Classification Systems, Five Kingdoms and Taxonomy Hierarchy
Diversity in Living Organisms: Classification Systems, Five Kingdoms and Taxonomy Hierarchy
Classification Systems, Five Kingdoms and Taxonomy Hierarchy
Diversity in Living Organisms
What you'll learn
- Why we classify living organisms.
- Aristotle → Linnaeus → Whittaker — history of classification.
- The Five Kingdom classification (Monera, Protista, Fungi, Plantae, Animalia).
- The taxonomy hierarchy (Kingdom → Species).
- Major animal phyla and plant divisions.
Key concepts
Why classify?
- ~8.7 million known species on Earth.
- Classification organises diversity, reveals evolutionary relationships, helps in communication (one universal name), aids in medicine and agriculture.
- Biodiversity: variety of life — genetic, species, ecosystem levels.
History of classification
| Scientist | Contribution |
|---|---|
| Aristotle (~350 BC) | First systematic — animals: with/without red blood; plants: herbs/shrubs/trees |
| Carolus Linnaeus (1758) | Two-kingdom (Plant/Animal); binomial nomenclature; Systema Naturae |
| Ernst Haeckel (1866) | Added third kingdom: Protista |
| R.H. Whittaker (1969) | Five-kingdom classification (modern standard) |
| Carl Woese (1977) | Six-kingdom / Three-domain (Archaea/Bacteria/Eukarya) — used in advanced biology |
Binomial Nomenclature (Linnaeus)
- Each organism has a two-part Latin name: Genus + species.
- Written in italics (printed) or underlined (handwritten).
- Genus starts with CAPITAL, species in lowercase.
- Examples: Homo sapiens (human), Panthera leo (lion), Mangifera indica (mango), Felis catus (cat).
Taxonomy Hierarchy (8 levels)
King Phillip Came Over For Good Soup
| Level | Example (Human) | Example (Mango) |
|---|---|---|
| Kingdom | Animalia | Plantae |
| Phylum/Division | Chordata | Angiosperms |
| Class | Mammalia | Dicotyledonae |
| Order | Primates | Sapindales |
| Family | Hominidae | Anacardiaceae |
| Genus | Homo | Mangifera |
| Species | sapiens | indica |
- Kingdom = broadest; Species = most specific.
- Members of the same species can interbreed and produce fertile offspring.
Whittaker's Five Kingdom Classification
Kingdom 1: Monera (Prokaryotes)
- No nucleus (prokaryotic); no membrane-bound organelles.
- Unicellular; cell wall present (peptidoglycan in bacteria).
- Nutrition: autotrophic (some) or heterotrophic.
- Examples: Bacteria (E. coli, Lactobacillus, Rhizobium), Cyanobacteria (blue-green algae — Nostoc, Anabaena).
- Smallest and most abundant life forms.
Kingdom 2: Protista (Protists)
- Eukaryotic, mostly unicellular.
- Aquatic; some have cilia or flagella.
- Nutrition: autotrophic or heterotrophic.
- Examples: Amoeba, Paramecium (cilia), Euglena (flagella, both auto+heterotrophic), Diatoms (photosynthetic, glassy cell wall), Plasmodium (causes malaria).
Kingdom 3: Fungi
- Eukaryotic, mostly multicellular (except yeast — unicellular).
- Heterotrophic (saprophytes — feed on dead matter, or parasites).
- Cell wall: chitin (not cellulose).
- Reproduce by spores.
- Examples: Mushrooms (Agaricus), Bread mould (Rhizopus), Yeast (Saccharomyces), *Penicillium (produces penicillin), Aspergillus.
- Role: decomposers; food (mushrooms, cheese, bread); medicine (antibiotics).
Kingdom 4: Plantae (Plants)
- Eukaryotic, multicellular, autotrophic (photosynthesis).
- Cell wall: cellulose; large central vacuole; chloroplasts.
- Cannot move (sessile).
