Unit 1 Nature in the balance课时分层作业(一).单词拼写1Were going to spend a weekend on the South American continent(大陆).2Her old man left her a few million (百万)when he died.3This region is the home of many species (物种)of wild flower.4This area of France has a pleasing climate (气候)in August.5Hundreds of tree species is facing extinction(绝种).6He may say no，but theres no harm(伤害)in asking.7The cost of living(生活)has risen sharply.8Her nervousness quickly disappeared(消失)once she was on stage.9The development of the food industry depends on that of agriculture(农业).10The impact (冲击)of the blow knocked Jack off balance.阅读理解ABig cats have existed on the earth for millions of years，though scientists arent sure exactly how long.But a new study indicates that a skull(颅骨)of a snow leopard(豹)relative that was recently unearthed is 4.4 million years old.That makes it the oldest big cat fossil(化石)ever found.A team of US and Chinese scientists unearthed the skull in Tibet.This creature is not a direct ancestor to big cats，but it is closely related to the snow leopard，the study leader Jack Tseng told the Associated Press.The fossil lends evidence to the belief that big cats existed in Asia and spread out from there.Big cats are at the top of the food chain and have few predators of their own.Big cats include snow leopards，clouded leopards，tigers and lions.Based on genetic judgements，most scientists believe they first existed in Central Asia.But previously，the oldest known big cat fossil was 3.6 million years old and found in Africa.The new fossil findings were published in the November 13 issue of the science journal Proceedings of the Royal Society B：Biological Sciences.Tseng and his team were fossil hunting in the Himalayas in 2010 when they discovered some bones，including the buried cat skull.The researchers were able to determine its age by studying the surrounding rocks and soil.The skull indicates that the animal was about the size of a clouded leopard，which can grow up to 50 pounds.In 2012，the team returned to unearth more cat bones.David Polly from Indiana University told the Associated Press that the fossil is “convincingly older than the current record holder”He added that there could be even older big cat fossils in the Tibetan plateau to uncover.【语篇解读】本文讲述了最新考古发现一个大型猫科动物的颅骨化石。1What does the newlyunearthed skull prove?ABig cats might have their origins in Asia.BThe oldest fossil is 4.4 million years old.CThe snow leopard is the oldest big cat.DThe skull is of big cats direct ancestor.A推理判断题。由第二段最后一句“The fossil lends evidence to the belief that big cats existed in Asia and spread out from there.”可推知，该化石使我们相信大型猫科动物起源于亚洲，然后繁衍到其他地方。2What does the underlined word “predators” in paragraph 3 mean?ARelatives.BEnemies.CPartners. DProtectors.B词义猜测题。画线词所在句句意为：大型猫科动物位于食物链的顶端，所以几乎没有天敌。故选B。3How do the researchers know the skulls age?ABy measuring its size and forehead.BBy examining other bones around it.CBy studying its chemical composition.DBy exploring the rocks and soil around it.D细节理解题。由第四段第三句“The researchers were able to determine its age by studying the surrounding rocks and soil.”可知，研究者们通过研究化石周围的岩石和土壤来了解化石的年代。4Where was “the current record holder” in the last paragraph found?AAsia. BAfrica.CAmerica. DAustralia.B推理判断题。题干中引号内的词意为“现在的纪录保持者”，应该指的是新化石发现之前的最古老的化石；而第三段最后一句“But previously，the oldest known big cat fossil was 3.6 million years old and found in Africa.”可知，现在的纪录保持者是在非洲发现的。BThe goal of every plant and animal is the same：to create the next generation.The way a plant makes another generation of its species is by making seeds.Flowers are the tools that plants use to make their seeds.The job of a flower is to help its pollinator put pollen(花粉)exactly in the right place at the right time to make a seed.When a plants flower succeeds in this，the plant gets to pass the secret for this success to the next generation，through the genetic code in its seeds! When a plant fails to grow up and make seeds，its genetic code does not get passed on.It becomes a loser in the game of life.The environment is constantly testing each plant.Competition for sunlight，water，nutrients and space is fierce.Herbivores(食草动物)are hungry and plants are their breakfast，lunch and dinner! Only the strongest individuals survive long enough to reproduce.These survivors keep making seeds，letting the environment select the winners and losers.Through this selection process plants have evolved(进化)to survive life in every habitat on our planet.This evolution has filled even the harshest habitats with life，including cold high mountains.Although the pollination of a flower may appear to happen by accident，plants and pollinators have been practicing for millions of years to make sure that this “accident” happens.Often a plant and pollinator coevolve (evolve together)，adapting to(适应)changes in each other to improve t