BIOL 121L - GENERAL BIOLOGY: DIVERSITY & ECOLOGY LABORATORY #3: EVIDENCE REGARDING EVOLUTION INTRODUCTION There are many questions regarding the origin of species. These questions relate to topics such as the age of the earth and the species which inhabit it, mechanisms (such as natural selection) which are advanced to explain evolutionary change, means by which species might diverge and form separate species, and theories regarding the origin of life on earth. In this laboratory exercise we will not deal with any of these topics. Instead, we will examine some of the observations which have been cited as evidence for species change over long periods of time and common ancestry of different species. th The 19 century Natural Theology paradigm and contemporary young-earth creationism view each type of organism as being perfectly designed separately created. In Darwin's book "The Origin of Species by Means of Natural Selection," Darwin devoted a considerable amount of space to the examination of observations which he felt were better explained by common ancestry of species, as opposed to origin by separate creation of each species. Some of Darwin’s observations include the fossil record, biogeography, homologous structures in different species, embryological similarities, and vestigial structures. Since Darwin's time, other lines of evidence have been advanced. In this laboratory exercise, we will examine several of these lines of evidence. We will attempt to explain our observations from three different paradigm perspectives: from an evolutionary perspective, and from a young-earth creationist perspective, and from a progressive creationist perspective. Paradigm and theory choice by scientists involve many criteria beyond what we examine here. But ultimately, theories are selected which provide adequate explanations for observed phenomena, and which can adequately predict future observations. This exercise will introduce us to some of the evidence which forms the basis for discussion of origins. Various stations are set up around the lab. You can move from station to station, examine the material presented, and answer the questions related to the material. Richard Wright’s book Biology through Eyes of Faith provides background to how young-earth, progressive, and evolutionary creationists approach these issues. Your Campbell’s Biology text provides the currently accepted evolutionary explanation, which is similar in most respects to the evolutionary creationist perspective. OBJECTIVES 1. 2. 3. Define and cite examples of homologous structures, analogous structures, embryological structures, biogeography, and fossils. Interpret observations from evolutionary, progressive creationist and young-earth creationist perspectives. Evaluate the relative strengths of various interpretations. MATERIALS fossil casts of ammonites, trilobites, a dinosaur egg and an Archaeopteryx skeleton vertebrate skeletons of a human, a cat, a chicken, and a frog several examples of insects chick and pig embryos 12 - 1 pictures of marsupial and placental mammals FOSSILS 1. Observe the diagram of the geological column. This is a schematic depiction of the different layers of sedimentary rocks that are found in various locations around the world. Each layer is associated with characteristic fossils. While no one location on earth contains all of the strata, the strata are always located in the same relative positions, with strata at the bottom of the column located below strata that are depicted above. The geologic strata is first divided into major eras based on the different fossils they contain; eras are further divided into periods that contain similar major groups of fossils, but usually contain different species. Radioactive isotopes in the rocks have been used to estimate the age of each stratum, which is given in the table in millions of years before the present. 2. Observe the fossil casts of ammonites, which are an extinct group of marine animals. Many different fossil species of ammonites have been found in different layers of sedimentary rock, but always in Paleozoic and Mesozoic strata. No ammonites are found in Cenozoic strata or in the lowest Paleozoic fossil strata. The lowest strata containing ammonites is the Devonian period, and the highest strata containing them is the Cretaceous. 3. Observe the fossil casts of trilobites, which are another extinct group of marine animals. There are also many different species of trilobites in the fossil record, each species found in different sedimentary strata. However, trilobites are only found in Paleozoic strata — never in the Mesozoic or Cenozoic, and never in the Pre-cambrian strata. Most species of trilobites are found in Cambrian, Ordovician and Silurian periods. A few different species of trilobites can be found in Cevonian, Carboniferous and Permian strata. 4. Based on their location in the fossil record, how many years ago did ammonites first appear on earth, and when did they go extinct? 