Performance Benchmark L.12.D.1
Students know organisms can be classified based on evolutionary relationships. E/S
When teaching all of the L.12.D benchmarks, it is imperative to help students understand the
process of science. Most objections and misconceptions about evolution are directly related to
the misunderstanding of how science works. When students understand the nature of science,
they will understand how scientists have studied the process of evolution. As questions arise
about a “supernatural” creation of Earth and the Universe, students who understand the nature of
science will understand why supernatural forces cannot be studied as part of scientific processes.
Organisms can be classified into groups based on morphological, behavioral, and evolutionary
relationships. Classifying organisms is important to scientists as it provides a framework and a
common “language” which enables scientists everywhere to study and understand more about
life on Earth. Biological classifications are based on how organisms are related. Taxonomy is
the science of classification and includes the naming, describing, and classifying organisms into
various groups.
The Linnean system of classification is a hierarchical classification system that has been used by
scientists for nearly 200 years. This system, originally based on morphological and behavioral
characteristics is still in use today, although with many modifications. The highest category in
the hierarchy is “all living things” and the lowest category is a single species. A species is
generally identified as a group of organisms which are capable of reproducing with the
production of fertile offspring. The hierarchical divisions are as follows: Domain, Kingdom,
Phylum, Class, Order, Family, Genus, Species. The following table shows the Linnean
classification hierarchy of two organisms.
Category
Domestic cat
Common buttercup
Domain
Eukarya
Eukarya
Kingdom
Animalia (animals)
Planate (plants)
Phylum/Division
Chordata
(chordates)
Anthophyta
(flowering plants)
Class
Mammalia
(mammals)
Dicotyledons
(dicots)
Order
Carnivoria
(carnivores)
Ranunculales
Family
Felidae (cats)
Ranunculaceae
(crowfoot family)
Genus
Felis
Ranunculus
Species
silvestris
acris
Scientists currently recognize 3 Domains and 6 Kingdoms of living things:
Three Domains
Bacteria
Archaea Eukarya
The Six Kingdoms
Bacteria
Archaea Protista
Plantae Fungi
Animalia
To learn more about Linneas and the Linnean system of classification see:
http://huntbot.andrew.cmu.edu/HIBD/Exhibitions/OrderFromChaos/pages/intro.shtml and
http://anthro.palomar.edu/animal/animal_1.htm
Charles Darwin was a scientist/naturalist who gathered a significant amount of evidence
indicating that populations change over time as the population amasses adaptations to
environmental conditions. During voyages on the HMS Beagle, Darwin carefully observed,
characterized and categorized different populations that seemed to have arisen from common
ancestors. One of the classic examples is that of the Galapagos finches. Finches on different
islands, geographically isolated from each other, had specific variations that seemed to aid in
survival on the particular island. The finches were similar to each other and all had similarities
to the finches on the mainland of South America, yet all had specific adaptations that enabled
survival in their particular area. This type of evolutionary change is called adaptive radiation.
This diagram from http://www.pbs.org/wgbh/evolution/library/01/6/image_pop/l_016_02.html
illustrates the finches that Darwin observed. All of the finches are believed to have arisen from
a common ancestor, but evolved different characteristics due to environmental conditions and
available food sources on different islands.
These observations, as well as, other data collected on numerous organisms led Darwin to the
theory of natural selection as the mechanism for evolution.
To learn more about Darwin’s studies and theory, see:
http://www.geo.cornell.edu/geology/GalapagosWWW/Darwin.html
For a short video about Darwin and his studies, see
http://www.pbs.org/wgbh/evolution/library/11/2/e_s_2.html
Linneas, Darwin, and other early scientists classified organisms by comparing physical
characteristics. While physical characteristics are still useful in classification, it is now generally
agreed by scientists that the evolutionary history can be more useful and accurate in the
organization and classification of organisms. Organisms can be grouped according to their
shared evolutionary history. Organisms that have a recent common ancestor are more closely
related than those that have a more distant common ancestor. Phylogeny is the classification of
organisms based upon their evolutionary history. Evidence used to explain and determine
phylogeny includes fossils (see L.12.D.3), biochemistry (see L.12.D.2), genetics (see L.12.A.1),
and structure. Phylogenetic trees are used to illustrate evolutionary relationships. The following
phylogenetic tree illustrates the relationship of several animals. For example, the following
diagram indicates that salamanders and frogs are more closely related than mammals and turtles.
Figure from: http://www.med.nyu.edu/rcr/rcr/course/tree.gif
To learn more about phylogeny and its usefulness in classification see:
http://www.tolweb.org/tree/learn/concepts/whatisphylogeny.html
and http://evolution.berkeley.edu/evolibrary/article/phylogenetics_01
Homologous structures are anatomical features of different organisms that have a similar
appearance or function that are inherited from a common ancestor. The wing of a bird, the
forelimb of a cat, and the arm of a human are homologies because they are structurally and
functionally similar and they are inherited from a shared ancestor. The more homologies
different organisms have, the closer they probably are genetically.
