Focus on California Life Science 7th Grade Unit 2 - Chapter 7 Changes Over Time

Chapter . Changes Over ix Standards Preview , Biological evolution accounts for the diversity of species developed through gradual processes over many generations . As a basis for ' this concept a . Students know both genetic . tion and factors are ' causes of evolution and diversity of , organisms . Students know the reasoning used by Charles in reaching his . Conclusion that natural selection is ' the mechanism of evolution . Students know how independent lines of evidence from geology , fossils , and comparative anatomy provide the bases for the theory of evolution . Students know how to construct a ' simple branching diagram to classify ii i , living groups of organisms by shared derived characteristics and how to ) expand the diagram to include ! organisms . I . i . Students know that extinction of a , species occurs when the . merit changes and the adaptive ' characteristics of a species are ' insufficient for its survival . Evidence from rocks allows us to . understand the evolution of life on . Earth . As a basis for understanding this ' concept ' Students know fossils provide evidence of how life and ' mental conditions have changed ' Darwin observed Sally crabs and iguanas on the Galapagos Islands . 213

Gland Saul Changes Over Time ?

on the BIG Idea . What factors have caused the evolution and diversity of organisms ?

Check What You Know You plant a packet of seeds , and later , the zinnias begin to bloom . You notice that no two plants are exactly alike . For example , some flowers have different colors than others . What accounts for these differences ?

Write an explanation . Chapter 219 The images shown here represent some of the key terms in this chapter . You can use this vocabulary skill to help you understand the meaning of some key terms in this chapter . identify Multiple Meanings Some words , such as theory and cast , have different meanings in science and in everyday use . Look at the different meanings of theory and cast in the graphic below . Word Everyday Meaning ' A guess an idea of how or why something might happen Example Emily has a theory that basketball is harder to play than baseball . A device that protects a broken bone by preventing it from moving Example Tim broken elbow has healed , so the can be . Apply it ! in the sentences below , identify which meaning of the word everyday meaning or the meaning . The of evolution explains how organisms have changed overtime . Scientific Meaning A concept that explains a wide range of observations Example The cell ) ry says that all organisms are made of cells . A type of fossil that forms when a mold becomes filled with minerals Example The of the foot print shows that the extinct animal had five toes .

Chapter Vocabulary Section ( page 224 ) species fossil adaptation evolution ( theory natural selection variation Section ( page . comparative anatomy homologous structures mold cast petrified fossil trace fossil paleontologist gradualism equilibria Section page 241 ) habitat ( page 24 ) classification taxonomy binomial nomenclature genus Section ( page 255 tree diagram shared derived characteristic ' Build Science Vocabulary Online Visit Web Code chapter 221

Identify Supporting Evidence Scientific theories are always supported by a great deal of evidence . Evidence consists of facts that can be confirmed by testing or observation . A huge amount of evidence supports the theory of evolution . Section of this chapter identifies and explains this evidence . Look at the incomplete graphic organizer below . Notice that fossils provide one kind of evidence . Evidence Theory Evolution Apply It ! Copy the incomplete graphic organizer into your notebook . As you read Section , fill in the missing spaces with other kinds of evidence that support the theory of evolution .

1533 Standards Investigation Extinction and Fossils During the long history of life on Earth , many organisms have become extinct . Scientists have been able to learn a lot about many of these organisms because of the fossils they left behind . In this investigation , you will learn about an extinct organism whose fossils have been discovered in California . Your Goal To choose an extinct organism whose fossils have been discovered in California , and to research and present information about that organism To complete this project you must I research an extinct organism whose fossils have been found in California identify the environment that the organism probably lived in describe what may have led to the organism extinction create a way of displaying your findings to the class follow the safety guidelines in Appendix A Plan It ! Begin by choosing an extinct organism whose fossils have been discovered in California . Then find the information you need about the organism . Natural history museums and the Internet are good sources for identifying fossils found in California and for finding answers to your questions . Finally , decide how you will present that information to your class . Some possibilities include posters , booklets , and displays . Fossil of a grazing ground sloth found in the La Brea tar pits Chapter 223

Darwin Theory . 73 ' Standards Students know both genetic variation and environmental are causes of evolution and diversity of organisms . Students know the ing used by Charles Darwin in reaching his conclusion that natural selection is the mechanism of . What important observations did make on his voyage ?

How did Darwin account for the diversity of species and the differences between similar species ?

How does natural selection lead to evolution ?

Key Terms species fossil adaptation evolution I scientific theory natural selection variation FIGURE The Voyage of the Beagle Charles sailed on the Beagle to the Galapagos Islands . He saw many unusual organisms on the islands , such as giant tortoises and the booby . Interpreting Maps After leaving South America , where did the Beagle go ?

Replica of the Beagle 2249 How Do Living Things Vary ?

Use a ruler to measure the length and width of 10 sunflower seeds . Record each measurement . Now use a hand lens to carefully examine each seed . Record each seed shape , color , and number of stripes , Think It Over Classifying in what ways are the seeds in your sample different from one another ?

In what ways are they similar ?

How you group the seeds based on their similarities and differences ?

In December 1831 , the British ship Beagle set sail from England on a trip around the world . On board was a named Charles Darwin . Darwin eventually became the ships person who studies the natural world . His job was to learn as much as he could about the living things he saw on the voyage . Darwin observed plants and animals he had never seen before He wondered why they were so different from those in England . Darwin observations led him to develop one of the most important theories of all time the theory of evolution by natural selection .

Darwin Observations As you can see in Figure , the Beagle made many stops along the coast of South America . From there , the ship traveled to the Galapagos Islands . Darwin observed living things as he . He thought about relationships among those organisms . Darwin important observations included the diversity of organisms , the remains of ancient organisms , and the characteristics of organisms on the Galapagos Islands . Diversity Darwin was amazed by the tremendous diversity of living things that he saw . In Brazil , he saw insects that looked like and ants that marched across the forest like huge armies . In Argentina , he saw sloths , animals that moved very slowly and spent . much of their time hanging in trees . Today scientists know that organisms are even more diverse than Darwin could ever have imagined . Scientists have more than million species of organisms on Earth . A species is a group of similar organisms that can mate with each other and produce fertile offspring . Fossils Darwin saw the fossil bones of animals that had died long ago . A fossil is the preserved remains or traces of an ism that lived in the past . Darwin was puzzled by some of the he observed . For example , he saw fossil bones that resembled the bones of living sloths . The fossil bones were much larger than those of the sloths that were alive in Darwin time . He wondered what had happened to the giant creatures from the past . What is a fossil ?

Villa semi Changer Over A Giant tortoise A booby Chapter 225 FIGURE Comparing Iguanas Iguanas on mainland South America ( above ) have smaller claws than iguanas on the Galapagos Islands . Comparing and Contrasting In what other ways are the iguana different ?

