Kingdom

Overview of the Five Kingdoms & Viruses

• Five kingdoms: Animals, Plants, Fungi, Protists, Bacteria
• Viruses: Non-living entities, not classified in any kingdom.

Eukaryotes vs. Prokaryotes

Eukaryotes

• Nucleus: Present
• Cell size: 10–100× larger than prokaryotes
• Typical cell count: Multicellular
• Examples: Human, oak tree, mushroom, Euglena

Prokaryotes

• Nucleus: Absent
• Cell size: Small (0.5–5µm)
• Typical cell count: Usually single-celled
• Examples: E. coli, Salmonella

Key Characteristics of Kingdoms

Animals

• Species richness: ≈5–10 million species
• Key traits: Multicellular, heterotrophic, predominantly sexual reproduction

Plants

• Species count: ≈300,000
• Key traits: Multicellular, autotrophic (photosynthesis)

Fungi

• Forms: Multicellular (mushrooms) and unicellular (yeast)
• Nutrition: Heterotrophic (saprotrophic)
• Pathogenic potential: Some can cause disease (e.g., athlete’s foot)

Protists

• Cellularity: Mostly unicellular
• Nutritional strategies: Photosynthetic (e.g., Chlorella) and heterotrophic (e.g., Amoeba)
• Pathogenic potential: Certain species (e.g., Plasmodium → malaria)

Bacteria

• Cellularity: Unicellular prokaryotes
• Metabolic variety: Photosynthetic and heterotrophic
• Pathogenic potential: Some species cause diseases (e.g., Salmonella)

Viruses

• Size: Up to ~1 million viruses can fit on a fingernail
• Structure: Protein coat (capsid) surrounding DNA or RNA
• Reproduction: Must infect a host cell
• Pathogenicity: All cause diseases (e.g., influenza, HIV, SARS-CoV-2)

Comparative Summary

• Key distinctions: Cellular organization, number of cells, nutritional strategy
• Viruses: Stand apart as non-living particles relying on host cells for replication.