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 and shock resistant, and therefore fleas are highly resistant to the sprays and chemicals used to kill them.
Little spines are attached to this plate. The spines lie flat against the flea’s thin, narrow body as the flea scurries through an animal’s fur in search of food. However, if anything (like fingers or a self 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 starting 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.
Questions
1) The primary purpose of the passage is to
A. educate the reader about the physical characteristics of fleas
B. compare fleas to other members of the animal kingdom
C. relate the problems that can result from a flea infestation
D. explain why a flea infestation is hard to get rid of
2) The author’s tone in the passage is best described as
A. concerned
B. passionate
C. informative
D. opinionated
3) According to the passage, fleas are resistant to sprays and chemicals because they
A. have waterproof sclerites
B. are excellent jumpers
C. reproduce very rapidly
D. can stick to fur like Velcro
4) Fleas are difficult to squish because they have
I. sclerites
II. tough spines
III. resilin in their joints
A. I only
B. I and II only
C. II and III only
D. I, II, and III
5) According to the passage, which of the following statements is true?
A. Fleas extend their little spines if threatened.
B. Fleas have the ability to jump higher than humans.
C. Humans can jump higher if they consume foods containing resilin.
D. The resilin found in fleas is used to make rubber bands.
6) According to the passage, fleas are able to jump
I. with a high rate of acceleration
II. up and down and from side to side
III. because the blood they eat contains resilin
A. I only
B. I and II only
C. II and III only
D. I, II, and III
7) Based on information in the passage, the reader can understand that
A. fleas will die without access to blood
B. fleas survive at a higher rate in outdoor habitats
C. fleas will die after they produce 2,000 eggs
D. newly hatched fleas are the size of a grain of salt
8) The author mentions the Washington Monument in order to
A. estimate the extreme distance that a flea is able to jump
B. illustrate a comparison made between fleas and humans
C. clarify a point made regarding fleas and acceleration
D. demonstrate the superiority of fleas over humans
9) It can be inferred that fleas will emerge from eggs as adults
A. when they outgrow the cocoon
B. after a period of 3 weeks
C. when they sense there is access to blood
D. if there is too much carbon dioxide in the cocoon
10) Using the information in the passage as a guide, it can be concluded that
A. humans do not possess the physical characteristics of the flea because they have no use for them
B. humans do not pay much attention to fleas because they do not pose a serious threat
C. fleas have many physical advantages, although these are outweighed by their many disadvantages
D. fleas are designed in such a way as to give them unique physical advantages in life