The draft standards are posted on the website and you are invited to make comments until June 1st. Let's see what the new standards have to say about teaching evolution.
Here's what should be taught in middle school.
LS4.A: Evidence of Common Ancestry and DiversityNot bad, all things considered. I'd like to add that some evolution occurs by the chance increase in certain traits in a population, a process known as random genetic drift. Drift is part of the standards in my province of Ontario.
LS4.B: Natural Selection
- Fossils are mineral replacements, preserved remains, or traces of organisms that lived in the past. Thousands of layers of sedimentary rock not only provide evidence of the history of the Earth itself but also of changes in organisms whose fossil remains have been found in those layers. (a)
- The collection of fossils and their placement in chronological order (e.g., through the location of the sedimentary layers in which they are found or through radioactive dating) is known as the fossil record. It documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth. Because of the conditions necessary for their preservation, not all types of organisms that existed in the past have left fossils that can be retrieved. (c)
- Anatomical similarities and differences between various organisms living today, and between them and organisms in the fossil record, enable the reconstruction of evolutionary history and the inference of lines of evolutionary descent. (b)
- Comparison of the embryological development of different species also reveals similarities that show relationships not evident in the fully-formed anatomy. (d)
- Genetic variations among individuals in a population give some individual an advantage in surviving and reproducing in their environment. This is known as natural selection. It leads to the predominance of certain traits in a population, and the suppression of others. (e),(f)
- Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. (g)
- Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes. (f)
- In separated populations with different conditions, the changes can be large enough that the populations, provided they remain separated (a process called reproductive isolation), evolve to be separate species. (g)
I'd also like to delete "in response to changes in environmental conditions" and "in the new environment" from LS4.C. The idea that natural selection only occurs when the environment changes is a common misconception and there's no reason to perpetuate that misconception.
Here are the high school standards.
LS4.A: Evidence of Common Ancestry and DiversityI have more of a problem with the high school standards. High school students must learn about random genetic drift, especially if they are comparing sequences since most of the changes they will see are nearly neutral changes that have been fixed by drift.
LS4.B: Natural Selection
- Genetic information, like the fossil record, also provides evidence of evolution. DNA sequences vary among species, but there are many overlaps; in fact, the ongoing branching that produces multiple lines of descent can be inferred by comparing the DNA sequences of different organisms. Such information is also derivable from the similarities and differences in amino acid sequences and from anatomical and embryological evidence. (e)
- Natural selection occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information—that is, trait variation—that leads to differences in performance among individuals. (a),(c)
- The traits that positively affect survival are more likely to be reproduced, and thus are more common in the population. (b),(c),(d),(f)
- Natural selection is the result of four factors: (1) the potential for a species to increase in number, (2) the genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce, and (4) the ensuing proliferation of those organisms that are better able to survive and reproduce in that environment. (a)
- Natural selection leads to adaptation, that is, to a population dominated by organisms that are anatomically, behaviorally, and physiologically well suited to survive and reproduce in a specific environment. That is, the differential survival and reproduction of organisms in a population that have an advantageous heritable trait leads to an increase in the proportion of individuals in future generations that have the trait and to a decrease in the proportion of individuals that do not. (b),(c),(f)
- Adaptation also means that the distribution of traits in a population can change when conditions change. (d)
- Changes in the physical environment, whether naturally occurring or human induced, have thus contributed to the expansion of some species, the emergence of new distinct species as populations diverge under different conditions, and the decline–and sometimes the extinction–of some species. (d)
- Species become extinct because they can no longer survive and reproduce in their altered environment. If members cannot adjust to change that is too fast or drastic, the opportunity for the species’ evolution is lost. (d)
I think the standards should specifically mention that selection can occur in a constant environment since no organisms are perfectly adapted.
I hope the standards include specific attention to the relationship between humans and other species as shown by the combination of sequence comparisons, anatomical similarities, and the fossil record.
The source of mutations is covered in another section (LS3.B).
It would be nice to describe the differences between the fact of evolution and evolutionary theory.