原版英语RAZ 教案(Z) Hybrid Animals_DS.pdf

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1、Visit www.readinga- for thousands of books and materials.WritingWrite an informative article for a local paper on the science of hybrid animals.Include the benefits and challenges so readers are fully informed.MathResearch five different hybrid animals not included in the text.Describe how the hybri

2、ds compare to their two parent species.Use glossary words in your description.ConnectionsHybrid AnimalsA Reading AZ Level Z Leveled BookWord Count:1,647Hybrid AnimalsHybrid AnimalsWritten by Cheryl Reifsnyderwww.readinga-LEVELED BOOK ZZZ1Z2www.readinga-Written by Cheryl ReifsnyderHybrid AnimalsWhat

3、are the pros and cons of interbreeding different species?Focus QuestionCorrelationLEVEL ZUVN/A50Fountas&PinnellReading RecoveryDRAHybrid AnimalsLevel Z Leveled Book Learning AZWritten by Cheryl ReifsnyderAll rights reserved.www.readinga-adaptDNAfertilizegenetichybridsinterbreedingoffspringreproduces

4、peciessteriletest tubetransgenicWords to KnowPhoto Credits:Front cover,back cover:Tom Reed/AP Images;title page:courtesy of Holly Steinkraus/University of Wyoming;page 3:Jeff Pawloski/Barcroft Media/Landov;page 4:Funwayillustration/D;page 5:Yva Momatiuk&John Eastcott/Minden Pictures;page 7:Bettmann/

5、Corbis;page 8:Splash News/Corbis;page 9:Eriklam/iStock/Thinkstock;page 10:Chris Mattison/NPL/Minden Pictures;page 13:Steven Kazlowski/NPL/Minden PicturesCover:A four-day-old zedonka rare cross between a zebra and a donkeystands near her mom.Title page:You cant tell by looking,but twin kid goats Arms

6、trong(left)and Sweet Pea(right)contain DNA from spiders!Page 3:This wolphin is a cross between a bottlenose dolphin and a false killer whale.Even her teeth show that she is a hybrid:bottlenose dolphins have eighty-eight,false killer whales have forty-four,and she has sixty-six.15Animal Hybrids:Probl

7、em or Solution?In the past,scientists thought that animal hybrids represented an evolutionary dead end.Most hybrids were sterile,and even those that could reproduce usually carried a combination of their parents traits.The parents were probably well adapted to their specific environments;by combinin

8、g their characteristics,the hybrid would end up adapted to neither.In most cases,this is exactly what we see in nature:hybrid species are usually poorly adapted to their environments and often fail to survive and reproduce.However,when a species faces drastic environmental changes,it may not be able

9、 to adapt to the new conditions quickly enough to survive.Hybrids provide a way for two species to exchange genetic information.A hybrid animal could potentially gain traits that would allow it to survive where one or both parents could not.Are hybrid animals a threat to the survival of at-risk spec

10、ies like polar bears?Or are they natures way of helping species cope with rapidly changing environmental conditions?They may be a bit of bothonly time will tell!Hybrid Animals Level Z16Glossaryadapt(v.)change to fit a new or specific situation or environment(p.11)DNA(n.)a code that carries genetic i

11、nformation about a living thing(p.5)fertilize(v.)to combine male and female reproductive cells to create a new animal or plant(p.8)genetic(adj.)having to do with heredity and variation in living things(p.12)hybrids(n.)offspring produced from two different parent types,breeds,or species(p.4)interbree

12、ding mating two different species of (v.)animals to form offspring with a combination of traits from each parent;crossbreeding(p.8)offspring(n.)a persons child or another animals young;descendants(p.4)reproduce(v.)to make offspring that are similar to the original living thing(p.5)species(n.)a group

13、 of physically similar living things that can reproduce(p.4)sterile(adj.)not able to produce offspring(p.15)test tube(n.)a narrow glass tube that is closed at one end,commonly used in scientific laboratories(p.8)transgenic(adj.)of or relating to an organism whose DNA has been altered by the transfer

14、 of genes from another species or breed(p.14)www.readinga-Written by Cheryl ReifsnyderHybrid AnimalsWhat are the pros and cons of interbreeding different species?Focus QuestionCorrelationLEVEL ZUVN/A50Fountas&PinnellReading RecoveryDRAHybrid AnimalsLevel Z Leveled Book Learning AZWritten by Cheryl R

15、eifsnyderAll rights reserved.www.readinga-adaptDNAfertilizegenetichybridsinterbreedingoffspringreproducespeciessteriletest tubetransgenicWords to KnowPhoto Credits:Front cover,back cover:Tom Reed/AP Images;title page:courtesy of Holly Steinkraus/University of Wyoming;page 3:Jeff Pawloski/Barcroft Me

