时间:2019-01-17 作者:英语课 分类:英语时差8,16


英语课

 Food Chain Regulation Biologists who study nature’s food chain agree about the basic links in the chain: sunlight provides fuel for plants, plants are consumed by herbivores, and herbivores are eaten by carnivores. But researchers aren’t sure about all the factors that control the chain. Traditionally, they have thought that food-chain populations are regulated from the bottom up. According to this idea, the availability of plants as food determines the size of animal populations in an area. But a study of a food chain in Isle 1 Royal National Park, an island in Lake Superior, has shown that food-chain control can work in both directions. In the island’s food chain, balsam firs are eaten by moose, which, in turn, are eaten by wolves. When researchers tracked the effects of the moose and wolves on the balsam firs, they actually found that the number of wolves in the area affected 2 the growth of the firs. During the study, researchers recorded the width of the tree rings of balsam firs. Each ring marked a year of the tree’s growth. A narrow ring indicated that the tree’s growth had been suppressed that year. The narrow rings appeared only after wolf populations decreased, allowing a greater number of moose to survive and eat more balsam firs. The researchers concluded that wolves play an important role in maintaining the complex and delicate balance of the island’s food chain. This food chain appears to be regulated from the top as well as from the bottom.



n.小岛,岛
  • He is from the Isle of Man in the Irish Sea.他来自爱尔兰海的马恩岛。
  • The boat left for the paradise isle of Bali.小船驶向天堂一般的巴厘岛。
adj.不自然的,假装的
  • She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • His manners are affected.他的态度不自然。
学英语单词
acetylphosphoric acid
approbated
arteriola efferens
assembler loader package
babusar pass
basivolsella
beef stroganoffs
biosphere reserve
black teals
blandished
board bridge
breanna
calcium pyrophosphate
chemical insecticide
clear panel key
colouring book
computer forensics
cool-summer damage due to impotency
Cuproartinite
customs compound
customs supervision
decaudates
direct current source
documents-against-payment bill
DTRTT
electric resistance wire
enthalpy-entropy chart
excess mean portfolio return
firmware support
food-purchasing
four-address code
friction pressure
ghiaour
greys
Hawkins Point
hedonic price method
high-tempreature strain gauge
hovde
hyperpipecolatemia
intraploidy
job-lot production
kellwood
Keota
Koh Sla, Stung
lightly deformed crystal
lindeberg's condition
liquefaction temperature
Lloyd's anchors and chains proved
Loxwood
lymphonoduli aggregati
Madipelesa
magnaliums
mark sth up
megawatt (mw)
micromechanically
momentum cutoff
muhs
myristicic acid
nonutilized
obituarial
OGRL
Omlet
on-line cipher
orbiculately
ortho-nitraniline
Os Draconis
philosoph
piratesses
possessive pronoun
pritchie
pseudoprognathism
pulpitless
Q clearance
R. M. S.
rauca
reattend
remote sensing for atmospheric pollution
residual current operated protective device
Rhododendron mainlingense
sassen
sea language
see ... do
self-redemptions
simple HISAM data base
Skave
steam water interface
steering gear tube cam
stratum compactum of integument
stress bolt
suicide bombing
synchronization
tatouay
Thai Ridgebacks
thorotrast
turite
type of machine
varnish-treated tape
vigna angulariss
wage tax
wheeler and dealer
worm-gears