CHAPTER 8 Developing a Theory of Evolutionvegalee.weebly.com/uploads/2/3/6/9/23691378/bio11_ch08-hist_evol-smaller.pdf · Developing a Theory of Evolution ... these lower strata turn

Developing a Theory of Evolution

CHAPTER

8Specifi c Expectations In this chapter, you will learn how to . . .

• C2.1 use appropriate terminology related to evolution (8.1, 8.2)

• C2.3 analyze, on the basis of research, and report on the contributions of various scientists to modern theories of evolution (8.1)

• C3.1 explain the fundamental theory of evolution, using the evolutionary mechanism of natural selection to illustrate the process of biological change over time (8.1, 8.2)

• C3.2 explain the process of adaptation of individual organisms to their environment (8.2)

The word evolution is oft en used to describe a process of change over time. Cars, fashion, language, and many other things are said to “evolve.” Evolution in the biological sense is the process by which hereditary changes occur in one or more characteristics within a species over long periods of time, usually over many generations.

Evolution by natural selection is a scientifi c theory that explains how Earth’s vast biodiversity developed in the past, continues to develop in the present, and will continue to develop in the future. Many theories have been developed through collaborative eff orts, and the theory of evolution is no diff erent. As you will learn in this chapter, the theory of evolution is built on the work of many contributors and is based on diff erent kinds of evidence, such as fossils.

Th e fossils shown here are trilobites. Th ese fossils were found in rock that is about 515 million years old. Th ere were more than 15 000 species of trilobites living in Earth’s oceans, but they disappeared about 260 million years ago.

324 MHR • Unit 3 Evolution

CO08_BIO11.indd 324 12/05/10 5:54 PM

Launch Activity

Forming a HypothesisMany theories are developed and refi ned as a result of collaborating with team members and with other teams. In this activity, you will collaborate with members in your group and with another group to try to identify an animal from its paper fossil bones. You can assume that all the fossil bones in your envelope are from the same animal.

Materials• paper fossils• printout of fossil remains of various animals

Procedure 1. Work in groups of four. Open your envelope of fossils, and remove

three fossil bones. Do not look at the other fossil bones in your envelope. Try arranging the bones in diff erent ways to help you form a hypothesis about the identity of the animal. Record the group’s hypothesis or hypotheses in a table like the one below.

Fossil Data

StepNumber of

BonesTotal Number

of Bones Hypothesis Notes

1 3 32 3 63 4 1045

2. Remove three more bones from your envelope. If necessary, revise your hypothesis and record your new hypothesis in your table.

3. Remove four more bones from your envelope. If necessary, revise your hypothesis and record your new hypothesis in your table.

4. Compare your fi ndings with those of another group. If necessary, revise your hypothesis and record your fi nal hypothesis in your table.

5. Compare your fossil assembly with the printout of fossil remains of other animals. Note any similarities and diff erences.

6. Return your fossil bones to the envelope, and return the envelope to your teacher.

Questions1. Did your group reach an agreement on the identity of the animal?

Explain why or why not. 2. From looking at the fossil and the printout of fossil remains, what

could you say about how and where this animal lived? 3. What features of the nature of science do you think this activity

demonstrates?

Chapter 8 Developing a Theory of Evolution • MHR 325

324-325_CO08_BIO11.indd 325 17/05/10 8:07 AM

SECTION

8.1Scientifi c Contributions to a Theory of Evolution

Key Terms

paleontology

catastrophism

uniformitarianism

inheritance of acquired

characteristics

theory of evolution by

natural selection

evolution

survival of the fi ttest

descent with modifi cation

Scientifi c knowledge develops as people observe the world around them, ask questions, and seek answers to their questions. A scientifi c hypothesis is a statement that provides one possible answer to a question, or one possible explanation for an observation. Hypotheses are tested to determine their validity, mainly through experiments, observation, developing models from data, or a combination of these activities. Hypotheses that consistently lead to successful predictions and explanations are sometimes synthesized into a general statement that explains and makes successful predictions about a broad range of observations. Such a statement is called a scientifi c theory.

Th e question “Where did we come from?” has been asked and debated for thousands of years. Many of the earliest ideas about the origins of life were strongly infl uenced by religion and philosophy. Th ese ideas suggested that all forms of life have existed, unchanged, since their creation. In the 1600s, however, scholars in Europe began to use a system of empirical studies to explain the natural world. Empirical studies involve observation and experiment to form ideas and hypotheses about nature.

Th e fi rst scientist to carry out empirical studies of the natural world was John Ray (1627–1705), in England. He developed a classifi cation system for plants and animals based on anatomy and physiology. Th is system was later extended by the Swedish naturalist Carolus Linnaeus (1707–1778). Both systems helped scientists of the time recognize and think about similarities and diff erences between organisms.

Georges-Louis Leclerc, Comte de Buffon (1707–1788) One of the fi rst people to publicly challenge the idea that life forms are unchanging was French naturalist Georges-Louis Leclerc, Comte de Buff on. His 44-volume Histoire Naturelle compiled his understandings of the natural world. In this work, Buff on noted the similarities between humans and apes, and speculated that they might have a common ancestor, suggesting that species change over time. In other writings, Buff on suggested that Earth was much older than 6000 years, as was commonly believed.

Buff on’s ideas were revolutionary for his time. By 1830, however, other scholars from many other areas of inquiry—paleontology, geology, geography, and biology—began to share their ideas to explain how life could change with the passage of time.

The Science of Paleontology Fossils are important to the study of evolution. A fossil is the preserved remains of a once-living organism. Fossils include specimens preserved in amber, permafrost, dry caves, and the more common fossils preserved as rock. Mary Anning (1799–1847), shown in Figure 8.1, was a fossil hunter in England. Her most important discovery was the fi rst plesiosaur, an aquatic reptile. French naturalist Georges Cuvier (1769–1832) was doing important work with fossils around Anning’s time. Cuvier examined Anning’s drawing of the plesiosaur to see if it was genuine. Cuvier’s acknowledgment of her work essentially made Anning respectable in the scientifi c world, a diffi cult achievement for a young woman in a male-dominated fi eld.

Georges Cuvier is largely credited with developing the science of paleontology—the study of ancient life through the examination of fossils. Cuvier found that each stratum (layer of rock) is characterized by a unique group of fossil species. He also found that the deeper (older) the stratum, the more dissimilar the species are from modern life (see Figure 8.2). As Cuvier worked from stratum to stratum, he found evidence that new species appeared and others disappeared over the passage of time. Th is evidence showed that species could become extinct.

paleontology the study of ancient life through the examination of fossils

Figure 8.1 Mary Anning was very skilled at collecting fossils. As a result, she made many important contributions to the field of paleontology.


326-331_S81_BIO11.indd 326 17/05/10 10:59 AM

older stratumwith older fossils

younger stratum with more recent fossils

thicker layer of sediment

A fossil is formed when an organism falls into a body of water and settles in the sediment. The sediments, brought by rivers or streams to larger bodies of water, keep the organism or parts of the organism from decomposing.

More sediment is laid down on top of older sediments and on top of remains of the organism. These additional layers of sediment compress lower strata, and then these lower strata turn into rock. Over time, many strata of rocks are formed. Sometimes, each of the strata contains fossils.

Movements of the soil and erosion of the rock can result in fossil-laden rocks being exposed above water level.

A B C

Figure 8.2 Deep rock strata (layers of rock) are older than strata that are closer to the surface. Different species of fossilized organisms can be found in different sedimentary rock strata. This is evidence that not all life forms came into existence at the same time.

CatastrophismTo explain his observations, Cuvier proposed the idea that Earth experienced many destructive natural events in the past, such as fl oods and volcanic eruptions. Th ese events, which he called revolutions, were violent enough to have killed numerous species each time they occurred. Cuvier’s idea is now called catastrophism. Cuvier suggested that these revolutions, or catastrophes, corresponded to the boundaries between the strata he studied. He also thought they were limited to local geographical regions, and that the area would be repopulated by species from nearby unaff ected areas. Th is is how Cuvier explained the appearance of fossils of species that did not exist anymore.

Charles Lyell (1797–1875)Other scientists had ideas that diff ered from Cuvier’s theory. Scottish geologist Charles Lyell rejected catastrophism. He proposed instead, based on the work of geologist James Hutton, that geological processes operated at the same rates in the past as they do today in a process called uniformitarianism. Lyell reasoned that, if geological changes are slow and continuous rather than catastrophic, then Earth might be more than 6000 years old. He also theorized that slow, subtle processes could happen over a long period of time and could result in substantial changes. Th e forces that build and erode mountains, for example, and the rate at which such geological change happens, are no diff erent today than they were in the past. Floods in the past had no greater power than fl oods that occur today. Th is idea inspired naturalist Charles Darwin and others. If Earth is slowly changing, they wondered, could slow, subtle changes also occur in populations?

catastrophism the idea that catastrophes such as floods, diseases, and droughts periodically destroyed species living in a particular region, allowing species from neighbouring regions to repopulate the area

uniformitarianism Charles Lyell’s theory (based on Hutton’s theory) that geological processes operated at the same rates in the past as they do today

1. What is the empirical system? 2. Why were Buff on’s ideas revolutionary for his time? 3. Contrast uniformitarianism and catastrophism. 4. Georges Cuvier explained the appearance of fossils

of species that did not exist anymore. Why is this an important contribution to science?

5. Do you think Cuvier’s ideas on catastrophism suggest the idea that organisms change over time? Explain your answer.

6. Do you think that the same geological processes operate today as they did in the past, as Lyell suggests? Is anything diff erent today? Explain your answer.

Learning Check


326-331_S81_BIO11.indd 327 18/05/10 1:51 PM

Cocos Is.

KingGeorgeSound

Hobart

Sydney

NewZealand

Tahiti

Galapagos Is.

Callao

Valparaiso

Tierra del Fuego Falkland Is.Montevideo

Rio deJaneiro

Bahia

England

AzoresCanary Is.

Cape Verde Is.

Ascension Is.St. Helena Is.

MauritiusM

C

Jean-Baptiste Lamarck (1744–1829)In his book Philosophie Zoologique, French naturalist Jean-Baptiste Lamarck outlined his ideas about changes in species over time. By comparing current species of animals with fossil forms, Lamarck observed what he interpreted as a “line of descent,” or progression, in which a series of fossils (from older to more recent) led to a modern species. He thought that species increased in complexity over time, until they achieved a level of perfection.

Lamarck hypothesized that the organisms would become progressively better adapted to their environments. At the time, many thought that body parts that were used extensively to cope with conditions in the environment would become larger and stronger. Following this reasoning, giraff es stretched their necks to eat the foliage from tall trees. Over time, they would pass on this stretched neck condition to their off spring, resulting in tall giraff es that can eat from the tops of trees. (It is important to note that giraff es did not develop their long necks in this way.) Lamarck called his idea the inheritance of acquired characteristics. Lamarck also suggested that body parts not used would eventually disappear. Th is idea is called use and disuse.

Lamarck provided a hypothesis for how the inheritance of characteristics from one generation to the next might happen. More importantly, he noted that an organism’s adaptations to the environment resulted in characteristics that could be inherited by off spring. At the time, there was little understanding of cell biology and no understanding of genetics. Th e idea of inheriting acquired characteristics was generally accepted to explain observations that species are not static and could change. Even Charles Darwin, who is credited with developing a comprehensive theory to explain how change in populations can occur, accepted Lamarck’s idea of inheritance and acknowledged Lamarck in his writing. But Lamarck’s ideas were controversial to the many people who fi rmly believed that species never changed.

Charles Darwin (1809–1882)In 1831, 22-year-old Charles Darwin left England on the HMS Beagle, a British survey ship. Th e primary purpose of the expedition was to map the coast of South America. Th e journey also provided Darwin with an opportunity to explore the natural history of various countries and geographical locations. Figure 8.3 outlines the Beagle’s journey.

At fi rst, Darwin did not always understand the signifi cance of many of his observations. Years later, however, many of these observations (as well as ideas and observations resulting from new work by Darwin and others) became important to his theory of evolution by natural selection. Darwin’s main observations, and the questions he asked about these observations, are summarized in Table 8.1.

inheritance of acquired characteristics the idea that characteristics acquired during an organism’s lifetime can be passed on to its offspring

theory of evolution by natural selection a theory explaining how life has changed, and continues to change, during Earth’s history

evolution the process of genetic change in a population over time

Figure 8.3 The five-year voyage of the HMS Beagle took Darwin around much of the world. He spent most of his time exploring the coast and coastal islands of South America.


326-331_S81_BIO11.indd 328 17/05/10 11:25 AM

Table 8.1 Darwin’s Observations and Questions Arising from Them

Observations Questions

1. Th e fl ora and fauna of the diff erent regions the Beagle visited were distinct from those Darwin had studied in England and Europe. For example, the rodents in South America were structurally similar to one another but were quite diff erent from the rodents Darwin had observed on other continents.

If all organisms originated in their present forms during a single event, Darwin wondered, why was there a distinctive clustering of similar organisms in diff erent regions of the world? Why were all types of organisms not randomly distributed?

2. Darwin observed fossils of extinct animals, such as the armadillo-like glyptodont, that looked very similar to living animals.

A glyptodont, an ancient 4 m, 2 tonne animal from South America

A modern armadillo from South America (1.5 m)

Why would living and fossilized organisms that looked similar be found in the same region?

3. Th e fi nches and other animals Darwin saw on the Galapagos [guh-LA-pa-gos] Islands closely resembled animals he had observed on the west coast of South America.

The Galapagos Islands, shown in this satellite image, include more than 20 small volcanic islands located approximately 1000 km off the coast of Ecuador, some of which are shown here. They formed at approximately the same time and have similar abiotic conditions.

Why did the Galapagos species so closely resemble organisms on the adjacent South American coastline?

4. Galapagos species (such as tortoises and fi nches) looked identical at fi rst, but they actually varied slightly between islands. Each type of Galapagos fi nch, for example, was adapted to eating a diff erent type of food based on the size and shape of its beak. Ten fi nch species that occur on one of the islands, Santa Cruz, are shown here.

warbler finch (Certhidea olivacea)

cactus ground finch (Geospiza scandens)

woodpecker finch (Cactospiza pallida)

sharp-beaked ground finch (Geospiza difficilis)

small insectivorous tree finch (Camarhynchus parvulus)

small ground finch (Geospiza fuliginosa)

large insectivorous tree finch (Camarhynchus psittacula)

medium ground finch (Geospiza fortis)

vegetarian tree finch (Platyspiza crassirostris)

large ground finch (Geospiza magnirostris)

Why was there such a diversity of species in such a small area? Could these species have been modifi ed from an ancestral form that arrived on the Galapagos Islands shortly aft er the islands were formed?

5. Th rough his experience with artifi cial selection (breeding pigeons and studying breeds of dogs and varieties of fl owers), Darwin knew that it was possible for traits to be passed on from parent to off spring, and that sexual reproduction resulted in many variations within a species.

Could a process similar to artifi cial selection also operate in nature?

Fernandina

Santa Cruz

Santiago

Isabela


S81_BIO11.indd 329 12/05/10 8:31 PM

Darwin, Wallace, and the Theory of Evolution by Natural SelectionAft er his trip on the Beagle, Charles Darwin began to propose answers to his questions, and to organize his and others’ observations into a comprehensive theory to explain how species change over time. Alfred Russel Wallace (1823–1913), another British naturalist, reached conclusions that were similar to Darwin’s.

Darwin and Wallace accepted that populations changed as time passed, but they were unclear how populations changed. An essay by economist Th omas Malthus (1766–1834), called Essay on the Principles of Population, provided them with a key idea. Malthus proposed that populations produced far more off spring than their environments (for example, their food supply) could support. He said that the populations were eventually reduced by starvation or disease.

According to Darwin and Wallace, individuals with traits that helped them survive in their local environments were more likely to survive to pass on these traits to off spring. Th ey reasoned that competition for limited resources between individuals of the same species would select for individuals with favourable traits—traits that increased their chances of surviving to reproduce. Th us, a growing proportion of the population would have these traits in later generations and, as time passed, the population as a whole would have them. Th is is the idea of survival of the fi ttest, and Darwin called this process natural selection. He published his ideas in 1859 in a book whose title is oft en shortened, for convenience, to Th e Origin of Species.

He proposed that all life descended from some unknown organism. As descendants of this organism spread out over diff erent habitats during the millennia, they developed adaptations that helped them better survive in their local environments. Darwin’s theory of natural selection showed how populations of individual species became better adapted to their local environments over time. His ideas are summarized as follows: • Organisms produce more off spring than can survive. Th erefore, organisms compete

for limited resources.• Individuals of a population vary extensively, and much of this variation is heritable.• Individuals that are better suited to local conditions survive to produce more off spring.• Processes for change are slow and gradual.

Descent with Modifi cationDarwin did not use the word evolution in the original edition of Th e Origin of Species. Instead, he spoke of descent with modifi cation. Darwin felt the word evolution implied progress, the notion that each generation was somehow improving in some way. Natural selection does not demonstrate progress; it has no set direction. It results from the ability of certain individuals in any population to survive local environmental conditions and to pass on the traits that helped them survive in the fi rst place.

survival of the fittest the idea that the organisms that are the fittest leave the most offspring, so those organisms win the struggle for survival; phrase coined by John Spencer

descent with modification Darwin’s theory that natural selection does not demonstrate progress, but merely results from a species’ ability to survive local conditions at a specific time

SuggestedInvestigationThoughtLab Investigation 8-A, Comparing the Ideas of Lamarck and Darwin

In this activity, you will research the work of several scholars whose work infl uenced Darwin.

Materials• computer with Internet access • print resources

Procedure 1. Using print or Internet resources, research how the

following contributed to Darwin’s theory of evolution: Comte de Buff on, Charles Lyell, Thomas Malthus, Jean-Baptiste Lamarck, and Alfred Russel Wallace.

2. Create a presentation that includes the following: • one contribution from each that is not mentioned in

this textbook, and the evidence that supports it • societal infl uences at the time of each contributor • how Darwin was infl uenced by their work

QuestionIn your opinion, which contributor was the most infl uential to the development of Darwin’s theory of evolution by natural selection? Explain your answer.

Activity 8.1 Building a Theory


326-331_S81_BIO11.indd 330 18/05/10 2:28 PM

Section 8.1 R E V I E W

Review Questions 1. K/U Explain how the diagram shown below is

evidence that not all life forms came into existence at the same time.

2. C Imagine yourself to be Cuvier, examining fossils. You fi nd the fossil of a species of fi sh in one stratum but not in the next highest stratum. Write a brief letter to a peer that proposes an explanation for your observations.

3. C Using a graphic organizer, show the diff erence between catastrophism and uniformitarianism, and how these ideas relate to the development of the theory of evolution.

4. K/U How did Lyell’s observations about changes in Earth’s geological features inspire naturalists’ ideas about changes in life forms on Earth?

5. A How might Lamarck have explained an elephant’s long trunk?

6. A An athlete breaks her leg. Years later she has a child who walks with a limp. Is this an example of evolution? Explain your answer.

7. K/U How is the work of Malthus related to the concept of survival of the fi ttest?

8. K/U Describe the contributions of the following people to the understanding of evolution.

a. Cuvier c. Wallace e. Lamarck b. Malthus d. Lyell

9. C Create a concept map showing the individuals from this section whose contributions led to the development of the theory of evolution by natural selection. State their contributions.

10. A Nature writer Wallace Stegner once wrote of a population of trout in a mountain lake that were in a “Malthusian dilemma.” Explain what Stegner meant.

11. T/I Explain why Darwin used the phrase descent with modifi cation rather than evolution.

12. K/U Describe, using two examples, how Charles Darwin used observations of the world around him to develop his hypothesis about how species might change with the passage of time.

13. C Draw a concept map that summarizes Darwin’s four main ideas related to evolution.

14. T/I Much of the theory of evolution has been developed by interpreting certain observations or by making logical inferences about these observations. Outline the inferences that Darwin and other scientists made from each of the following observations.

a. Some species found on islands are very similar to species found on neighbouring continents.

b. No two individuals are exactly alike. c. Resources, such as food, are limited.

15. A Explain how breeding dogs would provide you with observations that would support Darwin’s theory of evolution by natural selection.

Section Summary• Scientifi c theories explain facts and connect them

in a comprehensive way, enabling scientists to make predictions about new situations and experimental outcomes.

• Th e question of whether living things have changed over the course of Earth’s history has been considered by many diff erent philosophers and scholars.

• In Histoire Naturelle, Buff on challenged the idea that life forms are unchanging and that Earth was 6000 years old. Cuvier founded the science of paleontology and proposed catastrophism as an explanation for fossil history.

• Geologist Charles Lyell noted that Earth’s geological features were in a slow, continuous cycle of change, which he called uniformitarianism. Lamarck proposed the idea of inheritance of acquired characteristics, which suggested that parents passed on learned adaptations to the environment, which resulted in evolution.

• Darwin brought together his own observations from his journey on the HMS Beagle, his observations from his selective breeding, and the work of many other great thinkers to develop his theory of evolution. His theory proposes natural selection as the mechanism for how new species arise from ancestral species in response to the local environment.


326-331_S81_BIO11.indd 331 17/05/10 11:05 AM

SECTION

8.2Sources of Evidence for Evolution

In Th e Origin of Species, Darwin assembled a group of facts that had previously seemed unrelated. Darwin certainly was not the only person to conclude that life had changed over long periods of time, but he was the fi rst person to publish these ideas in a comprehensive manner. Darwin’s ideas were developed, for the most part, by his observations of the distribution of organisms throughout the world (as outlined in Table 8.1 on page 329). Before and aft er publication of Th e Origin of Species, biologists, geologists, geographers, and paleontologists provided a wealth of information that supported and strengthened what Darwin called—and today’s scientists also call—the theory of evolution by natural selection.

Fossils: Evidence for the History of Life Sedimentary rock with fossils provides a fossil record of the history of life by showing the kinds of species that were alive in the past, such as those shown in Figure 8.4. For instance, when people examined the Burgess Shale fossil beds in British Columbia, they found fossils of animals that lived in an ancient ocean during the Cambrian period, over 500 million years ago. In addition to micro-organisms and soft -bodied animals, the Burgess Shale fossil beds also preserved some of the earliest animals with hard parts to be seen in the fossil record. Some of the fossilized animals found in the Burgess Shale are ancestors of animals that are common today. Others have long been extinct and are unlike anything in our modern oceans. Th e geological time scale in Figure 8.5 shows approximately when organisms fi rst appear in the fossil record.

fossil record the remains and traces of past life that are found in sedimentary rock; it reveals the history of life on Earth and the kinds of organisms that were alive in the past

Key Terms

fossil record

transitional fossil

vestigial structure

biogeography

homologous structures

analogous structures

embryology

Figure 8.4 The animals unearthed in the Burgess Shale lived over 500 million years ago during a period called the Cambrian explosion, when there was a sudden increase (on a geological scale) in the diversity of animal species.

Opabinia

trilobitesPikaia


S82_BIO11.indd 332 12/05/10 8:28 PM

Eon

s

Eras

Peri

odsMillions of

Years ago

0

1.8

65

144

206

248

290

354

417

443

490

543

900

1600

2500

3000

3400

3800

4500

Permian

Triassic

Jurassic

Cretaceous

Tertiary

Quaternary

Carboniferous

Devonian

Silurian

Ordovician

Cambrian

7 million years agoHominids first appear in the fossil record

135 million years agoFlowering plants first

appear in the fossil record

160 million years agoBirds first appear in the fossil record

225 million years agoDinosaurs and

mammals first appearin the fossil record

300 million years agoReptiles first appear in the fossil record

543 million years agoShelled animals first

appear in the fossil record

2.5–2.0 billion years agoEukaryotic cells first appearin the fossil record

3.5 billion years agoFossils of primitive

cyanobacteria first appearin the fossil record

Pale

ozoi

cLa

teM

iddl

eEa

rly

Late

Mid

dle

Earl

yH

adea

nA

rcha

ean

Prot

eroz

oic

Prec

ambr

ian

Phan

eroz

oic

Ceno

zoic

Mes

ozoi

c

400 million years agoSeed plants first appear

in the fossil record; tetrapodsand insects first appear

in the fossil record

450 million years agoLarge terrestrial colonizationby plants and animals

520 million years agoFirst vertebrates; first

land plants

533–525 million years agoCambrian explosion creates diverse animal life

590 million years agoBilateral invertebrate animalsfirst appear in the fossil record

1.5 billion years agoMulticellular eukaryotic

organisms first appearin the fossil record

3.8–3.5 billion years agoProkaryotic cells first appear in the fossil record

Figure 8.5 This geological time scale illustrates the approximate appearance in the fossil record of various organisms during Earth’s 4.6 billion year history. Note that this illustration is not to scale.


S82_BIO11.indd 333 12/05/10 8:28 PM

Paleocene Eocene Oligocene Miocene Present

26 million years ago




skull

toothleg bone

Evidence from the Fossil RecordTh e fossil record provides the following evidence:• Fossils found in young layers of rock (from recent geological periods and usually

closer to the surface) are much more similar to species alive today than fossils found in older, deeper layers of rock. For example, paleontologists have used fossils to trace the evolution of the modern camel. As you can see in Figure 8.6, the camel ancestor from the Miocene epoch is more similar to the modern camel than the ancestors from the more distant epochs.

• Fossils appear in chronological order in the rock layers. So, probable ancestors for a species are found in older rocks, which usually lie beneath the rock in which the later species is found.

• Not all organisms appear in the fossil record at the same time. For example, the fossil history of vertebrates shows that fi sh are the oldest vertebrates. In subsequent layers, the fossils of other vertebrates—amphibians, reptiles, mammals, and birds—appear. Th is reinforces scientifi c evidence that amphibians evolved from ancestral fi sh, reptiles evolved from ancestral amphibians, and both mammals and birds evolved from diff erent groups of reptiles (mammals fi rst, and then birds). It is important to remember that these changes were slow and took millions of years.

Figure 8.6 Paleontologists have used fossils to trace the evolution of the modern camel. The Paleocene, Eocene, Oligocene, and Miocene epochs are subdivisions of the Cenozoic era.

Evidence from Transitional FossilsTh e original fossil record gave only scattered “snapshots” of ancestral forms. Scientists wondered about the gaps between these snapshots. Th e ongoing discovery of hundreds of transitional fossils—fossils that show intermediary links between groups of organisms—has helped scientists better understand the evolutionary process and relationships between groups of organisms. Transitional fossils link the past with the present.

For example, scientists have found fossilized whales that lived 36 to 55 million years ago. Th ese fossils link present-day whales to terrestrial ancestors. Basilosaurus and Dorudon were ancient whales that had tiny hind limbs but led an entirely aquatic life. Dorudon was about the size of a large dolphin, about 5 m long. It had a tiny pelvis (located near the end of its tail) and legs about 10 cm long. Th ese characteristics would have been useless to an animal that lived an aquatic life. Structures that are the reduced forms of structures that were functional in the organism’s ancestors are called vestigial structures. Th e pelvic bone in the Dorudon whale—and in some modern whales, such as baleen whales—is called a vestigial pelvic bone.

Ambulocetus, a transitional form that was discovered more recently (announced in 1994), had heavier leg bones. Scientists hypothesize that it lived both on land and in water. In Figure 8.7, compare Ambulocetus with a modern toothed whale, as well as two other ancestors of present-day whales, Pakicetus and Rodhocetus. Th e discovery of Pakicetus and Rodhocetus has fi lled gaps in the fossil record of whales.

transitional fossil a fossil that shows intermediary links between groups of organisms and shares characteristics common to two now separate groups

vestigial structure a structure that is a reduced version of a structure that was functional in the organism’s ancestors


S82_BIO11.indd 334 12/05/10 8:28 PM

Pakicetus attocki lived on land, but its skull had already evolved features characteristic of whales.

Ambulocetus natans likely walked on land (as modern sea lions do) and swam by flexing its backbone and paddling with its hind limbs (as modern otters do).

Rodhocetus kasrani’s small hind limbs would not have helped it swim, much less walk.

Modern toothed whale

Gondwana

AfricaIndia

Australia

Antarctica

SouthAmerica

Archaeopteryx: A Transitional Fossil In 1995, the fossil of a previously unknown dinosaur called Atrociraptor (savage robber) was discovered near Drumheller, Alberta. Atrociraptor was a small meat-eating dinosaur, about the size of a 10-year-old child. It is thought to be a close non-birdlike relative of Archaeopteryx. Fossils of Archaeopteryx show a transitional stage in the fossil record because this species had characteristics of both reptiles (dinosaurs) and birds. Archaeopteryx had feathers, but, unlike any modern bird, it also had teeth, claws on its wings, and a bony tail.

Evidence from BiogeographyBiogeography is the study of the past and present geographical distribution of organisms. Many of the observations that Darwin and Wallace used to develop their theories were based on biogeography. Darwin and Wallace hypothesized that species evolve in one location and then spread out to other regions. Biogeography supports this hypothesis with examples such as the following:• Geographically close environments (for example, desert and forest habitats in South

America) are more likely to be populated by related species than are locations that are geographically separate but environmentally similar (for example, a desert in Africa and a desert in Australia). So, for instance, cacti are native only to the deserts of North, Central, and South America. Th ey are not found naturally in other deserts in the world, such as those in Australia and Africa.

• Animals found on islands oft en closely resemble animals found on the closest continent. Th is suggests that animals on islands have evolved from mainland migrants, with populations becoming adapted over time as they adjust to the environmental conditions of their new home. For example, the lizards found on the Canary Islands, off the northwest coast of Africa, are very similar to the lizards found in west Africa.

• Fossils of the same species can be found on the coastline of neighbouring continents. For example, fossils of the reptile Cynognathus have been found in Africa and South America. How can this be explained? Th e location of continents is not fi xed; continents are slowly moving away from one another. About 510 million years ago, the continents of Africa and South America were joined in one supercontinent, called Gondwana, as shown in Figure 8.8.

• Closely related species are almost never found in exactly the same location or habitat.

biogeography the study of the past and present geographical distribution of species populations

Figure 8.7 Fossil evidence suggests that modern toothed whales evolved from a terrestrial ancestor, Pakicetus attocki. Basilosaurusand Dorudon, not shown in this illustration, appear more recently in the fossil record, after the appearance of Rodhocetus.

Figure 8.8 As the southern supercontinent Gondwana broke apart about 150 million years ago, the land masses that became the current continents of Africa, Australia, South America, and Antarctica were isolated from each other.


332-340_S82_BIO11.indd 335 17/05/10 11:06 AM

Human Frog Bat Porpoise Horse

Evidence from AnatomyVertebrate forelimbs can be used for various functions, such as fl ying (birds and bats), running (horses and dogs), and swimming (whales and seals). Despite their diff erent functions, however, all vertebrate forelimbs contain the same set of bones, organized in similar ways. How is this possible? Th e most plausible explanation is that the basic vertebrate forelimb originated with a common ancestor.

Homologous structures are those that have similar structural elements and origin but may have a diff erent function. Th e limbs shown in Figure 8.9 have similar structures, such as number of bones, muscles, ligaments, tendons, and blood vessels. Th ese structural elements are arranged, however, to be best suited for diff erent functions: walking, fl ying, or swimming. Homologous structures are similar because they were inherited from a common ancestor. As you can see in Figure 8.9, homologous structures diff er in their anatomy based on an organism’s lifestyle and environment. For example, the bones in a horse’s leg are larger and heavier than the bones in a bat’s wing.

homologous structuresstructures that have similar structural elements and origin but may have a different function

7. What is the fossil record? 8. Explain two ways in which the fossil record has

helped scientists understand that organisms change over time.

9. Why are transitional fossils important? 10. How does the existence of vestigial pelvic bones

in whales refute Lamarck’s idea of use and disuse?

11. Compare each drawing in Figure 8.6 and describe the changes that you see from one epoch to the next.

12. Explain the following sentence: Islands have many unique species of animals and plants that are found nowhere else in the world.

Learning Check

Figure 8.9 These vertebrates have the same basic arrangement of bones (as indicated by the colours), but the bones have different uses.

Homologous structures can be similar in structure, function, or both. Th e limbs in Figure 8.9 are structurally similar. Th e lower limbs of the human, frog, and horse perform the same function: movement on land. Functional similarity in anatomy, however, does not necessarily mean that species are closely related. Th e wings of insects, birds, bats, and pterosaurs (extinct fl ying reptiles) are similar in function but not in structure. For example, bones support bird wings, whereas a tough material called chitin [KYE-ten] makes up insect wings. All of these organisms evolved independently of one another, and they do not share a common ancestor with wings.

Body parts that perform similar functions, even though the organisms do not have a close common evolutionary origin, are called analogous structures. Analogous structures evolve in species of diff erent origin who live in similar ecological units.

analogous structures structures of organisms that do not have a common evolutionary origin but perform similar functions


S82_BIO11.indd 336 12/05/10 8:28 PM

Mammals are the only animals that have hair. Among mammalian species, hair can vary in length, density, texture, and colour. The basic structure of hair, however, is the same in all mammals. Each hair has a central medulla that is surrounded by a dense cortex, which contains most of the pigment granules that give each strand of hair its colour. A layer called the cuticle covers the cortex. The scales of the cuticle are specifi c to a particular genus or even species of mammals. Thus, mammalian hair has a common origin, yet may serve diff erent functions. In this activity, you will investigate variations in the functions of mammalian hair.

cuticleCross Section of a Hair

cortexmedulla

cuticularscale

pigmentgranules

Materials• computer with Internet access • print resources

Procedure1. Work in a group of three or four.

2. Each person in your group should choose a diff erent type of mammalian hair from the following list:

• stout, strong hairs of a porcupine• dense underfur, or underhairs, of a sea otter• whiskers (vibrissae) of a cat • long, thick hair of a woolly mammoth• horn of a rhinoceros, which is made of densely

packed hair• thick mane of a lion• “scales” of a pangolin, which are modifi ed hairs• soft, fl uff y underfur (qiviut) of a musk-ox

3. Using print and Internet sources, research the structure of the hair you have chosen. Research how the animal’s lifestyle and habitat might explain the particular function(s) of its hair.

Questions1. Based on the information you collected and your

understanding of natural selection, hypothesize how the structure of the hair is related to abiotic conditions in an animal’s environment. Write a hypothesis stating how the variations might have arisen from the basic hair structure of a common mammalian ancestor.

2. Present your fi ndings to the others in your group in a written or oral report, a computer presentation, or another form that is easily shared.

3. In a graphic organizer, describe one similarity and one diff erence in the adaptation of the hair studied by the members of your group.

Activity 8.2 Homologies of Hair

porcupine

rhinoceros

sea otter

lion

cat

pangolin

woolly mammoth

musk-ox

Homologous HairIn mammals, hair is homologous. Compare variations in the functions of mammalian hair by completing Activity 8.2 below.


S82_BIO11.indd 337 12/05/10 8:29 PM

Fish Chicken Pig Human

Evidence from EmbryologyEmbryology is the study of early, pre-birth stages of an organism’s development. Embryology has also been used to determine evolutionary relationships between animals. Th e embryos of diff erent organisms exhibit similar stages of embryonic development. For example, all vertebrate embryos have paired pouches, or out-pocketings, of the throat. In fi sh and some amphibians, the pouches develop into gills. In humans, the pouches become parts of the ears and throat. At certain stages in the development of the embryo, the similarities between vertebrates are more apparent than the diff erences, as you can see in Figure 8.10.

Th e similarities between embryos in related groups (such as vertebrates) point to a common ancestral origin. It follows that related species share both adult features (such as basic arm-bone arrangements, as discussed earlier) and embryonic features (such as the presence of paired pouches in the throat).

embryology the study of early, pre-birth stages of an organism’s development

Figure 8.10 Similarities in the embryos of fish, birds, and mammals provide evidence of evolution of species from a common ancestor.

Describe the differences and similarities between the fish and the chicken embryos.

Evidence from DNAAs you learned in Section 1.2, the evolutionary relationships between species are refl ected in their DNA. Since DNA carries genetic information, scientists can determine how closely related two organisms are by comparing their DNA. If two species have similar patterns in their DNA, this indicates that these DNA sequences must have been inherited from a common ancestor. For example, by studying gene sequences, scientists have determined that dogs are related to bears and that whales and dolphins are related to ungulates [UN-gya-lets] (hoofed animals such as cows and deer).

Th e use of modern technology has led to many discoveries that support Darwin’s theory. Scientists now know how species pass on their traits to their off spring, and how the genes for these traits could change by mutation, as you learned in Section 7.1. Current evolutionary theory connects genetics with the theory of natural selection, and how natural selection operates on populations. Th us, genetic evidence and our understanding of heredity and mutations lend support to hypotheses that stem from observations of fossils, anatomy, biogeography, embryology, and DNA relationships.


332-340_S82_BIO11.indd 338 17/05/10 11:07 AM

softtissue

BIOLOGY ConnectionsS T S E

T. rex and chickens share a common ancestor?

Connect to Scientifi c Inquiry

Before researchers tested the reaction of protein and collagen in the soft tissue of chickens and dinosaurs, they had to formulate a hypothesis. Write a hypothesis that they might have tested.

The soft tissue from the T. rex was almost perfectly preserved.

In previous studies, physical similarities between early bird fossils and dinosaur fossils supported this link. For example, some fossils showed that the earliest birds had feet very similar to dinosaur feet. Several dinosaur fossils also show evidence of feathers.

THE TEST A group of scientists at North Carolina State University introduced a protein to chicken and the T. rex soft tissue. Th e protein reacted strongly in the presence of the collagen found in chickens. (Collagen is a protein found in the connective tissue of animals.) A similar reaction was observed when the protein was administered to the dinosaur tissue. Th is indicates a molecular similarity between chicken tissues and dinosaur tissues. In another study performed by a team of researchers from Harvard Medical School, scientists obtained protein sequences from the T. rex soft tissue. Th e amino acid sequence in the proteins was similar to the amino acid sequence in chickens, showing clear support for an ancestral link between chickens and dinosaurs. (Amino acids are compounds that form proteins.)

Two independent tests on the soft tissue found in the fossil indicate that the T. rex is likely related to the present-day chicken. Th is new research provides molecular evidence that supports hypotheses that a common ancestor linked birds and dinosaurs.

Aft er excavating a T. rex fossil in 2003, scientists found it was too big to transport by helicopter. Th e scientists carefully broke the thigh bone in half to ship the bone. Th e results of later tests on the broken bone were surprising—the bone held preserved soft tissues! Th ese tissues, shown in the photograph below, included connective tissue, blood vessels, and possibly even blood cells.

