第21套
The First Eyes（17年3月考过）
Putting a date on the first appearance of eyes depends on what one means by eye.If the term refers to a multicellular organ,even if it has just a few cells,then by definition,eyes could not form before there were multicellular animals.But many protists(animal-like,plantlike,or fungus-like unicellular organisms that require a water-bad environment)can detect light by using aggregations of pigment molecules,and they u this information to modify their metabolic activity or motility (the ability to move spontaneously and independently).One of the familiar living examples,probably known to anyone who has taken a biology class,is the aquatic protozoan Euglena,which has an eyespot near its motile flagellum(hairlike structure). Some living protists are very like their ancestral forms embedded in ancient dimentary rocks,and this similarity suggests that the ability to detect light and modify behavior in respon to light has been around for a very long time.Animals aro from one of such unicellular creatures,perhaps from one already specialized for a primitive kind of vision.
护肤指南1.The word aggregations in the passage is clost in meaning to
A.parts
2..Paragraph1supports all of the following statements about protists EXCEPT:
A.Some are multicellular.
B.Some are able to move.
C.Some have pigment molecules.
D.They live in environments that contain moisture.
3..According to paragraph1,what have scientists concluded from the fact that some living protists are very like their ancestral forms
A.The eye did not evolve until multicellular organisms aro.
B.The ability to detect light and change behavior in respon to light has existed for a long time.
C.The ancestral forms of the living protists likely had an eyespot near the motile flagellum.
D.The ancestral forms of the living protists depended primarily on light as the mechanism for modifying their metabolic activity or motility.
An eye is a collection of cells that are specialized for light detection through the prence of photonsitive pigment as well as a means of restricting the direction of incoming light that will strike the photonsitive cells.This definition says nothing
about image formation,lens,eye movements,or any of the other features we associate with our own eyes,but it does recognize the simplest form of functional and anatomical specialisation namely,detection of light.Everything el can be built up from this simple beginning,and some animals appear to have had eyes almost from the beginning of the animal kingdom.
4.The word lateral in the passage indicates a location at the
A.front
B.back
D.side
5..Paragraph2implies which of the following about the early eyes
A.They were able to detect simple movements almost from the beginning of their evolution.
B.They were not as nsitive to light as once thought.鞋子评价
C.They could not form images.
D.Their cells had more photonsitive pigment than do human eyes.
Animals were scarce600million years ago in the geological era called the Precambrian.【There are very few fossil remains from that time(though more keep turning up),and most evidence of the prence of animals is indirect,such as small tunnels in rock that could be ancient worm burrowings.】But just50million years or so later,fossilized bits and pieces of animals abound,suggesting that a great burst of evolutionary creativity occurred in the50-million-year interval.This surge of new life, marked by an abundance of animals,is called the Cambrian explosion.
6.Which of the ntences below best express the esntial information in the highlighted ntence in the passage Incorrect choices change the meaning in important ways or leave out esntial information.
【There are very few fossil remains from that time(though more keep turning up), and most evidence of the prence of animals is indirect,such as small tunnels in rock that could be ancient worm burrowings.】
A.There are few fossils from the Precambrian,though more keep turning up.
B.Most evidence of animals in the fossil record is indirect and little of it is from the Precambrian.
C.Tunnels in Precambrian rocks that may have been made by worms provide indirect evidence of the animals existing at that time.
D.There are very few fossils of animals from the Precambrian and most evidence of animal life from that period is indirect.
7.According to paragraph3,the Cambrian period was characterized by韩国白菜
A.a great abundance of animals
B.a slow rate of animal extinction
C.the rapid fossilization of animals
D.an increa in the life span of some animals
8.The phra little short of miraculous is clost in meaning to
A.very highly valued
B.amazing becau almost impossible
C.causing controversy
D.almost but not quite complete
The first direct evidence for the early origin of eyes comes from fossils that are about 530million years old,a time shortly after the Cambrian explosion;they were found on a mountainside in British Columbia in a deposit known as the Burgess Shale.The Burgess Shale fossils are extraordinarily important becau among them are remains of soft-bodied creatures,many of them lacking shells an
d other hard parts that fossilize easily.Conquently,their prervation is little short of miraculous(as are the delicate methods ud to reconstruct three-dimensional structure from the flattened fossils),and they are one of the few known repositories of early soft-bodied animals.
热火朝天的反义词9.According to paragraph4,all of the following are true of the Burgess Shale EXCEPT:
A.Its fossils were in a flattened condition when discovered.
B.Its fossils provide direct evidence about the origin of eyes.
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C.It contains fossils of both Precambrian and Cambrian animals.
D.It contains fossilized remains of soft-bodied organisms.
