Challenges Of Life文档格式.docx

1、This sort of advantagemay mean the difference between life and deathin the survival of the fittest.This series reveals the most spectacular and extraordinarystrategies that animals and plants have developed to stay alive.For every creature, every day is full of challenges,all of which must be overco

2、me, somehow, in order to survive.Kenya, famous for its big cats. The supreme hunters.Cheetahs specialise in hunting at speed.Though fast, they are fragile creatures, built to sprint after small prey.They dont have the strength or weight of a lionto bring down larger animals.This male is different. H

3、e doesnt hunt alone.Hes learnt that there is strength in numbers.But here there are not just two, but three cheetahs.A band of brothers.They have changed their tactics and, by doing so,have taken their prey by surprise.They have learnt that working togetherthey can bring down large prey.An ostrich.A

4、 bird that towers over a cheetah and is more than twice as heavy.It cant fly to escape danger, but it can lash out with a deadly kick.A female, unaware as yet, of any danger.Even with three of them this is still highly risky.If one gets injuredthe other two couldnt hope to tackle such large prey.On

5、the other hand,if they get it right, the rewards are huge.The male has spotted one of the brothers, but only one.Its not too worried.Then suddenly there are three!The female is slower to realise the dangerand the cheetahs switch targets.It takes the combined effort and weight of all three brothersto

6、 bring down this powerful bird.Even now the ostrich could land a fatal kick.So far, the brothers are winning.Ostriches have yet to find a way to foil such tactics.Other animals have also evolved surprising tactics to outmanoeuvrethe enemy, not with brute strengthbut with extraordinary weapons.Madaga

7、scar.A strange world where nothing is quite as it seems.To hunt here requires stealth and subterfuge.And living within the trees is a master of ambush.A preying mantis.Well camouflaged and lightning quick,these insects are highly efficient predators.But even they are outgunned.A chameleon.Its camouf

8、lage is exceptionalbecause it can change its skin colour to match its surroundings.Its eyes move independently to spot prey.It creeps towards to its victim, until just in range.Then it unleashes a super weapon.Its tongue shoots out at 15 metres per second.And not only hits, but grasps its target.But

9、 few hunters are always successful.For them a hunt is just one meal.For prey, the stakes are higher.s life.or death.As Antarctica moves from spring into summerthe inlets and bays, once choked with ice, become free.And animals move in to feed.These are crabeater seals. They dont actually eat crabsbut

10、 krill, small shrimps that swarm in their billions in these waters.Resting on a large ice floe,these crabeaters are safe.But as soon as they enter the water,they are on their guard,for good reason.Killer whales.Here in Antarctica, many killer whales prey only on fish.But these whales are different,

11、they specialise in hunting seals.This seal swimming to open wateris unaware of the danger heading his way.Until now.s in real trouble.There is no escape unless he can hide behind this small piece of floating ice.But hes been spotted and surrounded.Now agility is his only chance.He dodges for his lif

12、e, staying as close as he can to the iceberg.s tiring.And the whales tighten the circle, going for the kill.But hunters dont always get their own way.In the end, the seals determination and skill, usingthe ice for protection, kept him just out of reach.And the whales move on.Recently its been observ

13、ed that killer whalesare much more successful when hunting other types of seal.Crabeaters like this put up too much of a fight.For creatures living in the open oceanthere is nowhere to hide from predators.But there is safety in numbers.One fish, however, has evolved a different escape tactic.To leav

14、e the water completely, take to the air and fly!After a huge effort to get airborne, flying fishcan glide 200 metres or so,to escape the predators chasing them.Not all animals are hunters, many are vegetarians.But the battle between animals and plantscan also be intense.Boa Vista, central Brazil.Thi

15、s valley is peppered with strangely pitted rocks.These are not natural formationsbut the legacy of a long struggle between one animal and one plant.Brown-tufted capuchins, highly intelligent monkeys.They spend their nights in the safety of caves,emerging each morning to find food.Down in the valley

16、is a particular favourite.A nut palm.The palms produce huge seeds,but they have very strong shellsthat protect them against attack from hungry animals.For the capuchins this is a war of attrition.They check which seed is the ripest,and the battle commences.The first job is to tear the tough fibrous

17、husk from the nut.He doesnt try to crack the nut straight away,but drops it to the ground.s learnt that a nut should be given a week or so drying in the sun.These are ones he prepared earlier.He taps them to see if theyre ready.This huge flat rock is his anvil.And this is a hammer.s made of a differ

18、ent and much harder rock than the anvil.Now something extraordinary happens.The capuchins use of these stone tools requires an exceptional levelof intelligence, planning and dexterity.The nut finally cracksand exposes a rich, oily kernel.Youngsters watch and imitate the adults,just as human toddlers

19、 do.If they are to become independent, they must learn to crack their own nuts.But the learning process is long, with many frustrations.They learn early on that to do a job properly,you need the right tool.It can take eight years for a capuchin to master this artand overcome the palms formidable def

20、ences.But some plants have turned the tables and feed on animals.This is a highly sophisticated trap. The bait,sugary nectar around the rim of the disc.The triggers, fine hairs,two of which have to be touched within 20 seconds of each other.The victim, a flywhich finds the colour and nectar irresist

21、ible.When triggered, the trap snaps shut so fastthat the fly is imprisoned.The Venus flytrap now slowly digests its victim.Lifes challenges are more than just finding food.In every animals life there comes a timewhen its mind turns to breeding.One creatures approach is mind-boggling.Malaysia.This st

22、range insect has been lying dormant on the forest floor.Once safe in the trees,these males hide among the leavesand begin an extraordinary transformation.One that will make the difference between fathering offspring or not.He begins by gulping in air bubbles,forcing them up into his head.He then pum

23、ps the bubbles into the stalks supporting his eyes,just like blowing up a balloon.And this is what earns these creatures their name,the stalk-eyed fly.A few final adjustmentsto straighten out any remaining creasesand hes ready for action.They may look unwieldy,but eyes on stalks improve not only his

24、 ability to spot predators,but they are key when it comes to winning females.In the evening both males and females gatherand the males begin to size one another up,eyeball to eyeball.Having the widest eye spanputs you at the top of the pecking order.The eye stalks are not weapons,theyre measuring st

25、icks, used to gaugehow big, and so how strong, a male is.But theres trouble if two top males have exactly the same eye width.Then the contest descends into a brawl.Defeated.The winner.He now has the right to mate with all the females nearby.The rather gentlemanly way stalk-eyed fliessettle their dif

26、ferences over femalesis not the only way.Some animals are much more violent.s the dry season in Zambia.The lagoons are either baked dry,or the mud is so thick animals get stuck,with fatal consequences.This male hippo has been living in one small lagoon,but as it dries, its turning into a death trap.

27、Understandably, the females that once shared it with him have all left.Even if he wants to,he cant stay much longer.He needs water to keep cool and females to mate with.And this is where they all are.Almost all the hippos in the areaare in what is left of the Luangwa River,because its the last place

28、 where theres still deep water.This bend is controlled by an all-powerful male.Since the drought many more females have joined his herd.They are happy to live cheek by jowl,but any male who comes here in the hope of matingmust first defeat the overlord.The wandering male arrives and has a decision to