Overview
This lecture covers the classification, characteristics, and significance of microbes (bacteria, fungi, viruses, prions, viroids) and plants, highlighting their role in human welfare, adaptations, and key examples relevant for competitive exams.
Microbes and Human Welfare
- Microbes include bacteria, fungi, viruses, prions, and viroids, each with unique structures and impacts on humans.
- Bacteria are cosmopolitan (found everywhere) due to adaptability and simple cell structure, including gram-positive and gram-negative types.
- Fungi are also cosmopolitan with chitin-based cell walls, mainly heterotrophic, and often multicellular with body structures called mycelium (network of hyphae).
- Microbes (especially fungi and bacteria) play key roles in human welfare, such as decomposition, probiotics, and nutrient cycling.
Viruses, Prions, and Viroids
- Viruses have a protein-lipid outer covering and genetic material (DNA or RNA) and act as a bridge between living and non-living things.
- Examples: HIV and influenza have single-stranded RNA; M13 phage has single-stranded DNA; T4 phage has double-stranded DNA.
- Prions are infectious misfolded proteins without genetic material, mainly affecting the brain.
- Viroids are infectious RNA molecules lacking a protein coat, smaller than viruses and pathogenic in plants.
Plant Kingdom: Key Features and Classification
- Plants are generally multicellular, eukaryotic, usually with cellulose-based cell walls, mostly autotrophic (make their own food).
- Exceptions exist: insectivorous plants (e.g. Venus fly trap) rely on additional nutrients.
- Plants are classified into cryptogams (hidden reproduction: algae, bryophytes, pteridophytes) and phanerogams (seed-producing: gymnosperms and angiosperms).
Algae, Bryophytes and Adaptations
- Algae are mostly aquatic, can be unicellular or multicellular, have thallus-like body, show autotrophic nutrition, and exist in red, brown, or green forms due to different pigments.
- Bryophytes are called "amphibians of the plant kingdom" as they need moist environments; fertilization occurs in water.
- Bryophytes lack true vascular tissues, help prevent soil erosion, and can be used as fuel in dried form.
Key Terms & Definitions
- Cosmopolitan — Organisms found everywhere due to adaptability.
- Mycelium — Mass of hyphae (thread-like structures) in fungi.
- Micology — Study of fungi.
- Autotroph — Organism making its own food via photosynthesis.
- Heterotroph — Organism obtaining nutrition from other sources.
- Prion — Infectious misfolded protein without genetic material.
- Viroid — Infectious RNA molecule without a protein coat.
- Cryptogam — Plant with hidden reproductive organs (no flowers/seeds).
- Phanerogam — Seed-producing plant with visible reproductive organs.
Action Items / Next Steps
- Review examples and classification features of microbes and plants.
- Prepare brief notes on adaptation mechanisms of bacteria and fungi.
- Read further about plant nutrition exceptions and plant classification.