The Orange Circle Theory (Day #3 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 increase in number
  • the heritable genetic variation of individuals in a species due to mutation and sexual reproduction
  • 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! Please find the more intricate details of this lesson plan there.

Anticipatory Set ("Hook")

5 minutes

Please click here for the previous lesson in the series.

This instructional series represents the culminating climax to 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 prompt to assess what students have actually learned and can recall.

Turn & Talk- Recall two misconceptions commonly believed related to Natural Selection.

Sample responses might include:

1. Humans evolved from chimpanzees (monkeys).

2. Evolution can occur in very short time periods.

3. Organisms can evolve on a individual basis (within their lifetime). 

4. Natural Selection, like any theory, is proven to a 100% level.

5. Changes to the phenotype of an organism can be inherited by its offspring (basically Lamarckism).

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 students to persevere and grapple with complex tasks?

Teaching Challenge: How can I develop my students' ability to apply unifying ideas to make connections across science content?

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

To these points, I have upacked this complex task into mulitple parts:

1. The break down of the theory into five key factors related to Natural Selection (variation, adaptation, selection, reproduction, and speciation) while highlighting the interconnections that occur between the nature of science, genetics, natural selection, among other content areas.

2. A way of visualizing not only the nature of a theory (straw, stick, and brick houses) but also a way of conceptualizing Natural Selection (Orange Circle Theory) as two important scaffolds to the overarching goal (explaining with evidence).

3. The Orange Circle mental model that serves as a graphic organizer to support students analyzing one or more case studies of organisms cited as hallmark examples of natural selection at work.


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

I use the case study strategy to lead students toward applying what they have learned to this point; to take ownership of complex phenomena. Clyde Freeman Herreid of the University of Buffalo, State University of New York, has written extensively about the use of case studies (see The Use of Case Studies and Group Discussion in Science Education, easily accessible online). In Dr. Herreid's paper, he highlights several key criteria for choosing case studies (and already assumes his reader agrees in the value of case studies which is what I am trying to leverage here). He points out that a case ought to tell a good story, create some empathy between the student and the subject, is relevant to the student, is short, and contains concepts that can be generalized beyond the particular case study.

In light of these recommendations, the Howard Hughes Medical Institute has created a handful of very well-produced and compelling short films as part of its BioInteractive Initiative (Free Resources for Science Education). These films feature the following organisms (case studies) that make for a very fitting (pun intended) application of the self-same theory.

The Theory Lecture (slides #34-37)- Students will be provided with a Case Study Graphic Organizer upon which details relating to each of the five main concepts will be written. Once each case study has completed, the students will be prompted to discuss (along the lines of Think-Pair-Share strategy) their observations and attempt to explain how they would answer the prompt. Time is certainly the main factor here therefore one, two, or all case studies could be explored.

  • Case Study #1: Role of mutation on producing an antifreeze protein increasing the fitness of the Antarctic Ice Fish
  • Case Study #2: Role of variation (beak morphology) on differential survival and reproductive success in periods of drought and normal rainy conditions
  • Case Study #3: Role of camouflage (adaptation) on differential survival in light of predation pressure and subsequent shifts in population genetics.

The Theory Lecture (slides #38-44)- Lastly, the "bow" is placed upon the gift-wrapped package by synthesizing how the claims, evidences, and reasoning all come together for the Theory.

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

5 minutes

Quick Write (2.0)- Students will be prompted to revisit Quick Write (1.0) completed two days ago. They are to correct any mistakes and expand/deepen their written response based on what has been discussed during this three-part lecture series.

They are to cite at least three specific examples/evidences from nature that relate to explaining the underlying biological processes make evolution happen (refer to mental model for an organizing graphic organizer).

Lesson Extension & Follow-Up Activities

Finish Quick Write (2.0) as needed