Today, piranhas inhabit the freshwaters of South America from the Orinoco River Basin in Venezuela up to the Paraná River in Argentina. Though estimates vary, around 30 species inhabit the lakes and rivers of South America today. Fossil evidence puts piranha ancestors in the continent’s rivers 25 million years ago, but modern piranha genera may have only been around for 1.8 million years.
Piranhas are normally about 14 to 26 cm long (5.5 to 10.25 in), although some specimens have been reported to be up to 43 cm (17.0 in) in length.
Piranhas are known for their razor-sharp teeth and relentless bite. (The word piranha literally translates to “tooth fish” in the Brazilian language Tupí.) Adults have a single row of interlocking teeth lining the jaw. True piranhas have tricuspid teeth, with a more pronounced middle cuspid or crown, about 4 millimeters tall.
The shape of a piranha’s tooth is frequently compared to that of a blade and is clearly adapted to suit their meat-eating diet. The actual tooth enamel structure is similar to that of sharks.
All piranhas have a single row of sharp teeth in both jaws; the teeth are tightly packed and interlocking (via small cusps) and are used for rapid puncture and shearing. Individual teeth are typically broadly triangular, pointed, and blade-like (flat in profile). The variation in the number of cusps is minor; in most species, the teeth are tricuspid with a larger middle cusp which makes the individual teeth appear markedly triangular. The exception is Pygopristis, which has pentacuspid teeth and a middle cusp usually only slightly larger than the other cusps.
Sources: http://en.wikipedia.org/wiki/Piranha & http://www.smithsonianmag.com/science-nature/14-fun-facts-about-piranhas.
1. The text above is categorized as a report because … .
A. it tells the topic in great details
B. it focuses on one specific object
C. it describes in general a classification of thing
D. it tells in general about one specific object
E. it uses the simple present tense
2. According to the text, piranhas are known for their … .
A. soft meat
B. hard teeth
C. appetite for food
D. powerful bite
E. strong bones
3. The text says that piranhas live in … .
B. sea waters
D. small ponds
E. shallow waters
4. The presence of piranhas may be traced back to as far back as … .
A. 1.8 million years ago
B. 2 million years ago
C. 20 million years ago
D. 25 million years ago
E. 22 million years ago
5. Why does the writer compare a piranha tooth to a blade and that of a shark?
A. the writer wants to tell that piranhas eat meat
B. the writer wants to show how strong and sharp piranhas’ teeth are
C. the writer wants to emphasize how close piranhas and sharks are
D. the writer wants to suggest that piranhas like to tear their preys
E. the writer wants to describe the sharpness and strength of their teeth in details
6. What does the text suggest about the number of piranhas’ teeth?
A. in general there is a great disparity in number
B. in general they nearly have the same number of teeth
C. there is a great variation in number between species
D. one species defintely has much more teeth than another
E. experts don’t know exactly how many teeth piranhas have
7. How is a piranha tooth similar to a blade?
A. it is flat
B. it is pointed
C. it is small
D. it is round
E. it is large