Lecture Notes on Species and Taxonomy

Introduction

• The lecture covers broad concepts of species, taxonomy, and classification.
• Importance of understanding species in ecology and ecosystems.

Understanding Species

• Definition of Species:

  • Individuals that can breed and produce fertile offspring.
  • Reproductive success is key.
  • Asexually reproducing organisms like bacteria clone themselves.

• Reproductive Barriers:

  • Prezygotic Barriers:
    • Ecological Isolation: Different habitats prevent mating.
    • Temporal Isolation: Mating seasons/times do not align.
    • Behavioral Isolation: Differences in mating calls/behaviors.
    • Mechanical Isolation: Incompatibility of mating organs.
    • Gametic Isolation: Sperm and egg do not fuse.
  • Postzygotic Barriers:
    • Hybrid Inviability: Hybrids do not mature.
    • Hybrid Infertility: Hybrids are sterile (e.g., mules).
    • Hybrid Breakdown: Hybrids can reproduce, but their offspring cannot.

Taxonomy and Classification

• Classification based on genetic and phenotypic similarities.

• Taxonomy: Organism classification into domains and kingdoms.

• Phylogenetics: Evolutionary relationships based on DNA/protein sequences.

• Classification System:

  • Domains: Bacteria, Archaea, Eukarya.
  • Kingdoms within Eukarya: Plants, Animals, Fungi, Protists.

Domains and Kingdoms

Bacteria and Archaea

• Both are prokaryotic but differ genetically and functionally.
• Bacteria:
  • Cell wall made of peptidoglycan.
  • Some are photosynthetic and fix nitrogen.
  • Important for ecosystems and biotechnology.
• Archaea:
  • Cell wall of pseudopeptidoglycan.
  • Often extremophiles (methanogens, halophiles, thermoacidophiles).

Eukarya Domain

• Largest diversity; all cells have a nucleus.

Protists

• Extremely diverse kingdom.
• Photosynthetic Protists: Algae (key for aquatic ecosystems).
• Other Notable Protists: Dinoflagellates (red tides), Diatoms (silicon shells).

Fungi

• Important decomposers with unique reproductive structures (e.g., mushrooms).
• Symbiotic relationships with algae (lichens).
• Cell walls made of chitin.

Plants

• Multicellular, usually photosynthetic.
• Major Groups:
  • Bryophytes: Seedless, nonvascular (e.g., mosses).
  • Ferns: Seedless, vascular.
  • Gymnosperms: Seed, vascular, non-flowering (e.g., pine trees).
  • Angiosperms: Seed, vascular, flowering (e.g., grass).

Animals

• Characteristics: Chemo-heterotrophic, complex tissues (muscle and nervous).
• Major Phyla:
  • Arthropods: Insects, crustaceans (most diverse).
  • Chordata: Vertebrates and some invertebrates (e.g., fish, mammals).

Conclusion

• There is a vast diversity in species across different domains and kingdoms.
• Each classification plays a role in ecological stability and evolutionary history.
• Understanding these concepts is crucial for biology and ecology studies.