Overview of Organisms: Animals, Plants, Fungi, Protists, Bacteria, and Viruses

Introduction

• Aim: Understand the differences between animals, plants, fungi, protists, bacteria, and viruses.
• Five Kingdoms of Life: Animals, Plants, Fungi, Protists, Bacteria.
• Viruses are not part of the kingdoms as they're not living organisms.

Eukaryotes vs. Prokaryotes

• Eukaryotes (Animals, Plants, Fungi, Protists)
  • Made up of eukaryotic cells.
  • DNA in the form of chromosomes found in a nucleus.
• Prokaryotes (Bacteria)
  • No nucleus; DNA is loose in the cell.
  • 10 to 100 times smaller than eukaryotic cells.
• Viruses: Not classified as eukaryotic or prokaryotic, even smaller than prokaryotic cells.

Kingdoms

Animals

• Estimated 5-10 million species.
• Multicellular, heterotrophs, mostly reproduce sexually.
• Example: Humans, chickens, ladybirds, lionfish.

Plants

• Estimated 300,000 species.
• Multicellular, autotrophs (photosynthesis).
• Example: Redwood trees, bee orchids, tomato plants, water lilies.

Fungi

• Includes multicellular (mushrooms, molds) and unicellular (yeast) organisms.
• Cannot photosynthesize, are heterotrophs or saprotrophs.
  • Saprotrophic nutrition: Secreting enzymes to digest food externally.
• Multicellular fungi have mycelium made of hyphae.
• Some can be pathogenic (e.g., athlete’s foot).

Protists (Protocists, Protista, etc.)

• Mostly unicellular, wide variety.
• Some are like plant cells (photosynthesize), others like animal cells (consume organisms).
• Some can be pathogenic (e.g., Plasmodium causes malaria).

Bacteria

• Single-celled, live everywhere.
• Few can photosynthesize, most feed off other organisms.
• More species than other kingdoms combined.
• Some pathogenic (e.g., salmonella), others beneficial (digestive bacteria).

Viruses

• Not living organisms, extremely small particles.
• Structure: Protein coat around DNA or RNA.
• Reproduce only inside living cells (parasites).
• All are pathogenic.
• Examples: Influenza virus, Tobacco mosaic virus, HIV, COVID-19.

Conclusion

• Understanding these distinctions is key, not memorization.
• Encouragement to engage with content for further learning.