Biology
🔒 Log in to trackClassification, plants, hormones and animal facts
🔒 Log in to trackClassification
- Carolus Linnaeus — father of taxonomy; binomial nomenclature (genus + species, e.g. Homo sapiens).
- R.H. Whittaker (1969) — five-kingdom classification: Monera (bacteria), Protista, Fungi, Plantae, Animalia.
- Viruses are not placed in these kingdoms; they are 'living' only inside a host cell.
Scientific names (frequently asked)
| Organism | Scientific name |
|---|---|
| Human | Homo sapiens |
| Mango | Mangifera indica |
| Tiger / Lion | Panthera tigris / Panthera leo |
| Peacock | Pavo cristatus |
| Neem | Azadirachta indica |
| Rice / Wheat | Oryza sativa / Triticum aestivum |
| Potato | Solanum tuberosum |
| Pea | Pisum sativum |
| Onion | Allium cepa |
| Banyan | Ficus benghalensis |
| Housefly | Musca domestica |
Plant physiology
- Photosynthesis occurs in chloroplasts using chlorophyll; the oxygen released comes from water.
- Xylem carries water and minerals upward; phloem carries food (translocation).
- Transpiration — loss of water through stomata.
- Nitrogen fixation — Rhizobium bacteria in the root nodules of legumes (pulses); blue-green algae (e.g. Anabaena) in paddy fields.
- Insectivorous plants: pitcher plant (Nepenthes), Venus flytrap, sundew — they grow in nitrogen-poor soil. Parasite: Cuscuta (amarbel).
Plant hormones
| Hormone | Main role |
|---|---|
| Auxin | Cell elongation, apical dominance, phototropism, rooting |
| Gibberellin | Stem elongation, seed germination, fruit size |
| Cytokinin | Cell division, delays ageing of leaves |
| Abscisic acid (ABA) | 'Stress hormone' — dormancy, closes stomata, leaf fall |
| Ethylene | Fruit ripening (the only gaseous hormone) |
Edible parts
| Plant | Edible part |
|---|---|
| Potato | Stem (tuber) |
| Ginger, turmeric | Stem (rhizome) |
| Onion | Bulb (fleshy leaf bases on a short stem) |
| Carrot, radish, sweet potato, beetroot | Root |
| Cauliflower | Inflorescence (flower) |
| Apple | Thalamus (false fruit) |
| Mango | Mesocarp |
| Coconut | Endosperm |
| Spinach, cabbage | Leaves |
Animal facts
- Largest animal: blue whale. Largest bird: ostrich. Egg-laying mammals: platypus, echidna. The only mammal that truly flies: bat.
- Whales, dolphins and bats are mammals; fish breathe with gills; frogs are amphibians.
- Cold-blooded: fish, amphibians, reptiles. Warm-blooded: birds, mammals.
- Insects have 6 legs; spiders have 8 (arachnids, not insects). The earthworm is the 'farmer's friend'.
Detailed notes
Classification — the ladder
Carolus Linnaeus, the father of taxonomy, gave binomial nomenclature (two-word scientific name: genus + species, in italics — Mangifera indica). R.H. Whittaker (1969) gave the five-kingdom classification: Monera, Protista, Fungi, Plantae, Animalia (earlier: two kingdoms, plants and animals). Plants divide into cryptogams (seedless — algae, fungi, bryophytes, pteridophytes) and phanerogams (seed plants — gymnosperms, naked seed; angiosperms, seed inside fruit). Monocots (wheat, rice, maize): one seed leaf, parallel leaf veins, fibrous roots. Dicots (mango, pea, gram): two seed leaves, reticulate veins, taproot.
Plant hormones
Auxin — cell elongation, bending to light (phototropism). Gibberellin — stem elongation, seed germination. Cytokinin — cell division, delays leaf ageing. Ethylene (gas) — fruit ripening. Abscisic acid — the stress hormone: closes stomata, promotes wilting and dormancy.
Photosynthesis and transport
Photosynthesis in the chloroplast (green pigment chlorophyll): 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ in sunlight. Leaves exchange gases through stomata; transpiration pulls water up the xylem (phloem carries food). Excess water vapour escapes mainly through the leaf's lower surface.
Edible parts — the exam favourite
| Plant | Edible part |
|---|---|
| Carrot, radish, beetroot, turnip | Root |
| Potato, ginger, turmeric, onion (bulb), sugarcane | Stem (modified) |
| Cabbage, spinach, lettuce | Leaves |
| Cauliflower, broccoli | Flower |
| Tomato, brinjal, pumpkin, cucumber | Fruit |
| Groundnut, gram, mustard, rice, wheat | Seed |
| Apple, cashew | Fleshy thalamus (accessory fruit) |
Reproduction and scientific names
Vegetative propagation: runners, bulbs, and human-made grafting, layering, cutting, tissue culture. Pollination agents: wind (maize, wheat — light dry pollen), water, insects (bright petals, nectar). Common scientific names: mango Mangifera indica, neem Azadirachta indica, banyan Ficus benghalensis, tamarind Tamarindus indica, potato Solanum tuberosum, rice Oryza sativa, tiger Panthera tigris, frog Rana tigrina.
Quick revision
- Linnaeus = binomial nomenclature, father of taxonomy; Whittaker = 5 kingdoms (1969).
- Monocot: one cotyledon, parallel veins; dicot: two, reticulate veins.
- Auxin–elongation/phototropism; gibberellin–stem; cytokinin–division; ethylene–ripening; ABA–stress.
- Carrot root, potato/ginger/onion stem, cabbage leaf, cauliflower flower, tomato fruit, groundnut seed.
