The claim that the Next Generation Science Standards leave out content knowledge bothers me, because it seriously mis-represents the truth. For example, this piece on EdSource by Paul Bruno claims that MS-LS3 Heredity: Inheritance and Variation of Traits is an example of how the NGSS
…place relatively more emphasis on “scientific practices” – like asking questions and defining problems – and relatively less emphasis on factual scientific knowledge. Consequently, much important scientific content is omitted from the standards and much of what is present is stated only vaguely.
First, it is disingenuous to say that the NGSS place more emphasis on scientific practices than factual scientific knowledge. There are three equally important elements to the NGSS: science and engineering practices, disciplinary core ideas (DCIs), and cross-cutting concepts. The core ideas are factual scientific knowledge, and they are no less important than the scientific practices.
MS-LS3-1: Develop and use a model to describe why structural changes to genes (mutations) located on chromosomes may affect proteins and may result in harmful, beneficial, or neutral effects to the structure and function of the organism. [Clarification Statement: Emphasis is on conceptual understanding that changes in genetic material may result in making different proteins.] [Assessment Boundary: Assessment does not include specific changes at the molecular level, mechanisms for protein synthesis, or specific types of mutations.]
Here are the facts related to this performance expectation that students are expected to understand (these are taken directly from the orange “Disciplinary Core Ideas” box underneath the performance expectations):
Genes are located in the chromosomes of cells, with each chromosome pair containing two variants of each of many distinct genes.
Each distinct gene chiefly controls the production of specific proteins, which in turn affects the traits of the individual.
Changes (mutations) to genes can result in changes to proteins, which can affect the structures and functions of the organism and thereby change traits.
In addition to variations that arise from sexual reproduction, genetic information can be altered because of mutations.
Though rare, mutations may result in changes to the structure and function of proteins. Some changes are beneficial, others harmful, and some neutral to the organism.
These are major scientific facts that are fundamental to this performance expectation. These statements are not vague or unclear to me, I don’t think they would be unclear to science educators in general, and I don’t believe there are major omissions to what middle school students need to understand about how mutations can affect the traits of organisms.
The critics seem to believe that it is a serious omission that specific mutations are not mentioned. In fact, we should not require all students to memorize that a particular mutation causes a particular trait (such as how albinism or any number of genetic disorders can be caused by particular mutations). We should be interested in having students understand the scientific facts that underly particular examples, so students are able to generalize when they see a new example. These underlying facts are the facts that are outlined in the NGSS. The specific examples used to teach the concept and the specific examples that appear on any assessments should be irrelevant, if students actually understand these underlying concepts. We want students to be able to see a new example and recognize the deep structure behind it. Teachers, curriculum designers, and assessment writers should be free to choose the examples of these concepts that best fit their context.
The key is giving students lots of practice with many relevant examples, not cherry-picking one or two particular examples. That’s the path to having students memorize only those particular examples without understanding the fundamental concepts involved.