PassageTwo
Questions 51 to 55 arebasedonthefollowingpassage.
Whenwethinkofanimalsandplants, wehaveaprettygoodwayofdividingthemintotwodistinctgroups: oneconvertssunlightintoenergyandtheotherhastoeatfoodtomakeitsenergy. Well, thosedividinglinescomecrashingdownwiththediscoveryofaseaslug (海蛞蝓) that'strulyhalfanimalandhalfplant. It'sprettyincrediblehowithasmanagedtohijackthegenesofthealgae (藻类) onwhichitfeeds.
Theslugscanmanufacturechlorophyll, thegreenpigment (色素) inplantsthatcapturesenergyfromsunlight, andholdthesegeneswithintheirbody. Thetermkleptoplastyisusedtodescribethepracticeofusinghijackedgenestocreatenutrientsfromsunlight. Andsofar, thisgreenseaslugistheonlyknownanimalthatcanbetrulyconsideredsolar-powered, althoughsomeanimalsdoexhibitsomeplant-likebehaviors. Manyscientistshavestudiedthegreenseaslugstoconfirmthattheyareactuallyabletocreateenergyfromsunlight.
Infact, theslugsusethegeneticmaterialsowellthattheypassitontotheirfuturegenerations. Theirbabiesretaintheabilitytoproducetheirownchlorophyll, thoughtheycan'tgenerateenergyfromsunlightuntilthey'veeatenenoughalgaetostealthenecessarygenes, whichtheycan'tyetproduceontheirown.
"There'snowayonearththatgenesfromanalgashouldworkinsideananimalcell," saysSidneyPiercefromtheUniversityofSouthFlorida. "Andyethere, theydo. Theyallowtheanimaltorelyonsunshineforitsnutrition. Soifsomethinghappenstotheirfoodsource, theyhaveawayofnotstarvingtodeathuntiltheyfindmorealgaetoeat."
Theseaslugsaresogoodatgatheringenergyfromthesunthattheycanliveuptoninemonthswithouthavingtoeatanyfood. Theygetalltheirnutritionalneedsmetbythegenesthatthey'vehijackedfromthealgae.
51. Whatisthedistinctivefeatureofaseaslug?
A) Itlookslikebothaplantandananimal.
B) Itconvertssomeseaanimalsintoplants.
C) Itliveshalfonanimalsandhalfonplants.
D) Itgetsenergyfrombothfoodandsunlight.
52. Whatenablestheseaslugtolivelikeaplant?
A) Thegenesitcapturesfromtheseaplantalgae.
B) Themechanismbywhichitconservesenergy.
C) Thenutrientsithjacksfromotherspecies.
D) Thegreenpigmentitinberitsfromitsancestors.
53. Whatdoestheauthorsayaboutbabyseaslugs?
A) Theycanlivewithoutsunlightforalongtime.
B) Theycanabsorbsunlightrightaftertheirbirth.
C) Theycansurvivewithoutalgacforquitesometime.
D) Theycanproducechlorophylontheirown.
54. WhatdoesSidneyPiercesayaboutgenesfomanalga?
A) Theyarestolenfromanimalsliketheseaslug.
B) Theycan'tfunctionunlessexposedtosunlight.
C) Theydon'tusuallyfunctioninsideanimalcells.
D) Theycanreadilybeconvertedtoscasluggencs.
55. Whatdowelearnaboutseaslugsfromthepassage?
A) Theybehavethewaymostplantspeciesdo.
B) Theycansurviveformonthswithouteating.
C) Theywillturnintoplantswhentheymature.
D) Theywillstarvetodeathwithoutsunlight.