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.
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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
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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
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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.?
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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?
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