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Fossils, Finches & Farming: A Curriculum Unit for Evolution

William A. Siefert

 Introduction

Finding a fossil or other sign of previous life in a natural environment can be a very exciting and instructive experience.  Whenever I am lucky enough to find even the smallest fragment of a fossil it starts my mind to wondering how the earth and its life forms have changed and continue to change.  Remnants of life from long ago are invaluable pieces of a puzzle that can be built from many different angles by many different builders.  This curriculum unit will be a very brief note on the story of life that is 3.5 billion years long.  There are literally tons of academic materials covering the science of evolution.  Nevertheless, a small piece of petrified trilobite can still inspire us to contemplate the big picture of life on Earth.

Fossils tell the story of biological evolution.  Earth’s fossil record shows that over millions of years organisms have appeared, lived, and then disappeared only to be followed by slightly changed and related organisms in the history of life.  This biological evolution occurs continuously and cumulatively as genetic material is altered and passed on through heredity.  Evolution, referred to as descent with modification by Charles Darwin, is the process that has led to the wealth of biodiversity we observe on Earth today.

          Despite its importance, evolution runs counter to some of the most basic human assumptions about our origins, our place among other creatures, and some of our religious beliefs (Matthews, 2001).  Whenever the word evolution or the name Darwin is mentioned, emotions are stirred and student responses may be defensive as they perceive an attack on their own ideas or religious beliefs.  According to a Gallup poll (2000), 68% of the American public favors teaching creationism in schools along with evolution.  In this curriculum unit, evolution will be discussed as the unifying concept of biology.  Religious views, like “creation science” or “intelligent design” cannot be taught in the public schools as ruled by the U.S. courts and also because these viewpoints are nonscientific.

 Humans are inquisitive and intelligent beings.  We constantly seek to answer questions and assign explanations to mysteries in order to maintain a sense of security and control in our world.  Even questions like “How did life begin?” or “How did humans originate?” have been explained by numerous creation stories and myths from many different cultures and peoples throughout the world.  Most high school students come to biology class with some facts about evolution, but they also have their own nonscientific ideas about the origin of life.  This is a major challenge to biology teachers who must present scientific facts which are in direct opposition to students’ strongly held beliefs.

 Scientists and educators have long realized the difficulties involved with presenting new ideas and theories that run counter to popularly held beliefs.  It seems unbelievable to us that astronomers like Copernicus and Galileo and their concept of heliocentrism was not accepted because it opposed the literal interpretation of the Bible.  In modern times, teacher John Scopes was convicted by a Tennessee court for teaching the ideas of evolution.   In 1998, the National Academy of Sciences published the booklet Teaching about Evolution and the Nature of Science (NAS, 1998) for educators to use as a guide to implement the teaching of evolution as the central organizing principle in biology.  According to the NAS, to teach biology without explaining evolution deprives students of a powerful concept that brings great order and coherence to our understanding of life.

Academic Setting

This unit is designed for an introductory freshman biology course at the high school level.  Cibola High School is a large (2000+ students), middle-class school located in the rapidly growing northwest section of Albuquerque.  All 9^th graders at Cibola enter school as members of a team in the Freshman Academy.  Freshman teams consist of approximately 150 students who share the same biology, English, math, and health teachers for the entire year.  For the 2001-2002 school year, there were five freshman teams at Cibola.  Academy teachers meet weekly to discuss student progress and share ideas about addressing student needs within their team.

            This curriculum unit will be implemented over a two to three week period.   The goal of this unit is to present a few of the many possible ideas of how to teach about evolution.  In addition, the nature of science as a human endeavor based in our inherent curiosity and logical reasoning abilities will be weaved into the unit.  Students will find that science is an organized way to explain observations about the natural world.  Discovering new things entails observing with a creative and open mind and using your imagination to make connections and form an explanation.

Context and Background

Earth’s Geologic History

In the nineteenth century it was believed that the earth was approximately 6,000-10,000 years old.   As data contained in the strata of sedimentary rocks began to be analyzed, it became apparent that the earth was much older than previously thought.  Current information from radioactive dating of the oldest lead ores indicates that the earth has an age of about 4.5 billion years.  Using astronomical measurements and radioactive methods the age of our sun is placed at about 5 billion years and the age of our galaxy is between 9 and 16 billion years.

            Geologists and other scientists have studied the sequence in which the strata of Earth’s surface have been laid down.  Also, by studying the fossils contained in these layers, a sequence of life forms on Earth has also been established.  Table 1 shows the significant biological events occurring in each geological division.

