Biological Classification Overview

The earliest attempts to classify organisms were based on practical needs and used readily observable features. This approach was primitive and unsystematic.

Aristotle, a Greek philosopher known for his contributions to various fields, initiated a more structured system of classification based on morphological characteristics.

Linnaeus, a Swedish botanist, revolutionized biological classification with his Two Kingdom system, which categorized all living organisms into Plantae (plants) and Animalia (animals).

Whittaker's Five Kingdom Classification, proposed in 1969, expanded the classification system to include Monera (bacteria), Protista (unicellular eukaryotes), Fungi, Plantae, and Animalia.

The Five Kingdom system classifies organisms based on their cellular structure (prokaryotic vs. eukaryotic), body organization (unicellular vs. multicellular), mode of nutrition (autotrophic vs. heterotrophic), and reproductive methods.

Monera encompasses bacteria, a diverse group with diverse metabolic capabilities. Bacteria are ubiquitous, meaning they are found everywhere.

Archaebacteria are a special group of bacteria that thrive in extreme environments, such as hot springs, highly salty areas, and acidic conditions. They have distinct cell wall structures.

The Three-Domain System, another significant classification system, recognizes three primary domains: Bacteria, Archaea, and Eukarya. This system was developed based on evolutionary relationships.

Single-celled eukaryotic organisms with diverse forms and habitats, including photosynthetic algae (like diatoms) and heterotrophic protozoans.

Characterized by rigid cell walls, these prokaryotes can be photosynthetic (cyanobacteria) or heterotrophic.

Asexual reproduction in bacteria where one cell divides into two identical daughter cells.

A diverse kingdom of heterotrophic organisms, including mushrooms, molds, and yeasts.

Fungi that reproduce asexually, often lacking a sexual stage.

A unique life cycle involving alternating haploid and diploid phases, with both generations contributing to the life cycle.

Multicellular, eukaryotic organisms that lack cell walls, are heterotrophic, and exhibit complex sensory and locomotion mechanisms.

Acellular infectious agents consisting of a protein coat (capsid) and genetic material (RNA or DNA), invading host cells to reproduce.

Infectious agents made solely of RNA, lacking a protein coat, responsible for diseases like potato spindle tuber disease.

Symbiotic associations between fungi and algae, playing an important role in ecological balance and environmental monitoring.