Coen+2002

The Making of a Blossom

Introduction

  • Author: Enrico Coen

  • Focus on the evolutionary development of flowers

  • Key concept: Flower structure influenced by evolutionary history

Evolutionary Background

  • Lower and upper petals in Salvia blossoms differ in shape.

  • Flowers evolved from a radially symmetrical ancestor.

  • Adaptations were made to attract pollinators (e.g., flies and bees).

Bashford Dean: A Dual Passion

Overview of Bashford Dean

  • Dean's interests:

    • Fish development and evolution.

    • Arms and armor fascination.

  • Academic Career:

    • Became a professor at Columbia University (1891).

    • Curator at the American Museum of Natural History (1903).

Fascination with Armor

  • Childhood experience with a European helmet.

  • Contribution to the Metropolitan Museum of Art's armor collection.

  • Created diagrams illustrating the evolution of armaments, resembling species evolution charts.

Diagrams of Evolution

Evolutionary Diagrams

  • Dean's diagrams illustrate relationships in armament development.

  • Highlights the misconception that one object transforms directly into another, akin to the evolution of species.

  • Diagrams help organize the connection between artifacts and their historical context.

Evolution of Floral Forms

  • Emphasizes the importance of genetic understanding for flowers.

  • Early flowering plants' shapes reflect evolutionary changes.

  • Fossil records provide limited insights into ancient development processes.

Understanding Flower Symmetry

Types of Symmetry in Flowers

  • Radially symmetrical flowers:

    • Example: Buttercups and tulips (single type of petal around a center).

  • Bilaterally symmetrical flowers:

    • Example: Snapdragons and sweet peas (distinct upper and lower petals).

  • Evolution from radial to bilateral symmetry to accommodate pollinators.

Genetic Research in Symmetry

  • Snapdragon (Antirrhinum majus) as a model organism for symmetry study.

  • Gene of interest: cycloidea (cyc).

  • Contribution of cyc to floral symmetry—active at an early stage of bud development.

Genetic Activity in Flower Development

Ancestral Patterns in Gene Expression

  • Cyc gene influences the development of distinct upper/lower petals.

  • Gene activity pattern contrasts between snapdragons and Arabidopsis, a model for studying flower development.

Evolutionary Implications

  • Asymmetric patterns in gene activity can lead to physical differences in flowers.

  • Insights into the focuses of molecular evolution across plant species through genetic research.

The Evolution of Maize

Introduction to Maize Domestication

  • Changes brought about through selective breeding of plants, notably maize.

  • Teosinte represented the ancestor of modern maize, showing significant differences.

Genetic Findings

  • Discovery of tb1 gene responsible for branching patterns in maize vs. teosinte.

  • Relationship between tb1 and cyc genes highlighting their regulatory functions.

Reflection on Past and Present

Fascination with Gene Research

  • Gene studies as a form of "time travel" in biology.

  • Emphasis on understanding how ancient structures relate to modern organisms.

  • The past informs the present, providing insights into biological evolution.