The Four Factors of Evolution Model Task

Estimated Time: 45-60 minutes Materials: Computer with internet access, The Four Factors of Evolution Model simulation.

Part 1: Engage (Anchoring Phenomenon)

Take a look at a population of colorful, single-celled organisms (“blobs”) living in an environment. In the natural world, organisms are frequently hunted by predators. Why do some organisms survive longer than others, and how does a population’s overall appearance change over time in response to its environment?

1. Predict what will happen to a population of organisms if their environment suddenly changes color.
2. What traits might help an organism survive in a colorful environment?

Part 2: Explore (Simulation Investigation)

Open the The Four Factors of Evolution Model simulation. This model tracks a population of organisms. Organisms must eat food to increase their energy by 20 (up to a maximum). If their energy exceeds 80, they can reproduce, which costs 40 energy. Predators eat the organism that stands out the most from the environment color.

1. Observe Initial Conditions: Without changing any settings, press the Start button (btn-start). Observe the population (stat-pop) and the year (stat-year) for about 100 years. Watch the simCanvas to see how predators select organisms.
2. Genetic Variation (Mutation): Pause the simulation and press Reset. Ensure the Mutation Enabled checkbox is checked and set the Mutation Rate slider (rng-mutation) to a high value. Set the Environment Color (rng-env) to a specific hue (e.g., green). Start the simulation. How does the population color change over time on the traitChart?

Sample Data Collection Table

1. Competition for Resources: Pause and Reset. Adjust the Food Supply Rate slider (rng-food) to Low. Start the simulation. How does limited food affect the population (stat-pop) compared to when food is abundant?
2. Differential Survival: Pause and Reset. Change the Environment Color (rng-env) while the simulation is running. Watch the simCanvas. Which organisms are eaten first by the predator?

Part 3: Explain (Sensemaking)

Using your observations from the simulation, answer the following questions:

1. Competition: How did changing the food supply rate affect the number of organisms that could survive and reproduce?
2. Variation: How did the mutation rate affect the variety of colors seen in the population? Why is this variation important?
3. Survival: Describe the relationship between an organism’s color and the environment color. Which organisms were most likely to survive and why?

Part 4: Elaborate/Evaluate (Argumentation)

Construct a scientific explanation based on evidence from the simulation that the process of evolution in this population primarily resulted from four factors. In your explanation, be sure to include:

• How the species had the potential to increase in number.
• The role of heritable genetic variation (mutation) in the population.
• How competition for limited resources (food) affected survival.
• How differential survival (predation based on color matching) led to the proliferation of advantageous traits.

Teacher Notes & Alignment

This task maps to HS-LS4-2.

• Science and Engineering Practice: Constructing Explanations and Designing Solutions
  • Construct an explanation based on valid and reliable evidence obtained from a variety of sources (including simulations).
• Disciplinary Core Ideas:
  • LS4.B: Natural Selection: Natural selection occurs only if there is both variation in the genetic information and variation in the expression of that genetic information that leads to differences in performance.
  • LS4.C: Adaptation: Evolution is a consequence of the interaction of four factors: (1) the potential for a species to increase in number, (2) the genetic variation of individuals, (3) competition for limited resources, and (4) the ensuing proliferation of those organisms that are better able to survive and reproduce.
• Crosscutting Concept: Cause and Effect
  • Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.

Evidence of Student Performance:

1. Articulating the explanation: Students construct an explanation that includes a description that evolution is caused primarily by one or more of the four factors: (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.
2. Evidence: Students identify and describe evidence to construct their explanation, including that: (i) As a species grows in number, competition for limited resources can arise. (ii) Individuals in a species have genetic variation (through mutations and sexual reproduction) that is passed on to their offspring. (iii) Individuals can have specific traits that give them a competitive advantage relative to other individuals in the species.
3. Reasoning: Students use reasoning to connect the evidence, along with the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future, to construct the explanation. Students describe the following chain of reasoning for their explanation: (i) Genetic variation can lead to variation of expressed traits in individuals in a population. (ii) Individuals with traits that give competitive advantages can survive and reproduce at higher rates than individuals without the traits because of the competition for limited resources. (iii) Individuals that survive and reproduce at a higher rate will provide their specific genetic variations to a greater proportion of individuals in the next generation. (iv) Over many generations, groups of individuals with particular traits that enable them to survive and reproduce in distinct environments using distinct resources can evolve into a different species.

Part 5: Extension Options

1. Changing Environments: Design an experiment to test what happens if the environment color constantly oscillates between two extremes (e.g., green to red and back). How would this affect the long-term survival and genetic variation of the population?
2. Mathematical Modeling: Using the data from your simulated observations, calculate the rate of change of the population’s average color over time and predict what it would be at Year 500.