Table 1.   Geological History of Earth

Era	Period	Epoch	Years Ago	Significant Life
Cenozoic	Quaternary	Holocene	11,500 to present	Modern humans arise
		Pleistocene	1.7 million to 11,500	Humans spread
	Tertiary	Pliocene	12 to 1.7 million	Large carnivores arise
		Miocene	26 to 12 million	Mammals diversify
		Oligocene	40 to 26 million	Diverse grazing animals appear
		Eocene	55 to 40 million	Early horses arise
		Paleocene	65 to 55 million	Primitive mammals
Mesozoic	Cretaceous		135 to 65 million	Dinosaurs go extinct
	Jurassic		190 to 135 million	Dinosaurs diversify
	Triassic		230 to 190 million	Dinosaurs arise
Paleozoic	Permian		280 to 230 million	Seed plants arise
	Carboniferous		320 to 280 million	Reptiles arise
	Devonian		400 to 320 million	Amphibians arise
	Silurian		425 to 400 million	Land plants arise
	Ordovician		500 to 425 million	Fishes arise
	Cambrian		600 to 500 million	Marine invertebrates arise
Precambrian			4.6 billion to 600 million	Prokaryotes then eukaryotes arise

(Table modified from Modern Biology, by Towle.  Holt, Rinehart, and Winston, 1999.)

The use of naturally occurring radioactive elements to date ancient materials is a powerful scientific tool.  The method is based on the rate it takes for half of a sample of an unstable element or isotope to radioactively decay into another element.  The half-life of many elements and isotopes has been determined.  The best-known method for dating fairly young organic specimens is that of carbon-14 which has a half-life of 5,730 years.  Carbon-14 occurs in our atmosphere in CO₂ and living organisms pick up this isotope naturally until they die.  After death, the C-14 will decay while the amount of stable carbon-12 will remain constant.  By measuring the ratio of C-14 to C-12 we are able to determine how long ago an organism died.  As a dating method, C-14 is best suited for samples of materials less than 50,000 years old. 

            In order to date materials like fossiliferous rock older than 50,000 years other radioactive elements are used.  Additional methods include measuring the decay of potassium 40 into argon 40 with a half-life of 1.3 billion years and the decay of uranium 238 into lead 206 which has a half-life of 4.5 billion years.  By using isotopes with such long half-lives it is possible to date the age of Earth’s oldest rocks.   Also, if two layers of rock containing these radioactive elements have fossil-bearing rock in between them, the fossils can be accurately dated by determining the age of the over and underlying layers. 

            The fossil record is one line of evidence that supports the evolutionary change of organisms on Earth.  Usually only the hard parts of organisms like bone, teeth, shell, or wood are preserved as fossils.  Sedimentary fossils are formed when the body part is covered by sediment, like sand or mud, and over time minerals replace the organic tissue and create a petrified version of the original specimen.  In the process that creates mold and casts fossils, the sediment that surrounds an object are cemented until they become rock, forming a mold.  A cast is formed when minerals seep into the mold and create a solid model of the object.  In rare cases, entire organisms have been preserved in ice, tar, peat, and amber, the resin of ancient trees. 

The chances for a living thing to become fossilized are very small.  Therefore, scientists do not have a complete history of all life in the fossil record.  Even without a complete fossil record, paleontologists are able to reconstruct past environments by incorporating information obtained from other types of data.  Trace fossils are fossilized evidence of an animal’s activities.  Examples include footprints, burrows, and even fossilized feces, called coprolites.  Grains of pollen are often found with fossils or contained within layers of sediment.  By studying the types and amounts of pollen, palynologists can deduce plant associations that occurred as well as the past climate of an area.  A dental anthropologist that studies the microscopic striations and abrasions on the surface of teeth can reveal the type of diet and possible lifestyle of the organism. 

The Theory of Evolution 

Charles Darwin was not the first person to propose that similar species had descended form a common ancestor.  Ancient Greek philosophers and contemporaries of Darwin, like Alfred Russell Wallace, had developed similar hypotheses on the development of life on Earth.  The most significant event that helped Darwin develop his theory was his five-year trip aboard the HMS Beagle as the expedition’s naturalist.  Darwin was an excellent scientific observer and collected information on the plants, animals, rocks, climate, fossils, and native peoples of the lands they visited around the world.  After years of analyzing his data, Darwin published his famous work, On the Origin of Species by Means of Natural Selection (1859). 

            The key concept behind Darwin’s work was his theory of natural selection.  Darwin noted the great heritable variety that existed in all populations of species and that the environment acts on this variation.  If an organism’s traits offer it an advantage over other organisms in the same environment, then that organism is best fit to survive.  Greater fitness means greater reproductive success and more offspring will be produced showing the selected traits.  As these genetic differences accumulate over time in populations, new species will develop.  A species is defined as a group of organisms that can reproduce and create fertile offspring. 

            When the Beagle landed at the Galapagos Islands, a volcanic chain about 600 miles west of Ecuador, Darwin made some observations about the bird populations of the islands that would help him illustrate his theory of natural selection.  He categorized thirteen different species of finches, mostly based on differing characteristics of their beaks, which reflected different feeding habits.  Darwin postulated that the finches were not native to the Galapagos, and originally one or two ancestral species of finch made their way to the islands via floating debris or transported by a storm from the South American mainland.  Over time these ancestral finches adaptively radiated through natural selection into the thirteen phenotypically and genotypically distinct species now known as Darwin’s finches. 

