Archive for Tuesday, November 8, 2005

The standards they’re voting on

November 8, 2005

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Editor's note: The following was taken from the State Board of Education Science Standards that deal specifically with how biological evolution is taught in grades 8-12.

The "additional specificity" sections that follow the indicators contain much of the controversial sections of the standards that question evolution.

Benchmark 3: The student will understand the major concepts of the theory of biological evolution.

Grade 8-12 Indicators

The student . . .

1. . . . understands biological evolution, descent with modification, is a scientific explanation for the history of the diversification of organisms from common ancestors.

Additional Specificity

1. a. Biological evolution postulates an unguided natural process that has no discernible direction or goal.

b. The presence of the same materials and processes of heredity (DNA, replication, transcription, translation, etc., ) is used as evidence for the common ancestry of modern organisms.

c. Patterns of diversification and extinction of organisms are documented in the fossil record. Evidence also indicates that simple, bacteria-like life may have existed billions of years ago. However, in many cases, the fossil record is not consistent with gradual, unbroken sequences postulated by biological evolution.

d. The distribution of fossil and modern organisms is related to geological and ecological changes (i.e., plate tectonics, migration). There are observable similarities and differences among fossils and living organisms.

e. The frequency of heritable traits may change over a period of generations within a population of organisms, usually when resource availability and environmental conditions change as a consequence of extinctions, geologic events, and/or changes in climate.

f. The view that living things in all the major kingdoms are modified descendants of a common ancestor (described in the pattern of a branching tree) has been challenged in recent years by:

i. Discrepancies in the molecular evidence (e.g., differences in relatedness inferred from sequence studies of different proteins) previously thought to support that view.

ii. A fossil record that shows sudden bursts of increased complexity (the Cambrian Explosion), long periods of stasis and the absence of abundant transitional forms rather than steady gradual increases in complexity, and

iii. Studies that show animals follow different rather than identical early stages of embryological development.

2. . . . understands populations of organisms may adapt to environmental challenges and changes as a result of natural selection, genetic drift and various mechanisms of genetic change.

Additional Specificity

2. a. Genetic changes occur only in individual organisms. New heritable traits may result from new combinations of genes and from random mutations or changes in the reproductive cells. Except in very rare cases, mutations that may be inherited are neutral, deleterious or fatal.

b. Natural selection and genetic drift occur within populations or organisms.

c. Variation among individuals in a population allows individuals to respond differently to environmental challenges.

3. . . understands biological evolution is used to explain the earth's present day biodiversity: the number, variety and variability of organisms.

Additional Specificity

3. a. Separate populations within a species may become sufficiently different enough that new species develop. This process is called speciation.

b. Changes in inherited traits accumulate in populations.

c. Historically only a small percentage of species have survived to modern times.

d. Whether microevolution (change within a species) can be extrapolated to explain macroevolutionary changes (such as new complex organs or body plans and new biochemical systems which appear irreducibly complex) is controversial. These kinds of macroevolutionary explanations generally are not based on direct observations and often reflect historical narratives based on inferences from indirect or circumstantial evidence.

4. . . * Understands organisms vary widely within and between populations. Variation allows for natural selection to occur. (* Recommended Sr. High Assessed Indicator).

Additional Specificity

4. a. Heritable variation exists in every species.

b. New heritable traits result from new combinations of genes and from mutations or changes in the reproductive cells.

c. Variation of organisms within and among species increases the likelihood that some members will survive under changing environmental conditions.

5. . . . understands that the primary mechanism of evolutionary change (acting on variation) is natural selection.

Additional Specificity

5. a. Favorable heritable traits are more advantageous to reproduction and/or survival than others.

b. There is a finite supply of resources available for offspring; therefore, not all survive.

c. Individuals with beneficial traits generally survive to reproduce in greater numbers.

d. Favorable heritable traits tend to increase in the population through time if the selective pressure is maintained.

6 . . . understands biological evolution is used as a broad, unifying theoretical framework for biology.

Additional Specificity

6. a. Organisms are classified according to the rules of nomenclature, and are given scientific names.

b. The behavioral, physical and genetic characteristics upon which these classifications are based are used as evidence for common descent.

c. Natural selection, genetic drift, genomes and the mechanisms of genetic change provide a context in which to ask research questions and then help explain observed changes in populations. However, reverse engineering and end-directed thinking are used to understand the function of bio-systems and information.

7 . . . explains proposed scientific explanations of the origin of life as well as scientific criticisms of those explanations.

Additional Specificity

7. Some of the scientific criticisms include:

a. A lack of empirical evidence for a "primordial soup" or a chemically hospitable pre-biotic atmosphere;

b. The lack of adequate natural explanations for the genetic code, the sequences of genetic information necessary to specify life, the biochemical machinery needed to translate genetic information into functional biosystems, and the formation of proto-cells; and

c. The sudden rather than gradual emergence of organisms near the time that the Earth first became habitable.

Teacher Notes:

The life science standards provide a framework for a variety of courses in the life sciences. Evolution is a key theoretical framework for the life sciences; these indictors should be part of any life science course curriculum, including biology, botany, zoology and microbiology.

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