Variety of Living Organisms Notes

Eukaryotic Organisms

• Common features:
  • Plants: Multicellular, chloroplasts for photosynthesis, cellulose cell walls, store carbohydrates as starch or sucrose.
    • Examples: Flowering plants (maize), herbaceous legumes (peas, beans).
  • Animals: Multicellular, no chloroplasts, no cell walls, nervous coordination, movement, often store carbohydrate as glycogen.
    • Examples: Mammals (humans), insects (housefly, mosquito).
  • Fungi: Lack photosynthesis, mycelium of hyphae (many nuclei), some single-celled, chitin cell walls, saprotrophic nutrition, may store carbohydrate as glycogen.
    • Examples: Mucor (hyphal structure), yeast (single-celled).
  • Protoctists: Microscopic single-celled organisms.
    • Examples: Amoeba (animal-like), Chlorella (plant-like with chloroplasts), Plasmodium (pathogenic, causes malaria).

Prokaryotic Organisms

• Bacteria:
  • Microscopic single-celled organisms with cell wall, cell membrane, cytoplasm, and plasmids.
  • Lack a nucleus but have a circular chromosome of DNA.
  • Some can photosynthesize; most feed off other organisms.
    • Examples: Lactobacillus bulgaricus (yoghurt production), Pneumococcus (causes pneumonia).
• Comparison to Eukaryotic Cells
  • Eukaryotic cells have a nucleus and membrane-bound organelles; prokaryotic cells do not.

Non-living Organisms and Pathogens

• Pathogen Definition: Fungi, bacteria, protoctists, or viruses that cause disease.
• Viruses:
  • Non-living particles, smaller than bacteria.
  • Parasitic, reproduce only inside living cells.
  • Protein coat and either DNA or RNA.
    • Examples: Tobacco mosaic virus, influenza virus, HIV virus.