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
aeronautical navigational electronics
air craft
Aisimi
alpha-beta transition
annunziato
armyworms
as crazy as a loon
bag dust filter
beam bearing
Benangin
bf, bf.
black-cab
blockwood pavement
boisterously
boss-fern
Bukhoro
capacity for public rights
carthon
chlorophyll corpuscle
cladophoran
colloverthwart
computer interconnects
conversation control
Creusot-Loire Uddelholm process
CRSV
current operating performance income statement
derivational compound
diagnostically
digital-advertising
Eaton Park
ejector lift
excursion rate
fail-soft function
fan-guide
ferrobustamite
first-out
glass object
grapeseed oil
hemqtarrhachis
hickenlooper
high-speed sequential processing
Higi
hop on the bandwagon
hydrokonite (hydroconite)
ilmens
inter-organizational
iron halogenide
Isobutylisovalerate
jamt
jen
Jenolan
job dyeing
keystone-type piston ring
kneeboarding
La Cavada
load time his tory
martinhal
measure twice, cut once
mechanical face seals
method analysis
microsoft commercial internet system
midmarket
murska
nanoprocessor
nonreduced
obtuse-angle
optimal growth path
Percy cautery
profit allowance
put it this way
raw casting
readable news
reversal colo(u)r film
rotary slasher
rural erosion rate
scaraboids
Scots Gaelic
seam fat
seepage apron
seiters
self-propelled floating crane
separetionist
soapworts
splicing
splicing vise
spring hoop
submerged tooth
suburban areas
syllogisms
temporomaxillary
topographical parallel
townlets
Tracheophytas
trailing cavity
travelling roller pin
unextraneous
unit mass resolution
unyielding foundation
utility-company
Varaire
wakeys-wakeys
yoruba dance (w. africa)