When we are young, we learn that
tigers and sharks are dangerous animals. We might be scared of them because
they are big and powerful. As we get older, however, we learn that sometimes
the most dangerous animals are also the smallest animals. In fact, the animal
that kills the most people every year is one that you have probably killed
yourself many times: the mosquito.
While it may seem that all
mosquitoes are biters, this is not actually the case. Male mosquitoes eat plant
nectar. One the other hand, female mosquitoes feed on animal blood. They need
this blood to live and produce eggs. When a female mosquito bites a human
being, it transmits a small amount of saliva into the blood. The saliva may or
may not contain a deadly disease. The result of the bite can be as minor as an
itchy bump or as serious as death.
Because a mosquito can bite many
people in the course of its life, it can carry diseases from one person to
another very easily. Two of the most deadly diseases carried by mosquitoes are
malaria and yellow fever. More than 700 million people become sick from these
diseases every year. At least 2 million of these people will die from these
diseases.
Many scientists are working on
safer and better ways to kill mosquitoes, but so far, there is no sure way to
protect everyone in the world from their deadly bites. Mosquito nests can be
placed over beds to protect people against being bitten. These nets help people
stay safe at night, but they do not kill any mosquitoes. Mosquitoes have many
natural enemies like bats, birds, dragonflies, and certain kinds of fish.
Bringing more of these animals into places where mosquitoes live might help to
cut down the amount of mosquitoes in that area. This is a natural solution, but
is does not always work very well. Mosquitoes can also be killed with poisons
or sprays. Even though these sprays kill mosquitoes, they may also harm other
plants or animals.
Although mosquitoes may not seem
as scary as larger, more powerful animals, they are far more dangerous to human
beings. But things are changing. It is highly likely that one day scientists
will find a way to keep everyone safe from mosquitoes and the diseases they
carry.
Which of the following best
summarizes the information in paragraph 4?
Fleas are perfectly designed by
nature to feast on anything containing blood. Like a shark in the water or a
wolf in the woods, fleas are ideally equipped to do what they do, making them
very difficult to defeat. The bodies of these tiny parasites are extremely
hardy and well-suited for their job.
A flea has a very hard exoskeleton,
which means the body is covered by a tough, tile-like plate called a sclerite.
Because of these plates, fleas are almost impossible to squish. The
exoskeletons of fleas are also waterproof of fleas are also waterproof and shock
resistant, and therefore fleas are highly resistant to the sprays and chemicals
used to kill them.
Little spines are attached to his
plate. The spine the flea scurries through an animal’s fur in – search of
grooming pet tries to pull a flea off through the hair coat, these spines will
extend and stick to the fur like Velcro.
Fleas are some of the best jumpers
in the natural world. A flea can jump seven inches, or 150 times its own
length, either vertically or horizontally. An equivalent jump for a person
would be 555 feet, the height of the Washington Monument. Fleas can jump 30,000
times in a row without stopping, and they are able to accelerate through the
air at an incredibly high rate – a rate which is over ten times what humans can
withstand in an airplane.
Fleas have very long rear legs with
huge thigh muscles and multiple joints. When they get ready to jump. They fold their
long legs up and crouch like a runner on a staring block. Several of their
joints contain a protein called resilin, which helps catapult fleas into the
air as they jump, similar to the way a rubber band provides momentum to a
slingshot. Outward facing claws on the bottom of their legs grip anything they
touch when they land.
The adult female flea mates after
her first blood meal and begins producing eggs in just 1 to 2 days. One flea
can lay up to 50 eggs in one day and over 2,000 in her lifetime. Flea eggs can
be seen with the naked eye, but they are about the size of a grain of salt. Shortly
after being laid, the eggs begin to transform into cocoons. In the cocoon
state, fleas are fully developed adults, and will hatch immediately if
conditions are favorable. Fleas can detect warmth, movement, and carbon dioxide
in exhaled breath, and these three factors stimulate them to emerge as new
adults. If the flea does not detect appropriate conditions, it can remain
dormant in the cocoon state for extended periods. Under ideal conditions, the
entire life cycle may only take 3 weeks, so in no time at all, pets and homes
can become infested.
Because of these characteristics,
fleas are intimidating opponents. The best way to control fleas, therefore, is
to take steps to prevent an infestation from ever occurring.
The primary purpose of the passage
is to
The history of civilization shows how man
always has to choose between making the right and wrong use of the discoveries
of science. This has never been more true than in our own age. In a brief
period amazing discoveries have been made and applied to practical purpose.
It would be ungrateful not to recognize how
immense are the boons which science has given to mankind. It has brought within
the reach of multitudes benefits and advantages which only a short time ago
where the privilege of the few. It has shown how malnutrition, hunger and
disease can be overcome. It has not only
lengthened life but it has depended to his quality. Fields of knowledge,
experience and recreation open in the past only to few, have been thrown open
to million. Through the work of science the ordinary man today has been given
the opportunity of a longer and fuller life than was ever possible to his
grandparents.
Amazing discoveries of science have been made:
The history of the modern world is a
record of highly varied activity, of incessant change, and of astonishing
achievement. The lives of men have, during the last few centuries, increasingly
diversified, their powers have greatly multiplied, their powers have greatly
multiplied, their horizon been enormously enlarged. New interests have arisen
in rich profusion to absorb attention and to provoke exertion. New aspirations
and new emotions have come to move the soul of men. Amid all the bewildering phenomena,
interest, in particular, has stood out in clear and growing pre-eminence, has expressed
itself in a multitude of ways and with an emphasis more and more pronounced,
namely, the determination of the race to gain a larger measure of freedom than
it has ever known before, freedom in the life of the intellect and spirit,
freedom in the realm of government and law, freedom in the sphere of economic
and social relationship. A passion that has prevailed so widely, that has transformed
the world so greatly, and is still transforming it, is one that surely merits
study and abundantly rewards it, its operations constitute the very pith and
marrow of modem history.
Not that this passion was unknown to
the long ages that proceeded the modern periods. The ancient Hebrews, the
ancient Greeks and Roman blazed the was leaving behind them a precious heritage
of accomplishments and suggestions and the men who were responsible for the
Renaissance of the fifteenth century and the Reformation of the sixteen century
contributed their imperishable part to this slow and difficult emancipation of
the human race. But it is in modern times the pace and vigour, the scope and
sweep of this liberal movement have so increased unquestionably as to dominate
the age, particularly the last three centuries that have registered great
triumphs of spirit.
In what period of the history of the
world have the lives of men become increasingly diversified?
