Activity 2
The Formulation of Explanations: An Invitation to Inquiry on Natural Selection

This activity uses the concept of natural selection to introduce the idea of formulating and testing scientific hypotheses. Through a focused discussion approach, the teacher provides information and allows students time to think, interact with peers, and propose explanations for observations described by the teacher. The teacher then provides more information, and the students continue their discussion based on the new information. This activity will help students in grades 5 through 8 develop several abilities related to scientific inquiry and formulate understandings about the nature of science as presented in the National Science Education Standards. This activity is adapted with permission from BSCS: Biology Teachers' Handbook.3

Standards-Based Outcomes

This activity provides all students with opportunities to develop the abilities of scientific inquiry as described in the National Science Education Standards. Specifically, it enables them to:

  • identify questions that can be answered through scientific investigations,

  • design and conduct a scientific investigation,

  • use appropriate tools and techniques to gather, analyze, and interpret data,

  • develop descriptions, explanations, predictions, and models using evidence,

  • think critically and logically to make relationships between evidence and explanations,

  • recognize and analyze alternative explanations and predictions, and

  • communicate scientific procedures and explanations.  

This activity also provides all students opportunities to develop understandings about inquiry, the nature of science, and biological evolution as described in the National Science Education Standards. Specifically, it conveys the following concepts:

  • Different kinds of questions suggest different kinds of scientific investigations.

  • Current scientific knowledge and understanding guide scientific investigations.

  • Technology used to gather data enhances accuracy and allows scientists to analyze and quantify results of investigations.

  • Scientific explanations emphasize evidence, have logically consistent arguments, and use scientific principles, models, and theories.

  • Species evolve over time. Evolution is the consequence of the interactions of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection of those offspring better able to survive and leave offspring in a particular environment.

Science Background for Teachers

Many biological theories can be thought of as developing in five interrelated and overlapping stages. The first is a period of extensive observation of nature or analyzing the results of experiments. Darwin's observations would be an example of the former. Second, these observations lead scientists to ponder questions of ''how" and "why." In the course of answering these questions, scientists infer explanations or make conjectures as working hypotheses. Third, in most cases, scientists submit hypotheses to formal, rigorous tests to check the validity of the hypotheses. At this point the hypotheses can be confirmed, falsified and rejected (not supported with evidence), or modified based on the evidence. This is a stage of experimentation. Fourth, scientists propose formal explanations by making public presentations at professional meetings or publishing their results in peer-reviewed journals. Finally, adoption of an explanation is recognized by other scientists as they begin referring to and using the explanation in their research and publications.

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