Reading Essentials for Biology Glencoe (794133), страница 38
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Scientists also think that during the Paleozoic era fishes appeared.These were the first animals with backbones.Ferns, seed plants, and four-legged animals such as amphibiansand reptiles also appeared during the Paleozoic era. However,the Paleozoic era ended with the largest mass extinction thatshows up in the fossil record. At that time, about 90 percent ofspecies that lived in the oceans and about 70 percent of landspecies disappeared.6.
What is the “explosion”paleontologists refer to?________________________________________________________________________What changes occurred during the Mesozoic era?The third era, the Mesozoic era, would begin on December 10on your calendar. Many changes happened during this time. TheMesozoic era is divided into three periods: the Triassic Period,the Jurassic Period, and the Cretaceous Period.
Fossils show thatmammals appeared on Earth during the Triassic Period. Manyscientists think that birds evolved from dinosaurs during theJurassic Period.New types of mammals appeared during the Cretaceous Period.Also, flowering plants became plentiful on Earth. A mass extinction occurred at the end of the Mesozoic era. This was the end ofthe dinosaurs. Scientists estimate that at that time, two-thirds ofall living species became extinct.READING ESSENTIALSChapter 14155NameDateClassSection14.1The Record of Life, continuedWhy did this extinction happen?Some scientists propose that Earth was struck by a meteor atthis time. The collision could have caused a huge, possibly poisonous dust cloud to fill the atmosphere.
This may have changedthe climate and so fewer species survived. There is a huge craterin the waters off eastern Mexico that scientists suggest was theimpact site of this meteor.eaEurasiaangaNorthAmericaPAfricaSouthIndiaAmericaAustraliacticaraAntAAbout 245 million years ago, thecontinents were joined in a landmassknown as Pangaea.L auNorthAmericaAfGonSouthAmericarasiaEurasiaricdaIndiawa n aliaratusWhat life appeared during the Cenozoic era?AAntarcticaBBy 135 million years ago, Pangaeabroke apart resulting in two largelandmasses.NorthAmericaIt is thought that in the early part of the Mesozoic era,all the continents were joined together as one large landmass. Later, the landmass broke up and the continentsbegan to drift apart.
The figure to the left shows thisidea. By the end of the Mesozoic era, the position of thecontinents was similar to what we know today.What caused Earth to change? It may be that the continents are part of rigid plates on Earth’s surface. Theplates sit on top of a molten layer of rock, which allowsthe plates to move around. The theory of how continentsmove is called plate tectonics (tek TAH nihks). Theplates are still moving.
Today they move at a rate ofabout six centimeters per year. This is about the samerate at which hair grows.EurasiaThe current era, the Cenozoic, began about 65 millionyears ago. That is December 26 on your calendar. Welive in the Cenozoic era. During this time large mammalsand humans first appeared. The modern human species,to which you belong, first appeared about 200 000 yearsago. That is late in the evening of December 31 onthe calendar.AfricaSouthAmericaIndiaAntarcticaC156liaratusABy 65 million years ago, the end of theMesozoic, most of the continents hadtaken on their modern shapes.Chapter 14READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.How did Earth change during theMesozoic era?NameDateClassSection14.1The Record of Life, continued◗ After You ReadMini Glossaryfossil: physical evidence of an organism thatlived long ago that scientists use to studythe past; evidence may appear in rocks,amber, or iceplate tectonics (tek TAH nihks): geological explanation for the movement of continents overEarth’s thick, liquid interior1.
Read the terms and their definitions in the Mini Glossary above. Select one of the terms andcreate a drawing in the space below that will help you remember its definition.2. Place the statements below the table under the correct heading in the table.The Record of LifeCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.FossilsGeological Time Scalea. May be a bone, tooth, or imprintb. Divided into erasc. Provide information about the variety of life in the pastd. Eras are further divided into periodse. Divisions based on kinds of organisms that lived thenf. Can provide information about ancient climates3. Review the section, then read each sentence below and fill in the blanks.
Use the followingterms to fill in the blanks: sedimentary, radiometric, plate tectonics, Cenozoic.a. Humans and large mammals appeared in theb. The theory ofc. Most fossils are found ind. Scientists useEra.explains how continents move.rocks.dating to determine the age of rocks and fossils.Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about the record of life.READING ESSENTIALSChapter 14157NameDateClassSection14.2 The Origin of Life◗ Before You ReadSC.D.1.4.3 The student knows that changes in Earth’s climate, geological activity, and lifeforms may be traced and compared. SC.D.1.4.4 The student knows that Earth’s systemsand organisms are the result of a long, continuous change over time.In this section, you will explore hypotheses that scientists have developed to explain how life on Earthbegan.
Scientists develop experiments that help them test hypotheses. On the lines below, list something in biology that you would like to learn more about. Then write a sentence explaining an experiment that you could use to learn more about the topic.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify KeyPeople Underline the nameof each scientist introducedin this section.
Say the namealoud. Then highlight the sentence that explains the maincontribution the person madeto understanding the originof life.1. What did Francesco Redi’sexperiment prove?________________________________________________________________________Before the invention of microscopes and modern scientificequipment, ideas about the origin of life came from what peoplesaw in the world they lived in.
When people noticed maggots onmeat, it was easy to assume that the maggots came from the meat.Likewise, when people found baby mice in sacks of grain, theythought that the grain produced the mice. These types of observations led people to believe in spontaneous generation. Spontaneous generation is the idea that something that is not alive canproduce living things.How was spontaneous generation disproved?An experiment, performed in 1668, showed that maggots werenot produced by decaying meat. An Italian doctor, FrancescoRedi, put meat into different jars. He covered some of the jars,and left the other jars open. Flies buzzed around the tops of thecovered jars but could not get to the meat. However, the meat inthe open jars attracted many flies. Maggots were soon growing inthose jars.
The maggots developed into flies. No maggots or fliesappeared in the covered jars. It was easy to conclude from thisexperiment that maggots do not come from spontaneous generation. Flies produce maggots, which become flies.What did Pasteur’s experiments prove?With the development of the microscope, scientists couldsee that microorganisms live everywhere. They wondered ifmicroorganisms came from the air. Was there some vital force inthe air that caused microorganisms to arise spontaneously?158Chapter 14READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Origins: The Early IdeasNameDateClassSection14.2The Origin of Life, continuedThis was a more difficult idea to prove false.
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