226 Organisms In 1835 , the Beagle reached the Galapagos Islands . Darwin observed many unusual life forms on these small islands , such as giant tortoises , or land turtles . Some of these tortoises could look him in the eye ! After returning to England , Darwin thought about the organisms he had seen . He compared Galapagos organisms to organisms that lived elsewhere . He also compared organisms on different islands in the Galapagos group . He was su by some of the similarities and differences he saw . Comparisons to South American Organisms Darwin found many similarities between Galapagos organisms and those in South America . Many of the birds on the islands . including hawks , mockingbirds , and , resembled those on the mainland . Many of the plants were similar to plants Darwin had collected on the mainland . However , there were important differences between the organisms on the islands and those on the mainland . The nas on the Galapagos Islands had large claws that allowed them to grip slippery rocks . where they fed on seaweed . The iguanas on the mainland had smaller claws . Smaller claws allowed the mainland iguanas to climb trees , where they ate leaves . You can see these differences in Figure . From his observations , Darwin hypothesized that a small number of different plant and animal species had come to the Galapagos Islands from the mainland . They might have been blown out to sea during a storm or set adrift on a fallen log . Once the plants and animals reached the islands , they . their offspring became different from their mainland relatives .

. Comparisons Among the Islands As he traveled from one Galapagos island to the next , Darwin also noticed many differences among organisms . For example , the tortoises on one island had shells . Those on another island had shells . A government in the islands told Darwin that he could tell which island a tortoise came from just by looking at its shell . Adaptations Like the tortoises , the on the gos were noticeably different from one island to the next . The most obvious differences were the varied sizes and shapes of the birds beaks , as shown in Figure . An examination of the different showed that each species was well suited to the life it led . Finches that ate insects had narrow , beaks . Finches that ate seeds had strong , wide beaks . Beak shape is an example of an adaptation , a trait that helps an organism survive and reproduce in its environment . The beak structures help in obtaining food . Other adaptations help organisms avoid being eaten . For example , some plants , such as milkweed , are poisonous or have a bad taste . A variety of adaptations aid in reproduction . The bright colors of some attract insects . When an insect lands on a , the insect may pick up pollen grains , which produce sperm . The insect then may carry the pollen grains to another , enabling fertilization to take place . Roaring How did the beaks of Galapagos finches differ from one island to another ?

Ficus Galapagos Finches Darwin made these drawings of four species of Galapagos finches . The structure of each bird beak is an adaptation related to the type of food the bird eats . Comparing and Contrasting Identify some specific differences in these finches beaks . Bird Beak Adaptations Use this activity to explore adaptations in birds . Scatter a small amount of bird seed on a paper plate . Scatter 20 raisins on the plate to represent insects . Obtain a variety of objects such as tweezers , hair clips , and clothespins . Pick one object to use as a beak . See how many seeds you can pick up and drop into a cup in 10 seconds . Now see how many insects you can pick up and drop into a cup in 10 seconds . Use a different beak and repeat Steps and . Inferring What type of beak worked well for seeds ?

For insects ?

How are shaped beaks useful for eating different foods ?

Chapter 221 Evolution After he returned to England , Darwin continued to think about the diversity of species he had seen during his voyage . Darwin spent the next 20 years consulting with other scientists , ing more information , and thinking through his ideas . Darwin Reasoning Darwin especially wanted to stand the different adaptations of organisms on the Galapagos Islands . Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced environmental factors that were different from those on the mainland . Perhaps , Darwin hypothesized . the species gradually changed over many generations and became better adapted to the new ments . The gradual change in a species over time is called evolution . Darwin ideas are often referred to as the theory of tion . A theory is a concept that explains a wide range of observations . From the evidence he collected , Darwin concluded that organisms on the Galapagos Islands had changed over time . However , Darwin did not know how the changes had happened . Seattle Slew , A grandfather of Funny Selective Breeding Darwin studied other examples of changes in living things to help him understand how evolution might occur . One example that Darwin studied was the spring of animals produced by selective breeding . English farmers in Darwin time used selective breeding to produce sheep with wool . Pigeon breeders had produced pigeons with two or three times the usual number of tail feathers . The pigeon breeders did this by repeatedly allowing only those pigeons with many tail feathers to mate . Darwin thought that a process similar to selective breeding might happen in nature . But he wondered what process selected certain traits . is a theory ?

Distorted Humor . A father of Funny FIGURE Selective Breeding Race horses are selectively bred to obtain the trait of speed . Funny father , Distorted Humor , and , Seattle Slew , were known for their speed . 228 Turtles lay many eggs . Not all of the young will survive . Variation Each turtle has slightly different traits . For example , some turtles can move faster than others . Natural Selection In 1859 , Darwin published a book called On the Origin of Species by Natural Selection . In it , Darwin proposed that evolution occurs in nature through a mechanism he called natural selection . In natural selection , individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species . Darwin factors that affect the process of natural selection overproduction , tions , and competition . Figure and Figure show how natural selection might happen in a group of turtles . overproduction Darwin read Essay on the Principle of by an Englishman named Thomas Robert . argued that humans and other organisms tend to duce a lot of offspring . pointed out that sometimes the food supply is not large enough to feed all these offspring . Darwin knew that , in addition to food , living things needed other resources , such as water and living space . He also knew that overproduction occurs in many species . Many female insects , for example , lay thousands of eggs . It ' all newly hatched insects survived , they would soon crowd out all other plants and animals . Darwin knew that this doesn happen . Why not ?

Variations As you learned in genetics , members of a species differ from one another in many of their traits . A difference between individuals of the same species is called a genetic variation . For example , certain insects may be able to eat foods that other insects of their species avoid . This characteristic gives the insects an advantage over most insects in their species . FIGURE overproduction and Variation Like actual sea turtles , the turtles in this illustration produce many more offspring than will survive . some turtles are better adapted than others to survive in their environment . Relating Cause and Effect What adaptations might help young sea turtles survive ?

is Activity Making Models Scatter 15 black buttons and 15 white buttons on a sheet of white paper . Have a partner time you to see how many buttons you can pick up in 10 seconds . Pick up the buttons one at a time . Did you collect more buttons of one color than the other ?

Why ?

How can a variation such as color affect the process of natural selection ?

Chapter ?

6229 Turtles compete with one another . A faster turtle may escape from a predation such as speed make some turtles better able to ' sum in their environment . Competition Since food and other resources are limited , the members of a species must compete with each other to survive . Competition does not always involve direct physical between members of a species . instead , competition is usually indirect . For example , many insects do not enough to eat . Others are caught by predators . Only a few insects will survive . competition and Selection Darwin observed that some variations make Variations among turtles make better adapted to their environment . Those individuals ?

553 32 ?

are more likely to survive and reproduce . Their offspring may SU IVE . 85 SU We . become be able to helpful characteristic . The offspring , in turn , be more likely to survive and reproduce , and thus pass on the Applying Concepts What are characteristic to their offspring . After many generations , more af ha ' members of the species will have the helpful characteristic . might exhibit ?

