EVO 2.1 Natural Selection Theory- Pre AP Biology Study Notes - New Syllabus.

Scientific Discoveries That Informed the Theory of Natural Selection

🌱 Introduction

The theory of natural selection was not developed in isolation.
It was shaped by earlier scientific discoveries and ideas from naturalists and geologists that helped explain how species change over time and why Earth must be very old.

🧬 Key Scientific Discoveries Influencing Natural Selection

Darwin’s thinking was informed by:

• Early evolutionary models proposed by naturalists
• Geological discoveries showing slow, continuous changes on Earth

🧪 A. Contributions of Early Naturalists

Jean-Baptiste Lamarck (Early evolutionary thinker)

Key Discoveries / Ideas

• Species are not fixed and can change over time
• Environment influences organismal traits

Proposed Mechanism

• Use and disuse:
  Structures used frequently become stronger
  Structures not used deteriorate
• Inheritance of acquired characteristics:
  Traits acquired during life are passed to offspring

Importance to Natural Selection

• First to propose that organisms evolve
• Although the mechanism was incorrect, Lamarck introduced the idea that environment plays a role in evolution

Alfred Russel Wallace (Independent discoverer of natural selection)

Key Discoveries / Ideas

• Studied species distribution in different environments
• Observed variation within populations

Major Contribution

• Independently proposed natural selection
• Noted that individuals with favorable traits survive and reproduce more

Importance to Natural Selection

• His conclusions closely matched Darwin’s ideas
• Led Darwin to formally publish his theory

Charles Darwin (Primary developer of the theory)

Key Observations

• Variation exists among individuals in a population
• More offspring are produced than can survive
• Resources are limited, leading to competition

Core Discoveries

• Individuals with advantageous heritable traits survive and reproduce more
• Over generations, these traits become more common

Outcome

• Formulated the theory of natural selection
• Explained adaptation and evolution through differential survival and reproduction

🌍 B. Contributions of Geologists

Geological discoveries were critical because they showed that Earth is ancient, allowing enough time for evolution.

James Hutton (Founder of modern geology)

Key Discoveries

• Earth is shaped by slow, continuous geological processes
• Processes like erosion and sedimentation occur over long periods

Concept Introduced

• Deep time: Earth is millions of years old

Importance to Natural Selection

• Provided the time scale necessary for gradual evolutionary change

Charles Lyell (Expanded Hutton’s ideas)

Key Discoveries

• Proposed uniformitarianism
• Geological processes occurring today also operated in the past

Core Idea

• “The present is the key to the past”

Importance to Natural Selection

• Reinforced the idea that slow changes over long time periods can produce major biological changes
• Strongly influenced Darwin during his studies

🧠 How These Discoveries Informed Natural Selection

• Lamarck → species change over time
• Wallace → natural selection as a mechanism
• Darwin → unified observations into a scientific theory
• Hutton & Lyell → provided deep time required for gradual evolution

Together, these discoveries made the theory of natural selection scientifically possible.

📊 Summary Table

📦 Quick Recap 
✔ Natural selection developed from multiple discoveries
✔ Lamarck proposed early evolution ideas
✔ Wallace independently discovered natural selection
✔ Darwin explained evolution by differential survival
✔ Hutton introduced deep geological time
✔ Lyell showed Earth changes slowly over time
✔ These ideas together shaped natural selection