3 . A study has found that elephants possess a sense of smell that is likely the strongest ever identified in a single species, according to a study by Japanese scientists last week.
The African elephant’s genome (基因组) contains the largest number of olfactory receptor (嗅觉感受器) genes—nearly 2, 000—says the study in the journal Genome Research.
Olfactory receptors are aware of smells in the environment.
That means elephants’ sniffers (嗅探器) are five times more powerful than people’s noses, twice that of dogs, and even stronger than the previous known record-holder in the animal kingdom: rats.
“Apparently, an elephant’s nose is not only long but also superior, ”says lead study author Yoshihito Niimura of the University of Tokyo.
Just how these genes work is not well understood, but they likely helped elephants survive and navigate their environment over the ages.
The ability to smell allows creatures to find mates and food—and avoid predators.
The study compared elephant’s olfactory receptor genes to those of 13 other animals, including horses, rabbits, guinea pigs, cows, rodents and chimpanzees.
Primates (灵长类) and people actually had very low numbers of olfactory receptor genes compared to other species, the study found.
“This could be a result of our decreased reliance on smell as our sight improved, ” Niimura says.
1. Why do African elephants have the strongest sense of smell?
| A．Because their noses are very superior. |
| B．Because they have more olfactory receptor genes. |
| C．Because they are very strong. |
| D．Because they have long noses. |
2. Whose sniffer is the most powerful?
| A．Human. | B．Dog. | C．Rat. | D．Elephant. |
3. What makes elephants survive and guide their environment over the years?
| A．Their genes. | B．Their noses. | C．Their legs. | D．Their ears. |
4. Which is NOT the purpose of the ability to smell of the elephants?
| A．To find mates. | B．To have fun. |
| C．To find food. | D．To escape from hunters. |
5. What’s the main idea of the passage?
| A．People find elephants are very useful. |
| B．People like elephants’ noses. |
| C．Elephants possess “superior” sense of smell. |
| D．Elephants are smarter than other animals. |
