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| TIPS: Targeted Interventions for Proficiency in Science | |||
Life Science
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| 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.
Scientists currently recognize 3 Domains and 6 Kingdoms of living things:
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 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: 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.
To learn more about phylogeny and its usefulness in classification
see: 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.
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
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
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.
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 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, For NSTA’s position statement on scientific theories see: http://www.nsta.org/positionstatement&psid=10
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 2. The evolutionary history of an organism is
its 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: 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?
a. mammals and lizards 5. Which of the following characteristics did
Linnaeus use to classify organisms?
Students know organisms can be classified based on evolutionary relationships. E/S Answers to sample questions.
1. (c) Performance Benchmark L.12.D.1 Students know organisms can be classified based on evolutionary relationships. E/S Intervention Strategies and Resources
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/2061 Connections/2006/media/Evo_Handout_Teachers.pdf
2. For good
definitions of taxonomy, classification, phylogeny, etc.
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.
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:
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
8. The Skulls Lab
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/ |
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