In effect , the environment has selected organisms with helpful traits to become parents of the next generation . Darwin proposed that , over a long time , natural selection can lead to change . Helpful variations may gradually in a species , while unfavorable ones may disappear . Environmental Factors Factors in the environment can affect an organism ability to survive . Environmental factors can therefore lead to selection . For example , monkey are a type of plant . Most monkey can not grow in soil that has a high concentration of copper . However , because of genetic variation , some varieties of monkey now grow near copper mines , in spite of the copper in the soil . Here is how natural selection might have resulted in Go Dunne key flowers that can grow in soil . When ( the soil around a mine became contaminated , a small number of plants may have been able to survive in the high level of copper . These plants grew and reproduced . For Links on Charles Darwin ' After many generations , most of the seeds that sprouted in the soil produced monkey that could withstand the copper . 2300

Genes and Natural Selection Like environmental factors , genetic variation contributes to evolution . Without variations , all members of a species would have the same traits . Natural survival and Reproduction only a few turtles survive long enough to reproduce . The offspring may inherit the favorable traits of the parents . tion would not occur because all individuals would have an equal chance of surviving and reproducing . Darwin could not explain what caused variations or how they were passed on . As scientists later learned , variations can result from mutation and the of alleles during sis . Genes are passed from parents to their offspring . Because of this , only traits that are inherited , or controlled by genes , can be acted upon by natural selection . Section Vocabulary Skill Identify Multiple Meanings What does competition mean to a scientist studying evolution ?

What is another meaning of competition ?

Reviewing Key Concepts a . Listing List three general kinds of tions that Darwin made during his voyage . Comparing and Contrasting Contrast Galapagos iguanas to South American iguanas . Applying Concepts What is an adaptation ?

Explain how the claws of the Galapagos and South American iguanas are adaptations . a . Reviewing How did Darwin explain why Galapagos species had adaptations than similar South American species ?

I ) Developing Hypotheses How does selective breeding support Darwin hypothesis ?

Assessment . Writing , Reading a . Defining What is variation ?

What is natural selection ?

Relating Cause and Effect How do genetic variation and environmental factors work together to cause natural selection ?

Applying Concepts How do monkey near mines show that natural selection causes evolution ?

Writing in Science Interview . Chapter 231 Natu re at . Problem . Choose an event card . An card means the mouse survives . A or a card means How do species change overtime ?

the mouse dies . A card means the mouse skins Focus dies if its color contrasts with the white sand dunes . Only brown mice will die when a ' card is drawn . Record each death with a . tally mark in the data table . If the mouse lives , put the two mouse cards scissors in a live mice pile . If the mouse dies , put ' the cards in a dead mice pile . Putthe event ' card at the bottom of its pack . Repeat Steps through with the remaining Procedure mouse cards to study the first generation of mice . Record your results . Leave the dead mice cards untouched . Mix up the cards from the live mice pile . Mix up the events cards . Repeat Steps through for the second . Then repeat Steps through for the third generation . Work on this lab with two other students . One student should choose construction paper of one color and make the team 50 mouse cards , as described in Table . The second student should choose a different color construction paper and make the team 25 event cards , as described in Table . The third student should copy the data table and record all the data . PART A Forest Floor Environment . How would the data differ if the mice in this model lived on a dark brown forest floor ?

Record your prediction in your notebook . 10 . Make a new copy of the data table . Then use A White Sand Environment . Mix up the mouse cards . Begin by using the cards to model what might happen to a group of mice in an of white sand dunes . Choose two mouse cards . Allele pairs and duce a white mouse . Allele pair produces a brown mouse . Record the color of the mouse with a tally mark in the data table . the cards to test your prediction . Remember that a card now means that any mouse with white fur will die . Data Table Type of Environment Generation Brawn Mice White Mice Brown Mice I , 232

Table Mouse Cards Table Event Cards Dominant allele for white fur Recessive allele for brown fur Analyze and Conclude . Calculating In Part , how many white mice were there in each generation ?

How many brown mice ?

In each generation , which color mouse had the higher death rate ?

Hint To calculate the death rate for white mice , divide the number of white mice that died by the total number of white mice , then ply by 100 . Predicting If the events in Part occurred in nature , how would the group of mice change over time ?

Observing How did the results in Part fer from those in Part ?

Making Models How would it affect your model if you increased the number of cards ?

What would happen if you decreased the number of cards ?

Communicating Imagine that you are trying to explain the point of this lab to Charles Darwin . Write an explanation that you could give to him . To prepare to write , answer the following questions What are some ways in which this investigation models natural selection ?

What are some ways in which natural selection differs from this model ?

Mouse survives Disease kills mouse . Predator kills mice of all colors . kills contrast with the environment . Design an Experiment Choose a different species with a trait that ests you . Make a set of cards similar to these cards to investigate how natural selection might bring about the evolution of that species . Obtain your teacher permission before carrying out your investigation .

Evidence of Evolution , da , Focus Standards students know how What Can You Learn From Fossils ?

pendent lines of evidence from . Look at the fossil in the photograph . Describe 990109 ) and the characteristics in as much detail as anatomy provide the bases for the you can ' From your description in Step , out how the organism lived . How did it vide evidence of how life and . I . conditions have ?

are ' we Think It Over I Inferring What type of organism What do you think is related to the fossil ?

Why ?

theory oi evolution ?

How do fossils form ?

I , men I earn Does natural selection occur today ?

Evidence indicates that the answer is yes . Consider , for example , what happens when Key Terms called pesticides are used to kill harmful insects such as the comparative anatomy cockroaches below . When a pesticide is used in a building , it 1130 ' kills almost all the insects . But a few insects have traits that them from the pesticide . These insects survive . cast . fossil . The surviving insects reproduce . Some of their , trace fossil inherit the pesticide offspring , in turn , reproduce . Every time the pesticide is used , the only insects that gradualism survive are those that are not harmed by the pesticide . After ' punctuated equilibria many years , most of the cockroaches in the building are resistant to the pesticide . The development of pesticide resistance is one type of evidence that supports the theory of evolution . Forms of Evidence Since Darwin time , scientists have found a great deal of that supports the theory of evolution . Similar body structures , patterns of early development , molecular structure , and fossils all provide evidence that organisms mu have changed over time . Pesticide Resistance Many insect , including cockroaches such as these , are no longer killed by some pesticides . Increased pesticide resistance is evidence that natural selection is happening .

Similarities in Body Structure The comparison of the structures of different organisms is called comparative anatomy . An organisms anatomy is its body structure . Fishes , amphibians . reptiles , birds , and mammals all have a similar internal skeleton with a backbone . This is why classify all groups as vertebrates . All these groups probably inherited a similar structure from an early vertebrate ancestor that they shared . Figure shows that the bones of the front limbs of dolphins . birds , and dogs are arranged in a similar way . These similarities provide evidence that these three organisms all evolved from a common ancestor . Similar structures that related species have inherited from a common ancestor are known as homologous structures ( hoh uh gus ) Similarities in Early Development Scientists make about evolutionary relationships by comparing how ferent species develop before birth . During early . all vertebrates have a tail and rows of tiny slits in their throats . These similarities suggest that vertebrate species share a mon ancestor . Similarities in DNA and Proteins The structure of isms DNA and protein molecules also provides evidence of evolution . If two species have similar DNA and proteins , they probably evolved from the same ancestor . Eg , What are homologous structures ?

FIGURE Homologous Structures The structure of the bones in a flipper , a bird wing , and a dog leg is similar . Homologous bones are shown in the same color . Interpreting Diagrams How are all three orange bones similar ?

Look at the drawing below of the bones in a leg . Compare this drawing to Figure . Do you think that crocodiles share a common ancestor with birds , dolphins , and dogs ?

