Mini-Lesson

Lamarck vs Darwin:
Dueling Theories

EVOLUTION

 SYNOPSIS

 PRINCIPAL CONCEPTS

1. Evolution proceeds by the process of variation, a genetically random process, and selection, an environmentally driven non-random process.

2. Organisms do not get what they "need" through "inner wants" or through "use and disuse' "Individual intentions do not play a role.

3. Acquired characteristics are not passed on to offspring,

4. Mutations are not directed for the benefit of the individual.

5. Evolution is neither random nor teleological. It is, in fact, driven by both historical contingencies and the non-random, yet non-directed, process of selection.

 ASSOCIATED CONCEPTS

ASSESSABLE OBJECTIVES

Students will....

See suggestions under "Elaborate/Evaluate" in the "Procedures" section.

Given a scenario describing something comparable to the videos selected, each student will accurately explain the probable evolutionary mechanism operating, using terms and phrases properly applied to natural selection, and avoiding Lamarckian terms or phrases.

 MATERIALS

A video showing some unusual morphological, physiological, and/or behavioral adaptation. Good examples, that can be found in David Attenborough's The Trials of Life, are:
- the speed and grace of a cheetah in pursuit of a prey species
- blind and/or albino cave-dwelling animals
- the social behavior and morphology of the naked mole rat

A sheet of questions similar to those listed under "Explore" in the "Procedures" section, but appropriate to the video used.

 TIME

TEACHING STRATEGY

This lesson would fit best in the introductory evolution unit, in which Lamarck's and Darwin's explanations for a mechanism for evolution are presented, along with the evidence rejecting Lamarck's ideas, and a fair sampling of the evidence supporting natural selection.

LEARNING ABOUT SCIENCE
Constructivist learning theory tells us that changing this misconception will only take place if our students' minds have an active cognitive involvement in the processes that allow for the accommodation of new "replacement" knowledge. Mechanisms such as hands-on / minds-on laboratory activities, developing alternative hypotheses, designing evaluative experiments, and arguing about the phenomena under study facilitate this active involvement (Saunders 1992). This is especially true if the work is done in small groups and the students are asked to explain and/or defend their thinking to their peers-who may compare and contrast these ideas with their own constructions. The National Research Council (1996) tells us that teaching science as inquiry is the basic underlying principle of science education as well as the ultimate organizing concept for the selection of student activities. These activities should include: 1) asking appropriate questions, 2) planning and conducting investigations, 3) appropriate tools and techniques to gather data, 4) thinking critically and logically about the relationships between evidence and explanations, and 5) communicating scientific arguments. Following these recommendations, as well as the 5E cycle (engage, explore, explain, elaborate, and evaluate), this exercise is an attempt to accomplish the previously mentioned tasks by allowing the student to discover the inherent flaws in the Lamarckian view, while at the same time encouraging the appropriation of a more Neo-Darwinian concept.

The Conceptual Change Model (CCM), first introduced by Posner (1982) and recently investigated and modified by Demastes (1996) and Jensen and Finley (1996), shows us that in order for a misconception to be abandoned, the learner must come to see it as unsatisfactory, while the new conception must be intelligible, plausible, and fruitful, Here lies our problem: how best to make Lamarck's view the unsatisfactory concept, while showing Darwin to be more intelligible, plausible, and fruitful?

PROCEDURES

Click here for the full text of this article in PDF format (4 pages).

ENGAGE
The class should be shown an exciting video of some unusual morphological, physiological, and/or behavioral adaptation. As we all know our students are steeped in a visual world of rapid fire stimuli. The chalkboard or overhead projector stand little chance to excite them. Good examples, that can be found in David Attenborough's The Trials of Life, are:
- the speed and grace of a cheetah in pursuit of a prey species
- blind and/or albino cave-dwelling animals
- the social behavior and morphology of the naked mole rat

EXPLORE
The class should be broken into small groups (4 or 5) and presented with the following questions:

1. Cheetahs can run faster than 60 miles per hour when in pursuit of prey. How would an evolutionary biologist explain how this ability evolved, assuming their ancestors could only run 20 miles per hour?

2. Many cave organisms are blind. In fact, for many, their eyes have become vestigial structures. How would an evolutionary biologist explain how this inability to see evolved from sighted ancestors? (Both questions I and 2 have been modified from Bishop and Anderson 1986)

3. Naked mole rats have several morphological as well as behavioral adaptations which allow them to live in a eusocial system within a harsh and unforgiving environment. Make a list of as many of these characteristics as you can. How would an evolutionary biologist explain how these unique characteristics evolved from ancestors which did not possess these traits?

Each group is given ample time to research and discuss the question(s).

EXPLAIN
The groups then present their explanations to the class as a whole to foster comments, critiques, and criticisms of their hypotheses. It should be pointed out here that dissent, argument, and disagreement are all integral components of the scientific process. They are not negative, but rather positive, attributes of science. More than likely, many of the groups will present Lamarckian ideas. Therefore, the important points that need to be illustrated and discussed by the teacher, especially if they do not arise from student discussion, are:

1. Evolution proceeds by the process of variation, a genetically random process, and selection, an environmentally driven non-random process.

2. Organisms do not get what they "need" through "inner wants" or through "use and disuse' "Individual intentions do not play a role.

3. Acquired characteristics are not passed on to offspring,

4. Mutations are not directed for the benefit of the individual.

5. Evolution is neither random nor teleological. It is, in fact, driven by both historical contingencies and the non-random, yet non-directed, process of selection.

