Evidence of Evolution
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Science in Motion Ursinus College NAME_____________________________________ EVIDENCE FOR EVOLUTION LAB STANDARDS: 3.3.10D Explain the mechanisms of the theory of evolution 3.3.10A Explain the structural and functional similarities and differences found among living things INTRODUCTION: Evolution is not just a historical process; it is occurring at this moment. Populations constantly adapt in response to changes in their environment and thereby accumulate changes in the genes that are available to the species through its gene pool. In today's lab you will explore some of the evidence for evolution and will examine a few of the mechanisms through which evolution acts. In this laboratory you will review some of the classical examples used as evidence for evolution. Keep in mind that the support goes far beyond these simplistic examples and this selection is only intended as an introduction to the subject. GUIDING QUESTIONS: 1. What is a theory? 2. What is evolution? 3. What evidence is there to support the theory that living things evolved? 4. What is the difference between homologous and analogous structures? MATERIALS NEEDED: Code-numbered fossils: Various types, as available. Skeletons and/or forelimbs of a frog, turtle, rabbit, bat, fish, and human. Slides of early embryonic stages for a typical mammal (pig) and bird (chick). Immunology and Evolution lab materials. Wax pencils, spot plates, toothpicks. PROCEDURES: PART I: FOSSIL EVIDENCE Fossils are the remains or traces of an organism from prehistoric times (older than 4000 BC). Most organisms do not fossilize and those that do are usually destroyed by geological processes or they never surface for examination. Fossils are usually formed when an organism is covered by sediments that then harden into sandstone, slate, mudstone or flint. Organisms also fossilize when they are buried in volcanic ash or entombed in tar or tree sap. Several fossils specimens are on display. The display fossils are either mold or petrification fossils. A mold fossil forms when the material surrounding the organism hardens followed by removal of the organic matter. This leaves behind an impression (or mold) of the organism. Petrification fossils are formed through two main processes: permineralization and replacement. Permineralized fossils are created when ground water percolates through the remains of the organism and leaves behind minerals in the cellular spaces. Petrified wood is an example of a permineralized fossil. Replacement fossils are formed when ground water first dissolves out the tissue and then leaves minerals in their place. Both types of petrification fossils are generally composed of either SiO2 or CaCO3. Examine the fossils supplied and try to identify the fossils as to their method of formation. Record your identifications in the results section. PART II: COMPARATIVE ANATOMY The discipline of comparative anatomy is important in interpreting relationships among organisms. Structures are said to be homologous if they have similar embryonic origins and analogous if they are similar only in function. The wings of birds and flies are examples of analogous structures. They serve the same function, but obviously have different embryonic origins (one is made of bone and flesh, the other is composed largely of non-living chitin). On the other hand, the wings of birds and the foreleg of a frog are homologous structures (although these limbs have different functions, their embryonic origins are similar). To comparative anatomists, homologous structures are important because they imply an evolutionary linkage between two species. Several skeletons and/or foreleg preparations are on display. Compare the foreleg preparations and identify the bones that are in common among the different species. Where possible, determine how changes in the structure of the limbs reflect the differing lifestyles of the organisms. PART III: EMBRYOLOGY A study of an organism's embryonic development provides further clues to its evolutionary past. At one time it was asserted that "ontogeny recapitulates phylogeny". Simply put, this hypothesis suggests that, as an organism goes through its embryonic development (ontogeny) it repeats (recapitulates) the stages in its evolutionary history (phylogeny). At one point during your development, for example, you possessed folds in the neck area called pharyngeal pouches which in some animals become gills. Some believe that this is evidence that we seemingly passed through an aquatic phase in our evolutionary history. This notion of embryology as an "instant re-play" of evolution has been called the biogenetic law. Although the relationship between evolution and embryonic development is more complex than once thought, related organisms do show similarities in their embryonic development. These similarities can be traced to the conservative nature of embryology: small changes in early in development can have drastic consequences in later stages (through a “domino” effect). Although gills are not found in adult humans, all vertebrates have similar pouches from which they arise. In humans these pharyngeal pouches go on to become muscles for chewing and facial expression, bones of the middle ear, and endocrine glands in the neck. From an evolutionary perspective, many people believe similarities in embryology are valuable because they reveal our kinship with other members of our phylum. Study the demonstration slides of embryonic development in a mammalian species and the chick embryo. In the results section, list three similarities in the structure of the two embryos. PART IV: COMPARATIVE SEROLOGY As you are aware, people vary in their blood types, and these differences can be ascertained through immunological testing. Techniques similar to those used for blood typing can be used to test and compare the blood sera of different species. When so tested, closely related species show greater similarities in blood constituents than do more distantly related species. In this portion of the laboratory you will examine the relatedness of five organisms: human, cow, chimpanzee, frog, and monkey. Five synthetic sera will be used (each is labeled for the type of sera). Each group of two or three will work with only one of the synthetic sera. Do not dispose of your work until you have seen the results from all groups. Obtain a spot plate and label it with your assigned sera (human, cow, etc.). Number the plate depressions 1-8. Add your assigned sera and water according to the following table: Well Number Drops of Serum Drops of Water 1 8 0 2 7 1 3 6 2 4 5 3 5 4 4 6 3 5 7 2 6 8 1 7 Then add 8 drops of human antiserum to each of the wells. Use a toothpick to stir the mixtures (starting at well #8; wipe the toothpick dry between each well). Watch the reactions in the wells for two minutes before recording your results and then note in which cells agglutination occurs (the formation of a clumped precipitate). The more similar the blood proteins of the test species is to a human, the greater the amount of agglutination. Compare your data to that of other groups by scoring the results using "++++" for maximal agglutination, "+++" for a large amount, "++" for a small amount, and "+" for a trace of agglutination. If no precipitate is observed, score the depression as "-". From these data, rank the species as to their evolutionary relatedness to man. PART V: MOLECULAR BIOLOGY With the advancement of DNA technology, scientists now rely more upon comparisons of protein structure, amino acid sequences, and DNA sequences to determine evolutionary relationships. The more closely related the species, the more similar their genetic material will be. A fragment of aligned DNA sequences that codes for a protein common to each primate species and the chromosome banding patterns for the first chromosomes of each species are depicted in figure 3.1. Changes in the DNA sequences are double underlined. For the chromosomes, solid coloring indicates similar sequences. Changed patterns are spotted. On the results page, discuss how you would interpret the relationships between these organisms based on the genetic and chromosomal data given in this figure. Aligned DNA sequences of -globin Chromosome Banding Patterns Figure 3.1. Aligned DNA fragment and first chromosome banding patterns for man (Homo sapiens), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus). Adapted from “Evidence of Evolution Lab” from Bellarmine University with input by Janet Wolfe of Conestoga High School Science in Motion Ursinus College NAME _______________________________ EVIDENCE FOR EVOLUTION LAB – RESULTS PAGE PART I – FOSSIL EVIDENCE Enter the fossil identification (number on fossil), formation method (mold or pretrification), and a species of organism existing today that is similar to the fossil. Fossil Identification Method of Formation Present Species Similar to Fossil PART II – COMPARATIVE ANATOMY Look at the similarities in foreleg bones for the following animals. Briefly discuss how the design of the limbs reflects the differing lifestyles of the organisms. SPECIES HOW DESIGN OF LIMB RELATES TO LIFESTYLE Human Turtle Rabbit Bat Fish Frog PART III – EMBRYOLOGY A. List three similarities between the two embryos: 1. 2. 3. B. Explain how these similarities correlate to the evolutionary relatedness of these two species. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ____________ PART IV – COMPARATIVE SEROLOGY Enter the class results from the comparative serology simulation. Score your data as described in the procedure section. Then rank the species as to their genetic relation to humans (1 being the closest to 4 being the most distantly related). Organism Human Cow Chimp Frog Monkey 1 2 3 Species Cow Chimp Frog Monkey Rank Conclusion 4 5 6 7 8 PART V – MOLECULAR BIOLOGY Using the DNA sequences and chromosome banding patterns depicted in figure 3.1, discuss the relationships between the four species. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________ Science in Motion Ursinus College TEACHER NOTES EVIDENCE FOR EVOLUTION LAB Time needed to complete lab: two class periods Target Grade Level: 10-12 all levels (introduction to the topic of evolution) Objectives Analyze information that could be used to support the theory of evolution Understand the scientific use of the word theory Understand the concept that similarities in DNA, embryology, and anatomy are used to determine evolutionary relationships To realize the special importance of DNA in determining evolutionary relationships Differentiate between homologous and analogous structures Major Concepts (background information) One important thing that teachers should emphasize in this lab is the difference between the word “theory” in common speech and the word “theory” when used in science. In common speech, theory is a little more than a guess but in science, the work theory means an idea that has been supported by data. Over hundreds of years, humans have collected data on the variation and complexity of life and evolution is an explanation of how and why life has changed. In 1831 Charles Darwin began a five-year journey as ship's naturalist on the H.M.S. The Beagle. During this time he visited South America, Australia, South Africa, and islands of the Pacific and South Atlantic. He later published his travels in The Voyage of the Beagle where he introduced many themes that later became crucial to the arguments presented the more-familiar The Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life (published in 1859 and more commonly known as "The Origin of Species"). Majors in the sciences and those interested in philosophy should read this monograph. You won't find it easy reading because the language is often archaic and the arguments are sometimes difficult to follow, but it represents one of the most important contributions made to Western culture. Although Darwin is often referred to as "the father of evolution", he was not the first to introduce the idea of changing species. Maupertuis and Diderot in the mid 18th century, for example, wrote of evolution and the ideas of changing life are part of many religions. Darwin's contribution was to provide a mechanism through which evolution could function. Briefly, the Darwinian argument is as follows: Variation exists within a species. Although we may consider all houseflies as being more-or-less alike, on closer examination you find that they are nearly as recognizable as one person is from another. Some of this variation has a genetic basis. Evolution can act only on traits that are passed genetically from one generation to the next. Just as animal or plant breeders have no interest in non-genetic traits, evolution can not work on differences due to trauma, parasitism, and other environmental variation. The reproductive potential of organisms is vast. Darwin calculated that a single pair of elephants could have 19 million descendants within 750 years if each animal lived to be 100 and each pair had six calves. Calculations for other organisms produce similar increases in population size. Elephants are not the most common beasts, the oceans are not overflowing with fish and we aren't nose-deep in ragweed (although it sometimes seems that way). Therefore something must happen to all these extra offspring and, unless species other than man practice birth control, most of the young must die before they reproduce. Because individuals differ from one another, some should be more capable than others in eluding predators, coping with environmental extremes, or in competing with members of their own or other species. Those that are more capable should leave more offspring to the succeeding generation. Since some aspects of coping must be tied to genetic attributes, the favorable genes are passed on to the next generation. The genetic makeup of the population changes and evolution is said to occur. This varying reproductive success of individuals based on their different genetic constitutions is natural selection. Often the concept of natural selection is simplified to "survival of the fittest". Fitness in evolutionary terms has an exact meaning related to the number of surviving offspring produced by an individual in comparison to less well-endowed individuals. Evolutionary fitness is therefore more than just the ability to run quickly or fight off competitors. Preparation: This lab is best done as learning stations with the students moving from learning station to learning station. It is recommended that students move as lab groups and that each group is assigned one organism to do the serology work on. The results of the serology section should be put on the board so the results can be shared by the all the groups. Answers to questions: Other fossils can be used. The information below is for the fossils that come with this particular lab. Part I-Fossil Evidence Fossil Identification 1. 