UPSSSC PET · Bite-size lessons
Basic Biology
About 6 min · General Science · English
Time worked out from the lesson's 421 words at 150 words a minute, plus a minute for each question.
This topic covers the fundamental building blocks of life (cells), classification of living organisms (plant and animal kingdoms), major human body systems (digestive, circulatory, respiratory, nervous, excretory), and common diseases with their causative agents and prevention methods.
Key ideas
- Cell as the Basic Unit: All living organisms are made of cells; cells contain organelles that perform specialized life functions such as energy production, protein synthesis, and waste removal.
- Plant vs. Animal Cells: Plant cells have a rigid cell wall, chloroplasts for photosynthesis, and large central vacuoles; animal cells lack these structures but have centrioles for cell division.
- Five-Kingdom Classification: Living organisms are classified into Monera (bacteria), Protista (algae, protozoa), Fungi (mushrooms, yeasts), Plantae (mosses to flowering plants), and Animalia (sponges to mammals).
- Human Body Systems Work Together: The digestive system breaks down food; circulatory system transports nutrients and oxygen; respiratory system exchanges gases; nervous system coordinates responses; excretory system removes waste.
- Blood Composition and Function: Blood contains red blood cells (oxygen transport), white blood cells (immunity), platelets (clotting), and plasma (liquid medium); human blood groups are A, B, AB, O based on antigens.
Watch out for
- Confusing Plant and Animal Cell Structures: Students often forget that chloroplasts and cell walls are exclusive to plant cells, while centrioles are found only in animal cells. Fix: Create a comparison table and memorize the unique structures for each cell type.
- Mixing Up Arteries and Veins: Many believe arteries always carry oxygenated blood. Fix: Remember arteries carry blood away from the heart (pulmonary artery carries deoxygenated blood to lungs), veins carry blood toward the heart.
- Misidentifying Disease Causative Agents: Confusing bacterial diseases (treatable with antibiotics) with viral diseases (not treatable with antibiotics).
Quick reference
- Mitochondria = Powerhouse; Nucleus = Control centre; Ribosomes = Protein factory; Chloroplasts = Photosynthesis (plants only).
- Plant cells have: Cell wall, chloroplasts, large central vacuole. Animal cells have: Centrioles, small vacuoles.
- Human blood groups: A, B, AB (universal recipient), O (universal donor).
- Digestive enzymes: Amylase (starch), Pepsin (protein in stomach), Lipase (fats), Trypsin (protein in intestine).
- TB, Cholera, Typhoid = Bacteria; Polio, AIDS, COVID-19 = Virus; Malaria = Protozoan; Ringworm = Fungus.
Check yourself: 3 questions
1. Which of the following is known as the 'powerhouse of the cell' because it generates most of the cell's supply of ATP (adenosine triphosphate)?
2. The process by which plants lose water vapour through small pores in their leaves is called:
3. Which human body system is primarily affected by tuberculosis (TB), a disease caused by the bacterium Mycobacterium tuberculosis?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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