            Darwin was sure that it took thousands of years for this speciation to occur, but current research has shown that evolutionary changes can occur in far less time with certain species.  Peter and Rosemary Grant of Princeton University along with their students have studied the morphology and ecology of finch species in the Galapagos for 25 years.  The group found that drought occurring on the islands affects plant seed production which acts as a selective pressure on finch beak size.  During a drought year the plants that survive produce a larger and tougher nut, which favors birds with strong, wide beaks that can break the nut.  The Grants have estimated that if drought occurs about once every 10 years on the islands, a new species of finch might arise in only about 200 years (Grant, 1991). 

            Evidence for rapid evolutionary change is also observed with microorganisms and arthropods.  The development and use of medical antibiotics can create a selective force between resistant and nonresistant types of bacteria.  In a population of pathogenic bacteria, some members will have a natural genetic resistance to antibiotic substances.  During medical treatment with antibiotics, these resistant types may survive and pass on their genetic resistance to future offspring.  Organisms, such as bacteria, with short generation times can speed up the rate of evolution and therefore increase the rate of speciation.  Some insect species can develop similar resistance to agricultural insecticides used to control them. 

            Through modern advances in genetics and molecular biology the mechanisms that drive evolution and speciation are now well understood.  Genetic variation arises from random mutations that occur in an organism’s genetic material, deoxyribonucleic acid (DNA).  This change in the nucleotide sequence of DNA may alter the coded gene and thus lead to a different protein product of that gene.  Different forms of a gene are called alleles and the variation of alleles present in a population make up the gene pool.  Alleles occur in differing frequencies in the gene pool.  This is observed in the different phenotypes we see, like the ABO blood group in humans. 

            Therefore, populations will evolve, or change over time, as allele frequencies change.  Mutations and recombinations of the DNA in gametes can affect allele frequencies of a sexually reproducing population.  Migration of individuals between populations can alter allele frequencies; through new gene flow into the gene pool.  In a small population, the random contribution or lack of contribution by a few individuals may alter allele frequencies, this is called genetic drift.  The unit of evolution is the population and as the proportion of genes for favorable traits increases the population evolves. 

Human Evolution 

Paleoanthropologists have studied thousands of fossil specimens and artifacts in an attempt to piece together the stages of human evolution.  Finding hominid (human and their bipedal ancestors) fossils is rare, so modern science uses other types of evidence in order to show evolutionary relationships between humans and other primates.  Data derived from the molecular biological analyses of DNA, proteins, mitochondrial DNA (mtDNA), and Y-chromosome DNA provide additional lines of evidence in the study of human evolution.  Contrary to some religious opinions and beliefs, there is no scientific evidence for divine intervention in the creation of humans.  The same forces that have created the range of biodiversity on Earth are responsible for the evolution of human beings. 

            Our species, Homo sapiens, is the only surviving member of the family Hominidae.  Hominids belong to the order of mammals known as primates.  The anthropoid primates include marmosets, monkeys, apes, and humans.   The prosimian primates include lemurs, lorises, and tarsiers.  Humans are genetically most closely related to the chimpanzee; in fact 98% of our genetic material is identical to theirs.  Molecular analysis shows that we shared a common ancestor with the chimps less than 6 million years ago.  Unique human characteristics include bipedalism, a bowl-shaped pelvis, aligned toes, an S-shaped spine, and an advanced use of language.

              The first fossil hominids discovered date to about 4 million years ago.   These individuals found in Africa make up the genus Australopithecus and are called australopithecines.  Many australopithecine fossils have been found, showing that they exhibited characteristics of both apes and humans.  The most famous australopithecine fossil found was named Lucy by her discoverers.  Lucy probably lived in a woodland area, was about three and a half feet tall, walked upright, and had long arms to aid in climbing trees.  The australopithecine ancestors of humans died out about 2.5 million years ago.

                  The first fossils classified in the genus Homo were found in East Africa and date to 1.6 to 2.5 million years ago.  Homo habilis had a larger cranial capacity than Australopithecus, and marks on bones associated with the fossils show that H. habilis  used stone tools.

              Homo erectus fossils appear about 1.8 million to 50,000 years ago.  H. erectus specimens have been found in Java and China, indicating that they may have been the first hominid to leave Africa.  Compared to australopithecines, H. erectus was taller, had a large brow ridge, a reduced chin, and a less protruded face.  H. erectus cranial capacity was about two-thirds that of modern humans and they had human-like teeth.   Charred bones and advanced tools found at H. erectus cave sites indicate that they were meat eaters who used fire for cooking and possibly warmth.   There is evidence that early members of our species, Homo sapiens, may have coexisted with H. erectus before H. erectus went extinct.  Fossils found in the range of 800,000 to 50,000 years ago show signs of being transitional forms between the two species.

