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Question 1 of 25
In the twentieth century, electron microscopes have provided direct views of viruses and minuscule surface structures.
Question 2 of 25
2. Unlike conventional electron microscopy, x-ray microscopy enablesspecimens to be kept in air and in water,
Question 3 of 25
3. Because of the wavelength of the x-rays used, soft x-ray microscopes will never match the highest resolution possible with electron microscopes. Rather, their special properties will make possible investigations that will complement those performed with light- and electron-based instruments.
Question 4 of 25
4. A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals vegetations, or materials adversely.
Question 5 of 25
5. As the Earth developed, the concentrations of these pollutants were altered by various chemical reactions.
Question 6 of 25
7. The result is an increased concentration of noxious chemicals in the air.
Question 7 of 25
8. Sulfur dioxide has detectable health effects at 0.08 parts per million (ppm), which is about 400 times its natural level
Question 8 of 25
9. Many ants forage across the countryside in large numbers and undertake mass migrations
Question 9 of 25
9. As a worker ant returns home after finding a source of food, it marks the route by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone.
Question 10 of 25
10. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space
Question 11 of 25
11. In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself
Question 12 of 25
12. Europa was transformed-in our perception, at least-into one of the solar system’s most intriguing worlds.
Question 13 of 25
13. The tides on Europa pull and relax in an endless cycle.
Question 14 of 25
14. When the putrefied material is examined microscopically, it is found to be teeming with bacteria.
Question 15 of 25
15. Pasteur showed that structures present in air closely resemble the. microorganisms seen in putrefying materials
Question 16 of 25
16. He postulated that these bodies are constantly being deposited on all objects.
Question 17 of 25
17. The origins of nest-building remain obscure, but current observation of nest-building activities provide evidence of their evolution.
Question 18 of 25
18. Birds also display remarkable behavior in collecting building materials.
Question 19 of 25
19. It is only relative to their size and most birds are able to carry an extra load of just over twenty percent of their body weight.
Question 20 of 25
20. Other species may become better adapted to an Environment, resulting in competition and, ultimately, in the death of a species.
Question 21 of 25
21. One of the best-known examples of mass extinction occurred 65 million years ago with the demise of dinosaurs and many other forms of life.
Question 22 of 25
22. One interesting, and controversial, finding is that extinctions during the past 250 Million years have tended to be more intense every 26 million years.
Question 23 of 25
23. One researcher observed babies and their mothers in six diverse cultures and found that, in all six languages, the mothers used simplified syntax, short utterances and nonsense sounds
Question 24 of 25
24. Other investigators have noted that when mothers talk to babies who are only a few months old, they exaggerate the pitch, loudness, and intensity of their words.
Question 25 of 25
25. They also exaggerate their facial expressions, hold vowels longer, and emphasize certain words.