The Orange Circle Theory (Day #1 of 3)

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1. Construct an explanation based on the evidence that the process of evolution primarily results from four factors, including reproductive potential, heritable variation, scarcity of resources, and survival of the fittest. (HS-LS4-2) 2. Construct an explanation based on evidence for how natural selection leads to adaptation of populations. (HS-LS4-4)

Big Idea

The Theory of Natural Selection can be thought of an on-going cycle whereby generations of populations encounter an ever changing environment that selects winners and losers. To the winners go the spoils!

Learner Goals

Note: I recommend that you first check out this resource in order to get the most out of this lesson!

In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".

The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these.

With regard to this particular lesson...

1. students will construct an explanation based on the evidence that the process of evolution primarily results from four factors (HS-LS4-2):

  • the potential for a species to increase in number
  • the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, among other factors
  • competition for limited resources, and
  • the proliferation of those organisms that are better able to survive and reproduce in an environment

 2. students will construct an explanation based on evidence for how natural selection leads to adaptation of populations, including effect(s) of changing biotic and abiotic conditions on resulting in changing adaptations among members of a population. (HS-LS4-4)

I hope you get some value from my work!

Anticipatory Set ("Hook")

5 minutes

This instructional series represents the culmination of the instruction and learning that has been happening for some three weeks now. So there is a good body of concepts, facts, processes, and a mental model of "theory" thrown in.

Teaching Challenge: How do I support students to persevere and grapple with complex tasks?

It begins with activating prior knowledge (where we have been) and a clear sense of where we are presently. In light of this, I pose the following question to assess what students have actually learned and can recall. This response will be a foundation upon which to build during this, and the following two, lessons in this mini-series. Students should spend about five minutes during the first part of class and just free write; I emphasize that grammar, spelling, and organization are not the most important (in this particular case only).


Quick Write (1.0)- “What are the underlying biological processes make evolution happen?” In other words, explain how evolution works.

Instructional Input/Student Activities

45 minutes

Necessarily, my instructional plan accounted for several key hurdles that students will need to encounter and overcome:

1. How do I make sense of a really abstract idea (Theories in general and Natural Selection in particular)?

2. What should an argument look like? How do I meld a claim, its evidence, and underlying thinking (reasoning)?

3. What is the evidence brought forward by evolutionary biologists?

4. When looking at nature, how would Darwin explain its patterns and processes?

Teaching Challenge: How do I support my students to compose, communicate, and evaluate a clearly stated, evidence-based argument?

Teaching Challenge: How do I support students to develop and use scientific models?

Structure of the CER model (refer here for a more thorough explanation). Mental model of a scientific theory. Lines of evidence. Mental model of Natural Selection. Case study application.

These scaffolded elements will be necessary to help students walk through the process of explaining, based on evidence, the processes driving Natural Selection. This then is the output of this series built on the combined skills and knowledge leading up to this point. 


Using an interactive lecture strategy, the specific tenets of Natural Selection will be outlined and investigated in turn.

The Theory Lecture (slides #1- 18)- Emphasis on these concepts:

  • the nature of a theory (slide #6): With slides #1-3, as a class we discuss the general similarities and differences among the different birds and suggest reasons for those traits, how they became different (genetics), and suggest advantages and disadvantages for them. Slide #6 is a review for how to visualize a theory.
  • a mental model to guide the explanation of natural selection (slides #8-13): This is a super important set-up for what is to come next. While others may take exception to how I have packaged the theory of Natural Selection into this mental model, it is important for students to "hang their thinking" onto some framework. I see the theory (process) working at the population level and acting on each and every succeeding generation, itself influenced by a population's genetic variation that imbues certain adaptations to its members. The utility of these adaptations is judged by the selective pressures of the environment. Should this test be passed by the organism in question (at least for the present time), survival and possibly reproduction await it which then repeats the cycle. Should the population gene pool split for some reason (allopatric and/or sympatric speciation), the divergent cycle becomes fragmented from the original and the pathway to a new species has begun. Or it is just a bright orange circle. You can decide for yourself.
  • two common misconceptions (slides #14-18): By addressing and reframing these two misconceptions, much headway will be made to dispelling what too many people altogether claim as truth!

Closure: What did we learn? Where do we go from here?

5 minutes

3-2-1 Exit Task:

Students are prompted to jot down three things learned, two questions they still have, one thing they still wonder about.

Please click here for the next lesson in this series.

Lesson Extension & Follow-Up Activities

Finish “3-2-1” prompt as needed.