原版英语RAZ 教案(Z2) Symbiotic Wildlife.pdf

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1、Visit www.readinga- for thousands of books and materials.WritingImagine you are a scientist studying the ocean.What symbiotic relationships would you see?Write a journal entry detailing your discovery.ScienceChoose and research one symbiotic relationship from the book or another source.Write a repor

2、t that includes details about both species and their partnership.ConnectionsSymbiotic WildlifeA Reading AZ Level Z2 Leveled BookWord Count:2,577www.readinga-LEVELED BOOK Z2Symbiotic WildlifeZZ1Z2Written by M.T.Stark www.readinga-How do symbiotic relationships work,and why are they important?Focus Qu

3、estionSymbiotic WildlifeWritten by M.T.StarkSymbiotic WildlifeLevel Z2 Leveled Book Learning AZWritten by M.T.StarkAll rights reserved.www.readinga-Front cover:A yellow-billed oxpecker positions itself on the neck of an impala before cleaning its ears.Title page:A greater short-nosed fruit bat feeds

4、 on a banana plant.The banana is a bat-dependent plant.Pollen is carried on the bats fur to other banana plants,allowing them to reproduce.Page 3:A school of yellow tang fish clean the algae from a green sea turtle.Photo Credits:Front cover:Pete Oxford/Minden Pictures;title page:Merlin Tuttle/BCI/Ph

5、oto Researchers,Inc.;page 3:Masa Ushioda/age fotostock/SuperStock;page 4:Juniors Bildarchiv/Alamy;page 5:iStock/Kristian Sekulic;page 6:John Pavel/D;page 7:iStock/Derek Holzapfel;page 8:Alexandr Shestopalets/D;pages 9(top),11(top),12:iStock/Diane Labombarbe;page 9(bottom):Richard T Nowitz/C/DAMON/ag

6、e fotostock;page 10:Jamesdawson/D;page 11(bottom):Tui De Roy/Minden Pictures;page 13:Salpics32/D;page 14:Reinhard Dirscherl/Alamy;page 15(main):Dave Parker/D;page 15(inset):Rafael Angel Irusta Machin/D;page 16:Carol Buchanan/D;page 17:Richard Du Toit/Minden Pictures;page 18:Rolf Nussbaumer Photograp

7、hy/Alamy;page 19:Lorand Schuller/D;page 20:Melinda Podor/Alamy;page 21(main):Juniors Bildarchiv/Alamy;page 21(inset):Gerry Bishop/Visuals Unlimited,Inc.;page 22(main):Ralf Broskvar/D;page 22(inset):Frans Lanting/National Geographic Stock;page 23:Steffen Foerster/DCorrelationLEVEL Z2YZN/A70+Fountas&P

8、innellReading RecoveryDRAassumesfertilizeshygienistinterdependentintimidatingmucusnocturnal parasitespropagaterefugesymbiotic venomousWords to Know3Table of ContentsIntroduction .4Finding Food and Giving Protection .7Helping with Personal Hygiene .10Sharing a Home .12Teaming Up to Find Food .15Hitch

9、ing a Ride .16Pollinating and Fertilizing .18Spreading Seeds .20Conclusion .22Glossary .24Symbiotic Wildlife Level Z24IntroductionLiving in the wild is challenging.Food can be scarce,good homes are hard to find,pests abound,and theres almost always something out to eat you.Those reasons are why many

10、 species in the wild form unusual relationships in which they cooperate by performing separate tasks that benefit each other.For example,one may offer protection from predators in exchange for a good cleaning or a reliable supply of food.Such partnerships are called symbiotic relationships.The word

11、symbiosis comes from the ancient Greek words for“with”and“living.”Scientists first applied the word to wild species in 1877 while writing about lichenscomplex and often colorful organisms typically made up of a fungus and a type of algae that work and live closely together.A crocodile opens wide for

12、 a small Egyptian plover bird.The plover cleans bits of leftover food from the crocs teeth.5Since then,scientists have identified symbiotic relationships that exist all around usin deep oceans and dry deserts as well as in mountains and forests.Researchers have discovered unexpected partnerships,suc

13、h as those involving a sharp-sighted fish and an industrious shrimp,a venomous sea anemone(uh-NEM-uh-nee)and a colorful clownfish,or a towering tree and a ground-dwelling rodent.In the wild,these unusual partnerships are not only fascinating but can also mean the difference between life and death fo

14、r the species involved.Bees,for instance,would have a hard time surviving without the nectar of flowers and,similarly,those same flowers would have a tough time reproducing without the help of bees that distribute their pollen.Pals and PartnersYou may have your own symbiotic relationship at home.You

15、r pet dog,for instance,provides you with love,companionship,and protection.In return,your dog gets food,attention,and a safe place to live.You both benefit.Symbiotic Wildlife Level Z26Symbiotic relationships arent always equal,but those that have endured over thousands or even millions of years tend