This figure illustrates homologous structures in the forelimbs of several animals.
Source: http://virtuallaboratory.net/Biofundamentals/lectureNotes/Topic1-5_Evo.htm
Analogies are anatomical structures that have similar form or function in different species that
have no known common ancestor. For example, the wings of a bat and the wings of a moth are
similar in shape and function, but are very different internally and the wings did not evolve from
a shared ancestor.
For additional information and examples of homolgies and analogies, see:
http://evolution.berkeley.edu/evolibrary/article/0_0_0/similarity_hs_01
Biological evolution is the best scientific explanation for how life on Earth has changed and how
it continues to change. We do not understand everything about evolutionary relationships among
organisms. The evolutionary history of an organism is determined based on current knowledge,
evidence, observations, and testing, and as new data becomes available, our understanding of
relationships between organisms will continue to be revised. DNA analysis and other molecular
technology available today provide data and information which can be used in classification
system. (See L.12.D.2)
Performance Benchmark L.12.D.1
Students know organisms can be classified based on evolutionary relationships. E/S
Common misconceptions associated with this benchmark
1. Appearance Misconceptions
Students incorrectly think that if organisms look alike, then they must have a common
evolutionary history. When asked to classify organisms, students use obvious physical
features, rather than processes or genetic relationships.
Convergent evolution is the development of similar traits or characteristics by taxonomically
different groups of organisms. Convergent evolution often occurs when two groups of
organisms occupy similar niches. Just because two organisms may have developed a similar
characteristic trait, it does not necessarily mean that they are closely related. For examples, birds
and bats both have wings, an adaptation that allows them to fly. However, bats and birds
evolved independently of each other.
For a discussion of convergent evolution, go to
http://www.pbs.org/wgbh/evolution/library/01/4/l_014_01.html
2. Natural Selection Misconceptions
Students incorrectly believe that adaptations and hence, natural selection occurs as an
organism changes due to some need, desired use of function, or an environmental condition,
and that this change is then automatically passed to their offspring.
This misconception was held by Lamarck in the 1800’s, who concluded that parents can pass
acquired characteristics on to their offspring.
Students have difficulty understanding basic concepts of evolution such as natural selection.
They don’t conceptualize that mutations often occur randomly and that some of these random
changes are selected for because they help in the survival and reproduction of the organism.
To read more about Lamarck, see:
http://www.pbs.org/wgbh/evolution/library/02/3/l_023_01.html and
http://www.encyclopedia.com/doc/1E1-Lamarck.html
Evolution through natural selection occurs instead through variations and changes in DNA that
occur naturally and randomly. If a particular mutation is found in an organism which enables the
organism to better survive in its environment, the organism is more likely to live, and to
reproduce (survival of the fittest). Because the animal was born with that change and that it is in
the DNA of the organism, that DNA, and therefore the trait, can be passed on to the offspring.
Over time, when a significant number of changes have occurred, a new species may develop.
Mechanisms of evolutionary change include:
mutation—changes in the DNA of an organism
migration—a group of organisms from a particular species may migrate to a new,
geographically isolated area and begin interbreeding among themselves but not with the
parent population
genetic drift—normal variations that occur in the genes of organisms, related to
mutations
natural selection—the organisms most likely to live and reproduce will be the ones that
pass on their traits
More information about evolution through natural selection can be found at:
http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html
3. Scientific Theory Misconceptions
Students incorrectly think that evolution is “just a theory.” Students think that a scientific
theory is similar to a theory as used in everyday discussions, that is, a theory is just a guess
or a hunch, or what one person thinks.
The common-every-day use of the word theory means a guess or a hunch. A scientific theory
does not have the same meaning as this common every-day theory. A scientific theory is well
substantiated, supported by facts, laws, and tested hypotheses. A scientific theory is an
explanation based on observation, experimentation, and reasoning. It is recognized in the
scientific community as a general principal that helps explain natural phenomena. Theories can
be tested, modified, and at times, rejected as new information and scientific knowledge is
acquired. Scientific theories are valid and provide a basis for exploring new questions.
Additional definitions of scientific theory can be found at,
http://www.ncsu.edu/labwrite/res/res-glossary.html
For NSTA’s position statement on scientific theories see:
http://www.nsta.org/positionstatement&psid=10
(scroll down to the section entitled: The Nature of Science and Scientific Theories.
4. Human Evolution Misconceptions
Students incorrectly think that evolution of humans means the humans evolved from
monkeys.
A comparison of human to chimpanzee DNA shows about a 98% similarity indicating that there
is a genetic and evolutionary link. However, one species did not evolve from the other species.
Rather, about 5 million years ago, modern apes and humans had a common ancestor which was
not ape, nor human, nor monkey.