2. 3. 4. 5. Method of Formation Petrification Mold Petrification Petrification Petrification Present Species Similar to Fossil Some mollusk-ex. cuddlefish Fern or any fern species Any bony fish species Any tree An arthropod-ex. horseshoe crab Key to Numbered Fossils 1. Ammonite These are an extinct group of marine animals in the class Cephalopoda, phylum Mullusca. Even though they look a lot like a chambered Nautilus, they are more closely related to the octopus, squid, and cuddlefish. They became extince during the Cretaceous period about 65 m.y.a. and had first appeared during the Devonian Period about 400 m.y.a. They were named after the Egyptian god Ammon by Plinius the Elder because the god was typically depicted wearing ram’s horns. They lived in open seas and were thought to be good swimmers. They preyed on fish, crustaceans and other small animals. This fossil was found in England. 2. Fossil Fern These fern fossils are a good example of mold fossils. The fern material completely decomposed and an imprint of the fern frond is left behind. This particular fossil comes from Pennsylvania which is famous for its fossil ferns. Although many types of ferns exist today, the fern that formed this fossil is extinct. 3. Rhacolepsis (fish) This extinct bony fish lived 100 m.y.a. during the Cretaceous Period. It was a predator and was found in Brazil. 4. Petrified Wood This fossil is from is from Oregon. It consists of fossil wood where all the organic material has been replaced by minerals, while retaining the original structure of the wood. The petrifaction process occurred underground, when the wood was buried under sediment. Mineral-rich water flowing through the sediment deposited minerals in the plant’s cells and as the plant’s lignin and cellulose decayed away, stone took its place. Petrified wood can preserve all the original structure of the wood down to the microscopic level. The tree rings in this polished sample are very visible. 5. Trilobite These organisms were among the early arthropods. They have the classic hard shells, body segments and jointed legs that are characteristic of this phylum. There are 15,000 described species and new species are unearthed each year. This is the most diverse group of extinct organisms. They vary from under a millimeter to 70 cm in length. They filled a wide variety of niches in the environment from scavengers to predators. They existed 300 m.y.a. and lived in ancient seas. They became extinct before the time of the dinosaurs. Trilobite means “three lobes.” Looking from head to tail, this specimen has left and right lobes and a center lobe. This particular fossil is from Morrocco. Part II – Comparative Anatomy The purpose of this part of the lab is to have students become aware of the concept that organisms are modified to fit the environment and that in most cases the organisms have the same structures but their shape is different to perform a different task. Part III- Embryology Student answers will vary widely but the goal of this part of the lab is to see the great similiarity of organisms during the embryolic stages. Part IV-Comparative Serology Dilution 1 2 3 4 5 6 7 8 Chimp ++++ ++++ ++++ ++++ +++ +++ +++ ++ Gorilla ++++ ++++ ++++ ++++ ++ ++ + - Orang ++++ ++++ ++++ ++ +++ ++ + + Swine - - - + - - - - Part V – Molecular Biology If you look at the differences in DNA sequences, chimps and gorillas have three differences from the human code for this segment and orangutans have five. Banding pattern wise, the chimp and the orangutan look most similar to the human. From this information, I would say that the chimp is the most closely related to humans. Science in Motion Ursinus College Evidence of Evolution Prequiz 1. When something is called a “theory” in science, it is A. a proven fact B. a guess that may be true C. an explanation supported by data D. an idea that still has not been tested 2. Pigs and chickens are quite different animals. When comparing their embryos, A. they are fairly similar especially in earlier stages B. they show almost no similiarities C. they are always easy to recognize as either chicken or pig, even in the early stages D. they start looking different but as they develop they look more similar 3. Which data is probably the MOST valuable when determining if organisms are related? A. fossil evidence B. similar anatomy C. similar blood proteins D. similar DNA 4. The forelimb of the frog is homologous to which structure A. forelimb of a human B. wing of a bat C. forelimb of a turtle D. all of these are homologous 5. If a certain animals’ serum reacts with human antiserum and forms a large amount of precipitate, it means A. the animal has all the same proteins as a human B. the animal probably has many of the proteins of a human C. the animal is distantly related to a human D. the animal is not at all related