Support your answer with evidence . Chapter ?

235 FIGURE Fossil Formation Most fossils , such as the fossil An ancient crocodile dies and sinks to the bottom on river . crocodile shown here , form in sedimentary rock . Relating Cause and Effect In the process of fossil , what materials replace the crocodile remains ?

Preservation in Ice . Place fresh fruit , such as apple slices , strawberries , and blueberries , in an open plastic container . Completely cover the fruit with water . Put the container in a freezer . Place the same type and amount of fresh fruit in another open container . Leave it somewhere where no one will disturb it . After three days . observe the contents of both containers . Inferring use your tions to explain why fossils preserved in ice can include soft , fleshy body parts . 236 How Do Fossils Form ?

Fossil evidence supports the theory of evolution . The tion of any fossil is a rare event . Usually only the hard parts of the organism , such as the bones or shells of animals , form . Most fossils form when organisms that die become buried in sediments . Sediments are particles of soil and rock . When a river into a lake or ocean , the sediments that the river carries settle to the bottom . Layers of sediments may cover the dead organisms . Over millions of years , the layers may harden to become sedimentary rock . Molds and Casts The most common fossils are molds and casts . Both copy the shape of ancient organisms . A mold is a hollow area in sediment in the shape of an organism or part of an organism . A mold forms when the hard part of the ism , such as a shell . is buried in sediment . Later , water carrying dissolved minerals and sediment may seep into the empty space of a mold . If the water deposits the minerals and sediments there , the result is a cast . A cast is a solid copy of the shape of an organism . A cast is the opposite of its mold . Both the mold and cast preserve details of the mal structure . Petrified Fossils A fossil may form when the remains of an organism become . fossils are fossils in which minerals replace all or part of an organism . Fossil tree trunks are an example of wood . These fossils formed after sediment covered the wood . Then water rich in dissolved minerals soaked into spaces in the plant cells . Over time , the minerals came out of solution and hardened . Some of the wood remains in wood , but minerals have and preserved the wood .

The rock erodes . The fossil is exposed on the surface of a . Over millions of years . the sediments harden to become crocodile is preserved as a fossil . Trace Fossils Most types of fossils preserve the shapes of ancient animals and plants . In contrast , trace fossils provide of the activities of ancient organisms . A fossilized footprint is one example of a trace fossil . The mud or sand that the animal stepped in was buried by layers of sediment . Slowly the sediment became solid rock . preserving the footprint for millions of years . From fossil footprints , scientists can answers to tions about an animal size and behavior . Did the animal walk on two or four legs ?

Did it live alone or as part of a group ?

Other types of trace fossils also provide clues about ancient organisms . A trail or burrow can give clues about the size and shape of an organism , where it lived , and how it obtained food . Preserved Remains Some processes preserve the remains of organisms with little or no change . For example , some remains are preserved when organisms become trapped in tar . Tar is sticky oil that seeps from surface . Many fossils preserved in tar have been found at the Rancho La Brea tar pits in Los Angeles , California . Thousands of years ago , animals came to drink the water that covered these pits . Somehow , they became stuck in the tar and then died . The tar soaked into their bones , preserving the bones from decay . Ancient organisms also have been preserved in amber . Amber is the hardened resin , or sap , of evergreen trees . First , an insect is trapped on sticky resin . After the insect dies , more resin covers it , sealing it from air and protecting its body from decay . Freezing can also preserve remains . The frozen remains of woolly mammoths , huge ancient relatives of elephants , have been found in very cold regions of Siberia and Alaska . Freezing has preserved even the mammoths hair and skin . Reading What are three ways In which the remains of an organism can be preserved with little change ?

Go For Fossil activity Visit Web Code ( 231 It . yr . FIGURE to Fossil Clues to Past Environments Learning From Fossils Paleontologists ( pay lee . uh ) are scientists who of many different kinds of study fossils . collect . all over the were this world . The fossil record provides evidence about the ancient lakeshore environment . history of life and past environments on Earth . In addition , HOW think ' scientists use fossils to study the rate at which evolution has fossil of the bat was preserved ?

History of Life The oldest rock layers contain the oldest . The oldest fossils are simple organisms , such as bacteria . Much younger rocks contain the fossils of more more . such as plants and birds . In other words , the fossil record shows that life on has evolved , or changed overtime . Life began with organisms . After a long time , plants and animals appeared .

Past Environments ( use fossils to build up a picture of Earth past . The fossils found in an area tell whether the area was a desert , a . or a freshwater swamp . Suppose , for . a fossil looks a lot like a clam . Modern clams live in water . the fossil animal bly lived in water . too . Fossils can sh an environment has . For example , coal has been tound in But coal only forms from the remains of plants that grow in warm regions . Ice and snow new cover Antarctica , The presence of coal shows that the climate was once much warmer than today . Scientists can use fo to learn about changes in Earth surface . For . the fossils in Figure 10 are about 50 lion years old . were found in 21 region of dry plains and in . From these fossils , scientists have interred that back then the region had many shallow ' Sequoia

Gradualism Scientists also study fossils to try to determine the rate at which evolution occurs . Scientists are not sure how rapidly species change . One hypothesis , called gradualism , proposes that evolution occurs slowly but steadily . According to this hypothesis , tiny changes in a species gradually add up to major changes over very long periods of time . This is how win thought evolution occurred . If gradualism is correct , the fossil record should include intermediate forms between a fossil organism and its . However , there are often long periods in which fossils show little or no change . Then , quite suddenly , fossils appear that are very . One possible explanation for the lack of intermediate forms is that the fossil record is incomplete . may eventually more fossils to fill the gaps . Punctuated Equilibria The hypothesis of punctuated equilibria accounts for the gaps in the fossil record . According to this hypothesis , species evolve quickly during relatively short periods . These periods of rapid change are separated by long ods of little or no change . Today most scientists think that tion can occur gradually at some times and more rapidly at others . Reading What hypothesis proposes that evolution occurs . slowly but steadily ?

Assessment Target Reading Skill Identify Supporting a . Defining What is a paleontologist ?

Evidence Refer to your graphic organizer about , Reviewing can paleontologists evidence for evolution as you answer the from fossils ?

Inferring A paleontologist finds a fossil fish in rocks located in what is now a dry area What was the environment of that area probably like when the fish was alive ?

Reviewing Key Concepts a . Listing List four types of evidence that support evolution . Applying Concepts What is comparative anatomy and how do scientists use it to Interpreting Diagrams Compare the dolphin , bird , and dog forelimb bones in Mugging somatic with an adult Figure . List one specific way in which the family member , spread some mud in bone Structures are similar . shallow pan . Use to make What are sediments ?

How are footprints across the mud . Let the mud they involved in the formation of fossils ?

dry and harden . Explain how this is similar to fossil formation . Classifying Identify five types of fossils Comparing and Contrasting Which of the major types of fossils does not form in sediments ?

Describe how this type can form . 2400 0000 Students know that both genetic variation and tal factors are causes of evolution and diversity of organisms . Students know that tion of a species occurs when the environment changes and the adaptive characteristics of a are insufficient for its survival . What factors have contributed to the diversity of species ?

How do new species form ?

How do scientists infer evolutionary relationships among species ?