16、 to last for one reason:both species benefit enough to make the relationship worthwhile.Some scientists believe that these symbiotic relationshipswith different species interdependent on one anotherare one of the driving factors in why we have so many diverse plants and so much diverse wildlife on E

17、arth.Symbiosis may also contribute to variety within as well as across speciessome animals,for example,may disperse to less-than-ideal environments and collaborate with other native species to further their survival.Over time,this results in a subspecies that,while closely related to the original sp

18、ecies,now has different traits,features,or behavior.Lets look at some examples of the many types of symbiotic relationships to see how different kinds of living things work together in the natural world.A group of starlings stick close to a red deer for the chance to pick insects off its body.Word W

19、iseThe partners in a symbiotic relationship are called symbionts.7Finding Food and Giving ProtectionSometimes its nice to know someones got your back.Clownfish,such as the colorful ones that live in the Indian Ocean,need all the help they can get to remain safe from predators.One way they do this is

20、 by seeking refuge in the tentacles of venomous sea anemones.Although anemones look like plants,theyre actually marine animals that secure themselves to rocks or other surfaces and then wait for prey to come to them.When small fish or shrimp brush against an anemones soft tentacles,they are exposed

21、to a toxin.The toxin paralyzes them,and the anemone pulls the incapacitated prey into its mouth.Anemones have a different relationship with clownfish,though.Clownfish have developed a strategy for building up immunity to the anemones venomthey touch the anemones tentacles once or twice,wait awhile,a

22、nd then touch the anemone again.This repetitive exposure to small doses of venom gradually provides the clownfish with a protective layer of mucus on its skin.Sea anemoneSymbiotic Wildlife Level Z28The mucus coating shields the clownfish from any harmful contact with the anemone and allows the fish

23、to swim among the anemones tentacles without getting hurt.So,when a predator arrives to have a clownfish for lunch,the clownfish can dive into the protective cover of the anemone.Swimming among the tentacles,the clownfish acts as a lure and draws the predatory fish into the stinging arms of the anem

24、one,which kills the fish and provides a meal for both members of this partnership.A cautious striped clownfish hides from predators among the protective tentacles of a venomous sea anemone.9In Africa,ostriches and zebras often feed together and use their combined sensory strengths to help keep each

25、other safe from predators.Ostriches have good eyesight,and zebras have excellent hearing.Together,the two species have a much better chance of detecting a stalking lion or other predator on the prowl than they do alone,which enables these partners to make a speedy getaway before they are attacked.Af

26、ricas impalas and baboons have a similar relationship.Impalas have superb hearing,excellent vision,and an acute sense of smell.If they detect danger first,their alert body language and horn shaking warn the baboons to beware.The baboons then sound the alarm,using their loud screams and intimidating

27、teeth to frighten predators away.Groups of ostriches and zebras often feed together and warn each other if they detect approaching predators.AfricaIN D I A N O CE A NAT L A N T IC O CE A NEuropeSymbiotic Wildlife Level Z210Helping with Personal Hygiene Some animals need a friends help to clean those

28、 hard-to-reach places.On many ocean reefs,a silvery little fish called a cleaner wrasse provides just such a service,acting as a sort of deep-sea dental hygienist to larger fish such as angelfish or butterflyfish.The tiny wrasse sets up a“cleaning station,”and large fish wait patiently for their tur

29、n to be picked over.So why dont the larger fish just eat the wrasse?Its because the wrasse has developed a soothing,hypnotic dance that seems to relax the larger fish and eventually leads them to open their mouths to let the wrasse inside.The wrasse then darts in and out of the mouth and gills,clear

30、ing them of fungus,parasites,dead skin,and other debris.The industrious wrasse gets a snack and leaves the larger fish clean and healthy.A giant moray eel has its teeth and mouth cleaned by a bluestreak cleaner wrasse.11Some of Darwins ground finches provide a similar cleaning service to tortoises o

31、n the Galapagos Islands.When a tortoise is ready for cleaning,it assumes a particular posture,extending its neck and legs so that a neighboring group of ground finches can swoop in and peck away at parasites that the tortoise is unable to reach.The tortoise stands absolutely still and appears to be

32、in a trance as the finches do their work.When they are finished,the finches have fuller stomachs,and the tortoise is pest-free.Darwins ground finches cling to the neck and legs of a giant tortoise as they pick ticks from its body.GALAPAGOS ISLANDSSouth AmericaNorth AmericaPAC I F I C O C E A NAT L A

33、 N T I C O C E A NSymbiotic Wildlife Level Z212Sharing a HomeSharing a home can be tricky,especially when its with a species thats nothing like you.Two of natures most improbable roommates live on the high shoreline cliffs of New Zealand.One of them is a slow-moving,lizardlike reptile called a tuata