Not all of the Burgess animals had eyes.However,some did.(Gross features location, size,and hemispheric shape are responsible for the designation of some structures as eyes).The reconstructed eyes of the Burgess animals look superficially like eyes of some living crustaceans,particularly tho of shrimp and crabs who eyes are mounted on stalks that improve the range of vision by raising the eyes above the surface of the head.The eyes of some Burgess organisms sat on stalks;tho of others were on or a part of the body surface.One animal,Opabinia,h
ad five eyes:two lateral pairs and a single medial eye;at least one of the lateral pairs had stalks that could have been movable.And some trilobite-like animals in the Burgess Shale had faceted eyes much like tho of later fossil trilobites.
10.The word designation in the passage is clost in meaning to
A.evolution
B.identification暗香疏影的意思是
11.Why does the author point out that The eyes of some Burgess organisms sat on
stalks
A.To suggest that some Burgess organisms had a greater range of vision than do living shrimp and crabs
B.To explain why it is thought that one of the lateral pairs of eyes in Opabinia may have been movable
C.To explain why the eyes of some Burgess animals were not recognizable as such before they were reconstructed
D.To support the statement that the reconstructed eyes of Burgess animals look superficially like the eyes of some living crustaceans
Although the prence of eyes on some of the Burgess animals indicates that eyes have been around for a very long time,it is unlikely that the were the first eyes;they em much too large and(potentially)well developed to be brand new inventions. The best we can do is put the origin of eyes somewhere between the beginning of the Cambrian explosion,about600million years ago,and the death of the Burgess animals,some530million years ago.
12.Paragraph6suggests that the first eyes probably
A.came into existence long before600million years ago
B.came into existence at a late point in the Cambrian period
D.were larger than tho of animals found in the Burgess Shale
13..Look at the four squares that indicate where the following ntence could be added to the passage.
Molaria spinifera and H.optata,both of which lived in water levels beyond the reach of light,fit into this category.
Where would the ntence bestfit Click on a square to add the ntence to the passage.
Not all of the Burgess animals had eyes.However,some did.(Gross features location, size,and hemispheric shape are responsible for the designation of some structures as eyes).【】The reconstructed eyes of the Burgess animals look superficially like eyes of some living crustaceans,particularly tho of shrimp and crabs who eyes are mounted on stalks that improve the range of vision by raising the eyes above the surface of the head.【】The eyes of some Burgess organisms sat on stalks;tho of others were on or a part of the body surface.【】One animal,Opabinia,had five eyes: two lateral pairs and a single medial eye;at least one of the lateral pa
irs had stalks that could have been movable.【】And some trilobite-like animals in the Burgess Shale had faceted eyes much like tho of later fossil trilobites.
14..Drag your choices to the spaces where they belong.To review the passage,click on View Text.
Answer Choices
A.The ability of some unicellular organisms to detect light and change their behavior accordingly suggests that eyes did not originate with multicellular animals.
B.The earliest eyes apparently contained molecules that were capable of forming and focusing images.
C.Too few fossils from the Precambrian have been found to determine which if any Precambrian organisms had eyes.职称评审论文
D.Evidence from the Burgess Shale suggests that eyes of some early animals were similar to the eyes of living crustaceans.
E.Fossil evidence suggests that organisms in the Burgess Shale with faceted eyes developed later than organisms in the Burgess Shale with nonfaceted eyes.
F.The large size and possible complexity of the eyes of some organisms in the Burgess Shale suggest that their eyes were not thefirst eyes.
The Origin of Earth's Atmosphere
In order to understand the origin of Earth's atmosphere,we must go back to the earliest days of the solar system,before the planets themlves were formed from a disk of rocky material spinning around the young Sun.This material gradually coalesced into lumps called planetesimals as gravity and chance smashed smaller pieces together,a chaotic and violent process that became more so as planetesimals grew in size and gravitational pull.Within each orbit,collisions between planetesimals generated immen heat and energy.How violent the process were is suggested by the odd tilt and spin of many of the planets,which indicate that each of the planets was,like a billiard ball,struck at some stage by another large body of some kind.Visual evidence of the process can be en by looking at the Moon. Becau the Moon has no atmosphere,its surface is not subject to erosion,so it retains the marks of its early history.Its face is deeply scarred by millions of meteoric impacts,as you can e on a clear night with a pair of binoculars.The early Earth did not have much of an atmosphere.Before it grew to full size,its gravitational pull was insufficient to prevent gas from drifting off into space,while the solar wind(the great stream of atomic particles emitted from the
Sun)had already driven away much of the gaous material from the inner orbits of the solar system.So we must imagine the early Earth as a mixture of rocky materials,metals,and trapped gas,subject to constant bombardment by smaller planetesimals and without much of an atmosphere.
1.The word chaotic in the passage is clost in meaning to
A.rapid
B.disorganized
C.inten
D.long-lasting
2.All of the following are true of the planetesimals mentioned in paragraph1 EXCEPT:
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A.They were formed of rocky material spinning around the early Sun.