What causes the extinction of species ?

Key Terms habitat extinct Evolution of Species NIA Standards Which Is the Closer Relative ?

The pictures show a dog , a coyote . and a wolf . Compare and contrast the pictures carefully . On the basis of your comparison , decide which coyote or a more closely related to a dog . Think it Over Classifying Besides anatomical characteristics , what characteristics might scientists use to determine how closely organisms are related ?

You are hiking in the Mariposa Grove in Yosemite National Park . All around you are giant sequoias , those ancient evergreens that tower over the landscape . Sequoia needles cover the ground , and in some places you see the huge cones . You glimpse a bright spot of red on the forest and walk over to examine it . What in the world is it ?

It looks like a living thing . but you are sure what it is . Could it be a fungus ?

is it a plant ?

Whatever it is . it is both strange and beautiful . You have seen a flower of the snow plant , which grows in the Sierra Nevada mountains . Unlike most plants . the snow plant gets energy from dead and decaying material rather than through photosynthesis . The snow plant is just one of many interesting species of organisms that live in Yosemite . Flower of the snow plant Chapter 241

FIGURE 11 Lack of Diversity The worldwide population of cheetahs lacks genetic diversity . Relating Cause and Effect Why might this lack variation endanger the cheetah population ?

A Variety of Species Millions of species exist on , from tiny bacteria to huge sequoias . What factors account for this diversity of species ?

Over time , different environments and genetic variation have produced , through natural selection , the variety of organisms that exist today . Different Environments Think of the many different kinds of environments on Earth , from the deep sea to the tops of mountains . Organisms live in each of those environments . Over millions of years , natural selection has produced different , each with adaptations enabling it to live in a habitat . An organisms habitat is the environment that the things the organism needs to live , grow , and . Genetic Diversity Organisms within the same species do not all have identical traits . Think of how humans , for example , are different from one another . Therefore , organisms in a have different alleles for the genes that govern traits . Some genetic differences , or variations , may result from mutations in DNA . Others may be caused by the rearrangement of genes during meiosis . All the genetic variations in a species make up the total gene pool of that species . Many species have much variety in their gene pools . These species can often adapt to changes in the environment . That is because some individuals will have traits that let them survive in the new conditions . In some species , however , most of the organisms are cally similar . Those species may have difficulty surviving environ mental change . For example , a fungus once wiped out much of the corn crop in the United States . The corn plants were all very much like one another , and few plants had any resistance to the fungus . Today , many endangered species , such as , have little genetic variation . This lack of genetic variation may make them more likely to be destroyed by environmental change .

squirrel squirrel How Do New Species Form ?

Darwin theory on evolution by natural selection explains how variations can lead to changes in a species . But how does an entirely new species evolve ?

A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits . Geographic Isolation Scientists now hypothesize that graphic isolation is one of the main ways new species form . tion , or complete separation , happens when some members of a species become cut off from the rest of the species . Sometimes a group is separated from the rest of its species by a river , volcano , or mountain range . Even an ocean wave can separate a few individuals from the rest of their species . The wave can sweep some members of a species out to sea and later wash them up on an island . This may have happened to species on the Galapagos Islands . Once a group becomes isolated , members of the isolated group can no longer mate with the rest of the species . An Example of Isolation squirrel and the squirrel both live in forests in the Southwest . Look at the map in Figure . You can see that the populations of the two kinds of squirrel are separated by the Grand Canyon The and squirrels belong to the same species , but they have slightly different characteristics . For example , the rel has a black belly , while squirrel has a white belly . One day squirrel and the squirrel may become so ferent from each other that they will be separate species . How can some members of a species become separated from the main group ?

FIGURE 12 and Squirrels These two kinds of squirrels have been isolated from one another for a long time . Eventually , this isolation may result in two different species . 243 Inferring Species Relationships Some species are closely related to one another . Other species are distantly related . How do scientists determine relationships between species ?

Not too long ago , fossils , embryos , and body structures were the only tools that scientists had to determine how species were related . Today , scientists can also compare the DNA and protein sequences of different species . Scientists have combined the evidence from DNA , protein structure , fossils , early development , and body structure to determine the evolutionary relationships among species . Similarities in DNA Why do some species have similar body structures and development patterns ?

Scientists infer that the species inherited many of the same genes from a common ancestor Recently , scientists have begun to compare the genes of different species to determine how closely related the species are . Recall that genes are made of DNA . By paring the of nitrogen bases in the DNA of different species , scientists can infer how closely related the two species are . The more similar the DNA sequences , the more closely related the species are . For example . DNA analysis has shown that elephants and tiny elephant , shown in Figure 13 , are closely related . The DNA bases along a gene specify what type of protein will be produced . Therefore . scientists can also compare the order of amino acids in a protein to see how closely related two species are . Combining Evidence in most cases , evidence from DNA and protein structure has hypotheses based on , embryos , and body structure . For example . recent DNA comparisons show that dogs are more similar to wolves than they are to . Scientists had already reached this sion based on similarities in the structure and development of these three species . FIGURE 13 DNA and Relationships Because of its appearance , the tiny elephant shrew was thought to be closely related to mice and other rodents . However , DNA comparisons have shown that the elephant shrew is actually more closely related to elephants . 2440

Raccoons Lessor Pandas Present . 10 million years ago we . 25 million years ago 40 million years ago Giant Pandas Bears Common Ancestor Sometimes , however , scientists have changed their eses about species relationships . For example , lesser pandas were once thought to be closely related to giant pandas . Recently . however , DNA analysis and other methods have shown that giant pandas and lesser pandas are not closely related . Instead , giant pandas are more closely related to bears , while lesser pandas are more closely related to raccoons . Extinction of Species Thousands of years ago , artists painted graceful pictures of woolly mammoths on the walls of caves . Woolly mammoths , which looked a bit like elephants , once lived all over the world . However , they are now extinct . A species is extinct if no members of that species are still alive . Extinction and the Environment Most species that were preserved as fossils are now extinct . What makes a species become extinct ?

Extinction is caused by a change in a species environment . The members of the species may not have adaptations that allow them to survive and reproduce in the changed environment . There are many ways in which an environment can change . A new disease may strike a species . Predators may kill so many prey animals that the prey becomes extinct . For example , humans may have contributed to the extinction of woolly mammoths by hunting and killing too many of them . gall ! om What happened to most fossil species ?

Freon 14 Species Relationships This diagram shows how scientists now think that raccoons , lesser pandas , giant pandas , and bears are related . Interpreting Diagrams Are giant pandas more closely related to lesser pandas or to bears ?

Chapter 245 FIGURE 15 Wooly Mammoth Woolly mammoths became extinct after the climate warmed up . Section Assess Vocabulary Skill Identify Multiple Meanings in the term gene pool , what does pool mean ?

What is a more common meaning of pool ?

Reviewing Key Concepts Identifying Identify two factors that account for the diversity of species . Explaining What is genetic variation ?

Relating Cause and Effect Explain species with a diverse gene pool are usually less threatened by environmental change than are species whose members all have similar genes . a . Reviewing How can isolation lead to the formation of new species ?

Predicting A species of snake lives in a forest . A new road separates one group snakes from another . Is it likely that these two groups of snakes will become separate species ?