16、dia/Landov;page 4:Funwayillustration/D;page 5:Yva Momatiuk&John Eastcott/Minden Pictures;page 7:Bettmann/Corbis;page 8:Splash News/Corbis;page 9:Eriklam/iStock/Thinkstock;page 10:Chris Mattison/NPL/Minden Pictures;page 13:Steven Kazlowski/NPL/Minden PicturesCover:A four-day-old zedonka rare cross be

17、tween a zebra and a donkeystands near her mom.Title page:You cant tell by looking,but twin kid goats Armstrong(left)and Sweet Pea(right)contain DNA from spiders!Page 3:This wolphin is a cross between a bottlenose dolphin and a false killer whale.Even her teeth show that she is a hybrid:bottlenose do

18、lphins have eighty-eight,false killer whales have forty-four,and she has sixty-six.15Animal Hybrids:Problem or Solution?In the past,scientists thought that animal hybrids represented an evolutionary dead end.Most hybrids were sterile,and even those that could reproduce usually carried a combination

19、of their parents traits.The parents were probably well adapted to their specific environments;by combining their characteristics,the hybrid would end up adapted to neither.In most cases,this is exactly what we see in nature:hybrid species are usually poorly adapted to their environments and often fa

20、il to survive and reproduce.However,when a species faces drastic environmental changes,it may not be able to adapt to the new conditions quickly enough to survive.Hybrids provide a way for two species to exchange genetic information.A hybrid animal could potentially gain traits that would allow it t

21、o survive where one or both parents could not.Are hybrid animals a threat to the survival of at-risk species like polar bears?Or are they natures way of helping species cope with rapidly changing environmental conditions?They may be a bit of bothonly time will tell!Hybrid Animals Level Z16Glossaryad

22、apt(v.)change to fit a new or specific situation or environment(p.11)DNA(n.)a code that carries genetic information about a living thing(p.5)fertilize(v.)to combine male and female reproductive cells to create a new animal or plant(p.8)genetic(adj.)having to do with heredity and variation in living

23、things(p.12)hybrids(n.)offspring produced from two different parent types,breeds,or species(p.4)interbreeding mating two different species of (v.)animals to form offspring with a combination of traits from each parent;crossbreeding(p.8)offspring(n.)a persons child or another animals young;descendant

24、s(p.4)reproduce(v.)to make offspring that are similar to the original living thing(p.5)species(n.)a group of physically similar living things that can reproduce(p.4)sterile(adj.)not able to produce offspring(p.15)test tube(n.)a narrow glass tube that is closed at one end,commonly used in scientific

25、laboratories(p.8)transgenic(adj.)of or relating to an organism whose DNA has been altered by the transfer of genes from another species or breed(p.14)13Whats the Big Deal?So grizzlies and polar bears might have some brown-and-white grolar bear cubs.Is that really a big deal?If plenty of polar bears

26、roamed the world,the answer might be no.The problem is that polar bears are at risk of going extinctso every polar bear birth makes a difference.It becomes a numbers game:the more polar bears interbreed with grizzly bears,the more their genesspecialized for surviving in the harsh Arctic environmentg

27、et diluted by grizzly bear genes.Eventually,polar bears might simply disappear.On top of that,grolar bears may not be very well adapted to either of their parents environments.Grolar bears in a German zoo seem to have a polar bears instinct for seal hunting but not its strong swimming ability.At thi

28、s point,no one knows whether these hybrids survive as well as non-hybrids in the wild.While not a confirmed grolar bear,this bears body shape,short neck,and odd face(when compared to other polar bears)suggest that it is a grizzly-polar hybrid.Hybrid Animals Level Z14Creatures by DesignWhat if you wa

29、nt a hybrid animal that combines traits from species so different that even mating in a test tube wont work?How about these traits:the ability to produce spider silk(an ability unique to spiders)and the ability to produce lots of milk(an ability limited to mammals)?Spider silk is stronger and more f

30、lexible than steel or Kevlar,as well as resistant to bacterial growth.These traits make it ideal for many medical uses.Researchers hope to use it to create artificial ligaments or nearly invisible stitches for eye surgery patients.Unfortunately,it takes fourteen thousand spiders to make one ounce of

31、 silk.Since spiders tend to eat their neighbors,large-scale“spider farms”are out of the question.Instead,scientists used genetic engineering techniques(directly manipulating an animals genes)to insert spider silk proteins into goat DNA.The goats then produce spider silk proteins in their milk,which

32、is easy to collect.Someday,researchers hope to engineer goats that can produce commercially useful amounts of spider silk.Since spider genes were inserted into goat cells in a laboratory,“spider goats”are considered transgenic rather than hybrid animals.3Table of ContentsWhat Is a Hybrid Animal?.4Hu

