Overview of Key Features and Differences Between Organisms

Introduction

• Focus on the five kingdoms of life: Animals, Plants, Fungi, Protists, and Bacteria.
• Viruses are not considered living organisms and thus are not in any kingdom.
• Eukaryotes vs Prokaryotes:
  • Animals, Plants, Fungi, and Protists are eukaryotes (have a nucleus, DNA in chromosomes).
  • Bacteria are prokaryotes (no nucleus, DNA is loose in the cell).
  • Eukaryotic cells are larger than prokaryotic cells.
  • Viruses are even smaller than prokaryotic cells and are not classified as eukaryotic or prokaryotic.

Animals

• Estimated 5 to 10 million species.
• Key characteristics:
  • Multicellular.
  • Heterotrophs (get energy from other organisms).
  • Most reproduce sexually.

Plants

• Approximately 300,000 species.
• Key characteristics:
  • Multicellular.
  • Autotrophs (perform photosynthesis to obtain energy).

Fungi

• Includes both multicellular (e.g., mushrooms) and unicellular organisms (e.g., yeast).
• Key characteristics:
  • Cannot photosynthesize; are heterotrophs.
  • Often called saprotrophs due to saprotrophic nutrition (external digestion).
  • Multicellular fungi have mycelium made of hyphae.
  • Some fungi can be pathogens (e.g., cause athlete’s foot).

Protists

• Also known as protractists, protists, or protista.
• Nearly all are unicellular but very diverse.
• Key characteristics:
  • Some can photosynthesize (e.g., Chlorella, Euglena).
  • Others are like animal cells and consume organisms.
  • Some are pathogens (e.g., Plasmodium causes malaria).

Bacteria

• Single-celled organisms, found everywhere.
• Key characteristics:
  • Some can photosynthesize but don’t have chloroplasts.
  • Feed off other organisms.
  • More species than all other kingdoms combined.
  • Few cause diseases (e.g., Salmonella).
  • Many are helpful (e.g., aid in digestion).

Viruses

• Super small particles, not considered living cells.
• Key characteristics:
  • Basic structure: protein coat + genetic material (DNA/RNA).
  • Can only reproduce inside living cells (parasitic).
  • Always pathogens, causing harm when replicating.
  • Examples: Influenza virus, Tobacco mosaic virus, HIV, COVID-19.

Conclusion

• Aim to understand general differences among the organism groups.
• Not necessary to remember all details.
• Encouragement to engage with content for deeper learning.