Why or why not ?

2460 Climate Change Climate change has been the ing cause of extinction . Climate change can destroy organisms habitats . Suppose , for example , an area that was once warm and moist becomes cool and dry . Many plants that need warmth and a lot of water may die . Animals that feed on those plants will be affected , too . Animal species may compete for the few ing plants . This competition could result in the tion of the plants and the animals that eat them . Climate change may have helped cause the tion of woolly mammoths . Woolly mammoths had traits that helped them live in a cool climate , such as thick coats of hair . When the climate became warmer , however , these traits were no longer helpful . Adaptation and Survival Environmental change does not always lead to extinction . Some organisms in a species may have traits that help them survive in a changed environment . Horseshoe crabs . for example , appeared on Earth long before the dinosaurs . These animals , which are related to spiders , have changed little over time , in spite of the fact that climate has changed several times . Writing , Reading a . Listing What kinds of evidence indicate how closely species are related ?

Inferring Of the kinds of evidence you listed above , which are probably the most reliable ?

Explain your answer . a . Reviewing What causes extinction ?

Relating Cause and Effect What two factors may have caused the extinction of woolly mammoths ?

Making Generalizations Explain how natural selection is at work when a species becomes extinct . of is Telltale Molecules . i Problem Analyze and Conclude What information can protein structure reveal about evolutionary relationships among . Interpreting Data Which animal amino acid sequence was most similar to that of the organisms ?

horse ?

what similarities and difference ( did you observe ?

Focus . Drawing Conclusions Based on these data , interpreting data , drawing conclusions which is most ' Velated ?

horse ?

Which is most distantly related ?

Procedure . Interpreting Data For the entire protein , the , Examine the table below . It shows the horse amino acid sequence differs from the sequence of amino acids in one region of Other i ' 35 . a protein , cytochrome , for six different rabbit . 22 turtle . 11 whale , How do the relationships indicated . Predict which of the five other animals is the those for most closely related to the horse . Which reg . mal do you think is most distantly related ?

Compare the amino acid sequence of the why in . about and horse to that of the donkey How many can provide information about evolutionary amino acids differ between the two species ?

among Record th bar in ot a More to Explore . Compare the amino acid sequences of each of , an , the other animals to that of the horse . Record ' the number of differences in your notebook . library and world wide web research out Then write a report communicating what you have learned . Section of Cytochrome Protein in Animals chapter

Students know how to construct a simple branching gram to classify living groups of organisms by shared derived and how to expand the diagram to include fossil organisms . Why do biologists organize living things into groups ?

What do the levels of classification indicate about the relationship between organisms ?

What characteristics are used to classify organisms into domains and kingdoms ?

Key Terms classification taxonomy binomial nomenclature genus ' FIGURE 16 Classifying Vegetables Vegetables in the produce section of a supermarket are neatly organized . 2486 Classifying Organisms Standards ?

Can You Organize a . Junk Drawer ?

Your teacher you some items that you might find in drawer of a desk . Your job is to organize the items . Examine the objects and decide on three groups into which you can sort them . Place each object into one of the groups , based on how the item features match the characteristics of the group . Compare your grouping system with those of your classmates . Think It Over Classifying Which of your classmates grouping systems seemed most useful ?

Why ?

Suppose you had only ten minutes to run into a supermarket to get what you and tomatoes . Could you do it ?

In most supermarkets this would be an easy task . You bly find out where the dairy and produce sections are , and head straight to those areas . Now imagine if you had to shop for these same items in a market where things were randomly placed throughout the store . Where would you begin ?

You have to search through a lot of things before you found what you needed . You could be there for a long time ! , Why Do Scientists Classify ?

just as shopping can be a problem in a disorganized store , ing information about a organism can also be a lem . Recall that scientists have more than million species . imagine how difficult it would be to information about one particular organism if you had no idea even where to begin . It would be a lot easier if similar organisms were placed into groups . Biologists group organisms based on similarities , just as grocers group mill with dairy products and tomatoes with produce . is the process of grouping things based on their similarities . Biologists classify fossil organisms as well as those that are alive today . Biologists use to organize living things into groups so that the organisms are easier to study . The study of how living things are is called taxonomy ( tak uh mee ) Taxonomy and evolution are closely related . Scientists infer that organisms in the same group , such as the beetles in Figure 17 , descended from a common ancestor . Taxonomy is part of the larger called . addition to classifying organisms , systematics tries to out their evolutionary relationships . sometimes change the way they classify organisms . New evidence , such as the organisms DNA , might show that the organism belongs in a different group . Also , may look at old evidence in a new way . Reading What is the study of how living things are ) classified called ?

FIGURE 17 Classifying Beetles These beetles belong to a large insect collection in a natural history museum . They have been classified according to characteristics they share . Observing What characteristics may have been used to group these beetles ?

chapter 249 The Naming System of In addition to grouping organisms , taxonomy involves naming them . In the 17505 , the Swedish naturalist Carolus devised a system of naming organisms that is still used today . placed organisms in groups based on their observable features . Based on his observations . gave each ' ism a unique , name . This naming system These three 5996395 Of Cats used is called binomial nomenclature ( by NOH mee belong to the same genus . Their names written ul NOH men ) The word means two names . in Latin , share the same first word , Fe , second word of and The word in an organisms their names name Is Its genus . A genus ( plural genera ) 15 a grouping that contains similar , closely related What characteristics do these organisms . For example . pumas , marbled cats , and house cats are all in the genus Felis . Organisms that are in the genus Felis share characteristics such as sharp , able claws and behaviors such as hunting other animals . The second word in a name often describes a feature of an organism , such as where it lives or its appearance . Together , the two words indicate a unique species . Recall that species is a group of similar organisms that can mate with each other and produce offspring that can also mate and reproduce . Reading What kind of name did give each ) organism ?

species share ?

concolor ( Puma ) Felis Fells ( Marbled cat ) Concolor means the same color , House ( at ) Notice the marbled pattern of this Notice that this animal coat is means animal coat . means mostly the same color . of the marble . 250 Using Binomial Nomenclature Notice in Figure 19 that a complete name is written in italics . Only the first letter of the word is capitalized . Notice also that names contain Latin words . used Latin because it was the language that scientists used during that time . Binomial nomenclature makes it easy for scientists to because everyone uses the same name for the same organism . Using different names can get confusing . For instance , people call the animal in Figure 19 a woodchuck , groundhog , or . Fortunately , it has only one . Levels of Classification The system that scientists use today is based on the contributions of . But today system uses a series of many levels to classify organisms . To help you understand the levels in , imagine a room with everybody from your state . First , all of the people from your town raise their hands . Then , those from your neighborhood raise their hands . Then , those from your street raise their hands . Finally , those from your house raise their hands . Each time , fewer people raise their hands . But you be in all of the groups . The most general group you belong to is the state . The most group is the house . The more levels you share with others , the more you have in mon with them . Of course , organisms are not grouped by where they live , but rather by their shared characteristics . The Major Levels of Classification Most biologists today classify organisms into eight levels . First , an organism is placed in a broad group , which in turn is divided into more groups . The more levels that two organisms share , the more characteristics they have in common . Here are the eight levels that biologists commonly use . A domain is the highest level of organization . Within a domain , there are kingdoms . Within kingdoms , there are phyla ( FY luh ) singular phylum ) Within phyla are classes . Within classes are orders . Within orders are families . Each family contains one or more genera . Each genus contains one or more species . FIGURE 19 Although there are many common names for this animal , it has only one scientific name . I For links on kingdoms Visit Web Code Chapter 251

Classifying an Owl Look at Figure 20 to see how the great horned owl is . The top row shows a wide variety of organisms that share the owl domain . Notice that as you move down the levels , there are fewer kinds of organisms in each group . The organisms in each new group have more in common , however . For example , the class Aves includes all birds . The order includes only owls . Flow 20 Classifying an Owl As you move down the levels of classification , the number of organisms decreases . The organisms at lower levels share more characteristics with each other . Interpreting Diagrams Do robins have more in common with lions or with owls ?

