 18 speed bikes from several European countries. Chinese food cooked and served by Chinese Canadians, not all of it authentic Cantonese or Szechuan or whatever, got steadily more popular as I grew up. And pizza. And espresso coffee. And holopchi from Ukraine and pyrogies from Poland. French perfumes. Mexican leather goods. Smorgasbords. All of these were virtually unknown to me when I was in grade 1, but were common by the time I was in university. I could go on and on. Other countries are going through similar experiences, some more slowly that Canada has, some actually a bit faster.
Then there are the subtler things, the ways of thinking and living. Yoga, tai-chi, zen, existentialism, deconstructionism, post-modernism, Marxism, supply side economics and on and on.
This world is a globalized one now, and it has been getting gradually more and more so for a long time. There is no going back. We learn to live together on Starship Earth or we exterminate ourselves.
Answer:
The digestive tract runs from the mouth to the anus. It looks like a lengthy muscular tube with digestive organs connected along the way, up to 10 meters long. The large intestine and, to a lesser extent, the remainder of the digestive system contain a significant reservoir of microorganisms, such as bacteria.
