时间:2018-12-27 作者:英语课 分类:英语时差8,16


英语课

Mammals developed from land-based reptiles 1 two hundred million years ago, and most of the mammals we see today are still land based. A notable exception are the  cetaceans, which we all know as dolphins and whales. How did they move from land to sea? The ancestor of modern whales moved into the water about fifty-two million years ago. One whale fossil,about forty million years old, provides an interesting snapshot from this gradual change. This early whale fossil had rudimentary legs growing from its sides. These were puny 2 compared to the bulk of the whale, so they were probably vestigial, in the slow process of disappearing. Moving from land to salt water requires more changes than simply trading in legs for fins 3, however. For example, the kidney of a modern whale allows it to drink salt water, but early whales must have been restricted to fresh water like other mammals. Scientists have recently discovered that this important kidney change happened about forty eight million years ago to a whale called Indocetus. Kidneys don't leave behind fossils like bones do, so how can these scientists be sure? The answer comes from the ancient whales' tooth enamel 4. Oxygenin an animal's tooth records information about the type of water they drank. The very earliest proto-whales had tooth enamel that indicated a fresh water diet.They probably lived in rivers, or at least returned to rivers to drink. Indocetus, however, had teeth that indicated a salt water diet. This means it had specialized 5 kidneys, and was probably the first mammal to swim the open ocean. That's a lot of information from some old teeth!



1 reptiles
n.爬行动物,爬虫( reptile的名词复数 )
  • Snakes and crocodiles are both reptiles. 蛇和鳄鱼都是爬行动物。 来自《简明英汉词典》
  • Birds, reptiles and insects come from eggs. 鸟类、爬虫及昆虫是卵生的。 来自《现代汉英综合大词典》
2 puny
adj.微不足道的,弱小的
  • The resources at the central banks' disposal are simply too puny.中央银行掌握的资金实在太少了。
  • Antonio was a puny lad,and not strong enough to work.安东尼奥是个瘦小的小家伙,身体还不壮,还不能干活。
3 fins
[医]散热片;鱼鳍;飞边;鸭掌
  • The level of TNF-α positively correlated with BMI,FPG,HbA1C,TG,FINS and IRI,but not with SBP and DBP. TNF-α水平与BMI、FPG、HbA1C、TG、FINS和IRI呈显著正相关,与SBP、DBP无相关。 来自互联网
  • Fins are a feature specific to fish. 鱼鳍是鱼类特有的特征。 来自辞典例句
4 enamel
n.珐琅,搪瓷,瓷釉;(牙齿的)珐琅质
  • I chipped the enamel on my front tooth when I fell over.我跌倒时门牙的珐琅质碰碎了。
  • He collected coloured enamel bowls from Yugoslavia.他藏有来自南斯拉夫的彩色搪瓷碗。
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。
学英语单词
Abreks
acrylic acid butyl ester
aegisthus spinulosus
air-gap flux waveform
alcoholic strength
alignment tolerance
ALIT (automatic line insulation tester)
awakenest
Ban Ta Keo
batted an eye
benzin soap
biological chemistry
Blackmun, Harry Andrew
bretignies
burn out life
car transfer
cinnfuradione
circumflex scapular vein
closure-vein
clothing indices
combined variance
consumer promotions
cryogenic container
cyberwedding
deal off
definite equation
dormant stage
DVI-A
early maturity culture
earth tunnel
erection error
everett
fibrinfiakes
form of life
gellie
geognosts
give me your hand
heptaploid
hold the balance
hypermodernist
i-slepen
injection-air
internetwork high-level communication protocol
irene arisanensis
irrevalent
itc (international telecommunication convension)
juno and the paycock
Kargil District
Kodori Valley
Kroken
latrodectism
limited right over things
linear equivalence classes
locomotive servicing
marine pollution from any source
Mead Lake
method of elastic weight
mistimings
movable core transformator
musya
Mycetia glandulosa
Nemo, Vulkan
nepotist
Nghi Khanh
nuclear turbine
on/off control system
overdrive protection
package structure
pariphyllin
petrographic microscopes
polyphosphoric
portfolio transfer
post-deflection accelerating ele-ctrode
privilegentsia
ramamurthy
re-embrace
relic bar
rotor flow meter
royishly
Saint Michael and Saint George
serum alkaline phosphatase determination
sextic congruence
stratimetry
strictly convex
submarine pitches
subsocial
supercities
tenuated
termini
the central bank
Thornwaldt's disease
tightening nut
tilting screw
Tinaquillo
to yearn after...
tricolour phosphor screen
type of weld
tyrs
unimpaired capital
uritive
visual monitor
X-linked dominant inheritance