Natural Selection Today

Grade Level

9th Grade Biology

Duration

90 Minutes

Class Size

25 Students

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Standards Alignment

Texas Essential Knowledge and Skills (TEKS) for Biology:

• 112.34. Biology, Adopted 2017:
  • (7)(A): Analyze how natural selection leads to adaptation and evolution of populations.
  • (7)(B): Explain how genetic variation and environmental factors influence natural selection.
  • (7)(C): Evaluate scientific explanations concerning the role of natural selection in the evolution of populations.

Crosscutting Concepts:

• Cause and effect: Mechanism and explanation
• Systems and system models

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Lesson Overview

This lesson explores the principles of natural selection and adaptation with a focus on Texas-specific examples such as the Texas horned lizard and the Guadalupe bass. Students will analyze genetic variation, environmental pressures, and evolutionary outcomes in local ecosystems. The lesson includes advanced activities such as data analysis of allele frequency changes and a case study on invasive species impact in Texas.

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Learning Objectives

By the end of this lesson, students will be able to:

• Explain the mechanism of natural selection and its role in evolution.
• Analyze how genetic variation and environmental factors contribute to adaptation in Texas ecosystems.
• Model changes in allele frequencies over generations using real data.
• Critically evaluate scientific explanations of natural selection in the context of Texas species.

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Lesson Activities

1. Introduction and Review (15 minutes)

   • Brief review of key concepts: genetic variation, mutation, phenotype, genotype.
   • Discuss natural selection as a mechanism of evolution with Texas-specific examples (e.g., Texas horned lizard camouflage, Guadalupe bass habitat adaptations).

2. Case Study Analysis (20 minutes)

   • Students work in groups to analyze a case study on the impact of invasive fire ants on Texas native species.
   • Identify selective pressures and hypothesize potential evolutionary responses.

3. Data Modeling Activity (30 minutes)

   • Using provided allele frequency data from a population of Texas horned lizards over several generations, students will graph and interpret changes.
   • Discuss factors influencing these changes and predict future trends.

4. Class Discussion and Scientific Explanation (15 minutes)

   • Groups present findings and engage in a guided discussion on the role of natural selection in shaping populations.
   • Emphasize evidence-based reasoning and scientific argumentation.

5. Assessment and Reflection (10 minutes)

   • Short quiz with data interpretation and explanation questions.
   • Reflective writing prompt: Describe how natural selection might affect a species in your local environment.

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Materials Needed

• Case study handouts on Texas invasive species
• Allele frequency data sets and graphing tools (digital or paper)
• Projector or whiteboard for presentations
• Quiz sheets and reflection prompts

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Assessment

• Formative assessment through group discussions and data activity participation.
• Summative assessment via quiz and reflective writing to evaluate understanding of natural selection concepts and application to Texas biology contexts.