Three Domains Fungi Plants Domains and Kingdoms Today , a system of is commonly used . Shown in Figure 21 , the three domains are Bacteria , Archaea , and . Within the domains are kingdoms . Organisms are placed into domains and kingdom based on their cell type , their ability to make food . and the number of cells in their bodies . Bacteria Although you may not know it , members of the domain Bacteria are all around you . You can them in the yogurt you eat , on every surface you touch , and inside your body , both when you are healthy and sick . Some bacteria are autotrophs , while others are . Members of the domain Bacteria are ( prob KA ree ) are organisms whose cells lack a nucleus . Remember that a nucleus is a dense area in a cell that contains nucleic chemical instructions that direct the activities . In , nucleic acids are not within a nucleus . Archaea Deep in the Ocean , hot gases and molten rock spew out from a vent in the ocean floor . Surprisingly , a group of tiny organisms thrives there . They are members of the domain Archaea ( KEE uh ) whose name comes from the Greek word for Archaea can be found in some of the most extreme environments on Earth , including hot springs , very salty water , swamps , and the intestines of cows ! Scientists think that the harsh conditions in which archaea live are lar to those of ancient Earth . Like bacteria , archaea are unicellular . And like bacteria , some archaea are autotrophs while others are . Archaea are in their own domain , ever , because their structure and chemical makeup from that of bacteria . What Is a nucleus ?

From 11 Three Domains In the system of classification all known organisms belong to one of three Bacteria , Archaea , or . Activity Classifying Test your classifying skills using Figure 20 . Look carefully at the organisms pictured together at the kingdom level . Make a list of the characteristics that the organisms share . Then make two more lists of shared for the organisms at the class level and the other for those at the genus level . How does the number of shared characteristic on your lists change at each level ?

Chapter ?

9253 22 Domain The four kingdoms in domain are , fungi , plants , and animals . Making Generalizations what characteristic do all share ?

Protist What do seaweeds , mushrooms . tomatoes , and dogs have in common ?

They are all members of the domain . Organisms in this domain are ( yoo KA ree ) with cells that contain nuclei . classify into one of four kingdoms , fungi , plants , and animals . Other than having cells with nuclei , the members of the four kingdoms are very different from one another . A protist ( is any that can not be as a plant , an animal , or a fungus . Most are unicellular . Mushrooms , molds , and mildew are all fungi jy ) All fungi are , and most are multicellular . In contrast , all plants are multicellular autotrophs . All animals , such as a dog and a on the dogs ear , are . In addition , all animals are . section Assessment it Vocabulary Skill Identify Multiple Meanings . Identifying What are the three domains Contrast the common meaning of kingdom with into which organisms are classified ?

the meaning of kingdom in the of . Classifying Which two domains include living things . only organisms that are ?

Comparing and Contrasting How do the Reviewing Key , members of the two domains of a . Reviewing Why do biologists classify ?

differ ?

Inferring A is in the same genus as a house cat . What characteristics do you think a might have ?

a . Listing order the levels of , beginning with domain . Applying Concepts Woodchucks are in the same family as squirrels . but in a ent family than mice . Do woodchucks have more characteristics in common with squirrels or mice ?

Explain . At Home Activity Kitchen Classification With a family member , go on a classification hunt in the kitchen . Look in your refrigerator , cabinets , and drawers to discover what classification systems your family uses to organize items . 2540 Section Branching Trees I . Standards Focus Standards warn St . Note the characteristics of A organisms by shared derived A and . and how to expand die which is most similar to Figure ?

gram to include fossil organisms . Think It Over How does a branching tree diagram show Inferring Suppose these shapes are fossils of extinct organisms . Which organism do you think might be the ancestor of all the others ?

Explain your reasoning . Key Terms branching tree diagram , sham , derived Characteristic Two groups of organisms with similar characteristics may be descended from a common ancestor . The more similar the two groups are , the more recent the common ancestor probably is . To understand this , think of human families . Brothers and sisters usually look more like one another than they look like their cousins . Cousins share one set of grandparents . But ers and sisters share a more recent parents . A branching tree diagram shows probable evolutionary relationships among organisms . It also shows the order in which characteristics may have evolved . Branching tree diagrams begin at the base with the common ancestor of all the organisms in the diagram . Figure 23 , for example , begins with the ancestor of all animals . Amphibians Reptiles Fishes Invertebrates Egg with shell Four limbs FIGURE 23 A Branching Tree Branching trees such as this show relationships between groups of organisms . Interpreting Diagrams Are reptiles more closely related to or to invertebrates ?

Ancestor of animals , 255 Reptiles Amphibians Fishes Invertebrates Ancestor of animals FIGURE 24 Groups of Animals This branching tree shows relationships between groups of animals . Data Math Statistics . Data Analysis . and Probability Shared Derived Characteristics A branching tree diagram shows evolutionary relationships organisms tics . A shared derived characteristic is usually a homologous structure , such as a backbone , that is shared by all organisms in a group . Notice that . above each fork in Figure 24 , a label indicates a shared derived characteristic , such as a backbone or four limbs . On a branching tree , all the organisms above the label have the trait . In Figure 24 , for example , all organisms above the Backbone label have a backbone . Evolutionary Groups A branching tree has groups within groups . In Figure 24 , the largest subgroup is the group with backbones . Of the animals shown in the diagram , the bone group includes , amphibians , and reptiles . Within that group is a smaller with four limbs . Fishes are not in this group . but amphibians and reptiles are . The smallest group consists only of animals that produce eggs with . Species within any group are more closely related to one another than to species not in the group . Order of Characteristics Characteristics that appear lower on a branching tree probably developed before characteristics higher on the tree . Figure 24 shows that , during evolutionary history , animals with backbones appeared earlier than animals with both a backbone and four limbs . I What is a branching tree diagram ?

Data , for a Branching Tree Diagram The data in the table show shared derived Characteristics of Plants characteristics of different types of plants . Interpreting Data Do mosses have any of the characteristic indicated at the top of the table ?

Interpreting Data Which plant has the greatest number of the characteristics ?

Drawing Conclusions Use the information in the table to draw a branching tree . Hint Masses go at the base of the tree . Inferring A fossil plant shows evidence of flowers . Where in the diagram would the plant go ?

