Evidence for Evolution

Overview

• Learn about the theory of evolution and how it's supported by direct observation, homologies, fossils, and biogeographical patterns.

Key Points

• Macroevolution evidence: anatomy, embryology, molecular biology, biogeography, and fossils.
• Homologous Features: Shared due to common ancestry.
• Analogous Features: Similar due to similar selective pressures, not common ancestry.
• Molecular Similarities: DNA sequence comparisons show relationships.
• Biogeography: Geographical distribution of organisms provides evolutionary insights.
• Fossils: Document long-term evolutionary changes and extinct species.

Introduction

• Microevolution: Observable small-scale evolution, e.g., drug-resistant bacteria.
• Macroevolution: Large-scale evolution over long time periods.
• Evolution as "descent with modification": species change and give rise to new species over generations.
• Evolution involves changes in the genetic makeup of populations over time.

Evidence for Evolution: Tracing Histories

Anatomy and Embryology

• Shared anatomical features suggest common ancestry.
• Homologous Features: Inherited from a common ancestor, e.g., forelimbs of whales, humans, birds.
• Embryonic homologies: Vertebrate embryos share features during early development.
• Vestigial Structures: Reduced features indicating ancestry, e.g., human tailbone.

Analogous Features

• Features that evolved independently in different organisms due to similar environments, e.g., Arctic fox and ptarmigan color changes.
• Convergent evolution: Process where similar traits evolve independently.

Molecular Biology

• Shared genetic material and processes suggest common ancestry.
• Homologous Genes: Related genes in different species help determine evolutionary relationships.
• DNA differences in homologous genes indicate the degree of relatedness.

Biogeography

• Evolutionary patterns explained by tectonic plate movements and geographical isolation.
• Unique species on islands, e.g., Australian marsupials, illustrate evolution and geography intersection.

Fossil Record

• Fossils provide evidence of extinct species and evolutionary changes.
• Fossils are dated using strata and radiometric dating.
• Fossil records help reconstruct evolutionary histories, e.g., horse lineage.

Summary

• Multiple evidence types used for tracing evolutionary changes over time.
• Homologous features, molecular similarities, biogeographical patterns, and fossils provide insights into species' relatedness.
• Fossil record, though incomplete, offers valuable historical information.