SOFT TISSUE In 2007, the fossil of the 68-million-year-old T. rex was tested for the fi rst time to see if dinosaurs could be shown to share genetic markers with modern animals. Th e examination of dinosaur fossils allows scientists to understand how life on Earth has changed over time. Th e discovery of soft tissue allows new tests to be performed. It is possible that many more dinosaur bones contain soft tissue samples.

Molecular evidence suggests that the Tyrannosaurus rex and the chicken are related. (These images are not to scale.)


S82_BIO11.indd 339 12/05/10 8:29 PM

Section 8.2 R E V I E W

Review Questions 1. K/U Charles Darwin was not the only person to

discuss the idea of evolution. Why is his name oft en synonymous with the idea of evolution?

2. T/I Evolutionary biologist John Haldane once said, “I’d give up my belief in evolution if someone found a fossil rabbit in the Precambrian.” Explain this quote.

3. K/U How does the discovery of transitional fossils in the fossil record help you understand the evolutionary events of the past?

4. C Choose a fossil (either one described in this textbook or another one you have researched) and describe what information it provides that helps you understand evolution.

5. K/U A scientist fi nds a rare organism—a whale with hind legs. Explain how this fi nding is evidence for evolution.

6. A Th e island of Madagascar is thought to have split from Africa about 150 million years ago. Discuss the types of organisms you would expect to fi nd on this island. Explain your reasoning.

Africa

Madagascar

The island of Madagascar is just east of Africa.

7. T/I Make a hypothesis about what species changes and environmental changes you would expect to see on Madagascar, aft er a long period of time, if it were somehow reconnected to mainland Africa today. How might a scientist test your hypothesis?

8. K/U Describe how comparing the anatomy of animals is used to support the theory of evolution by natural selection.

9. K/U What kinds of structures are the arm of a human and the forelimb of a horse?

10. K/U Explain the diff erence between analogous structures and homologous structures.

11. K/U Are bird wings and bat wings homologous structures or analogous structures? Explain your answer.

12. K/U Defi ne vestigial structure. Provide an example. 13. T/I Scientists discover that the pharyngeal (gill)

pouches are similar in the early embryological stages of vertebrates such as snakes, cats, bats, and human embryos. Yet, the later stages of development show many more diff erences between these organisms. Explain why the early stages are so similar.

14. C Create a concept map that shows how diff erent types of scientifi c evidence support the theory of evolution. Go to Using Graphic Organizers in Appendix A to learn more about making a concept map.

15. T/I A person tells you that evolution, like the big bang, is “just a theory.” Explain to the person what a theory means in a scientifi c sense, and provide four facts that support the theory of evolution.

16. T/I Baleen whales, such as grey and humpback whales, have teeth and body hair while they are embryos, but they lack these features as adults. What does this tell you about the evolutionary history of these animals?

17. C Use a diagram such as a fl owchart to illustrate the process of evolution by natural selection in a giraff e population competing for leaves in the high canopy of trees. Go to Using Graphic Organizers in Appendix A to learn more about making a fl owchart.

Section Summary• Th e theory of evolution connects facts to provide a logical

framework that explains how life on Earth has changed and is still changing.

• Charles Darwin and Alfred Russel Wallace both developed hypotheses to explain natural selection.

• New discoveries of fossils, called transitional fossils, help fi ll in the gaps in the fossil record.

• Homologous structures have similar structural elements and origin but may have a diff erent function. Analogous structures perform similar functions, even though the organisms do not share a recent common ancestor.

• Th e fossil record, biogeography, anatomy, embryology, and relationships in DNA all provide evidence for evolution.


332-340_S82_BIO11.indd 340 16/07/10 8:10 AM

S k i l l C h e c k

Initiating and Planning

✓ Performing and Recording

✓ Analyzing and Interpreting

✓ Communicating

Comparing the Ideas of Lamarck and DarwinDarwin and Lamarck both developed ideas about the inheritance of characteristics. Although Darwin read Lamarck’s work and learned from his ideas, Darwin eventually proposed an alternative hypothesis that gave a diff erent explanation for the mechanism that resulted in biological change. Read the quotations from the writings of Lamarck and Darwin on the left .

Pre-Lab Questions 1. List two ideas proposed by Lamarck’s theory of evolution. 2. List two ideas proposed by Darwin’s theory of evolution.

QuestionWhat is the key diff erence between the ideas of Lamarck and Darwin?

Organize the Data 1. Rewrite each quotation in your own words.

Analyze and Interpret 1. How does Lamarck’s idea of “use or disuse” diff er from Darwin’s idea, which

was later called “descent with modifi cation”? 2. Flying fi sh (Exocoetus volitans) use large pectoral fi ns to glide in air to

escape predators. Explain how Lamarck and Darwin might account for the origin of these large pectoral fi ns and the ability to glide.

Conclude and Communicate 3. A farmer spends much of her time outdoors. As a result, her skin has

become very tanned. What would Lamarck predict about her children? What would Darwin predict about her children? How does this refl ect the key diff erence in their theories?

Extend Further

4. INQUIRY According to Lamarck’s ideas, “functions create organs.” What does this statement mean? Do you agree or disagree with this statement? Explain your answer.

5. RESEARCH In his book Philosophie Zoologique, Lamarck describes organic beings as existing on a ladder of life. Research the Great Chain of Being. Explain how this idea fi t into Lamarck’s view of species change over time.

8-AThoughtLabI N V E S T I G AT I O N

This is an artist’s impression of Jean-Baptise Lamarck.

This is an artist’s impression of Charles Darwin.

“The environment exercises a great influence over the activities of animals, and as a result of this influence the increased and sustained use or disuse of any organ are causes of modification of the organization and shape of animals and give rise to the anomalies observed in the progress of the complexity of animal organization.”

—Jean-Baptiste Lamarck in Philosophie Zoologique, 1809

“[N]atural selection, or survival of the fittest, does not necessarily include progressive development—it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life. And it may be asked what advantage, as far as we can see, would it be to an … intestinal worm … to be highly organised. If it were no advantage, these forms would be left, by natural selection, unimproved or but little improved, and might remain for indefinite ages in their present lowly condition.”

—Charles Darwin in The Origin of Species, 1859


341-347_REV_BIO11.indd 341 17/05/10 10:48 AM

SUMMARYChapter 8

Scientific Contributions to a Theory of Evolution Section 8.1

The work of many great thinkers supported Darwin’s direct observations and led to Darwin’s formulation of the theory of evolution by natural selection.

KEY TERMScatastrophismdescent with modifi cationevolutioninheritance of acquired characteristicspaleontologysurvival of the fi ttesttheory of evolution by natural selectionuniformitarianism

KEY CONCEPTS• Scientifi c theories explain facts and connect them in a

comprehensive way, enabling scientists to make predictions about new situations and experimental outcomes.

• The question of whether living things have changed over the course of Earth’s history had been considered by many diff erent philosophers and scholars.

• In Histoire Naturelle, Buff on challenged the idea that life forms are unchanging and that Earth was 6000 years old. Cuvier founded the science of paleontology and proposed catastrophism as an explanation for fossil history.

• Geologist Charles Lyell noted that Earth’s geological features were in a slow, continuous cycle of change, which he called uniformitarianism. Lamarck proposed the idea of inheritance of acquired characteristics, which suggested that parents passed on learned adaptations to the environment, which resulted in evolution.

• Darwin brought together his own observations from his journey on the HMS Beagle, his observations from his selective breeding, and the work of many other great thinkers to develop his theory of evolution. His theory proposes natural selection as the mechanism for how new species arise from ancestral species in response to the local environment.

Sources of Evidence for EvolutionSection 8.2

Many diff erent lines of scientifi c evidence from before, during, and after Darwin’s time all support the theory of evolution by natural selection.