34、ra(too-uh-TARR-uh),which usually cant be bothered to build its own nest.The other is a fast-flying bird called a sooty shearwater.The two species occupy the same residence,but not simultaneously.The tuatara is nocturnal,so it usually spends the day in the burrow and goes out at night.When home,it pe

35、rforms housecleaning duties by eating the burrow bugs and parasites that annoy the shearwater.While the tuatara is tidying up,the sooty shearwater hunts.The shearwater returns to the shared burrow at night when its roommate is gone,loosening the burrow dirt and producing droppings that attract insec

36、ts the tuatara loves to eat.Its a perfect arrangement for this odd couple.Although they rarely see each other,they share both a home and a welcome partnership.NEW ZEALANDAustraliaPA C I F I C O C E A NI N D I A N O C E A NAsia13Burrowing owls,the smallest owls in North America,make great neighbors.T

37、hey cant actually dig holes,but they do use them as a safe place to hide from predators.Their petite proportions make them a perfect fit for abandoned burrows once inhabited by prairie dogs or gopher tortoises.When a tiny owl chooses a vacant burrow,the former occupant may have relocated to the burr

38、ow next door.Each animal helps the other by sounding a warning if a predator approaches.Forest mice and burrow beetles also have a home-sharing arrangement that benefits both species.While the mouse sleeps in the burrow,the beetle roots through the mouses fur,snacking on fleas.When the mouse is away

39、,the beetle scours their home for other burrow bugs.The beetle eats well,and the mouse gets a pest-free home.The tiny burrowing owl builds its nest underground in abandoned burrows.It warns neighbors of approaching predators.Symbiotic Wildlife Level Z214Some ocean animals share homes as well.Surviva

40、l is the name of the game for all animal species,but it can be hard to survive when you cant spot danger.Thats the plight of snapping shrimp,which inhabit the ocean floor.The near-blind shrimp dig burrows into the seabed.As they move sand to construct their homes,the shrimp are at risk of being eate

41、n by hungry predators.Fortunately,the shrimp have a clever partner with a real knack for spotting troublethe alert and sharp-sighted goby fish.As shrimp excavate sand,goby fish hover near their antennae and act as lookouts.When danger lurks nearby,the fish flick their tails,touching the antennae and

42、 sending a signal to the shrimp that theyd better take cover.In return,the shrimp share their burrows with the goby fish,providing the fish with a safe place to sleep at night as well as a convenient place to hide.Its a perfect partnership for these symbiotic sea dwellers.A goby fish and a snapping

43、shrimp team up to build a home.15Teaming Up to Find FoodHigh in Americas Rocky Mountains,grizzly bears,red squirrels,and white bark pine trees are part of a cycle that helps them all thrive.The pine trees provide pine nuts,a high-calorie food source for both bears and squirrels.Red squirrels eat som

44、e of the nuts and bury others to retrieve and eat later.The bears strong sense of smell helps them locate and consume the squirrels caches of nuts.The droppings that the bears leave behind after digesting the nuts disperse some of the tree seeds,which causes new trees to sprout and grow,eventually p

45、roviding even more pine nuts for future generations of both bears and red squirrels.The huge grizzly bear and the small red squirrel depend on each other and nuts from the white pine tree to maintain a healthy diet.Symbiotic Wildlife Level Z216Hitching a RideMost small fish wisely keep their distanc

46、e from sharks.A slender fish called a remora,though,does everything it can to get up close and personal with sharks.The remora has a flat,ribbed disc on the top of its head that functions as a suction cup to help the fish attach itself to the underside of a shark.Remoras are capable of swimming on t

47、heir own,and they often do,but hitching a ride on a shark or other large creature is sometimes just an easier and more efficient way to get around.Once attached,a remora goes everywhere the shark hunts and feeds,eating any scraps of food that escape the sharks powerful jaws.The remoras provide a ser

48、vice,too,by consuming parasitic hitchhikers and helping to keep their host animals free of less beneficial passengers.A small remora fish(arrow)attaches itself to a sharks belly to travel with it and share its meals.Do You Know?A remoras suction disc is actually a dorsal fin that changed and evolved

49、 over thousands of years.17Remoras arent the only creatures with strange headgear.Some hermit crabs that live in the Mediterranean Sea wear an odd-looking hat.The hat is actually a hitchhiking sea anemone.The sea anemones long tentacles are venomous,but the hermit crab is protected from them by its

50、hard shell.The anemone protects the hermit crab from predators.In exchange,the anemone benefits from the crabs messy eating habits by eating scraps of food suspended in the surrounding water.Not all symbiotic hitchhikers are in the sea.In Africa,a small bird called an oxpecker often hitches a ride o