教材试题Unit5ListeningandSpeaking

1、Unit 5 Meeting your ancestorsListening and speakingThe work on early people depends on the dates that are given tothe bones found. If the dates are wrong, all the data about earlypeople may also be wrong. So Zhou Heping is very interested tofindouthowarchaeologistsmakesurethattheirdatesareaccurate.1

2、 Listen to the tape and fill the layers in the“ wastepaper basket”diagram on the right.2Listen to the tape again. Pay attention to the methods archaeologists use to date bonesand how those methods work, then fill in the chart below.MethodHow it worksEach layer looks different as they are uncovered,

3、so you can tellwhere one layer starts and another finishes. In the wastepaper1Layers in the groundbasket,the most recent layer is_, an older layer is belowthat and the _ layer is _.All living things have _ in their bodies. When they die, thecarbon _ at a _ rate. The method measures_ of2Radiocarbon d

4、atingcarbon in bones or plants using radioactivity and can _ howold the remains are.3 Look at this archaeological drawing of a section showing buildings at different times and work out their chronologicalorder.Writeyouranswerbelow,thencheckwith a partner.Remember to give reasons for your answer in y

5、our discussion.1 _2 _3 _LISTENING TEXTDATING METHODSZhou Heping has come to ask the archaeologist, Richard Leakey, how he dates the bones he finds.ZH: How can you tell how old the bones are when you find them?RL: There are two main ways: the first uses layers in the ground and the second uses therad

6、iocarbon dating.ZH: How does the layer method work?RL: Well, many layers of soil were produced at different times. Eachtime peoplebuildhouses and live somewhere, they make an occupation layer. Each has a different colour and texture.ZH: How does that help?RL: Look at the diagram in your book. Think

7、of your wastepaper basket. When you cameinto work you threw the orange skin into it. Later someone threw their empty yogurt potsinto it. Thensomewastepaperwas added.Finallysomeonethrewawaysome usedenvelopes. How many layers are there?ZH: There are four layers.RL: Good. Now which layer is the latest?

8、ZH: Now, let me think! Yes,it ll be the one on the top, which is the used envelopes.RL: And where s the oldest layer?ZH: At the bottom.RL: Well done. When we find bones in layers of soil, we know they are the same age asthe soil.ZH: I see.RL: Now let sthink about the second method.ZH: I remember.It

9、s called the radiocarbon dating method. That s a strange name.RL: Yes. It uses the radioactivity to measure the amount of carbon in living things. The carbon in a dead body disappears at a fixed rate. We know how long this takes, so we can measure the amount of carbon and work out how old a bone or

10、plant is.How it worksEach layer looks different as they are uncovered, so you can tell where onelayer starts and another finishes. In the wastepaper basket, the most recent layer is at the top, an older layer is below that and the oldest laver is at thebottom.All living things have carbon in their b

11、odies. When they die, the carbon startsto disappear at a fixed rate. The method measures the amount of carbon inbones or plants using radioactivity and can work out how old the remains are.ZH: That s very clever. Is it very accurate too?RL: There are some problems, so you are always given a date plu

12、s or minus some years.For example, your bone may be dated to 10,000 years ago plus or minus l00 years. Thismeans the bone is between 9, 900 years and l0,100 years old.ZH: How clever! How old are the bones from the Zhoukoudian Caves?RL: They are between 250,000 and 40,000 years old.ZH: Perhaps we can

13、 go and visit the site together sometime?RL: Of course. Whenever you like!Answer key for Exercise 1:used envelopeswastepaperyogurt potsorange skinAnswer key for Exercise 2:Method1 Layers in the ground2 Radiocarbon datingAnswer key for Exercise 3:This exercise may look difficult but is really very simple. The age of the building dependson the number of layers it is resting on. The more layers, the more recent the building.The oldest building is B because it has no layers underneath it.The second old