              An early group of H. sapiens, called Neanderthals, after the Neander Valley in Germany where they were found in 1856, date from 230,000 to 30,000 years ago.  Neanderthals lived in caves and shelters during the last ice age.  Physically they had a large brow ridge, protruding teeth, were heavily built, and had a larger cranial capacity than modern humans.  Neanderthal gravesites have been found showing elaborate ritualized burials, advanced tool making, and the production of works of art.  Paleoanthropologists are not in agreement as to the relationship between modern humans and the Neanderthals.  Were the Neanderthals an archaic ancestral form of humans or were they and evolutionary dead end?  Current molecular biological research is focusing on the study of mtDNA for the answers.  By studying mtDNA, researchers can trace the evolution and migration of the human species and determine when a common ancestor to humans and Neanderthals lived.

              Modern humans evolved in Africa around 200,000 years ago.  By 11,000 years ago humans had spread to all parts of the world except Antarctica.  There are two major models that explain the diffusion of human populations on Earth.  The Multiregional Model states that populations of H. erectus emigrated from Africa a million years ago into areas, which are now Asia and Europe.  From these three centers, three distinct subspecies, or races of humans evolved.  The Out of Africa Model states that humans evolved in Africa and from there spread to the rest of the world.

              The last continents to be conquered by human settlement were North and South America.  Much research is still devoted to establishing the route taken and the time frame for the peopling of the Americas.  At the end of the Pleistocene, as ice sheets melted and the environment began to warm, humans from Asia could have crossed the Bering land bridge into North America and dispersed from there to the southern reaches of the continents.  Whether they used a land route or floated south along the Pacific coast is still a topic for discussion.  We do know through archaeological findings that humans existed in North America around 11,500 years ago with now extinct ice age mammals.  Human made tools and weapons are found associated with mammoth and bison remains at numerous kill sites in western North America.  South American sites possibly dating to before 11,500 years ago have been described and may point to an even earlier date for human entrance into the New World.

              Once humans had inhabited most of the earth by 10,000 years ago, the Agricultural Revolution would allow the growth of populations to occur like no other time before.  Farming developed in many regions simultaneously in the world.  By domesticating animals and growing crops people were able to maintain a steady food supply that was more reliable than hunting and gathering.  As people stayed in one place longer and families grew larger, permanent settlements began to grow in size and number.  The rise of agriculture also promoted the development of society and technology in the human world.  The causative factors that led to the Agricultural Revolution are still debated, but the incredible population growth that it fostered continues today as humans number six billion on Earth.   The effects of modern industrialized agricultural practices can be negative as habitats and ecosystems are destroyed and biodiversity is consequently diminished.

The Nature of Science and Human Culture

The goal of science is to objectively describe and explain natural phenomena through observation and experimentation.  Vocabulary and terminology are important in reporting and maintaining accurate scientific information.  A fact in science describes a repeatedly observed occurrence.  It is a fact that the earth revolves around the sun.  A hypothesis is a testable statement about the natural world.  You can hypothesize that certain stellar constellations will be visible in the night sky.  Hypotheses can be rejected or accepted after collecting the appropriate data.  Scientific laws are descriptions of how the natural world behaves given certain circumstances, such as the ideal gas laws.  A theory is more than an educated guess.  A theory is well supported by facts, laws, and experimental data.  Theories can be continually built upon or changed with the addition of new data.  The theory of evolution, so to speak, is always evolving.

            We all are brought up in a certain culture.  From the day we are born, we learn culture from those around us.  Just as the human organism is a complicated and evolving being, so too is culture.  Our culture affects how we view the history of human evolution.  Are we the pinnacle of life, divinely influenced and able to sustain our lifestyles in spite of natural limits?  Or are we merely another evolutionary step in a long genetic progression of change based in a process of selection beyond our control?

Science and religion are both products and part of human culture.  These two activities should be mutually exclusive based on their different objectives and utility to humans.  However, science and religion often clash as noted in the numerous discussions over evolution and creationism.  Anthropologist W. W. Howells used an analogy in his 1993 book Getting Here to explain the coexistence of science and religious views in human society.  Howells said that science can be thought of as a large building made of many wings and levels.  New information can be added like building blocks and rejected hypotheses can be removed.  Religious and mythical creation stories can be described as paintings in the building.  The paintings are beautiful, explanative, and meant to last forever.  Both building and painting can exist separately.  There is no need for a conflict between the two.

Implementation

New Mexico State Content Standards for Excellence

This unit is designed to meet the following New Mexico State Content Standards for science for students in grades 9-12.

Content Standard 6:  Students will understand the process of scientific inquiry.

            Benchmark 20:  Explain and interpret the results of investigations to teachers,                         peers, parents, and others.

Content Standard 10:  Students will know and understand the characteristics that are the basis for classifying organisms.

Benchmark 5:  Apply information about living things to themselves and the world around them including:

     (e) the functions of DNA and RNA in genes and the process of heredity.
      (f) Discussion of the evidence that the great diversity of life is the result of more than 3.5              billion years of natural selection and biological evolution which have filled every              available niche with life forms.

