Overview of Organism Groups and Viruses

Introduction

• Aim: Understand differences between animals, plants, fungi, protoctists, bacteria, and viruses.
• Five Kingdoms of Life: Animals, plants, fungi, protoctists, and bacteria.
• Viruses: Not part of the kingdoms of life, not considered living organisms.
• Eukaryotes: Animals, plants, fungi, protoctists (have eukaryotic cells, DNA in chromosomes/nucleus).
• Prokaryotes: Bacteria (lack nucleus, DNA is loose, smaller than eukaryotic cells).
• Virus Size: Smaller than prokaryotic cells.

Animals

• Species Estimate: 5-10 million.
• Characteristics: Multicellular, heterotrophs, mostly reproduce sexually.
• Multicellular: Organisms made up of many cells.
• Heterotrophs: Obtain energy from other organisms (e.g., eating plants/animals).

Plants

• Species Estimate: Around 300,000.
• Characteristics: Multicellular, autotrophs.
• Autotrophs: Obtain energy from the sun using photosynthesis.

Fungi

• Types: Multicellular (e.g., mushrooms, moulds) and unicellular (e.g., yeast).
• Characteristics: Cannot photosynthesize, heterotrophs (saprotrophs).
• Saprotrophic Nutrition: Secrete enzymes, digest food externally, absorb nutrients.
• Mycelium: Multicellular body made of hyphae.
• Pathogens: Some fungi cause diseases (e.g., athlete’s foot).

Protoctists (Protoctista, Protists)

• Characteristics: Nearly all unicellular, diverse.
• Types: Some like plant cells (photosynthesize), others like animal cells (consume organisms).
• Pathogens: Some can cause diseases (e.g., Plasmodium causing malaria).

Bacteria

• Characteristics: Single-celled, live everywhere.
• Feeding: Some photosynthesize (no chloroplasts), many feed on organisms or decaying matter.
• Species: Likely more bacterial species than other kingdoms combined.
• Pathogens: Some cause diseases (e.g., salmonella), many are beneficial (e.g., gut bacteria).

Viruses

• Nature: Non-living particles, cannot reproduce independently.
• Structure: Protein coat with genetic material (DNA/RNA).
• Reproduction: Must infect living cells (parasites).
• Pathogens: All viruses cause harm to host cells.
• Examples: Influenza, tobacco mosaic virus, HIV, COVID-19.

Conclusion

• Main Takeaway: General understanding of differences between these groups.
• Reminder: Not necessary to remember all details, focus on understanding.