精选
0308托福试题
阅读（55minutes） Question 1-11
If food is allowed to stand for some time, it putrefies .When the putrefied material
is examined microscopically ,it is found to be teeming with bacteria. Where do these
bacteria come from , since they are not seen in fresh food? Even until the mid-nineteenth
century, many people believed that such microorganisms originated by spontaneous
(5 ) generation ,a hypothetical process by which living organisms develop from nonliving matter.
The most powerful opponent of the theory of spontaneous generation was the French chemist and microbiologist Louis Pasteur(1822-1895).Pasteur showed that structures
present in air closely resemble the microorganisms seen in putrefying materials .He did
(10) this by passing air through guncotton filters, the fibers of which stop solid particles. After
the guncotton was dissolved in a mixture of alcohol and ether, the particles that it had
trapped fell to the bottom of the liquid and were examined on a microscope slide .Pasteur
found that in ordinary air these exists a variety of solid structures ranging in size from
0.01 mm to more than 1.0 mm .Many of these bodies resembled the reproductive
(15)structures of common molds, single-celled animals, and various other microbial cells .
As many as 20 to 30 of them were found in fifteen
欢迎下载
精选
liters of ordinary air ,and they could
not be distinguished from the organisms found in much larger numbers in putrefying materials .Pasteur concluded that the organisms found in putrefying materials originated
from the organized bodies present in the air .He postulated that these bodies are constantly (20)being deposited on all objects.
Pasteur showed that if a nutrient solution was sealed in a glass flask and heated to
boiling to destroy all the living organisms contaminating it, it never putrefied .The proponents of spontaneous generation declared that fresh air was necessary for
spontaneous generation and that the air inside the sealed flask was affected in some way
(25)by heating so that it would no longer support spontaneous generation. Pasteur constructed a swan-necked flask in which putrefying materials could he heated to boiling, but air
could reenter. The bends in the neck prevented microorganisms from getting in the flask.. Material sterilized in such a flask did not putrefy.
1,What does the passage mainly discuss?
(a)Pasteur’s influence on the development of the microscope.
(b)The origin of the theory of spontaneous generation . (c)The effects of pasteurization on food.
(d)Pasteur’s argument against the theory of spontaneous generation .
2,The phrase “teeming with ”in line 2 is closest in meaning to (a)full of
欢迎下载
精选
(b)developing into (c)resistant to (d)hurt by
3,Which of the following questions did the theory of spontaneous generation attempt to answer?
(a)What is the origin of the living organisms are seen on some food?
(b)How many types of organisms can be found on food? (c)What is the most effective way to prepare living organisms for microscopic examination?
(d)How long can food stand before it putrefies?
4,The word “resemble” in line 9 is closest in meaning to
(a)benefit from
(b)appear similar to (c)join together with (d)grow from
5,The purpose of the “guncotton” mentioned in paragraph 2 was to
(a)trap particles for analysis
(b)slow the process of putrefaction
(c)increase the airflow to the microscopic slide (d)aid the mixing of alcohol and ether
6,The author mention “1.0mm”in line 14 in describing the
(a)thickness of a layer of organisms that was deposited on an object
(b)diameter of the fibers that were in the guncotton filters
(c)thickness of the microscope slides that were used (d)size of the particles that that were collected
欢迎下载