 --Discuss the various mechanisms proposed to explain and interpret the evolutionary process including but not limited to:  natural selection, mutations, punctuated equilibrium, genetic drift, isolated subpopulations, the neo-Darwinian (or modern) synthesis.

          Benchmark 6:  Use biological classification to sort organisms and understand how they are                related.

 --Classify the relationships among organisms into groups and subgroups based on structural similarities.  Compare the relationships obtained by comparing anatomical similarities with those obtained from DNA and protein sequences.

Content Standard 11:  Students will know and understand the synergy among organisms and the
environments of organisms.

             Benchmark 25:  Predict an organism’s behavioral responses to internal changes and to external                   stimuli as a function of inherited and acquired traits.

 --Research the present understanding of how specific organisms may have evolved.   Identify the specific mechanisms by which such evolution at a genetic level could have happened.

 --Investigate and discuss evidence from fossils, comparative anatomy, etc. that indicates species change over time.

Content Standard 12:  Students will know and understand properties of earth science.

               Benchmark 18:  Use fossil and other evidence to investigate how the Earth has changed                   or remained constant.

 --Construct a geologic time line showing the positions of index fossils; discuss how the index fossils are used for stratigraphic correlations, and for determining rock age.

 --Describe the conditions normally required for fossilization of a living organism to occur.

 In addition to the following activities, students will be assigned textbook reading, review questions, and vocabulary as homework.  These assignments will serve as the source of background knowledge for teacher lectures and class discussions.

 Vocabulary list

adaptation	half-life	palynology
adaptive radiation	hominid	population
anthropology	hypothesis	primate
archaeology	heredity	radioactive dating
australopithecine	law	radioactive decay
bipedal	Lucy	species
culture	Multiregional model	strata
creationism	mitochondrial DNA	theory
evolution	natural selection	trace fossil
fossil	Out of Africa Model	variation
fitness	Neanderthal
fact	paleontology

Activity #1        Introductory Questionnaire

The Nature of Science and Evolution Information Inventory

This written-response questionnaire is designed to assess the amount of background knowledge students possess concerning the nature of scientific inquiry and evolutionary concepts.  An oral interview can be used in place of written answers for those students with limited English proficiency or with special needs.

            The questionnaire will be graded and used to generate discussion and an introduction to the material to be covered in the unit.

Directions:  Write brief answers to the following questions using complete sentences.

1.  Briefly outline or describe the steps of the scientific method.
2.  Give definitions in your own words for the following:
      a.       fact
      b.      hypothesis
      c.       theory

3.  How do scientists calculate the age of very old rocks and fossils?
4.  Did humans and dinosaurs live on Earth at the same time?
5.  Before Christopher Columbus and other Europeans sailed to the New World there were people living in North America.  How did these original native people arrive in North America?

Activity #2        The Stringy Time Line of Earth and Life

Objectives:  Students will

• Understand the total age of the earth and the progression of life forms based on the fossil record
• NM State Standard:  12 Benchmark 18

Background:  After class discussion and reading about fossil formation, sedimentary layers of Earth’s crust, extinct life forms, and radioactive dating techniques students will create a geologic time scale.

Procedure:  The class will use the following scale to represent time on a length of string:  1 meter = 1 billion years, 10 centimeters = 100 million years, 1 cm = 10 million years, and 1 millimeter = 1 million years.  On a length of string 5 meters long label one end “Formation of Earth” and one end “Today” fix this string to a wall in the classroom.  Each student will then be assigned one of the significant life events and the years ago that it happened from table 1 of this curriculum unit.  On a 3”x 5” index card each student will illustrate their event and label the time of the event.  Using the above scale and a meter stick, each student will determine were to attach their event on the string time line.  After each student has attached their assigned event to the string, the entire time line can be displayed in the room.

Assessment:  Teacher will check the placement of events and for correct conversion of time to the metric scale.  Students will be assigned the following discussion questions:   Why are there such large ‘gaps’ in the time line before 1 billion years ago?  Why is the ‘today’ end of the time line more crowded with life forms than the ‘formation of Earth’ end?

Activity #3        Swinging from the Hominid Family Tree

Objectives:  Students will

• Develop a time sequence for ordering Hominid fossil evidence
• NM State Standard:  10 Benchmark 5, 6

Background and Procedure:  This activity can be used as a take home follow up to activity #2 “The Stringy Time Line of Earth and Life.”  After class discussion of the fossil evidence and current research of the genera Australopithecus and Homo, students will create their own time line or branching tree diagram showing the progression and overlapping existence of the hominid fossils.  Students will have to establish their own time scale and mathematical conversion based on the metric system.  Students are required to arrange the following six hominids on a time line or branching tree diagram: 

1.  A. afarensis 4 mya-3 mya
2.  A. africanus 3 mya-2.3 mya
3.  A. robustus 2 mya-1.5 mya
4.  H. habilis 2.5 mya-1.8 mya
5.  H. erectus 1.8 mya-50,000 ya
6.  H. sapiens 700,000 ya-present

Assessment:  Student work will be checked for correct time scale conversions and understanding of the different genera.  Also students will be asked to explain why some of the fossils overlap in time range.