For a brief explanation of the Man from Monkey misconception see #6 at this link:
http://www.bio.ilstu.edu/Armstrong/misconceptions.doc
Performance Benchmark L.12.D.1
Students know organisms can be classified based on evolutionary relationships. E/S
Sample Test Questions
1. A horse and a donkey may interbreed with each other and produce offspring. The offspring
are generally sterile, however, because the horse and the donkey are of different
a. orders
b. kingdoms
c. species
d. phyla
2. The evolutionary history of an organism is its
a. taxonomy
b. morphology
c. classification
d. phylogeny
3. The wings of a bird and the arms of a human are similar in structure and function. Structures
such as these in different species are called:
a. analogous structures
b. homologous structures
c. phylogenous structures
d. hybrid structures
4. The following illustration represents a phylogenetic tree which includes several different
organisms. Based upon this diagram, which of the following groups of organisms have the
closest evolutionary relationship?
Figure is from:
http://www.med.nyu.edu/rcr/rcr/course/tree.
gif
a.
b.
c.
d.
mammals and lizards
mammals and frogs
lungfish and frogs
lizards and snakes
5. Which of the following would provide the best data for determining the phylogeny
(evolutionary history) of three very closely related species?
a. fossil records
b. comparison of anatomical structures
c. comparisons of their scientific names
d. comparison of DNA sequences
6. Which of the following characteristics did Linnaeus use to classify organisms?
a. DNA similarities
b. Environments in which the organisms lived
c. The color of the fur, skin, or feathers
d. Shape, size and structure
Performance Benchmark L.12.D.1
Students know organisms can be classified based on evolutionary relationships. E/S
Answers to Sample Questions
1.
2.
3.
4.
5.
6.
(c)
(d)
(b)
(d)
(d)
(d)
Performance Benchmark L.12.D.1
Students know organisms can be classified based on evolutionary relationships. E/S
Intervention Strategies and Resources
The following list of intervention strategies and resources will facilitate student understanding of
this benchmark.
1. For additional general background on evolution standards for the teacher, see:
National Science Teacher’s Association (NSTA) position statement on evolution:
http://www.nsta.org/positionstatement&psid=10
NSTA Questions and Answers regarding evolution, as well as suggestions on how to respond to
student questions and oppositions: http://nsta.org/evolutionqanda
To read the National Science Standards Content Standard C, Molecular basis of heredity and
Biological evolution pieces. http://www.nap.edu/readingroom/books/nses/6e.html
For additional information on what is recommended in evolution education, see: Evolution on
the Front Line: An Abbreviated Guide for Teaching Evolution from Project 2061 at AAAS.
http://www.project2061.org/publications/2061Connections/2006/media/Evo_Handout_Teachers.
pdf
2. For good definitions of taxonomy, classification, phylogeny, etc.
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookDivers_class.html
3. The University of Arizona has developed “The Tree of Life Web Project.” The goal of the
project is to compile an online database about the biodiversity and evolutionary relationships of
all organisms. The site contains identification keys, images, phylogenetic trees, and other
information as well as links to activities and other useful information. This could be used in the
classroom in a number of ways, including giving students the opportunity to study phylogenetic
relationships between many organisms. Access it at: http://tolweb.org/tree/phylogeny.html
4. A collaborative project of the University of California Museum of Paleontology and the
National Center for Science Education shows students how evolutionary trees are constructed.
http://evolution.berkeley.edu/evolibrary/article/phylogenetics_01
5. Is Classification Arbitrary or Not?
This is an introductory lesson that demonstrates how biological classification inherently reflects
ancestral relationships. http://www.indiana.edu/~ensiweb/lessons/cl.intro.html
6. PBS has established a valuable resource website with online lessons for teachers and students
on Nature of Science, Darwin, Evidence for Evolution, how evolution works, human evolution,
ethics involved in evolution education. See specifically:
a. Eight-session professional development course, where you'll examine major
evolutionary concepts, explore teaching methodologies, and address obstacles to teaching
evolution. http://www.pbs.org/wgbh/evolution/educators/course/index.html
b. Online lessons for students. http://www.pbs.org/wgbh/evolution/educators/index.html
c. Students can build family trees using molecular, embryonic, reproductive, etc.
characteristics. http://www.pbs.org/wgbh/evolution/change/family/index.html
7. Students can use a lesson called “Who was Charles Darwin” to learn more about how Darwin
arrived at his conclusions http://www.pbs.org/wgbh/evolution/educators/lessons/index.html
Also at this site, video clips and readings from and about Darwin can be accessed
http://www.pbs.org/wgbh/evolution/library/02/index.html
8. The Skulls Lab
This is a version of the classic classroom activity in which students compare skulls of different
hominids. This activity can demonstrate that documentation of similarities and differences
between species helps in the understanding of biological and evolutionary relationships and
classification. Excellent skull pictures with key.
http://www.indiana.edu/~ensiweb/lessons/hom.cran.html
9. Charles Darwin’s The Origin of Species can be read online. Teachers and students could use
all or parts of the book in discussions about evolutionary relationships between organisms. For
the online book, go to: http://www.literature.org/authors/darwin-charles/the-origin-of-species/