33、man-Made Hybrids .6Natural Hybrids and the Tricky Definition of Species .9When Species Overlap .11Whats the Big Deal?.13Creatures by Design .14Animal Hybrids:Problem or Solution?.15Glossary .16Hybrid Animals Level Z4What Is a Hybrid Animal?The ancient Greeks imagined creatures that were half one ani

34、mal and half anothercentaurs and minotaurs,griffons and manticores.These creatures may not exist,but animal hybrids do.They combine the traits of different speciesand they are more common than most people realize.A hybrid is an animal that has parents of two different species.For instance,horses and

35、 donkeys are different species,but they are similar enough in appearance and behavior that they can mate with one another.If the mother is a horse,the baby is called a mule,and if the mother is a donkey,the baby is called a hinny.If different species mate,they dont always give birth to hybrid young.

36、Parent species that are too different may not have live offspring,or their young may be weak or unhealthy.When two species do produce healthy offspring,though,the young usually have a combination of the parent species characteristics.The more closely related the parent species are,the more likely th

37、ey are to have healthy hybrid offspring.3Table of ContentsWhat Is a Hybrid Animal?.4Human-Made Hybrids .6Natural Hybrids and the Tricky Definition of Species .9When Species Overlap .11Whats the Big Deal?.13Creatures by Design .14Animal Hybrids:Problem or Solution?.15Glossary .16Hybrid Animals Level

38、Z4What Is a Hybrid Animal?The ancient Greeks imagined creatures that were half one animal and half anothercentaurs and minotaurs,griffons and manticores.These creatures may not exist,but animal hybrids do.They combine the traits of different speciesand they are more common than most people realize.A

39、 hybrid is an animal that has parents of two different species.For instance,horses and donkeys are different species,but they are similar enough in appearance and behavior that they can mate with one another.If the mother is a horse,the baby is called a mule,and if the mother is a donkey,the baby is

40、 called a hinny.If different species mate,they dont always give birth to hybrid young.Parent species that are too different may not have live offspring,or their young may be weak or unhealthy.When two species do produce healthy offspring,though,the young usually have a combination of the parent spec

41、ies characteristics.The more closely related the parent species are,the more likely they are to have healthy hybrid offspring.13Whats the Big Deal?So grizzlies and polar bears might have some brown-and-white grolar bear cubs.Is that really a big deal?If plenty of polar bears roamed the world,the ans

42、wer might be no.The problem is that polar bears are at risk of going extinctso every polar bear birth makes a difference.It becomes a numbers game:the more polar bears interbreed with grizzly bears,the more their genesspecialized for surviving in the harsh Arctic environmentget diluted by grizzly be

43、ar genes.Eventually,polar bears might simply disappear.On top of that,grolar bears may not be very well adapted to either of their parents environments.Grolar bears in a German zoo seem to have a polar bears instinct for seal hunting but not its strong swimming ability.At this point,no one knows whe

44、ther these hybrids survive as well as non-hybrids in the wild.While not a confirmed grolar bear,this bears body shape,short neck,and odd face(when compared to other polar bears)suggest that it is a grizzly-polar hybrid.Hybrid Animals Level Z14Creatures by DesignWhat if you want a hybrid animal that

45、combines traits from species so different that even mating in a test tube wont work?How about these traits:the ability to produce spider silk(an ability unique to spiders)and the ability to produce lots of milk(an ability limited to mammals)?Spider silk is stronger and more flexible than steel or Ke

46、vlar,as well as resistant to bacterial growth.These traits make it ideal for many medical uses.Researchers hope to use it to create artificial ligaments or nearly invisible stitches for eye surgery patients.Unfortunately,it takes fourteen thousand spiders to make one ounce of silk.Since spiders tend

47、 to eat their neighbors,large-scale“spider farms”are out of the question.Instead,scientists used genetic engineering techniques(directly manipulating an animals genes)to insert spider silk proteins into goat DNA.The goats then produce spider silk proteins in their milk,which is easy to collect.Somed

48、ay,researchers hope to engineer goats that can produce commercially useful amounts of spider silk.Since spider genes were inserted into goat cells in a laboratory,“spider goats”are considered transgenic rather than hybrid animals.11When Species OverlapEvidence suggests that ring species members chan

49、ge slowly as they adapt to specific environmental conditions.The ranges of individual species overlap in some regions;where they do,hybrids arise.With far more of each parent species than the hybrids,though,the parent populations are not greatly affected.Ring species Ensatina eschscholtziiNow imagin

50、e them playing a game of telephone:the first child whispers to the second,who whispers to the next,and so on.When the last child gets the message,its usually completely different from the starting words!The changes in the whispered message are similar to the changes seen around a circle of ring spec