Cell, Plant Life and Classification of Living Things: Biology Notes for Lok Sewa

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Biology questions in Lok Sewa General Science usually come from three areas: the cell, plant life (photosynthesis, hormones, plant parts) and the classification of living things. This note gives you the facts examiners ask most, in short tables you can revise in ten minutes.

1. The cell: discovery and cell theory

FactAnswer
Cell first described (in cork)Robert Hooke, 1665
First to see living cellsAnton van Leeuwenhoek
Nucleus discoveredRobert Brown
Cell theorySchleiden and Schwann
Basic unit of lifeCell
Largest single cellOstrich egg
Longest cell in the human bodyNerve cell (neuron)
Smallest known cellMycoplasma (PPLO)

2. Parts of a cell and their work

Part (organelle)Main function
NucleusControl centre; contains DNA (genetic material)
Mitochondria“Powerhouse of the cell”: makes energy (ATP) by respiration
RibosomeMakes proteins
Endoplasmic reticulumTransport channel inside the cell
Golgi bodyPacks and sends out materials
Lysosome“Suicide bag”: digests waste and old parts
ChloroplastPhotosynthesis (plant cells only); contains chlorophyll
Cell wallRigid outer layer made of cellulose (plants)
VacuoleStores water and materials; large in plant cells
CentrosomeHelps cell division (animal cells)
Plant cellAnimal cell
Has cell wallNo cell wall
Has chloroplastsNo chloroplasts
One large vacuoleSmall or no vacuoles
Centrosome usually absentCentrosome present

Prokaryotic cells (bacteria) have no true nucleus. Eukaryotic cells (plants, animals, fungi) have a true nucleus with a membrane.

3. Plant life

Photosynthesis: 6CO₂ + 6H₂O → (sunlight, chlorophyll) → C₆H₁₂O₆ + 6O₂. Green plants make glucose and release oxygen. It happens in the chloroplast.

TermMeaning
StomataTiny pores on leaves for gas exchange
TranspirationLoss of water as vapour from leaves
XylemCarries water and minerals upward from the roots
PhloemCarries food made in the leaves to other parts
PollinationTransfer of pollen to the stigma
Plant hormoneMain role
AuxinGrowth of shoots, bending towards light
GibberellinStem elongation, seed germination
CytokininCell division
Abscisic acidStress hormone; dormancy, closing stomata
EthyleneRipening of fruits (a gas)

4. Classification of living things

  • Carl Linnaeus is the father of taxonomy and gave binomial nomenclature (genus + species), e.g. Homo sapiens.
  • Order of ranks: Kingdom → Phylum → Class → Order → Family → Genus → Species.
  • R.H. Whittaker proposed the five-kingdom system: Monera, Protista, Fungi, Plantae and Animalia.
KingdomExamples
MoneraBacteria (prokaryotes)
ProtistaAmoeba, Paramecium
FungiMushroom, yeast, mould
PlantaeMosses, ferns, pine, mango
AnimaliaInsects, fish, birds, humans

5. Groups of plants

GroupKey featureExample
ThallophytaBody not divided into root, stem, leafAlgae
Bryophyta“Amphibians of the plant kingdom”Mosses
PteridophytaFirst plants with vascular tissue; no seedsFerns
GymnospermsNaked seeds (no fruit)Pine, cycas
AngiospermsFlowering plants; seeds inside fruitMango, rice, rhododendron
MonocotDicot
One cotyledonTwo cotyledons
Parallel veinsNet-like veins
Fibrous rootsTap root
Rice, wheat, maizePea, gram, mango

Common scientific names: Rice Oryza sativa, Wheat Triticum aestivum, Maize Zea mays, Mango Mangifera indica, Rhododendron (national flower) Rhododendron arboreum.

6. Cell parts and functions

PartFunction
Cell membraneControls what enters and leaves
NucleusControls the cell; holds DNA
MitochondriaPowerhouse; produces energy
ChloroplastPhotosynthesis (plants only)
Cell wallGives shape and support (plants only)
VacuoleStores water and food; large in plants

7. Quick facts

  • The cell was discovered by Robert Hooke in 1665.
  • Cell theory: Schleiden (plants) and Schwann (animals).
  • Photosynthesis: carbon dioxide + water + sunlight → glucose + oxygen.

8. How this topic is asked in the exam

Objective questions ask the functions of cell parts, the differences between plant and animal cells and who discovered the cell. Health and agriculture papers also ask about photosynthesis and plant parts.

📌 Key points to remember

  • Robert Hooke discovered the cell (1665); Robert Brown the nucleus.
  • Mitochondria = powerhouse; lysosome = suicide bag; ribosome = protein factory.
  • Cell wall and chloroplast are found in plant cells, not animal cells.
  • Photosynthesis takes place in chloroplasts and releases oxygen.
  • Xylem carries water up; phloem carries food.
  • Ethylene ripens fruit; auxin controls growth towards light.
  • Linnaeus: binomial nomenclature. Whittaker: five kingdoms.
  • Bryophytes are the amphibians of the plant kingdom.
📝 Quiz

Test yourself: Cell, Plant Life and Classification of Living Things

50 questions check what you read about The cell: discovery and cell theory, Plant life and Groups of plants. Each attempt picks 25 at random.

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📚 Related notes

More notes in Science and Technology · Full package: Paper I Complete Package · Practise: Nayab Subba Model Question 2083

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