Overview of Kingdoms of Life and Viruses

Introduction

• Aim: Understand key features and differences between animals, plants, fungi, protists, bacteria, and viruses.
• Viruses are not classified as living organisms, unlike the five kingdoms of life (animals, plants, fungi, protists, bacteria).
• Eukaryotes (animals, plants, fungi, protists) have eukaryotic cells with DNA in chromosomes within a nucleus.
• Bacteria are prokaryotes with DNA not contained in a nucleus, smaller than eukaryotic cells.
• Viruses are non-living, much smaller than prokaryotic cells.

Animals

• Estimated 5-10 million species (humans, chickens, ladybirds, lionfish).
• Characteristics:
  • Multicellular (made up of many cells).
  • Heterotrophs (derive energy from other organisms).
  • Mostly reproduce sexually.

Plants

• About 300,000 species (redwood trees, bee orchids, tomato plants, water lilies).
• Characteristics:
  • Multicellular.
  • Autotrophs (use photosynthesis to get energy from the sun).

Fungi

• Includes mushrooms, molds (multicellular) and yeast (unicellular).
• Cannot photosynthesize; heterotrophs, often referred to as saprotrophs.
• Use saprotrophic nutrition (external digestion using enzymes).
• Some fungi can be pathogens (e.g., causes athlete's foot).
• Multicellular fungi have a mycelium made of hyphae.

Protists (Prototista/Protocists)

• Unicellular organisms, huge variety among species.
• Some can photosynthesize (like plant cells), others consume organisms (like animal cells).
• Some are pathogens (e.g., Plasmodium causing malaria).

Bacteria

• Single-celled organisms, ubiquitous (found on skin, intestines).
• Some photosynthesize but lack chloroplasts.
• Most feed off other organisms (living or dead).
• More species than all other kingdoms combined.
• Some are pathogens (e.g., salmonella), others are beneficial (e.g., aid digestion).

Viruses

• Non-living particles, extremely small.
• Structure: protein coat with DNA or RNA inside.
• Can only reproduce inside living cells (parasites).
• All viruses are pathogens (cause harm to host cells).
• Examples: influenza virus, tobacco mosaic virus, HIV, COVID-19.

Conclusion

• Focus on understanding differences between groups rather than memorizing details.
• Encouragement to like and subscribe for more content.