1. Whittaker's Five Kingdoms
| Kingdom | Cell type / organisation | Cell wall | Nutrition / examples |
|---|---|---|---|
| Monera | Prokaryotic; unicellular | Generally non-cellulosic | Autotrophic or heterotrophic; bacteria, cyanobacteria |
| Protista | Eukaryotic; unicellular | Variable | Autotrophic or heterotrophic; diatoms, Euglena, protozoans |
| Fungi | Eukaryotic; mostly multicellular | Chitin | Heterotrophic, absorptive; yeast, mushrooms, moulds |
| Plantae | Eukaryotic; multicellular | Cellulose | Usually autotrophic; algae to angiosperms |
| Animalia | Eukaryotic; multicellular | Absent | Heterotrophic, ingestive; animals |
Whittaker's criteria Cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships.
2. Archaebacteria vs Eubacteria vs Mycoplasma
| Feature | Archaebacteria | Eubacteria | Mycoplasma |
|---|---|---|---|
| Cell wall | Different structure, enabling extreme survival | Rigid cell wall | Cell wall absent |
| Habitat / type | Halophiles, thermoacidophiles, methanogens | Ubiquitous true bacteria; may be photosynthetic or chemosynthetic | Smallest living cells; can survive without oxygen |
| Special feature | Methanogens produce biogas in ruminant gut | Cyanobacteria may fix nitrogen in heterocysts | Many are pathogenic in plants and animals |
| Examples | Methanogens | Nostoc, Anabaena | PPLO / mycoplasma |
3. Major Protistan Groups
| Group | Distinctive feature | Examples / importance |
|---|---|---|
| Chrysophytes | Diatoms have silica walls forming two overlapping shells; planktonic | Diatomaceous earth used in polishing and filtration |
| Dinoflagellates | Mostly marine; cellulose plates and two flagella | Gonyaulax can cause red tides |
| Euglenoids | Protein-rich pellicle; photosynthetic in light, heterotrophic in darkness | Euglena |
| Slime moulds | Saprophytic; aggregation forms plasmodium; resistant spores | Spore dispersal by air |
| Protozoans | Heterotrophic predators or parasites | Amoeboids, flagellates, ciliates and sporozoans |
4. Protozoan Groups Compared
| Group | Locomotion / feature | Examples |
|---|---|---|
| Amoeboid protozoans | Pseudopodia; some marine forms have silica shells | Amoeba, Entamoeba |
| Flagellated protozoans | Flagella; free-living or parasitic | Trypanosoma causes sleeping sickness |
| Ciliated protozoans | Thousands of cilia; gullet directs food inward | Paramecium |
| Sporozoans | Infectious spore-like stage in life cycle | Plasmodium causes malaria |
5. Major Fungal Classes
| Class | Mycelium / asexual reproduction | Sexual spores / examples |
|---|---|---|
| Phycomycetes | Aseptate, coenocytic; zoospores or aplanospores in sporangia | Zygospore; Mucor, Rhizopus, Albugo |
| Ascomycetes | Branched, septate; conidia on conidiophores | Ascospores in asci / ascocarps; Aspergillus, Claviceps, Neurospora |
| Basidiomycetes | Branched, septate; asexual spores generally absent | Basidiospores on basidia / basidiocarps; Agaricus, Ustilago, Puccinia |
| Deuteromycetes | Only asexual or vegetative phase known | Called imperfect fungi; Alternaria, Colletotrichum, Trichoderma |
Fungal sexual cycle Plasmogamy → karyogamy → meiosis. Ascomycetes and basidiomycetes show a dikaryotic (n+n) phase.
6. Viruses vs Viroids vs Prions vs Lichens
| Entity | Composition / nature | Key fact |
|---|---|---|
| Virus | Nucleic acid enclosed in protein coat (capsid); obligate parasite | Can be crystallised; replicates only inside living host cells |
| Viroid | Small infectious RNA without protein coat | Discovered by T. O. Diener; causes potato spindle tuber disease |
| Prion | Infectious proteinaceous particle | Causes bovine spongiform encephalopathy (mad cow disease) |
| Lichen | Symbiosis of alga (phycobiont) and fungus (mycobiont) | Alga prepares food; fungus gives shelter and absorbs water/minerals; pollution indicator |