ELABORATE / EVALUATE
Feedback on the progress and effectiveness of the learning activity can be used to evaluate its success and to adjust the ongoing process. This "formative evaluation" can be accomplished informally during the preceding stage. More formal assessment of the outcome at the end of the process (summative evaluation) can be performed by offering similar problems for each student to solve on the evaluation tool of one's choice-An example follows:

Many insular species of both plants and animals have lost defense mechanisms that are frequently found on their continental relatives. Several species of birds and insects have become flightless and many plant species have lost defense mechanisms such as thorns or toxic chemicals. How would an evolutionary biologist explain how these losses came about?

CONCLUSIONS
On the surface it seems that to replace the conceptual belief that species change is driven by characteristics acquired during the organism's lifetime with one based on the processes of random variation and non-random selection should be rather an easy task. However, personal experience, as well as most of the research cited, indicates this is not the case. Let's face it, misconceptions concerning evolution are deeply embedded and the concept itself is a lightning rod - one that many of our teachers fear holding in the tempest of today's classroom. As minor as it may seem, the alleviation of any misconception dealing with biology's most important central theme, as well as its most misunderstood concept, is a major step in the right direction for science education. As Bumbry (1979) has pointed out, the acceptance of Lamarckian beliefs, for all intents and purposes, totally blocks the learning of Darwinian principles. Obviously this must be changed. I have found the preceding exercise to be one of the most fruitful in accomplishing this goal.
The term eusocial as defined by Krebs and Davies (1993) includes animals that exhibit: 1) cooperative care of the young; 2) a reproductive division of labor - that is, some castes or classes are less fecund or sterile; 3) an overlap of at least two generations; that is, the offspring assist the parents during some period of their life.

ASSESSMENT

EXTENSIONS

& VARIATIONS

Go to our "Introduction to Evolution" page of suggestions, scroll down to "A Few Very Common Misconceptions", where pointers are given for using the "Comparing Evolution Mechanisms" sheets (to print out Information and Worksheet back to back), both sheets available as PDF files at the bottom right, along with a key.

Another approach would be to print a number of passages on a sheet of paper, some appropriate examples or statements consistent with a Lamarckian explanation, and some appropriate for Darwin's natural selection process. Give one copy to each team of 2-4 students, along with an envelope.

1. Students are to cut these apart, and place each phrase on a sheet under the heading "Lamarck's Inheritance of Acquired Characteristics", or on another sheet with the heading "Darwin's Natural Selection", as considered appropriate by the team.

2. After most teams have finished sorting, have each team report out its results, followed by discussion (other students suggesting changes, giving reasons), until class consensus is reached. Repeat with each team, if necessary. If any statements are inappropriately placed, and the class does not challenge it, ask a leadng question to get that team to consider changing its selection, or defend it. Continue until all phrases are properly aligned.

 OTHER RESOURCES

REFERENCES
Alters B. Whose nature of science? Journal of Research in Science Teaching 1997; 34(1): 39-55.

Bishop B, Anderson C. Student conceptions of natural selection and its role in evolution. E. Lansing (Ml): Institute for Research on Teaching (ERIC Document Reproduction Service No. ED 269 254),1986.

Bumbry M. Student perceptions and learning styles associated with the concept of evolution by natural selection. Unpublished doctoral dissertation, University of Survey. UK, 1979.

Deadman J, Kelly P. What do secondary school boys understand about evolution and heredity before they are taught the topic? Journal of Biological Education 1978; 12(l):7-15.

Demastes S, Good R, Peebles P. Patterns of conceptual change in evolution. Journal of Research In Science Teaching. 1996; 33(4):407-31.

Firenze R. Have the creationists already won? The reaching of faux-biology. Reports of the National Center for Science Education 1997 Mar/Apr; 17(2):10-4.

Greene E. The logic of university students' understanding of natural selection. Journal of Research in Science Teaching 1990, 10(4):541-52.

Humphreys J. Lamarck and the general theory of evolution. Journal of Biological Education 1996; 30(4):295-303.

Jensen M, Finley F. Changes in students' understanding of evolution resulting from different curricular and instructional strategies. Journal of Research in Science Teaching 1996; 33(8):879-900

Krebs J, Davies N. An introduction to behavioral ecology. London Blackwell Publications, 1993.

McComas W. Investigating evolutionary biology in the laboratory. Reston (VA): National Association of Biology Teachers, 1994.

National Research Council. National science education standards. Washington: National Academy Press, 1996.

Posner G, Strike K, Hewson P, Gertzog W. (I982). Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education 1982; 66(2), 211-27.

Saunders W. The constructivist perspective: Implications and teaching strategies for science. School Science and Mathematics 1992; 92(3), 136-41.

Settlage J. Conceptions of natural selection: A snapshot of the sense-making process. Journal of Research in Science Teaching 1994; 31(4), 449-57

Storey R. (1997). A plea to biology professors. The American Biology Teacher 1997; 59(2), 68-9.

 ATTRIBUTION

Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

1. Original Source: Lamarck vs Darwin: Dueling Theories,
by Richard Firenze, in Reports of the National Center for Science Education, July/Aug 1997, vo.17, no.4, pp.9-11
AUTHOR'S ADDRESS:
Richard Firenze
Biology Department
State University of New York
Broome Community College
Binghamton, NY

2. Edited / Revised for website by L. Flammer 12/1/2001