Taxonomy Overview and Systematics

Taxonomy Overview

• Taxonomy involves the classification of living and extinct organisms based on evolutionary relationships.
• The hierarchical system of taxonomy has several levels, and each group within this system is called a taxon.
• The highest level is the domain, with all life classified into three domains: Bacteria, Archaea, and Eukarya.

Eukaryotic Subgroups

• The Eukarya domain further includes various subgroups such as:
  • Excavata
  • Land plants
  • Alveolata
  • Stramenopila
  • Rhizaria
  • Amoebozoa
• Large kingdoms within Eukarya include Plantae and Opisthokonta, which encompasses Fungi and Animalia.

Systematics

• Systematics studies biological diversity and the evolutionary links between both extinct and modern organisms.
• Fungi were classified as eukaryotic only in recent years, separated from Protista and Plantae in 1969 due to similarities in metabolism with animals (e.g., chitin cell wall, heterotrophy).

Unicellular Organisms

• Unicellular organisms are primarily bacteria (e.g., E. coli, streptococcus) and some protists (e.g., Amoeba, Euglena).
• All algae fall under the protist category, existing as both unicellular (e.g., Chlorella) and multicellular forms (e.g., seaweeds).

Multicellular Protists

• Multicellular protists are recognized as primary producers and are plant-like, lacking true leaves, stems, and roots.
• Types include:
  • Brown algae (Phaeophyta)
  • Red algae (Rhodophyta)
  • Green algae (Chlorophyta)

Groups of Protists

• Protists can be categorized based on feeding mechanisms and locomotor abilities:
  • Heterotrophs with no permanent locomotion
  • Heterotrophs with limited movement
  • Heterotrophs utilizing flagella
  • Photosynthetic protists

Characteristics of Living Things

• Eight essential characteristics define living organisms:
  • Composed of one or more cells
  • Contain genetic material (DNA/RNA)
  • Reproduce asexually
  • Grow and develop
  • Exchange energy and materials with the environment
  • Maintain homeostasis
  • Respond to stimuli
  • Evolve as a species
• Viruses are not considered living as they only possess four of these characteristics.

Taxonomic Hierarchy

• The organized structure of life follows this chronological sequence:
  • Domain
  • Supergroup
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• The relationship between taxonomic levels and the number of species is inversely proportional.

Binomial Nomenclature

• Naming organisms uses a two-part system (genus name + species epithet), indicated in italics or underlined, with the genus capitalized.

Phylogenetic Trees

• Phylogeny refers to the evolutionary history of species, depicted using phylogenetic trees, which hypothesize evolutionary relationships based on morphological and genetic data.
• They can illustrate how new species arise through:
  • Anagenesis: evolution of a single species into different forms
  • Cladogenesis: divergence of a species into multiple new species

Taxonomic Groupings

• Taxonomic groups can be:
  • Monophyletic (clades): include a common ancestor and all its descendants
  • Paraphyletic: include a common ancestor but not all descendants
  • Polyphyletic: group species with different common ancestors
• Reorganization of taxonomic groups can occur as scientific understanding progresses.

Homology and Morphological Analysis

• Homology refers to similarities between species due to common ancestry, such as the structure of limbs in bats, humans, and cats.
• Morphological analysis examines these structures for systematic classification.

Explore the classification of living and extinct organisms through the hierarchical system of taxonomy. This quiz covers key concepts such as domains, eukaryotic subgroups, and the significance of systematics in understanding biological diversity. Test your knowledge of taxonomy and systematics!