Activity #4  “Tell us what you know about evolution” and “Position Paper” on the Theory of Evolution

Objectives:  Students will

• As a class discuss and list their current knowledge about the topic of evolution
• Conduct independent research on the concept of biological evolution
• NM State Standard:  11 Benchmark 25

Background:  This two-part lesson first elicits students’ background knowledge about evolution and the second part requires that they research and defend their position concerning the theory of evolution.

Procedure:  The “Tell us what you know” part of this activity should take place before any formal class lecture or reading assignment is given on the topic of evolution.  In class students are given time to write at least three facts they know about evolution and at least three questions they have on the concept.  The responses will be collected and compiled by writing them on a large piece of paper in the front of the room.  The class will decide how to organize their responses on the paper.  There are no right or wrong answers, the goal is to generate discussion and gauge class background knowledge.  The teacher will guide and help the students arrange their ideas without lecturing or providing too much information about the topic.

            Based on the class discussion, the students will have some idea where they stand on evolution.  The second part of this activity is for the students to conduct research and provide scientific evidence to support their position on evolution.  Students must produce a two-page minimum, typed paper using at least two print resources and at least two Internet sites.  Students will be instructed on how to cite their references.  The teacher will provide resources and references and help in organizing the paper.

Assessment:  Student reports will be graded on meeting the specified requirements for length and proper citation of resources used.  The content of the paper will be assessed based on the validity of the scientific proof offered in support of their position.

Activity #5        Comparison of Primate Features

Objectives:  Students will

• Discover the similarities and differences between two primate species by comparing physical features
• NM State Standards:  10 Benchmark 5, 11 Benchmark 25

Background:  Physical and structural similarities can indicate an evolutionary relationship between organisms.  Similarities may suggest that the organisms may have shared a common ancestor.  Differences are evidence of the organisms’ continual evolution.  A goal of this activity is to dispel the common misconception that humans evolved from apes.  By comparing the anatomies of humans and apes it can be illustrated that the two species are individual descendants who share a common ancestor.

Note:  Teachers will have to appropriately and legally obtain images of both human and ape skeletons, skulls, dental arcades, hips, hands, and feet.  Possible sources include student textbooks, comparative anatomy texts, and primate reference books.

Procedure:  As a ‘warm-up’ activity to introduce the concept of adaptations, pairs of students will explore the usefulness of their opposable thumbs.  Write this list of tasks on the board: 1) Remove one shoe, 2) Put shoe on again and tie laces, 3) Unbutton a button and button it again, 4) Unscrew a bottle cap, 5) Open a door, 6) Write your name and address, 7) Comb your hair, 8) Take off wristwatch and put back on.

Have students copy this list on their paper.  Now each student will carry out these tasks as their partner records the time it takes to complete each task.  When both students have completed the tasks and recorded the times, each will now secure their thumbs with tape, string, or rubber band and make them non-movable.  Now the students will complete each task and record the time.   Without the use of their thumbs, the tasks become much more difficult and the recorded times will reflect this.  Use this activity to generate discussion about adaptations and natural selection for favorable traits in organisms.  Also note that all primates have opposable thumbs, and apes have opposable big toes.

For the second part of this activity, students will individually compare the physical characteristics shown on the teacher provided images and diagrams of ape and human skeletons.   Depending on what images are available students are to answer the applicable questions that follow:

1.        Based on the skeletal diagrams, compare how the spinal column attaches to the skulls of the              human and the gorilla.  Describe the major difference you observe and how this difference              contributes to the organism’s ability to walk on two legs (bipedal) or on all four limbs              (quadrupedal).
2.        Explain one adaptive advantage of being bipedal over being quadrupedal.
3.        The ape’s opposable big toe allows it to grip objects with all four limbs.  This is a very helpful              trait.  Explain one reason why humans do not have this adaptation.
4.        Describe the relative length of the arms to legs for each of the skeletons.
5.        Describe the difference in the shape of the spine between the ape and human.
6.        Describe the difference between the pelvises of each species.
7.        Describe one similarity and one difference between the teeth of the two species.

Assessment:  Student responses will be collected and graded based on completeness of answers and for understanding of the material.

Activity #6        Analysis of Biomolecules to Determine Evolutionary Relationships or “What Time is it on the Molecular Clock?”

Objectives:  Students will

• Compare differences in biochemical sequences between different species
• Determine evolutionary relationships among species based on analysis of biochemical sequences
• NM State Standard:  10 Benchmark 6

Background:  This activity can be used as a follow up to activity #5, “Comparison of Primate Features.”   Biochemical comparisons are another line of evidence used to show evolutionary relationships between species.  Mutations in DNA nucleotide sequences occur fairly regularly with time and create a “molecular clock” in an organism’s DNA.  In general, the longer two species have been separated, the greater the number of changes between similar fragments of their DNA.  Of course, changes in protein amino acid sequence is the result of changes in DNA, and the differences between these polypeptide sequences can also be compared. With the advances and availability of DNA and amino acid sequences for a variety of species, this technique and the molecular clock concept are useful tools in classification and deducing evolutionary relationships.