Plant divisions:
| Division | Features | Examples |
|---|---|---|
| Thallophyta (Algae) | No root/stem/leaf; aquatic | Spirogyra, Chara, Ulothrix |
| Bryophyta | No vascular tissue; grow in damp; "amphibians of plant world" | Moss (Funaria), Liverwort (Marchantia) |
| Pteridophyta (Ferns) | Vascular tissue; no seeds; reproduce by spores | Fern (Dryopteris), Horsetail (Equisetum) |
| Gymnosperms | Vascular; seeds naked (no fruit); mostly evergreen trees | Pine, Cedar, Cycas, Pinus |
| Angiosperms | Vascular; seeds enclosed in fruit; flowers | Mango, Rose, Wheat, Maize |
Angiosperms further split:
- Monocots: 1 cotyledon; parallel veins; fibrous root (Maize, Wheat, Rice, Grass, Lily)
- Dicots: 2 cotyledons; reticulate veins; tap root (Mango, Rose, Pea, Sunflower)
Kingdom 5: Animalia (Animals)
- Eukaryotic, multicellular, heterotrophic.
- No cell wall; no chloroplasts.
- Most can move; have nervous system (except sponges).
Major phyla:
| Phylum | Key features | Examples |
|---|---|---|
| Porifera | Pores; water canal system; sessile; no tissues | Sponge (Sycon, Spongilla) |
| Coelenterata (Cnidaria) | Stinging cells (nematocysts); radial symmetry; aquatic | Jellyfish, Coral, Hydra, Sea anemone |
| Platyhelminthes | Flatworms; bilateral symmetry; no body cavity | Tapeworm, Planaria, Liver fluke |
| Nematoda | Roundworms; pseudocoelom; tiny; parasitic | Roundworm (Ascaris), Pinworm, Filarial worm |
| Annelida | Segmented worms; true coelom; closed circulation | Earthworm (Lumbricus), Leech, Nereis |
| Arthropoda | Exoskeleton; jointed legs; largest phylum | Insects, Spiders, Crabs, Scorpions, Centipedes |
| Mollusca | Soft body; shell (usually); open circulation | Snail, Octopus, Squid, Clam, Pila |
| Echinodermata | Spiny skin; water vascular system; radial symmetry | Starfish, Sea urchin, Sea cucumber |
| Chordata | Notochord at some stage; dorsal hollow nerve cord; gill slits | Fish, Amphibians, Reptiles, Birds, Mammals |
Chordata sub-groups:
| Class | Features | Examples |
|---|---|---|
| Pisces (Fish) | Aquatic; gills; scales; cold-blooded | Rohu, Shark, Tuna |
| Amphibia | Land + water; moist skin; 3-chambered heart | Frog, Toad, Salamander |
| Reptilia | Scales; dry skin; cold-blooded; 3-chambered heart (croc: 4) | Snake, Lizard, Crocodile, Turtle |
| Aves (Birds) | Feathers; hollow bones; warm-blooded; 4-chambered heart; beak | Pigeon, Sparrow, Ostrich |
| Mammalia | Hair/fur; mammary glands; warm-blooded; 4-chambered heart | Human, Whale, Bat, Horse |
Evolutionary significance
- Classification reflects evolutionary relationships (phylogeny).
- Organisms in the same kingdom share a common ancestor further back in time.
- Modern classification uses DNA sequencing in addition to morphology (molecular phylogenetics).
Quick check
- Who proposed the Five Kingdom classification? Name the five kingdoms.
- What is binomial nomenclature? Write the scientific name of humans and mango.
- Differentiate Gymnosperms and Angiosperms with examples.
- Which phylum has the most species? Name two examples.
- What makes Mammalia different from Aves? Give two differences.
Open the Practice tab for graded questions on Diversity in Living Organisms.
Key Takeaways (TL;DR)
- What you'll learn
- Key concepts
- Quick check
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