时间:2018-12-27 作者:英语课 分类:英语时差8,16


英语课

 Last time we were thinking about why some birds hop 1 and other birds walk. We decided 2 that you can't make any blanket statements about this, because there will always be exceptions. But in general it's true that larger birds are more likely to walk and smaller birds to hop, just because of the amount of energy it takes. But there's more to it than that. Ornithologists are actually very interested in bird legs and feet. The differences between different kind of legs are used in bird classification. For example, what we commonly call "songbirds"--cardinals, wrens 3, mockingbirds, warblers--are also called "perching birds." They have specialized 5 structures in their feet that include three toes pointing forward and one more called the "hallux" that points back. That three-and-one design is excellent for holding on to branches, which is an important skill to possess if you are a bird. Okay, so far so good. But now, what does that kind of foot make more difficult? You got it--a foot with a conspicuous 6 hallux toe won't be very good at walking. Some birds manage it, and there are different kinds of hallux toes that make it easier or harder. But to move around with feet like that, sometimes you just might be better off hopping 7. So, evolution has to make a choice. Is it better to perch 4 safely on branches or walk comfortably on the ground? Do I catch food with my feet or my beak 8? And so on. The end result can be birds with different kinds of feet, and different kinds of walks.



1 hop
n.单脚跳,跳跃;vi.单脚跳,跳跃;着手做某事;vt.跳跃,跃过
  • The children had a competition to see who could hop the fastest.孩子们举行比赛,看谁单足跳跃最快。
  • How long can you hop on your right foot?你用右脚能跳多远?
2 decided
adj.决定了的,坚决的;明显的,明确的
  • This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
  • There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
3 wrens
n.鹪鹩( wren的名词复数 )
  • Other songbirds, such as wrens, have hundreds of songs. 有的鸣鸟,例如鹪鹩,会唱几百只歌。 来自辞典例句
4 perch
n.栖木,高位,杆;v.栖息,就位,位于
  • The bird took its perch.鸟停歇在栖木上。
  • Little birds perch themselves on the branches.小鸟儿栖歇在树枝上。
5 specialized
adj.专门的,专业化的
  • There are many specialized agencies in the United Nations.联合国有许多专门机构。
  • These tools are very specialized.这些是专用工具。
6 conspicuous
adj.明眼的,惹人注目的;炫耀的,摆阔气的
  • It is conspicuous that smoking is harmful to health.很明显,抽烟对健康有害。
  • Its colouring makes it highly conspicuous.它的色彩使它非常惹人注目。
7 hopping
n.鸟嘴,茶壶嘴,钩形鼻
  • The bird had a worm in its beak.鸟儿嘴里叼着一条虫。
  • This bird employs its beak as a weapon.这种鸟用嘴作武器。
学英语单词
a'cockbill
A.F.C
active sleep
alveololabial groove
assinuate
balloonry
beagled
bitter almond camphor
BLUS resifual vector
carpetbagging
case bay part
Chelidonium majus
clean cutting
Colbeckite
Confederate flag
copped tanke
crude test
cruzen i.
depressure tank
Dianthus sinensis L.
directional intermolecular force
down-faulting
duosecant
duration units
earn a good reputation
ex-dividend stock
fatuousnesses
ferryer
floorspace
foreign-exchange dealer
future commission merchant
galvanometer
Gangean
genus Uma
gone poof
half-neighbo(u)rhood
harbor craft
hawse-pipe
heat-resistant coating
helitankers
hoarhead
hyperinsulinemic obesity
instruction-based architecture
intussusceptive growth
lacinia falcata
ladening
leariest
limiter amplifier
lyeth
marchment
merry-go-round machine
microsaccades
microwave acoustics
mildew-retarding agent
missionise
Mitha Singh
molecular heat conduction
morality of law
mystinus
neocerebellar agenesis
no-load field voltage
nuclear power generation
oonin
pentastomiasis
photoerythema
pick-and-mix
pinch for
plywood ceiling
poison parsley
polynomial hazard function models
pop hole
Population-weighted
postflood
practicing
prognathometer
ricers
rippling edit
rober'
s's
Santorini's caruncula major
senior reactor operator
separating yarn
shock incarceration
shunting yard
slaw
small-denomination
starting air distributor
symploce furcata
tape speed
taxloss
Tellerette packing
temporary import
time per piece
to put to use
treib
unlabeled statement
vaginal hysterotomy
valvulae fossae navicularis
vertical photograph
wet process of parting
white gum
X-ray Luminosity of cluster of galaxies