Vets 1060 Lecture 6

Introduction to Animal Diversity and Molecular Evolution

  • Lecture focus: explore the diversity of animal life and the molecular basis of evolution.
  • Key objectives:
    • Classify the diversity of animals using historical and molecular biology perspectives.
    • Understand how molecular changes influence traits and evolution.
    • Visualize relationships among organisms and classification systems.

Scale of Biodiversity

  • Approx. 8,700,000 living eukaryotic species on Earth, but only 1.2 million described.
  • Major concern: loss of species due to human impact (environmental disruption and population growth).
  • Of described species, around 1 million are insects (most diverse).
  • Microbial diversity: potential trillions of microbial species, with only 10% characterized.

Understanding Diversity through Evolutionary Theory

  • Evolution as a theory: explains the unity and diversity of species.
  • Biological evolution: gradual changes leading to new species over time.
    • Involves deep time, allowing for gradual change in populations.
    • Explains genetic similarities and diversity across species.
  • Variation within species as a concept:
    • Example: Different breeds of dogs (e.g., Chihuahua vs. Great Dane) show morphological and physiological variation.
  • Natural variation arises from:
    • Mutations at the molecular level.
    • Impact on individuals and populations, especially if mutations are heritable.

Historical Classification of Life

  • Early classification systems shaped by understanding of local environments (e.g., the Inuit classification of snow and ice).
  • As exploration increased, recognition of global diversity led to the limitations of local classification systems.
  • Carolus Linnaeus (1707-1778): founding figure of modern taxonomy.
    • Developed hierarchical classification (taxa) and binomial nomenclature (genus + species).
  • Example of naming:
    • Homo sapiens: genus name "Homo" (human) and species epithet "sapiens" (wise).
    • Buffo marinus (now Rinella mariner): originally referred to a marine toad.

Taxonomy and Classification Systems

  • Taxonomy: science of naming and classifying organisms.
    • Linnaeus’s system retains relevance but is expanded by molecular biology.
  • Definitions of species:
    • Groups capable of interbreeding and producing fertile offspring.
    • Difficulty arises with overlaps and exceptions (insects, parasites).
  • Hierarchical Classification:
    • Classification moves from species to genus, family, order, class, phylum, kingdom.
    • Example: American black bear: Ursus americanus under the family Ursidae (bears).

Nomenclature and Naming

  • Linnaeus’s binomial system:
    • Two-part name: Genus (capitalized) + species (lowercase), both italicized.
    • Example: Equus caballus (horse).

Morphological and Genetic Criteria for Classification

  • Identification based on morphological characteristics, ecological attributes, and more recently, molecular biology (DNA and RNA comparisons).
    • Nucleic acid sequencing plays a crucial role in contemporary taxonomy.
  • Use of dichotomous keys:
    • Logical decision-making tool to classify organisms based on distinct features.

Phylogenetics and Taxonomy

  • Phylogenetic trees: visual representations of evolutionary relationships.
    • Each branch point indicates a common ancestor.
    • Understanding these relationships is crucial for fields such as medicine and ecology.
  • Distinguishing between homologous (similar structures, different functions) and analogous (similar functions, different origins) traits is vital in classification and understanding evolutionary history.

Conclusion

  • Importance of understanding and classifying diversity for conservation efforts and biological research.

  • The evolving methods of taxonomy reflect the complexity of life and pave the way for future discoveries and conservation initiatives.

  • Next lecture to continue discussing these topics in-depth.