🌿 Biology — Biological Classification
1. Classification Systems
HIERARCHY OF CLASSIFICATION
- Species (Lowest) → Genus → Family → Order → Class → Phylum → Kingdom (Highest)
- Binomial Nomenclature: Proposed by Linnaeus in Species Plantarum
- Generic name (capital) + Species name (small) — e.g., Homo sapiens, Musca domestica
EVOLUTION OF CLASSIFICATION SYSTEMS
- Two Kingdom: Linnaeus (1758) — Plantae & Animalia
- Three Kingdom: Ernst Haeckel — Protista, Plantae, Animalia
- Four Kingdom: Copeland (1956) — Monera, Protista, Plantae, Animalia
- Five Kingdom: R.H. Whittaker (1969) — Monera, Protista, Fungi, Plantae, Animalia
- Six Kingdom: C. Woese, O. Kandler, M.C. Wheelis (1990) — Archaebacteria + Eubacteria (split Monera)
2. Kingdom — Monera
CHARACTERISTICS
- Prokaryotic (no nuclear membrane)
- Includes: Bacteria, Archaebacteria, Mycoplasma, Actinomycetes, Cyanobacteria, Rickettsia
ARCHAEBACTERIA
- Methanogens: Methane-producing (e.g., Methanobacterium)
- Halophiles: Marine bacteria (e.g., Halobacterium)
- Thermoacidophiles: Sulphur bacteria (e.g., Sulfolobus)
EUBACTERIA (True Bacteria)
- Cellulosic cell wall
- Shapes: Cocci (spherical), Bacillus (rod-shaped), Spirillum (spiral)
- Flagella arrangement:
- Atrichous (without flagella) — Lactobacillus
- Monotrichous (single) — Xanthomonas
- Amphitrichous (one each end) — Alkaligens
- Lophotrichous (group at one end) — Spirillum
- Peritrichous (whole body) — Proteus
- Plasmid: Extra DNA used as cloning vector in biotechnology
GRAM STAINING
- Developed by Christian Gram
- Gram Positive: Violet/purple colour; exotoxins; low lipid content
- Gram Negative: Red colour; endotoxins; high lipid content
REPRODUCTION IN BACTERIA
- Asexual: Binary fission (common), Budding
- Sexual:
- Transformation: F. Griffith (1928) — DNA uptake
- Conjugation: Lederberg & Tatum (1946) — through sex pili
- Transduction: Zinder & Lederberg (1952) — via bacteriophages
HUMAN DISEASES CAUSED BY BACTERIA
| Disease | Pathogen |
|---|---|
| Cholera | Vibrio cholerae |
| Plague | Yersinia pestis |
| Tuberculosis | Mycobacterium tuberculosis |
| Typhoid | Salmonella typhi |
| Diphtheria | Corynebacterium diphtheriae |
| Tetanus | Clostridium tetani |
| Syphilis | Treponema pallidum |
MYCOPLASMA (Joker of Microbiology)
- Discovered by Nocard & Roux (1898)
- Smallest; lack cell wall; pleomorphic; called PPLO
ECONOMIC IMPORTANCE OF BACTERIA
- Antibiotics: Penicillin (from Penicillium notatum), Streptomycin (from Streptomyces griseus)
- Industrial: Acetic acid, Acetone, Butanol, Lactic acid
- Biogas: Methane by Methanobacillus
3. Kingdom — Protista
CHARACTERISTICS
- Eukaryotic, single-celled organisms
- Includes: Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds, Protozoa
- Mostly marine
PATHOGENIC PROTOZOANS
| Disease | Pathogen | Vector |
|---|---|---|
| Kala-azar | Leishmania donovani | Sandfly |
| Malaria | Plasmodium vivax | Female Anopheles mosquito |
| Sleeping sickness | Trypanosoma gambiense | Tse-tse fly |
| Amoebic dysentery | Entamoeba histolytica | Food/water |
| Leucorrhoea | Trichomonas vaginalis | Sexual contact |
4. Kingdom — Fungi
CHARACTERISTICS
- Cell wall: Chitin
- Heterotrophic; body made of hyphae (network = mycelium)
- Reproduction: Fragmentation, Asexual spores, Sexual spores
HUMAN DISEASES CAUSED BY FUNGI
- Athlete's foot: Tinea rubrum
- Ringworm: Trichophyton, Microsporum, Epidermophyton
- Aspergillosis: Aspergillus species
- Candidiasis: Candida albicans
PLANT DISEASES CAUSED BY FUNGI
- Late blight of potato: Phytophthora infestans
- Black rust of wheat: Puccinia graminis tritici
- Red rot of sugarcane: Colletotrichum falcatum
- Blast disease of rice: Pyricularia oryzae
ECONOMIC IMPORTANCE
- Penicillium: Penicillin antibiotic
- Saccharomyces cerevisiae (Yeast): Ethyl alcohol, Vitamin-B & D
- Mushrooms: Edible (Agaricus campestris)
- Aflatoxins: Produced by Aspergillus (carcinogenic)
5. Kingdom — Plantae
CHARACTERISTICS
- Chlorophyll-containing, eukaryotic organisms
- Cell wall: Cellulose
- Includes: Algae, Bryophytes, Pteridophytes, Gymnosperms, Angiosperms
- Some are insectivorous (Bladderwort, Venus flytrap) or parasitic (Cuscuta)
ALGAE
- Aquatic, autotrophic, thalloid plants
- Algal bloom: Massive growth; red tide caused by red algae
- Economically important:
- Agar-agar: Gelidium, Gracilaria
- Iodine: Laminaria, Macrocystis
- Biofertilisers: Nostoc, Anabaena
- Chlorellin (antibiotic): Chlorella
BRYOPHYTES
- "Amphibians of plant kingdom"
- Found in moist areas; no true organs
- Gametophyte (main) → male/female gametes → sporophyte (foot, seta, capsule) → spores
PTERIDOPHYTES
- First terrestrial plants with vascular tissue (xylem & phloem)
- Found in cool, shady places
- Sporophyte (main) → spores → prothallus → gametes → fertilisation
GYMNOSPERMS
- "Naked ovules" — seeds not covered
- Includes: Cycas, Pinus, Sequoia (giant redwood)
- Mycorrhiza: Fungal association in Pinus roots
- Coralloid roots: N₂-fixing cyanobacteria in Cycas
ANGIOSPERMS
- Flowering plants; fruit-bearing
- Range: Wolffia (smallest) to Eucalyptus (tallest)
- Dicots: Two cotyledons
- Monocots: One cotyledon
- Includes: Parasitic (Cuscuta), Epiphytic (grow on other plants)
6. Kingdom — Animalia
CHARACTERISTICS
- Heterotrophic, multicellular organisms
- Invertebrates (no backbone) or Vertebrates (backbone)
- Symmetry: Asymmetrical, Radial, Bilateral
VERTEBRATE CLASSES
- Cyclostomata: Jawless fishes (6-15 gill slits)
- Chondrichthyes: Cartilaginous fishes (shark, ray)
- Amphibia: Moist skin, 3-chambered heart, external fertilisation
- Reptilia: Dry thick skin, internal fertilisation, 4-chambered (crocodile)
- Aves: Feathers, 4-chambered heart, uric acid excretion
- Mammalia: Hair, mammary glands, diaphragm
DISEASE CARRIER INSECTS
| Insect | Diseases |
|---|---|
| Housefly | Diarrhoea, Typhoid, Cholera, Leprosy |
| Mosquito | Malaria, Filariasis, Dengue, Yellow fever |
| Sand fly | Kala-azar |
| Tse-tse fly | Sleeping sickness |
| Rat flea | Bubonic plague |
7. Viruses
CHARACTERISTICS
- Term given by Pasteur; discovered by Ivanowski in diseased tobacco plant
- Obligate parasites — lack enzymes for energy generation
- Exist as crystals outside host; insert DNA/RNA into host
- Contain small fragment of DNA or RNA (single/double-stranded)
TYPES BASED ON GENETIC MATERIAL
- ds DNA: Adenoviruses, Herpes viruses, Pox viruses
- ss DNA (+ sense): Parvo viruses
- ds RNA: Reoviruses
- ss RNA (+ sense): Picornoviruses, Tongoviruses
- ss RNA (- sense): Orthomyxoviruses, Rhabdoviruses
- ss RNA-RT (+ sense): Retroviruses (HIV)
- ds DNA-RT: Hepadnaviruses
COVID-19
- Infectious disease caused by SARS-CoV-2 (coronavirus)
- Outbreak began in Wuhan, China (December 2019)
- Symptoms: Fever, dry cough, tiredness, loss of taste/smell
- Transmission: Through droplets from nose/mouth
- Prevention: Washing hands, wearing masks, social distancing
VIRAL DISEASES OF HUMAN BEINGS
| Disease | Pathogen |
|---|---|
| AIDS | HIV (Retrovirus) |
| Chickenpox | Varicella zoster |
| Influenza | Influenza virus |
| Measles | Paramyxovirus |
| Polio | Poliovirus |
| Rabies | Rhabdovirus |
| Swine flu | H1N1 virus |
| Dengue | Dengue virus (Flavivirus) |
| Chikungunya | Chikungunya virus |
Summary: Biological Classification at a Glance
| Kingdom | Key Features | Examples |
|---|---|---|
| Monera | Prokaryotic, cell wall polysaccharide | Bacteria, Mycoplasma |
| Protista | Eukaryotic, unicellular | Protozoa, Algae |
| Fungi | Chitin cell wall, heterotrophic | Penicillium, Mushrooms |
| Plantae | Cellulose cell wall, autotrophic | Bryophytes, Angiosperms |
| Animalia | No cell wall, heterotrophic | Mammals, Birds |
KEY TAKEAWAYS FOR UPSC
- Binomial Nomenclature: Linnaeus — Homo sapiens, Musca domestica
- 5 Kingdom: Whittaker (1969) — Monera, Protista, Fungi, Plantae, Animalia
- 6 Kingdom: Woese et al. (1990) — Archaebacteria + Eubacteria
- Gram Staining: Christian Gram — Positive (purple) vs Negative (red)
- Mycoplasma: Smallest, no cell wall (PPLO)
- Bryophytes: Amphibians of plant kingdom
- Mycorrhiza: Fungus + root association in Pinus
- Retroviruses: ss RNA-RT (+ sense) — HIV
- COVID-19: SARS-CoV-2; Wuhan, China (2019)
High-Yield Interactive UPSC Quiz (Biology — Biological Classification)
Q1. Who proposed the Five Kingdom classification?
Correct Answer: C. R.H. Whittaker proposed the Five Kingdom classification in 1969.
Q2. Which kingdom has prokaryotic cells?
Correct Answer: B. Monera (bacteria and cyanobacteria) have prokaryotic cells.
Q3. The cell wall of fungi is made of:
Correct Answer: C. Fungi have cell walls made of chitin.
Q4. Which plant group is known as the "amphibians of the plant kingdom"?
Correct Answer: B. Bryophytes are known as the amphibians of the plant kingdom.
Q5. Malaria is caused by which protozoan?
Correct Answer: B. Malaria is caused by Plasmodium species, transmitted by female Anopheles mosquito.
Q6. Which virus causes AIDS?
Correct Answer: C. AIDS is caused by HIV, a retrovirus (ss RNA-RT virus).
Q7. Gram-positive bacteria appear which colour in Gram staining?
Correct Answer: B. Gram-positive bacteria appear violet/purple in Gram staining.
Q8. The naked ovules are characteristic of which plant group?
Correct Answer: B. Gymnosperms have naked ovules (not enclosed in an ovary).
Q9. Which disease is transmitted by the tse-tse fly?
Correct Answer: C. Sleeping sickness is transmitted by the tse-tse fly.
Q10. The causative agent of COVID-19 is:
Correct Answer: B. COVID-19 is caused by SARS-CoV-2 (a coronavirus).