KEY TERMSanalogous structuresbiogeographyembryologyfossil recordhomologous structurestransitional fossilvestigial structure

KEY CONCEPTS• The theory of evolution connects facts to provide a logical

framework that explains how life on Earth has changed and is still changing.

• Charles Darwin and Alfred Russel Wallace both developed hypotheses to explain natural selection.

• New discoveries of fossils, called transitional fossils, help fi ll in the gaps in the fossil record.

• Homologous structures have similar structural elements and origin but may have a diff erent function. Analogous structures perform similar functions, even though the organisms do not share a recent common ancestor.

• The fossil record, biogeography, anatomy, embryology, and relationships in DNA all provide evidence for evolution.


341-347_REV_BIO11.indd 342 17/05/10 10:57 AM

REVIEWChapter 8

Knowledge and UnderstandingSelect the letter of the best answer below. 1. Which of the following sources of evidence of

evolution is used to establish genetic relationships between organisms?

a. the fossil record d. embryology b. transitional fossils e. DNA c. biogeography

2. How do vestigial structures provide evidence for evolution?

a. Th ey show direction of change. b. Th ey show shared ancestry. c. Th ey show genetic relationships. d. Th ey show how new structures evolve. e. Th ey show geographical relationships.

3. Which of the following is a main point of Lamarck’s idea of biological change over time?

a. Organisms produce more off spring than can survive, so they compete for limited resources.

b. Individuals of a population vary extensively, and some of this variation is heritable.

c. All body parts not used will eventually disappear. d. Individuals that are better suited to local conditions

survive to produce off spring. e. Processes for change are slow and gradual, and

Earth is much older than 6000 years. 4. Lamarck and Darwin proposed diff erent explanations

for how characteristics are passed from parent to off spring, but their theories had some similarities. Which of the following points is true?

a. Th e men disagreed that there was a line of descent in organisms.

b. Both believed that organisms adapt to their environments.

c. Both believed in catastrophism and the idea that if a body part were not used, it would simply disappear over time.

d. Both believed that characteristics were acquired in each generation.

e. Both believed that giraff es acquired their long necks by stretching to reach leaves high in trees.

5. Which of the following are homologous structures? a. the wings of a sparrow and the wings of an owl b. the wings of a sparrow and the wings of a dragonfl y c. the legs of an ant and the legs of a horse d. the jaws of a Venus’s-fl ytrap and the jaws of a clam e. the wings of a moth and the wings of a hummingbird

6. Which of the following scientists infl uenced Darwin’s views on the nature of population growth?

a. Cuvier b. Malthus c. Lyell d. Wallace e. Buff on

7. Which of the following scientists infl uenced Darwin’s views on slow, subtle changes in populations?

a. Cuvier b. Malthus c. Lyell d. Wallace e. Buff on

8. In support of evolution, Archaeopteryx is known to be a transitional form between

a. birds and mammals b. mammals and reptiles c. fi sh and amphibians d. dinosaurs and birds e. amphibians and reptiles

Answer the questions below. 9. Aft er Th e Origin of Species was published, many

scientists accepted the concept of evolution but not the mechanism of natural selection. Explain why.

10. Why do homologous structures demonstrate evidence of evolution?

11. Summarize the observations that Darwin made while on the voyage of the Beagle, which he later incorporated into his theory of evolution by natural selection.

12. Some caves contain fi sh that are blind. Th ese fi sh have eye sockets and vestigial eyes. How would Lamarck account for the origin of sightlessness in these fi sh and other blind cave-dwellers? How would Darwin account for it?

This southern cave fish (Typhlichthys subterraneus) is blind but still has vestigial eye sockets.


341-347_REV_BIO11.indd 343 17/05/10 10:58 AM

REVIEWChapter 8

13. How does the study of embryology support evolution?14. Insects reproduce fast enough that they could quickly

populate and overrun Earth. a. Explain why this does not occur. b. How was this signifi cant to Darwin?

15. Explain how scientists can use DNA to determine the evolutionary relationships between two organisms.

16. What is the signifi cance of a vestigial structure as evidence of evolution?

Thinking and Investigation17. Examine the fossils found in the sedimentary rocks

shown in the diagram below. Explain what these rock strata and the fossils in them can tell you about evolution.

These sedimentary rock layers contain various fossils.

18. Lamarck proposed an incorrect inheritance mechanism for how evolution can occur, but his ideas were instrumental for Darwin’s future work. Which aspect of Lamarck’s work did Darwin build upon?

19. Red Island and Blue Island are hypothetical islands 500 km off the coast of South America. Red Island is volcanic in origin and is only 5 million years old. Blue Island separated from South America more than 80 million years ago. Predict the origins of the animals on both islands, and explain how they may be similar to or diff erent from the animals of South America.

20. Many organisms found in tidal pools along the west coast of Vancouver Island look almost identical to organisms found in tidal pools along the east coast of New Brunswick. Would you expect these species to be closely related? Explain your answer.

21. Suppose you fi nd two identical fossils in two adjacent sedimentary strata. What can you conclude?

22. Malthus pointed out that all populations eventually face limits to their population because of limited resources. Compare a micro-organism (such as the bacterium Staphylococcus aureus), a plant species (such as a tree), and a mammal (such as a deer) with respect to the types of factors that might limit the growth of their populations.

23. Darwin applied Malthus’s ideas to various organisms. For example, Darwin calculated that a single pair of elephants could have 19 million descendants in 750 years. He knew that population explosions of this kind do not happen, and he began to think about the mechanism that must be controlling the populations of all species on Earth. Th e largest possible number of off spring produced by one individual is called the biotic potential of a species.

a. Calculate the maximum biotic potential of a pumpkin. Assume that there are 70 seeds in one pumpkin. Th ese 70 seeds are planted, and each seed grows into plants that produce two pumpkins. Calculate the number of seeds produced by this generation.

b. If you plant all the seeds from part (a), how many seeds are available at the end of the next generation?

c. Why is the maximum biotic potential impossible to reach in nature?

24. If the science of genetics had been established in Darwin’s time, would it have been easier or more diffi cult for him to reach his conclusions about evolution? Explain your answer.

25. Adult chickens and other birds have four digits in their feet. A research study in the fi eld of embryology reveals that during early development of the chicken, there is a fi ft h digit that later disappears.

a. How do you interpret this scientifi c fi nding? b. How does this fi nding provide evidence for evolution?

As embryos, chickens have five digits, but they only grow four digits.


341-347_REV_BIO11.indd 344 17/05/10 10:52 AM

Communication 26. Evolution is the process of biological

change over time based on the relationships between species and their environments. Does evolution mean that organisms are becoming progressively better with each generation? Explain your answer in one or two paragraphs.

27. Th e theory of evolution is a scientifi c explanation based on a large accumulation

of evidence. Use a graphic organizer to summarize the diff erent kinds of evidence for evolution. Go to Using Graphic Organizers in Appendix A to learn more about which graphic organizer to choose.

28. Use a Venn diagram to show the diff erences between homologous and analogous structures.

29. Explain the theory of evolution by natural selection in a presentation format of your choice, such as a poster, a computer slide presentation, or a wiki page.

30. Two populations of fl owers of the same species are found in nearby meadows. Th ere are slight diff erences in the plants between the two populations, such as fl ower colour and leaf shape. In a diagram, express how Darwin might have interpreted these observations.

31. Compare and contrast Darwin’s and Lamarck’s views on the importance of variation and how variation is inherited. Write your answer as a brief dialogue between the two men if they were to meet and have a debate.

32. You have your own web page that explains the theory of evolution by natural selection. List the points you would include on the site, as well as links to other sites.

33. Use a graphic organizer to distinguish between fact and theory. Go to Using Graphic Organizers in Appendix A to learn more about which graphic organizer to choose.

34. Explain to a younger sibling what the following statement means: Th e fossil record gives us a “snapshot” of ancestral forms.