Note:  Teachers will have to appropriately and legally obtain DNA nucleotide and amino acid sequence data for this activity.  There are many published data sets of human, primate, and other vertebrate sequences available in beginning texts, like Modern Biology, and college level genetics texts.

Procedure:  Data sets showing the DNA nucleotide or amino acid sequences of certain proteins will be needed for each student.  Two well-established and documented proteins used for this type of study are cytochrome c and hemoglobin.  Students are to compare and count the number of differences between the human DNA (or amino acid) sequences with those of other vertebrates.  The number of differences can be logged in a data table for ease of comparison.   By noting the number of differences between human and other species, students will be able to determine which organisms are more closely related to humans.  Also, the time since the organisms had shared a common ancestor can be inferred based on the total number of differences accumulated.

Assessment:  Student work will be checked for organization of data, and for understanding of the concept behind analyzing biomolecule sequences to show evolutionary relationships.

Activity #7        Human Variation and the Concept of Race

Objectives:  Students will

• Observe and document the occurrence of heritable phenotypes in the class
• Calculate class percentages of those with certain dominant traits
• Discuss the biological and social meanings of race
• NM State Standards:  10 Benchmark 5

Background:  Some genetic traits are easily observed and explained in terms of dominant and recessive inheritance.   Most traits, like skin color, are under the influence of the action of many genes and are also affected by environmental factors.   The genetic and environmental components that interact to form the phenotypes we see will be explored, with a focus on the complexities behind the development of skin color.  After establishing the genetic and environmental basis for observed skin colors, a discussion of the social concept of race and its ramifications will follow.

Procedure:  Students will work in pairs to observe and record their phenotypes for a list of simple inheritance traits.   A list of traits could include: 1) hairline (dominant=widow’s peak, recessive= straight), 2) thumb shape (dom.=straight, rec.=hitchhiker’s), 3) tongue rolling (dom.=can, rec.=cannot), 4) earlobe shape (dom.=free, rec.=attached), 5) number of fingers (dom.=six, rec.=five).  Additional traits can be added if necessary.  Students will record their phenotypes on their paper and then construct a class data table on the board.  Using the entire class data set, compute the percentage of dominant traits present in each category.  The purpose of the percentages is to show students the natural variation of traits present in their class.   By expanding this concept to the larger school population, students can understand the meaning of the term gene pool.

            After this demonstration of simple inheritance, traits of complex inheritance can be introduced.  Height and skin color are two traits that show great variation as a result of many influencing factors.   The range of heights in the class can be shown by arranging the students according to height and then graphing the results.  It must be explained that height is influenced not only by genes, but also by environmental and developmental factors.  The range of skin tones present in the class will be explained based on the physical production of the pigment melanin by specialized skin cells called melanocytes.  The genetic and environmental aspects of skin tone will be discussed.  After explaining the scientific background of skin color, the social concept of race will be introduced.  Students will be asked to explain, by writing an essay, their views on race, both from a biological view and a social or cultural view.  Students will be required to consult their textbooks or class notes to explain the biology behind skin color, and then they will have to provide their own personal view of the social aspect of race.

            Assessment:  Student essays will be checked for correct understanding of the biological basis of variation in skin color.  Their personal viewpoints will be checked for complete ideas and meaningful discussion of the topic.

Activity # 8       Neanderthal Research Project (This activity is adapted from the “Neanderthals” lesson plan by Joy Brewster for DiscoverySchool.com, 2002.)

Objectives:  Students will

• Individually conduct research on a specific aspect of Neanderthal life
• In small groups, produce and present a poster that depicts Neanderthal habitat and living conditions
• NM State Standard:  6 Benchmark 20

Background and Procedure:  Before assigning this research project, the class will view NOVA’s Neanderthals on Trial.  This video, produced in 2002, provides the latest information from recent fossil evidence and Neanderthal mtDNA analysis that scientists are using to determine the relationship between Neanderthals and modern humans.  After viewing the film, students will gain enough background information to generate lively class discussions which in turn provides the motivation to conduct further research on Neanderthal topics.

            This activity has both an individual research component and a group project component.  Students will be randomly placed into groups of four.  Each group member will be assigned one of the following research topics: 1) Neanderthal physical features, 2) Neanderthal hunting and diet, 3) Neanderthal tools, weapons, and shelter, and 4) Neanderthal culture: art, language, religion, and burial rituals.  Each student is required to write a two-page, typed research paper with images of their topic and citations of the references used.  Individual papers must include an introductory section describing when and where Neanderthals lived on Earth. 

