Types of Living Organisms
Classification (Taxonomy) is the science of grouping organisms based on shared characteristics. Carl Linnaeus is the Father of Taxonomy.
A. Five Kingdom Classification (Whittaker, 1969)
Five Kingdom Comparison
| Kingdom | Cell Type | Nutrition | Examples |
|---|---|---|---|
| Monera | Prokaryotic (no nucleus) | Autotrophic or Heterotrophic | Bacteria, Cyanobacteria (blue-green algae) |
| Protista | Eukaryotic, unicellular | Autotrophic or Heterotrophic | Amoeba, Paramecium, Euglena, Algae |
| Fungi | Eukaryotic, mostly multicellular | Heterotrophic — saprophytic (absorb dead matter) | Mushrooms, Moulds, Yeast, Penicillium |
| Plantae | Eukaryotic, multicellular | Autotrophic (photosynthesis) | Mosses, Ferns, Conifers, Flowering plants |
| Animalia | Eukaryotic, multicellular | Heterotrophic (ingestion) | Insects, Fish, Amphibians, Reptiles, Birds, Mammals |
Monera
Cell TypeProkaryotic (no nucleus)
NutritionAutotrophic or Heterotrophic
ExamplesBacteria, Cyanobacteria (blue-green algae)
Protista
Cell TypeEukaryotic, unicellular
NutritionAutotrophic or Heterotrophic
ExamplesAmoeba, Paramecium, Euglena, Algae
Fungi
Cell TypeEukaryotic, mostly multicellular
NutritionHeterotrophic — saprophytic (absorb dead matter)
ExamplesMushrooms, Moulds, Yeast, Penicillium
Plantae
Cell TypeEukaryotic, multicellular
NutritionAutotrophic (photosynthesis)
ExamplesMosses, Ferns, Conifers, Flowering plants
Animalia
Cell TypeEukaryotic, multicellular
NutritionHeterotrophic (ingestion)
ExamplesInsects, Fish, Amphibians, Reptiles, Birds, Mammals
⚡ MCQ Tips Fungi cell wall = chitin (NOT cellulose). Viruses are NOT in any kingdom — they are acellular. Largest phylum = Arthropoda. Whittaker proposed 5 kingdoms in 1969.
B. Viruses — Special Case
Why Viruses are NOT Living Organisms
- Viruses are acellular — they have no cells of any kind
- Structure: genetic material (DNA or RNA) enclosed in a protein coat (capsid)
- Obligate intracellular parasites — can ONLY reproduce inside a living host cell
- Cannot carry out metabolism independently — not considered truly "alive"
- Not classified in any of the 5 kingdoms
- Examples: Influenza (flu), HIV (AIDS), SARS-CoV-2 (COVID-19), Bacteriophage (infects bacteria)
C. Taxonomy & Classification
Levels of Classification
DomainEukarya (most broadest group)
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderPrimates
FamilyHominidae
GenusHomo
Speciessapiens (most specific)
⚡ Mnemonic Dear King Philip Came Over For Good Soup
Binomial Nomenclature (Linnaeus)
Genus (capital) + species (lowercase) — in italics
Examples: Homo sapiens (human), Panthera leo (lion), Felis catus (cat)
D. Major Animal Phyla
9 Major Phyla of Kingdom Animalia
| Phylum | Key Features | Examples |
|---|---|---|
| Porifera | Pore-bearing body; no true tissues; simplest animals; filter feeders | Sponges |
| Cnidaria | Stinging cells (nematocysts); radial symmetry; diploblastic; tentacles | Jellyfish, Coral, Hydra, Sea anemone |
| Platyhelminthes | Flatworms; bilateral symmetry; acoelomate; parasitic or free-living | Tapeworm, Liver fluke, Planaria |
| Nematoda | Roundworms; pseudocoelom; non-segmented; highly abundant | Ascaris, Hookworm, Pinworm |
| Annelida | Segmented worms; true coelom; setae for movement | Earthworm, Leech, Nereis |
| Mollusca | Soft body; usually with shell; mantle; radula for feeding | Snail, Octopus, Clam, Squid |
| Arthropoda | Exoskeleton (chitin); jointed appendages; segmented body — LARGEST phylum | Insects, Spiders, Crabs, Scorpions, Centipedes |
| Echinodermata | Spiny skin; water vascular system; radial symmetry in adults; deuterostomes | Starfish, Sea urchin, Sea cucumber |
| Chordata | Notochord, dorsal nerve cord, pharyngeal gill slits at some life stage | Fish, Amphibians, Reptiles, Birds, Mammals |
Quick MCQ Revision
| Fact | Answer |
|---|---|
| Five Kingdom classification by | R.H. Whittaker (1969) |
| Father of Taxonomy | Carl Linnaeus |
| Fungi cell wall made of | Chitin (NOT cellulose) |
| Largest animal phylum | Arthropoda (insects, spiders, crabs) |
| Viruses are | Acellular — not in any kingdom; obligate intracellular parasites |
| Binomial nomenclature | Genus (capital) + species (lowercase), in italics |
| Classification mnemonic | Dear King Philip Came Over For Good Soup |
| Homo sapiens classification | Kingdom Animalia, Phylum Chordata, Class Mammalia |