35. Summarize your learning in this chapter using a graphic organizer. To help you, the Chapter 8 Summary lists the Key Terms and Key Concepts. Refer to Using Graphic Organizers in Appendix A to help you decide which graphic organizer to use.

Application 36. Your friend shows you a snake skeleton and points out

tiny bones that would make up the pelvis in an animal with legs. Your friend tells you this was a mutant snake. Do you agree or disagree? Explain your answer.

37. Birds and dinosaurs are very diff erent organisms. In the past, scientists who proposed that birds were descended from ancestors of dinosaurs were ridiculed. What evidence is there to support the idea that birds and dinosaurs have a common ancestor?

38. Richard Dawkins, a world-renowned evolutionary biologist, refers to natural selection as the “blind watchmaker,” meaning that natural selection is totally blind to the future. Explain what Dawkins means by this statement.

39. Dolphins and sharks share many similarities and diff erences. Use Internet or print resources to research dolphins and sharks. Create and complete a table like the one below, and include an image of each animal. Are the similarities analogous or homologous?

Comparison of Dolphins and Sharks

Question Dolphin Shark

How does each animal breathe?Does the animal nurse its young?What is its skeleton made of?Is the animal a mammal?Does the animal have a fi n on the top of its body?Is the body shape streamlined?Does the animal have teeth?

40. A hoatzin is a tropical bird about the size of a chicken. It lives in swampy areas near the Amazon River in South America. Hoatzin chicks have claws on their wings. Th e chicks use the claws to cling to branches, to keep them from falling.

As the hoatzin chick matures, its claws disappear.

a. What other (extinct) bird has claws on its wings? b. What might you conclude about bird ancestors?

41. You discover the remains of an extinct animal that has a small amount of brain tissue preserved in its skull. Outline the scientifi c techniques you might use to learn more about the evolutionary history of this animal.


341-347_REV_BIO11.indd 345 17/05/10 10:53 AM

Chapter 8 SELF-ASSESSMENT

Select the letter of the best answer below. 1. K/U Why was Lamarck’s work important to Darwin’s

development of his theory of evolution by natural selection?

a. He supported a fi xed, static view of life. b. He established the principle of uniformitarianism. c. He emphasized organisms adapting to their

environment. d. He wrote about unchecked human population

growth. e. He suggested a longer time period on Earth for

evolution to occur. 2. K/U How did Lyell’s work contribute to evolutionary

thought? a. He devised a classifi cation system that is still used

today. b. He suggested that constant geological processes

have shaped Earth over a long period of time. c. He proposed that species are related by descent

from a common ancestor. d. He proposed the theory of acquired characteristics

and the idea of “use and disuse.” e. He viewed nature as fi xed along a progressive scale.

3. K/U What is evolution? a. Organisms adapt to their environment. b. Species go extinct and thus are no longer on Earth. c. Populations vary in their traits. d. Organisms produce more off spring than can survive. e. Genetic changes in characteristics of species over

time. 4. K/U How does the idea of catastrophism relate

directly to observations in the fossil record? a. Species suddenly disappear, while new species

appear, in the fossil record. b. Th ere are transitional species that link diff erent

groups of organisms. c. Older species are found in lower strata of the fossil

record. d. Recently evolved species are found in the most

recent layers of the fossil record. e. Fossils are very similar throughout the fossil record.

5. K/U Which scientist developed a theory of evolution by natural selection at the same time as Darwin?

a. Malthus d. Cuvier b. Lyell e. Wallace c. Buff on

6. K/U What was the widely accepted view about life on Earth prior to Darwin’s publication of Th e Origin of Species in 1859?

a. Earth is 6000 years old, and the natural world does not change.

b. Earth is 6000 years old, and populations change over time.

c. Earth is millions of years old, and populations rapidly change.

d. Earth is billions of years old, and populations are unchanging.

e. Earth is millions of years old, and the natural world gradually changes.

7. K/U Which of the following is an intermediate fossil illustrating the evolution of whales?

a. Pakicetus b. Archaeopteryx c. Atrociraptor d. Gondwana e. Pikaia

8. K/U Which of these conditions favours the evolution of traits in a population according to Darwin’s theory of natural selection?

a. Some of the variation between individuals is heritable.

b. Organisms produce only a few off spring in each generation.

c. Resources are unlimited in the population, and there is no competition for those resources.

d. Th e population lives in a habitat where there is no competition for resources.

e. Individuals acquire traits from the environment and pass on those acquired traits to off spring.

9. K/U Which is an idea that Darwin used from the work of Malthus?

a. Populations do not change and life is static. b. Populations produce far more off spring than can

survive. c. Earth has changed through a series of catastrophic

revolutions. d. Th e fi ttest individuals survive due to favourable

adaptations. e. Earth is more than 6000 years old, and life forms

are unchanging.


341-347_REV_BIO11.indd 346 17/05/10 10:54 AM

10. K/U Which is a plausible question that came from Darwin’s observations during the voyage of the Beagle?a. Are organisms becoming perfect over time?b. Why do living species and fossilized organisms

look so diff erent within the same country in South America?

c. Why is there so much species diversity on small, isolated islands?

d. Could all species have been created at the same time?

e. Why did the Galapagos fi nch species look just like the European fi nches?

Use sentences and diagrams as appropriate to answer the questions below.11. K/U What is a homologous structure? Include an

example in your answer.12. T/I Use the diagram below to answer the following

questions.

Surface

A

B

C

D

a. Which layer of rock contains the youngest fossils?b. Which layer of rock contains fossils most similar to

species alive today?c. In which layer are the oldest fossils found?

13. C Design a brochure to explain to Grade 5 students two sources of evidence for evolution. Be sure to use visuals in your brochure.

14. K/U If you teach children to look both ways before they cross the street, this action will help them survive.

a. How would Lamarck intrepret this behaviour? b. Do you agree with this interpretation? Explain your

answer.

15. K/U What was important about the discovery of the transitional fossil Archaeopteryx?

16. T/I Explain Lamarck’s idea of the inheritance of acquired traits. Explain why the idea is not a theory and why it is incorrect.

17. K/U How can embryo development reveal clues about evolutionary history?

18. T/I You are doing research on birds and you discover that certain birds possess reptile-like scales on the lower parts of their legs and feet. Another research lab you are working with reports that these “scales” are chemically identical to feathers.

a. How do you interpret this fi nding? b. Assuming reptiles are older than birds in the fossil

record, what does this tell you about the origin of feathers?

19. K/U Would Darwin support the statement “No species is really more primitive or advanced than any other”? Explain your answer.

20. A When entering Canada from abroad, you are asked if you are bringing in any live specimens. Why do countries try to avoid non-indegenous species being brought in?

21. T/I Infer how a functionless gene could be considered a vestigial trait.

22. C Use a graphic organizer such as a Venn diagram to compare and contrast homologous structures, analogous structures, and vestigial structures. Go to Using Graphic Organizers in Appendix A to learn more about Venn diagrams.

23. C Use a graphic organizer to summarize the similarities and diff erences between catastrophism and uniformitarianism. Go to Using Graphic Organizers in Appendix A to learn more about which graphic organizer to choose.

24. K/U What important contribution did Charles Lyell make to science?

25. K/U Defi ne biogeography in your own words. In your defi nition, include an example.

Self-Check

If you missed question... 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Review section(s)... 8.1 8.1 8.1 8.1 8.1 8.1 8.2 8.1 8.1 8.1 8.2 8.2 8.2 8.1 8.2 8.2 8.2 8.2 8.1 8.1 8.2 8.2 8.1 8.1 8.2


341-347_REV_BIO11.indd 347 17/05/10 3:43 PM

Documents

CHAPTER 8 Developing a Theory of Evolutionvegalee.weebly.com/uploads/2/3/6/9/23691378/bio11_ch08-hist_evol-smaller.pdf · Developing a Theory of Evolution ... these lower strata turn