Evolution and Darwin's Theory

Introduction

• Organisms are adapted for their environments
• Many life forms share characteristics
• Life is diverse.
• Evolution is the process of species accumulating differences from ancestors.
• This is described as "descent with modification."

Darwin’s Theory of Evolution

• Darwin's On the Origin of Species (1859) changed scientific thought.
• Darwin's ideas built upon the work of others, including Carolus Linnaeus (1707-1778) who developed a classification system for species.
• Linnaeus established the binomial naming system for species (e.g., Homo sapiens).
• Darwin studied fossils, remains of past organisms.
• Fossils are found in sedimentary rock layers called strata.

Lamarck’s Hypothesis

• Jean-Baptiste Lamarck (1744-1829) proposed two principles of evolution:
  • Use and disuse: Body parts used extensively grow larger, unused parts deteriorate.
  • Inheritance of acquired characteristics: Modifications acquired during life are passed to offspring.
• This mechanism is not supported by evidence.

Darwin's Theory of Natural Selection

• Darwin reasoned that species from the mainland colonized and diversified on islands.
• Adaptations are inherited traits that help an organism survive and reproduce in its environment.
• Darwin's theory of natural selection states that individuals with traits best suited to their environment survive and reproduce at higher rates.
• Darwin's work was influenced by Alfred Russel Wallace, who independently reached the same conclusion about natural selection.
• Darwin viewed the history of life as a branching tree, with common ancestors and diverging lineages.
• Extinct lineages help explain differences between modern species.

Artificial Selection

• Artificial selection is the process of humans breeding organisms with desired traits, selecting for specific characteristics.