Fleas
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1
READTHEORY
Name________________
Date________________ ii ii Level 7
Read the passage. Then answer the question
Fleas are perfectly designed by nature to feast on anything containing blood. Like a shark in the below. 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 selfgrooming 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
1
READTHEORY
Name________________
Date________________ ii ii Level 7
Read the passage. Then answer the question
Fleas are perfectly designed by nature to feast on anything containing blood. Like a shark in the below. 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 selfgrooming 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