Question

FATAL ATTRACTION

1. Rats have evolved a strong, innate aversion to the smells of their predators. Healthy rats-even those bred for hundreds of generations in the laboratory-show distinct anxiety around feline odors. When the amoebic parasite 'Toxoplasma gondii' gets into their brains, however, many of the rodents seem to lose their fear.

2. Zoologist Manuel Berdoy, epidemiologist Joanne Webster, and colleagues at the University of Oxford have studied the life cycle of 'T. gondii' to test the hypothesis that the parasite manipulates the behavior of its intermediate host, the rat, to reach its ultimate target, the cat. The researchers infected captive rats with oocysts of the parasite and then placed them in large outdoor pens containing both cat and rabbit urine. Uninfected rats tended to shun the cat-scented areas, while the parasitized rats became substantially less afraid. With their fear of felines diminished, parasitized rats may become uninhibited about approaching their arch predators, with the predictable result of ending up as dinner.

3. Although all mammals are susceptible to infection by 'T. gondii', the amoebas can reproduce only within members of the cat family. Once 'T. gondii' has bred in the brain of a cat that has ingested an infected rat, the parasite's oocysts are expelled with the cat's feces. After being washed away by rain, these oocysts can remain infectious in moist soil for more than a year. They can be ingested by beetles and worms, which are readily eaten by rats.

4. While the parasite affects rats' fear of cats, it appears to leave other aspects of rat behavior intact and to leave cat behavior completely unchanged, The Oxford researchers believe that 'T. gondii' has evolved to alter rat behavior in this specific way and that the reduction of fear is not simply a side effect of cerebral malfunction.
("Fatal Attraction in Rats Infected With 'Toxoplasma gondii'," Proceedings of the Royal Society of London B 267, 2000)
Natural History 4/01

1-Após ler o texto, retire frases dele com os seguintes tempos verbais, caso não encontre deixe em branco


TEMPO VERBAL FRASE

SIMPLE PRESENT

SIMPLE PAST

PRESENT OR PAST CONTINUOUS

FUTURE

PRESENT OR PAST PERFECT

MODAL VERB

Answer 1

Simple past é o certo