            As a group, students will make a poster depicting the habitat, with appropriate flora and fauna, of the Neanderthal.  Each student will be responsible for contributing to the overall diagram as well as illustrating their particular research topic in the poster.  After completing the poster, groups will present and explain their research findings to the entire class.

Assessment:  Student work will be evaluated based on the specified requirements of the research paper given in class.  Also, a three level rubric will be used to judge content:  1) strong research, 2) average research, and 3) weak research, each based on the clarity, amount, and accuracy of material and images presented.

Other Possible Activities

Class activities based on observing sets of fossil organisms can be very helpful in explaining evolutionary concepts.  Many fossils, authentic and replications, can be purchased from biological supply houses.

Describe and highlight a local or regional fossil bearing geologic formation either as a field trip destination or a slide presentation in class.

Arrange a field trip to a museum or visit university collections which house natural history or archaeological displays.  A field trip to a zoo, aquarium, or natural area is a great way to observe the biodiversity and genetic variation present in living organisms.

Topics for Discussion

Present and debate conflicting theories of current anthropological and biological topics.  For example, the dating and location of the first humans in the New World, or the genetic connection (if any) between the Neanderthals and modern humans.

Review the climatic and global factors that interacted to create ice ages in the Pleistocene.  Discuss the role of current human activities and our potential to affect natural phenomena like global warming or the extinction of species.

Documentation

References Cited

Gallup, G. The Gallup Poll.   Wilmington, DE: Scholarly Resources, Inc., 2000.

Grant, P. “Natural Selection and Darwin’s Finches.” Scientific American, October 1991, 82-87.

Howells, W.W. Getting Here: The Story of Human Evolution. Washington, DC: Compass Press,         1993.

Matthews, D. “Effect of a Curriculum Containing Creation Stories on Attitudes about Evolution.”
        The American Biology Teacher, 63 (2001): 404-409.

 National Academy of Sciences. Teaching about Evolution and the Nature of Science.                    
        Washington, DC: National Academy Press, 1998.

Neanderthals on Trial. Writ., dir., and prod. by Mark J. Davis. Videocassette. WBGH  Boston,            MA, 2002.

Towle, A. Modern Biology. Austin, TX:  Holt, Rinehart, and Winston, 1999.

Reading List for Students

 Fossil (Eyewitness Books), by Paul D. Taylor, 1990.

A photo essay explaining different types of fossils, fossil formation, the history of paleontology, and the use of fossils to illustrate evolutionary concepts.

Genetics and Evolution:The Molecules of Inheritance, by Jill Bailey, 1995.

 This edition covers the main topics of genetics and evolutionary biology through the use of numerous drawings, photos, and diagrams within topical essays which are cross-referenced with a complete keyword glossary.

 Giants from the Past, published by National Geographic Society, 1983.

 This book has excellent descriptions and photography of megafauna fossils and displays found in museum collections.  Essays explain the development and extinction of many large North American mammal species after the last ice age.

Ice Ages, by Windsor Chorlton, 1983.

This volume of the Planet Earth series explores the geologic history of the Pleistocene glaciations including their causes, effects on organisms, and methods of studying past climates based on ice core samples.

 Mammoths, by Adrian Lister and Paul Bahn, 1994.

 A very thorough work, this book is full of diagrams, photos, and excellent descriptions and                discussions covering the natural history of mammoths.

 Neanderthal, by Douglas Palmer, 1994.

  A very explanative and complete text accompanied by photos from a BBC television    series where costumed actors portrayed and acted out various activities based on the    life of Neanderthals.

 The Cambridge Guide to Prehistoric Man, by David Lambert, 1987.

 Using many illustrations, charts, maps, and graphs this book traces the biological and    cultural evolution of humans.

 Reading List for Teachers

 Evolution, by Monroe W. Strickberger, 1990.

This encyclopedic edition is a very complete and thorough presentation of the science of evolutionary biology.

Fossils: The Evolution And Extinction Of Species, by Niles Eldredge, 1991. 

Full of rich and large photographs, this book shows various types of fossils (including hominids) and explains their relevance in the continuing story of the evolution of life.

 Human Variation: Races, Types, and Ethnic Groups, by Stephen Molnar, 2002.

A very informative text that uses the latest research data to explain the genetic basis and inheritance of the variation observed in human traits. 

Science and Creationism: A View from the National Academy of Sciences, National Academy              Press, 1999.

This booklet contains the essential background information for teaching about the nature of science, the origin of life, biological evolution, and why creationism cannot be taught in public schools.

 The Great Journey: The Peopling of Ancient America, by Brian Fagan, 1987.

  A detailed work that reviews the scientific evidence for the first human migration into     the New World through descriptions of archaeological sites in the Americas.

The Last Neanderthal: The Rise, Success, and Mysterious Extinction of our Closest Human              Relative, by Ian Tattersall, 1995.

 A great resource on all things Neanderthal; filled with photos and explanations of the    latest findings and research in the field of ancient humans.