5. Based on their location in the fossil record, how many years ago did trilobites first appear on earth, when did most species of trilobites go extinct, and when did the last trilobites go extinct? 6. How would progressive creationists and evolutionary biologists differ on the appearance of trilobites and ammonites? 7. Young earth creationists believe fossils are the result of a single flood event that is described in Genesis 9 - 11. How would young earth creationists differ in their explanation of ammonite and trilobite fossil distribution. How might they account for the lack of either fossil in higher or lower strata? 8. Observe the fossil cast of a dinosaur egg. Dinosaur fossils are only found in Mesozoic strata. Based upon the dates provided in your geologic column diagram, what is the range of possible age of this dinosaur egg? 9. How would young-earth creationists, progressive creationists and evolutionary biologists differ in their explanation of why dinosaur fossils are only found in Mesozoic strata? 10. Observe the replica of an Archaeopteryx fossil. The skeleton of Archaeopteryx is very similar to some small dinosaur fossils, but it also shares many features with birds, including casts of 12 - 2 feathers on some specimens. How would evolutionary biologists, progressive creationists and young earth creationists differ in their explanation of the Archaeopteryx fossils? VERTEBRATE SKELETONS 1. Examine the various vertebrate skeletons presented. Look for similarities in their structure. Look for differences as well. Structures which show a common underlying form in different species are termed homologous structures. 2. Compose a table with two columns. In one column, record some of the similarities between species. In the second column, record some of the differences between the species. 3. In a paragraph, describe the evolutionary explanation for the similarities. Describe the evolutionary explanation for the differences. 4. In a paragraph, describe the scientific creationist explanation for the similarities. Describe the scientific creationist explanation for the differences. 5. Note the wings of an insect. Analogous structures are ones which have a common function, but lack a common underlying structure. Which vertebrate structure would be analogous to the insect wing? EMBRYOLOGY 1. Observe the embryos of a chick and a pig using the dissecting microscopes. Would you consider these embryos more similar or less similar to each other than adult chickens and pigs? 2. Each contains structures in the neck region called “gill pouches” , which is thought to be homologous to gill slits in fish. What would be an evolutionary explanation for gill pouches? What would be a young-earth or progressive creationist explanation for gill pouches? 3. BIOGEOGRAPHY 1. Observe the pictures of various marsupial mammals. Marsupials are mammals which give birth to very small, immature offspring that are protected and nursed in a pouch. Most marsupials are found in Australia, but they are not common to Asia. The only mammal fossils found in Australia are marsupial. 2. Observe the pictures of various placental mammals. Some look superficially like marsupials, but they form a separate natural group. Placental mammals allow their offspring to grow to a larger size in the uterus of the mother and nourish their young by a placenta. Placental mammals are much more common around the world than marsupials, but the only placental mammals native to Australia are bats, marine mammals, and several mice species. However, Australia is a good environment for placental mammals because the placental mammals (like rabbits, sheep and dogs) that humans have brought to Australia have spread and established themselves throughout the continent. Some introduced placentals are threatening to drive marsupial species to extinction. 3. What would be an evolutionary explanation for this distribution of marsupial and placental mammals in Australia and Asia.? 12 - 3 4. 5. What would be a progressive creationist explanation for this distribution of marsupial and placental mammals? What would be a young-earth creationist explanation for this distribution of marsupials and placentals? VESTIGIAL STRUCTURES 1. Vestigial structures are those for which no function is known. Observe the list of diagrams of several vestigial structures. 2. What would be an evolutionary explanation for vestigial structures? 3. What would be a scientific creationist explanation for vestigial structures? FOR THOUGHT AND DISCUSSION 1. 2. Summarize your understanding of the relative strengths and weaknesses of the different methods of interpreting these observations used by evolutionary biologists, young earth creationists, and progressive creationists. While scientists cannot travel back in time to see earth’s history directly, a good theory should be able to predict new observations and discoveries. What kind of new evidence might either support or contradict an evolutionary, progressive creationist or young-earth creationist viewpoint? 12 - 4
© Copyright 2024