The Concrete Jungle: Anole Lizard Adaptation

Introduction

In the tropical city of San Juan, Puerto Rico, a small lizard is undergoing a big change. The Puerto Rican crested anole (Anolis cristatellus) has lived in the island’s forests for thousands of years. But as concrete, glass, and metal replace trees and soil, the lizards are changing. Biologists have noticed that urban anoles have significantly larger toe pads than their forest-dwelling cousins. In this investigation, you will use a simulation to determine why this is happening and how natural selection is driving this rapid adaptation.

Part 1: Engage

Look at the two environments shown in the simulation: the Forest (textured, cool bark) and the City Center (smooth, hot surfaces).

Need to Know Questions:

  1. What physical challenges might a lizard face on a smooth glass window that it wouldn’t face on a rough tree trunk?
  2. How might “heat” in a city affect a cold-blooded lizard’s ability to survive?
  3. Generate one question of your own about how the city environment might change a lizard population over many generations.

Part 2: Explore

Open the Anole Lizard Urban Adaptation simulation. Your goal is to collect data on how the “Urbanization Level” affects the average toe pad size of the lizard population.

Investigation Steps:

  1. Initial State: Set the Urbanization Level to 0% (Deep Forest). Click Reset Population. Record the initial Avg Toe Pad Size (Generation 0).
  2. Experiment 1 (Forest): Click Run and let the simulation proceed for 20 generations. Record the final Avg Toe Pad Size.
  3. Experiment 2 (Suburban): Reset the population. Set the Urbanization Level to 50% (Suburban). Run for 20 generations and record the final Avg Toe Pad Size.
  4. Experiment 3 (City Center): Reset the population. Set the Urbanization Level to 100% (City Center). Run for 20 generations and record the final Avg Toe Pad Size.

Data Table:

Environment Level Initial Avg Toe Pad Size (mm) Final Avg Toe Pad Size (mm) Change in Size (mm)
0% (Deep Forest)      
50% (Suburban)      
100% (City Center)      

Part 3: Explain

Use your data and observations from the simulation to answer the following questions:

  1. Phenomenon Analysis: Describe the trend you observed. As urbanization increased, what happened to the average toe pad size of the population over time?
  2. Evidence of Selection: Why do you think lizards with larger toe pads were more likely to survive in the “City Center” environment? (Hint: Check the “The Science” section in the simulation for details on gripping smooth surfaces).
  3. Heredity: In the simulation, when an anole survives, it reproduces. What does the offspring “inherit” from its parent? How does “mutation” contribute to the variety of traits in the population?

Part 4: Elaborate & Evaluate

Construct a scientific explanation for the following prompt:

“Explain how the change in surface type (from bark to smooth concrete) acts as a selective pressure that leads to adaptation in the anole lizard population.”

In your explanation, be sure to include: