Diversity of Life and Taxonomy - Quick Reference

Genes and Diversity

  • Genes are hereditary units passed from parents to offspring; they drive the diversity of life.
  • Organizing genes/classifications helps in easy identification.

Learning Objectives

  • Explain the importance of classifying living things.
  • Compare early classification with the modern Linnaean system.

Early System of Classification (Aristotle)

  • Organisms viewed as either plants or animals.
  • Species considered unique, distinct, and unchanging.
  • Plant groups: Herbs (Based on Blood), Trees, Shrubs.
  • Animal groups: Enaima (with RBCs) vs Anaima (without RBCs); Aquatic, Terrestrial, Flying.

Limitations of Aristotle's System

  • Evolutionary relationships not considered.
  • System had many limitations but helped organize organisms.

Modern System of Classification: Linnaean System

  • Introduced by Carolus Linnaeus (1707–1778).
  • First formal system of taxonomic organization.
  • Based on empirical study of physical characteristics and behaviors.

Classification in Birds (Beaks) [Illustrative Example]

  • Beak types used to illustrate grouping: e.g., crest beak (sparrow), long/sharp (kingfisher), long/slender (hummingbird), hooked (eagle), chisel-like (woodpecker), wide/flat (duck).

Classification: General Concept

  • Classification groups objects by specific criteria.
  • Modern science uses tools like electron microscopes, PCR, and data from DNA, RNA, and amino acid sequences to assess relationships.

Systematics vs Taxonomy

  • Systematics: study of biological diversity and relationships among organisms.
  • Taxonomy: naming, describing, and classifying organisms (often called the science of classification).
  • Modern System: Linnaean framework.

Linnaean System: Levels of Classification

  • Domain (most inclusive)
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species (most specific)
  • Example hierarchy for Homo sapiens:
    • Domain: Eukarya
    • Kingdom: Animalia
    • Phylum: Chordata
    • Class: Mammalia
    • Order: Primates
    • Family: Hominidae
    • Genus: Homo
    • Species: Homo sapiens

Binomial Nomenclature and Taxonomic Hierarchy (Two Components)

  • Binomial Nomenclature: each species has a unique two-part name (genus + specific epithet).
  • Names prevent confusion from common names.
  • Taxonomic Hierarchy: organisms are classified into nested groups; each level has its own name (taxon).

Two Components of Linnaean System

  • Binomial Nomenclature: genus name + specific epithet form the scientific name.
  • Taxonomic Hierarchy: classification into hierarchical levels (domain to species).

Binomial Nomenclature Guidelines

  • Names are based on Latin.
  • Scientific names are italicized (printed) or underlined (hand-written).
  • Genus name is capitalized; species epithet is lowercase.
  • Examples: Homo sapiens, Felis catus, Canis lupus familiaris.

Scientific Names: Examples

  • Allium cepa — Onion
  • Allium sativum — Garlic
  • Mangifera indica — Mango
  • Panthera leo — Lion
  • Helianthus annuus — Sunflower

Taxonomic Hierarchy Recap

  • Domain is the most inclusive level; three domains exist: Bacteria, Archaea, and Eukarya.
  • The hierarchy narrows from Domain to Species.

Domains

  • Bacteria, Archaea, Eukarya
  • Bacteria and Archaea: prokaryotes; lack true nucleus and membrane-bound organelles.
  • Eukarya: organisms with eukaryotic cells.

Kingdoms within Domains (Overview)

  • 6 kingdoms (Woese, 1977): Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia.
  • 5-kingdom model (Whittaker, 1969): Monera, Protista, Fungi, Plantae, Animalia.

Kingdom: Archaebacteria

  • Prokaryotes; unicellular; lack true nucleus and membrane-bound organelles.
  • Thrive in extreme environments: halophiles, methanogens, psychrophiles, thermophiles.

Kingdom: Eubacteria

  • Prokaryotes; unicellular; shapes include cocci, spirilla, bacilli, spirochetes, vibrio.
  • Examples: Staphylococcus, Streptococcus, Escherichia coli, Lactobacillus.

Kingdom: Protista

  • Eukaryotes; mostly unicellular, not plants or animals.
  • Some multicellular forms (e.g., certain algae); examples include Amoeba, Paramecium, Volvox.

Kingdom: Fungi

  • Eukaryotic; heterotrophic; rigid cell walls; do not photosynthesize.
  • Include yeasts, molds, mushrooms.

Kingdom: Plantae

  • Photosynthetic, autotrophic, multicellular.
  • Two major groups: Vascular (with transport systems) and Non-vascular (no true tissues for transport).
  • Angiosperms (flowering, seed enclosed in ovary) vs Gymnosperms (non-flowering, naked seeds).

Kingdom: Animalia

  • Eukaryotic, multicellular, heterotrophic; lack cell walls; mostly motile.
  • Divided into vertebrates and invertebrates; warm-blooded vs cold-blooded.

Phylum, Class, Order, Family, Genus, Species

  • Phylum: major grouping below Kingdom.
  • Class: below Phylum; Grouping like Mammalia, Aves, Reptilia.
  • Order: below Class; groups with more in common.
  • Family: below Order; e.g., Canidae, Felidae, Hominidae.
  • Genus: below Family; one or more closely related species (e.g., Homo, Felis, Canis).
  • Species: basic unit; capable of interbreeding; includes epithet to form the full name (e.g., Homo sapiens).