2560 Constructing a Branching Tree Suppose you have a list of organisms and their characteristics . gems of Show You want to use this information to draw a branching tree . At that it has a backbone but no legs . the base of the tree , write Common lust above the common ancestor , put the group of organisms with none of the characteristics . On the next higher fork , put the group with one of the shared derived characteristics . On the branch above that , put the organism with two of the characteristics . Continue this process until you get to the organism or group with the greatest number of shared derived characteristics . That group goes at the top of the tree . In Figure 24 , that group is reptiles . Branching tree diagrams can sometimes show fossils as well as living organisms . For example . look at the fossil in Figure 25 . The fossil has a backbone . but does it have four limbs ?

No . 50 you would put the fossil on the branch with . In fact , the fossil in the photograph is an extinct . Writing section Assessment ' a Vocabulary Skill Identify Multiple Meanings In the term branching tree , what does tree mean ?

What is a common meaning of tree ?

Reviewing Key Concepts Suppose that a . Reviewing How does a branching tree diagram ' divide organisms into groups ?

Interpreting Diagrams Choose one animal group in Figure identify the characteristics shared by group members . Classifying A fossil animal has four legs . What additional information would you need to put it on a branch in Figure 23 ?

Chapter 257 Chapter Genetic Idea . lY ' I . Darwin Theory Key Concepts , Darwin important observations included the diversity of organisms , the remains of ancient organisms , and the characteristics of organisms on the Galapagos Islands . Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced environmental factors that were different from those on the mainland . Perhaps , Darwin hypothesized , the species gradually changed over many generations and became better adapted to the new environments . Darwin proposed that , over a long period . natural selection can lead to change . Helpful variations may accumulate in a species , while unfavorable ones may disappear . Key Terms species theory fossil natural selection adaptation variation evolution Evidence of Evolution Key Concepts . Similar body structures , patterns of early development . molecular structure , and fossils all provide evidence of evolution . Most fossils form when organisms that die become buried in sediments . The fossil record provides evidence about the history of life and past environments on Earth . Key Terms comparative anatomy homologous structures mold cast fossil trace fossil paleontologist gradualism punctuated equilibria 2580 Evolution of Species Key Concepts , Over time , different environments and genetic variation have produced , through natural selection , the variety of organisms that exist today . A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits . Extinction is caused by a change in a species environment . DNA , protein structure , fossils , early development , and body structure are used to determine species relationships . Key Terms habitat Classifying Organisms Key Concepts Biologists use to organize living things into groups so that the organisms are easier to study . The more levels that two organisms share , the more characteristics they have in common . extinct Organisms are placed into domains and kingdoms based on cell type , ability to make food . and the number of cells in their bodies . Key Terms genus taxonomy binomial nomenclature Branching Trees ( Key Concepts A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristics . Key Terms branching tree diagram shared derived characteristic

Review and Assessment ' Target Reading Skill Identify Supporting Evidence In Section , you learned how scientists infer how closely species are related . To review this information , copy the partly completed graphic organizer at the right . Fill in the kinds of evidence that are missing . Choose the letter of the best answer . Go For Visit , Web Code Evidence relationships Reviewing Key Terms ( Ly . Changes in a species over long periods of time are called theories . evolution . homologous structures . developmental stages . A trait that helps an organism survive and reproduce is called a ( variation . adaptation . species . selection . Similar structures that related species have inherited from a common ancestor are called adaptations . punctuated equilibria . ancestral structures . homologous structures . The environment that provides an organism needs is called the organisms genus . taxonomy habitat . natural selection . An organism whose cells lack nuclei is called a ( protist fungus . Complete the following sentences so that your answers clearly explain the key terms . Darwin theory of evolution is an example of a theory , which is a ( Comparative anatomy is the comparison of . A species is extinct only if . brings order to the study of organisms because it is the process of 10 . A branching tree diagram shows evolutionary relationships by Writing in Science the write entry unusual have found ant ! a description of how trig adapted to to environment . moo HUI Changes Over Time Chapter 159

Review and Assessment Checking Concepts 11 . What role does the overproduction of organisms play in natural selection ?

12 . On the basis of similar body structures , scientists hypothesize that two species are closely related . What other evidence would support their hypothesis ?

13 . Contrast the hypothesis of gradualism to the hypothesis of punctuated equilibria . 14 . Explain how geographic isolation can result in the formation of a new species . 15 . What is meant by extinct ?

Explain how environmental factors might cause extinction . 16 . What are the advantages of identifying an organism by its name ?

17 . What is a shared derived characteristic ?

Thinking Critically 18 . Relating Cause and Effect Why did Darwin visit to the Galapagos Islands have such an important on his development of the theory of evolution ?

19 . Applying Concepts Some insects look just like sticks . How could this be an advantage to the insects ?

How could this trait have evolved through natural selection ?

20 . Predicting Which of the organisms shown below is least likely to become a fossil ?

Explain . 21 . Making Judgments What type of evidence is the best indicator of how closely two species are related ?

Explain your anwer . 22 . Comparing and Contrasting How are selective breeding and natural selection similar ?

How are they different ?

2609 Applying Skills Use the diagram below to answer Questions . Birds Reptiles Amphibians ' Feathers Scales Common ancestor 23 . Applying Concepts In the branching tree diagram above , what are the shared derived characteristics ?

24 . Interpreting Diagrams Which organisms in the diagram have scales ?

How do you know ?

25 . Interpreting Diagrams On the basis of the diagram , which group probably appeared , birds or reptiles ?

a Standards Investigation Performance Assessment Complete your poster . booklet , or whatever way you choose to present your findings to the class . Be prepared to explain why you chose the fossil species that you did . Also indicate where you found information about that fossil .

Choose the letter of the best answer . The process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species is called A natural selection . evolution . competition . overproduction . Which of the following is the best example of an adaptation that helps an organism survive in its environment ?

A green coloring in a lizard living on gray rocks a thick coat of fur on an animal that lives in the desert extensive root system in a desert plant thin , delicate leaves on a plant in a cold climate . Which of the following is the weakest evidence supporting a close evolutionary relationship between two animals ?

A The bones of a bird wings are similar to the bones of a dog legs . Human embryos look like turtle embryos in their early development . Lesser pandas look like bears . The amino acid sequence in mouse hemoglobin is similar to the amino acid sequence in chimpanzee hemoglobin . Most members of species of cat depend mainly on mice for food . For several summers in a row , a disease kills off most of the mice in an area . Over time , what is the most likely effect on the cat species ?

A All of the cats will die of starvation . Those cats that can eat foods other than mice will survive and reproduce . The cat species will lose its genetic diversity . There will be no effect on the cat species . at Use the table below and your knowledge of science to answer Questions . Some Types of Trees Bird cherry Plants Flowering cherry Plants minor Plants aria . Which of the following organisms is most different front the other three ?

A Primus minor Sorbus aria . Which of the following pairs of organisms should share the most characteristics ?

A and minor and Sorbus aria and and minor . Scientists have discovered fossils of ancient whalelike animals that had legs instead of . This evidence most likely indicates that the ancestors of whales A lived in the ocean . lived on land . evolved gradually rather than during short periods of rapid change . never became extinct . Predict how an extreme change in climate might affect natural selection in a species with little genetic variation . 161