- Photosynthesis: 6CO₂ + 6H₂O → glucose + 6O₂; stomata = gas exchange; xylem water, phloem food.
Types of questions asked
Every way this subtopic shows up in exams — how to recognise it, the formula or logic to use, and a solved example.
Type 1: Classification history and systemsvery common3 practice Q
'Who gave binomial nomenclature / five-kingdom classification', 'which kingdom does a bacterium belong to', two-kingdom vs five-kingdom, cryptogam vs phanerogam.
- Linnaeus — binomial nomenclature, father of taxonomy (species plantarum, 1753). Whittaker (1969) — five kingdoms: Monera, Protista, Fungi, Plantae, Animalia.
- Bacteria sit in Monera (prokaryotes); moulds and mushrooms in Fungi.
- Cryptogams = seedless (algae to ferns); phanerogams = seed-bearing (gymnosperms naked seed, angiosperms covered). Why: one scientist = one system; the kingdom of bacteria is the standard trap.
Example: The five-kingdom classification was proposed by —
R.H. Whittaker (1969) — Monera, Protista, Fungi, Plantae, Animalia. Linnaeus earlier gave binomial nomenclature.
Type 2: Edible part of the plantvery common4 practice Q
'Potato is a modified…', 'carrot is which plant part', 'onion is a modified…', match-the-column of plants and their edible parts.
- Roots: carrot, radish, beetroot, turnip, sweet potato.
- Stems: potato (tuber), ginger/turmeric (rhizome), onion/garlic (bulb), sugarcane.
- Leaves: cabbage, spinach, lettuce. Flower: cauliflower, broccoli. Fruit: tomato, brinjal, pumpkin. Seed: groundnut, gram, mustard.
- The double trap: sweet potato is a ROOT, ordinary potato a STEM; onion is a bulb (stem with fleshy leaves). Why: recall by family groups — roots cluster, stems cluster, one fruit list.
Example: The potato we eat is a modified —
Stem — an underground tuber with 'eyes' (buds). Sweet potato, despite the name, is a modified root.
Type 3: Plant hormonesvery common3 practice Q
'Which hormone ripens fruits', 'which hormone causes bending towards light', 'stress hormone of plants', 'which hormone promotes cell division'.
- Auxin — elongation, phototropism (bending to light). Gibberellin — stem length, germination. Cytokinin — cell division, delays ageing.
- Ethylene (a gas) — fruit ripening; abscisic acid — stress, stomatal closure, wilting.
- Ripening = ethylene; bending = auxin; wilting = ABA — three fixed one-word answers.
Example: The plant hormone responsible for fruit ripening is —
Ethylene — the only gaseous plant hormone. Ripening bananas release it, so they can ripen other fruit kept nearby.
Type 4: Photosynthesis and transportcommon3 practice Q
'Which gas is released in photosynthesis', 'which pigment absorbs light', 'xylem carries…', 'stomata are found on…', photosynthesis word equation.
- 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ — inputs CO₂ + water, outputs glucose + oxygen; pigment = chlorophyll in chloroplasts.
- Xylem carries water/minerals up; phloem carries food both ways.
- Stomata (mostly on the leaf's lower surface) do gas exchange and transpiration.
Example: In photosynthesis, plants release —
Oxygen, splitting water in the chloroplast: 6CO₂ + 6H₂O → glucose + 6O₂ in sunlight.
Type 5: Monocot vs dicot and reproductioncommon2 practice Q
'Which is a monocot', 'parallel venation indicates…', 'pollination by insects / wind', 'grafting is a method of…', number of cotyledons.
- Monocots — wheat, rice, maize, onion: one cotyledon, parallel veins, fibrous roots. Dicots — mango, pea, gram, sunflower: two cotyledons, reticulate veins, taproot.
- Insect pollination: bright petals + nectar + scent (mustard, rose). Wind: light dry pollen (maize, wheat).
- Grafting, layering, cutting, tissue culture = vegetative (asexual) propagation.
Example: Which of these shows parallel venation (a monocot)?
Maize/wheat/rice/onion — monocots have parallel veins and fibrous roots; mango and pea are dicots with net-like veins.
Type 6: Scientific names and firstscommon2 practice Q
'The scientific name of mango / neem / rice', match-the-column of plants and binomials, father-of-taxonomy questions.
- Mango Mangifera indica; neem Azadirachta indica; banyan Ficus benghalensis; tamarind Tamarindus indica.
- Potato Solanum tuberosum; rice Oryza sativa; wheat Triticum aestivum; cat Felis catus; tiger Panthera tigris.
- First word = genus (capital), second = species (small), both italic — the binomial rule of Linnaeus.
Example: The scientific name of mango is —
Mangifera indica — genus Mangifera, species indica. Neem is Azadirachta indica.
Formulas
O₂ comes from water
Shortcut tricks
⚡ Underground but not a root
Potato, ginger, turmeric, onion grow underground but are stems (they have nodes/buds or 'eyes'). Carrot, radish, sweet potato, beetroot are true roots.
Example: The edible part of ginger is?
A modified stem (rhizome).
⚡ Five kingdoms: 'My Pet Fish Plays Alone'
Monera, Protista, Fungi, Plantae, Animalia — Whittaker, 1969.
Where students lose marks
Calling sweet potato a stem and potato a root — it is the other way round.
Saying the oxygen from photosynthesis comes from CO₂ — it comes from water.
Calling the bat a bird or the whale a fish — both are mammals.
Practice sets — 19 questions
Sets of 10, mixed across the question types above. Each answer comes with a step-by-step explanation.
Topic test · 10 questions
Suggested time 3 min · wrong answers go to your mistake notebook automatically.